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Scott, Abigail L., Paul H. York e Michael A. Rasheed. "Spatial and Temporal Patterns in Macroherbivore Grazing in a Multi-Species Tropical Seagrass Meadow of the Great Barrier Reef". Diversity 13, n. 1 (2 gennaio 2021): 12. http://dx.doi.org/10.3390/d13010012.
Testo completoAbstract (sommario):
Macroherbivory is an important process in seagrass meadows worldwide; however, the impact of macroherbivores on seagrasses in the Great Barrier Reef (GBR) has received little attention. We used exclusion cages and seagrass tethering assays to understand how the intensity of macroherbivory varies over space and time in the seagrass meadows around Green Island (Queensland), and what impact this has on overall meadow structure. Rates of macroherbivory were comparatively low, between 0.25–44% of daily seagrass productivity; however, rates were highly variable over a one-year period, and among sites. Loss of seagrass material to macroherbivory was predominantly due to fish; however, urchin herbivory was also taking place. Macroherbivory rates were of insufficient intensity to impact overall meadow structure. No macroherbivory events were identified on video cameras that filmed in the day, indicating that feeding may be occurring infrequently in large shoals, or at night. While relatively low compared to some meadows, seagrass macroherbivory was still an important process at this site. We suggest that in this highly protected area of the GBR, where the ecosystem and food webs remain largely intact, macroherbivory was maintained at a low level and was unlikely to cause the large-scale meadow structuring influence that can be seen in more modified seagrass systems.
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Rattanachot, Ekkalak, Milica Stankovic, Supaphon Aongsara e Anchana Prathep. "Ten years of conservation efforts enhance seagrass cover and carbon storage in Thailand". Botanica Marina 61, n. 5 (25 settembre 2018): 441–51. http://dx.doi.org/10.1515/bot-2017-0110.
Testo completoAbstract (sommario):
Abstract Seagrasses are known as engineering ecosystems that play important roles in coastal environments. Globally, seagrass areas have been declining, and many conservation projects have been carried out to prevent further decline. The goal of this work was to determine how successful conservation efforts have been in a seagrass meadow at Koh Tha Rai in the Nakhon Si Thammarat Province of southern Thailand in terms of meadow extent, coverage and organic carbon storage. A study was conducted in 2017 and compared to a previous study from 2006 to determine the effects of the various conservation efforts devoted to this area. The results show that the total seagrass area increased by 0.7 ha with a rate of increase of approximately 0.06 ha year−1. The total coverage of seagrass increased by approximately 3 times. The organic carbon in existing seagrass meadows (2006) was 53.35 Mg ha−1, while growth was 32.34 Mg ha−1 in the areas of new seagrass. Moreover, the total organic carbon storage in the sediment increased by 26.86 MgC from 2006 to 2017 (from 211.60 MgC to 235.46 MgC). In conclusion, this study demonstrated the importance of successful conservation efforts in terms of increasing seagrass meadow areas, seagrass coverage and carbon storage within the meadow.
3
Titioatchasai, Jatdilok, Komwit Surachat, Ekkalak Rattanachot, Piyalap Tuntiprapas e Jaruwan Mayakun. "Assessment of Diversity of Marine Organisms among Natural and Transplanted Seagrass Meadows". Journal of Marine Science and Engineering 11, n. 10 (6 ottobre 2023): 1928. http://dx.doi.org/10.3390/jmse11101928.
Testo completoAbstract (sommario):
Seagrass ecosystems have been declining, and restorations are conducted in many parts of the world to compensate for habitat loss and restore the ecosystem services seagrasses provide. Assessment of transplantation success requires the monitoring of the level of biodiversity between the donor and transplanted sites. In this study, we assessed a seagrass ecosystem after restoration in terms of the diversity of marine organisms using environmental DNA (eDNA) to compare four sites: (1) bare sand, (2) a natural meadow of Cymodocea serrulata, (3) a natural meadow of Halophila ovalis, and (4) a transplanted seagrass meadow. The results showed the presence of 3 domains, 34 phyla, 59 classes, 92 orders, 155 families, 156 genera, and 121 species. Proteobacteria, Actinobacteria, Cyanobacteria, and Bacteroidetes were the dominant bacterial phyla. Among eukaryotes, Phragmoplastophyta/Charophyta (epiphytes), Ascomycota (fungi), Cnidaria (jelly fish), and Arthropoda (Crabs and bivalves) were the dominant phyla. Dugong tails and commercial species (sea cucumber, dog conch, and swimming crab) have been observed in both the natural and transplanted meadows. Relative abundance among the four sites was significantly different. There were no differences in species richness and evenness between the four sites and no differences in species richness and evenness between the natural meadows and the transplanted seagrass meadow. It is possible that transplanted seagrass meadow can be successfully restored and established and can provide habitat for fauna and microbes. Additionally, fauna are not limited in their capacity to move between the natural and transplanted habitats. This study provides an assessment of biodiversity of restored seagrass patches and a better understanding of a seagrass ecosystem after restoration. However, to assess seagrass ecosystem services after restoration and the success of restoration actions, long-term monitoring of marine organism diversity and additional assessments are needed.
4
Hendriks, I. E., Y. S. Olsen, L. Ramajo, L. Basso, A. Steckbauer, T. S. Moore, J. Howard e C. M. Duarte. "Photosynthetic activity buffers ocean acidification in seagrass meadows". Biogeosciences 11, n. 2 (28 gennaio 2014): 333–46. http://dx.doi.org/10.5194/bg-11-333-2014.
Testo completoAbstract (sommario):
Abstract. Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5–12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.
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Hendriks, I. E., Y. S. Olsen, L. Ramajo, L. Basso, A. Steckbauer, T. S. Moore, J. Howard e C. M. Duarte. "Photosynthetic activity buffers ocean acidification in seagrass meadows". Biogeosciences Discussions 10, n. 7 (22 luglio 2013): 12313–46. http://dx.doi.org/10.5194/bgd-10-12313-2013.
Testo completoAbstract (sommario):
Abstract. Macrophytes growing in shallow coastal zones characterized by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH ranges is in shallow (5–12 m) seagrass (Posidonia oceanica) meadows from 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean and max pHNBS and max ΩAr. Oxygen production positively influenced the range and maximum pHNBS and the range of ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. ΩAr was positively correlated with the calcium carbonate load of the leaves, demonstrating a direct link between structural parameters, ΩAr and carbonate deposition. There was a direct relationship between ΩAr, influenced directly by meadow LAI, and CaCO3 content of the leaves. Therefore, calcifying organisms, e.g. epiphytes with carbonate skeletons, might benefit from the modification of the carbonate system by the meadow. The meadow might be capable of providing refugia for calcifiers by increasing pH and ΩAr through metabolic activity. There is, however, concern for the ability of seagrasses to provide this refugia function in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, both strongly linked to LAI. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.
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Leemans, Luuk, Isis Martínez, Tjisse van der Heide, Marieke M. van Katwijk e Brigitta I. van Tussenbroek. "A Mutualism Between Unattached Coralline Algae and Seagrasses Prevents Overgrazing by Sea Turtles". Ecosystems 23, n. 8 (18 febbraio 2020): 1631–42. http://dx.doi.org/10.1007/s10021-020-00492-w.
Testo completoAbstract (sommario):
AbstractSeagrass meadows are threatened biodiversity hot spots that provide essential ecosystem services. Green sea turtles may overgraze meadows, further enhancing seagrass decline. However, we observed an unexpected, remarkable recovery of seagrasses in a previously overgrazed meadow with abundant unattached branched coralline algae, suggesting that turtle grazing had ceased. We hypothesize that this recovery is due to an effective grazing-protection mutualism, in which the spiny coralline algae structures protect the seagrass meadows from overgrazing, while the seagrasses protect the algae from removal by currents and waves. Removing coralline algae from recovered seagrass plots allowed the turtles to resume grazing, while addition of coralline algae to grazed plots caused cessation of grazing. Coralline algae that were placed on bare sand were quickly displaced by wave action, whereas those placed in grazed or ungrazed seagrass remained. Our experiments demonstrate a grazing-protection mutualism, which likely explains the witnessed recovery of an overgrazed seagrass meadow. To our knowledge, this is the first account of a plant–plant grazing-protection mutualism in an aquatic environment. Our findings show that grazing-protection mutualisms can be vital for the maintenance and recovery of ecosystems shaped by habitat-structuring foundation species, and highlight the importance of mutualisms in coastal ecosystems. As seagrasses, sea turtles and coralline algae share habitats along tropical shores worldwide, the mutualism may be a global phenomenon. Overgrazing is expected to increase, and this mutualism adds a new perspective to the conservation and restoration of these valuable ecosystems.
7
Bongolan, V. P., G. M. Torres e J. E. Branzuela. "MODELLING, SIMULATION AND VISUALIZATION OF A MULTISPECIFIC PHILIPPINE SEAGRASS MEADOW". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W19 (23 dicembre 2019): 77–82. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w19-77-2019.
Testo completoAbstract (sommario):
Abstract. Seagrass meadows are constantly under threat from natural and man-made stresses due to its shallow existence in the coastal environment. Restoration and preservation of seagrasses by means of rehabilitation or transplanting strategies is possible, but the studies have been limited. An agent-based model of a mixed Philippine seagrass meadow is presented. Three species were used for testing: Enhalus acoroides, Thalassia hemprichii, and Cymodocea rotundata. The model features parameter-based clonal growth of seagrass species, recruitment of new seagrass apices through basic flowering/seeding, and a crowding logic for multiple coexisting species in a single meadow. Seagrass clonal growth is modeled using a modified Diffusion-Limited Aggregation (DLA) model. Each species has a preconfigured set of parameters for clonal growth including rhizome elongation, branching rate, vertical elongation rate, rhizome branching angle and shoot age. Seed recruitment is applied through occasional flowering/seeding events configurable per species. We developed a simple three-species competition model which controls the growth and direct competition effects based on a configurable population size and comparison radius. Upon further calibration and validation, the model would enable more accurate long-term predictions for different rehabilitation and transplanting strategies of mixed seagrass meadows. Further improvements can also be implemented, particularly taking into account the environmental variables within the meadows such as light attenuation and salinity, among other factors.
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Ivajnšič, Danijel, Martina Orlando-Bonaca, Daša Donša, Veno Jaša Grujić, Domen Trkov, Borut Mavrič e Lovrenc Lipej. "Evaluating Seagrass Meadow Dynamics by Integrating Field-Based and Remote Sensing Techniques". Plants 11, n. 9 (28 aprile 2022): 1196. http://dx.doi.org/10.3390/plants11091196.
Testo completoAbstract (sommario):
Marine phanerogams are considered biological sentinels or indicators since any modification in seagrass meadow distribution and coverage signals negative changes in the marine environment. In recent decades, seagrass meadows have undergone global losses at accelerating rates, and almost one-third of their coverage has disappeared globally. This study focused on the dynamics of seagrass meadows in the northern Adriatic Sea, which is one of the most anthropogenically affected areas in the Mediterranean Sea. Seagrass distribution data and remote sensing products were utilized to identify the stable and dynamic parts of the seagrass ecosystem. Different seagrass species could not be distinguished with the Sentinel-2 (BOA) satellite image. However, results revealed a generally stable seagrass meadow (283.5 Ha) but, on the other hand, a stochastic behavior in seagrass meadow retraction (90.8 Ha) linked to local environmental processes associated with anthropogenic activities or climate change. If systemized, this proposed approach to monitoring seagrass meadow dynamics could be developed as a spatial decision support system for the entire Mediterranean basin. Such a tool could serve as a key element for decision makers in marine protected areas and would potentially support more effective conservation and management actions in these highly productive and important environments.
9
Digdo, A. A., E. Astari, B. R. Arinda e J. Arendege. "Humans and seagrass: a complex and intertwining links - an illustration from North Sulawesi, Indonesia". IOP Conference Series: Earth and Environmental Science 1220, n. 1 (1 luglio 2023): 012027. http://dx.doi.org/10.1088/1755-1315/1220/1/012027.
Testo completoAbstract (sommario):
Abstract Interactions between humans and seagrasses in a rural area in North Sulawesi (North Minahasa) were determined by applying the ecosystem goods and services concept and related social-ecological system. The main role in the villages is small-scale fishermen and the general public. By conducting interviews, questionnaires, focus group discussions, community immersion, and field surveys, we discovered complex social-ecological ties that are essential for local society and the ecosystem. Nursery ground and habitat for fish and invertebrates, traditional medicine, indicative for Ramadan season-opening, and sites for bait collection were within the significant seagrass meadow ecosystem services for the local coastal people. We identified 183 traditional fish names that are associated with seagrass. Gleaning (banyare) and trapping fisheries (“soma”, “sero” and “bubu”) in the areas captured seagrass-associated fishes (Siganidae) that contribute a major livelihood source for the fishermen. The seagrass meadow overlaps with species habitats, for instance, dugongs and sea turtles. Out of 90 fishing grounds, 13 overlapped with seagrass beds, which also have dugong feeding trails. Most of the seagrass beds are open and free for all areas, except around LMMAs managed by villages, which likely create positive effects on seagrass meadows.
10
Strydom, Simone, Roisin McCallum, Anna Lafratta, Chanelle L. Webster, Caitlyn M. O'Dea, Nicole E. Said, Natasha Dunham et al. "Global dataset on seagrass meadow structure, biomass and production". Earth System Science Data 15, n. 1 (1 febbraio 2023): 511–19. http://dx.doi.org/10.5194/essd-15-511-2023.
Testo completoAbstract (sommario):
Abstract. Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in climate change mitigation and adaption. Understanding the natural history of seagrass meadows across environmental gradients is crucial to deciphering the role of seagrasses in the global ocean. In this data collation, spatial and temporal patterns in seagrass meadow structure, biomass and production data are presented as a function of biotic and abiotic habitat characteristics. The biological traits compiled include measures of meadow structure (e.g. percent cover and shoot density), biomass (e.g. above-ground biomass) and production (e.g. shoot production). Categorical factors include bioregion, geotype (coastal or estuarine), genera and year of sampling. This dataset contains data extracted from peer-reviewed publications published between 1975 and 2020 based on a Web of Science search and includes 11 data variables across 12 seagrass genera. The dataset excludes data from mesocosm and field experiments, contains 14 271 data points extracted from 390 publications and is publicly available on the PANGAEA® data repository (https://doi.org/10.1594/PANGAEA.929968; Strydom et al., 2021). The top five most studied genera are Zostera, Thalassia, Cymodocea, Halodule and Halophila (84 % of data), and the least studied genera are Phyllospadix, Amphibolis and Thalassodendron (2.3 % of data). The data hotspot bioregion is the Tropical Indo-Pacific (25 % of data) followed by the Tropical Atlantic (21 %), whereas data for the other four bioregions are evenly spread (ranging between 13 and 15 % of total data within each bioregion). From the data compiled, 57 % related to seagrass biomass and 33 % to seagrass structure, while the least number of data were related to seagrass production (11 % of data). This data collation can inform several research fields beyond seagrass ecology, such as the development of nature-based solutions for climate change mitigation, which include readership interested in blue carbon, engineering, fisheries, global change, conservation and policy.
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Cavalcante, Lorraine Lopes, Cristiane Xerez Barroso, Pedro Bastos de Macêdo Carneiro e Helena Matthews-Cascon. "Spatiotemporal dynamics of the molluscan community associated with seagrass on the western equatorial Atlantic". Journal of the Marine Biological Association of the United Kingdom 99, n. 06 (28 marzo 2019): 1285–94. http://dx.doi.org/10.1017/s0025315419000183.
Testo completoAbstract (sommario):
AbstractThis study aimed to qualitatively and quantitatively analyse the molluscan assemblages associated with a Halodule wrightii seagrass bed in a rarely studied area within a conservation unit in north-eastern Brazil. Seasonal and spatial changes in several seagrass meadow characteristics, including sediment, were evaluated to explain temporal and spatial variations in the molluscs found there. The molluscan community differed in its structure among periods and meadows, as well as in the composition of its infaunal and epifaunal assemblages. The results of this study indicated that molluscs are affected by the particular characteristics of a seagrass meadow, especially by its location in the intertidal zone, more than by the area of the meadow. Molluscs were also affected by other characteristics of the seagrass meadow, such as above-ground biomass and shoot density. Changes in all molluscan assemblages were also mediated by differences among months and seasons in this region of the western equatorial Atlantic, but not by seasonal changes of the meadow. The studied meadow was found to be one of the densest in Brazil, which has considerable importance to its associated fauna.
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Ward, Melissa, Tye L. Kindinger, Heidi K. Hirsh, Tessa M. Hill, Brittany M. Jellison, Sarah Lummis, Emily B. Rivest, George G. Waldbusser, Brian Gaylord e Kristy J. Kroeker. "Reviews and syntheses: Spatial and temporal patterns in seagrass metabolic fluxes". Biogeosciences 19, n. 3 (3 febbraio 2022): 689–99. http://dx.doi.org/10.5194/bg-19-689-2022.
Testo completoAbstract (sommario):
Abstract. Seagrass meadow metabolism has been measured for decades to gain insight into ecosystem energy, biomass production, food web dynamics, and, more recently, to inform its potential in ameliorating ocean acidification (OA). This extensive body of literature can be used to infer trends and drivers of seagrass meadow metabolism. Here, we synthesize the results from 56 studies reporting in situ rates of seagrass gross primary productivity, respiration, and/or net community productivity to highlight spatial and temporal variability in oxygen (O2) fluxes. We illustrate that daytime net community production (NCP) is positive overall and similar across seasons and geographies. Full-day NCP rates, which illustrate the potential cumulative effect of seagrass beds on seawater biogeochemistry integrated over day and night, were also positive overall but were higher in summer months in both tropical and temperate ecosystems. Although our analyses suggest seagrass meadows are generally autotrophic, the effects on seawater oxygen are relatively small in magnitude. We also find positive correlations between gross primary production and temperature, although this effect may vary between temperate and tropical geographies and may change under future climate scenarios if seagrasses approach thermal tolerance thresholds. In addition, we illustrate that periods when full-day NCP is highest could be associated with lower nighttime O2 and increased diurnal variability in seawater O2. These results can serve as first-order estimates of when and where OA amelioration by seagrasses may be likely. However, improved understanding of variations in NCPDIC:NCPO2 ratios and increased work directly measuring metabolically driven alterations in seawater pH will further inform the potential for seagrass meadows to serve in this context.
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Lee, Kevin M., Megan Ballard, Kyle Capistrant-Fossa, Andrew R. McNeese, Colby W. Cushing, Thomas S. Jerome, Preston S. Wilson e Kenneth H. Dunton. "Temporal dependence of acoustic propagation in a seagrass meadow over diurnal and annual timescales". Journal of the Acoustical Society of America 153, n. 3_supplement (1 marzo 2023): A26. http://dx.doi.org/10.1121/10.0018032.
Testo completoAbstract (sommario):
Seagrasses serve major ecological roles in biodiversity promotion, coastal protection, and nutrient cycling. Furthermore, seagrasses have been proposed as a nature-based solution to mitigate effects of climate change due to their capacity for sequestering marine carbon. Current global estimates of seagrass coverage are uncertain; therefore, developing improved methods to assess seagrass coverage and rates of decline are critical to promote sustainable seagrass conservation efforts. Acoustic propagation in seagrass meadows is highly sensitive to oxygen bubble production via photosynthesis and gas volumes encapsulated within seagrass tissue, both acting as biophysical markers. This paper discusses an acoustic method to monitor seagrass oxygen production and biomass with high temporal resolution and over long time-scales. An 18-month acoustic propagation experiment was conducted in a seagrass meadow located in a shallow bay on the Texas Gulf of Mexico Coast. A piezoelectric sound source transmitted broadband frequency-modulated chirps (0.5–100 kHz) every ten minutes, and the signal was measured on horizontal hydrophone array. Dissolved oxygen, photosynthetically active radiation, water temperature, salinity, and depth were concurrently measured with oceanographic probes. Additionally, cores were collected for point-estimates of seagrass biomass. Our work demonstrates that acoustic propagation offers a valuable alternative to experimental measurements of photosynthesis. [Work sponsored by NSF.]
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Kindeberg, Theodor, Karl Michael Attard, Jana Hüller, Julia Müller, Cintia Organo Quintana e Eduardo Infantes. "Structural complexity and benthic metabolism: resolving the links between carbon cycling and biodiversity in restored seagrass meadows". Biogeosciences 21, n. 7 (8 aprile 2024): 1685–705. http://dx.doi.org/10.5194/bg-21-1685-2024.
Testo completoAbstract (sommario):
Abstract. Due to large losses of seagrass meadows worldwide, restoration is proposed as a key strategy for increasing coastal resilience and recovery. The emergence of a seagrass meadow is expected to substantially amplify biodiversity and enhance benthic metabolism by increasing primary productivity and respiration. Nevertheless, open questions remain regarding the metabolic balance of aging seagrass meadows and the roles benthic communities within the seagrass ecosystem play in overall metabolism. To address these questions, we investigated a chronosequence of bare sediments and adjacent Zostera marina meadows of 3 and 7 years since restoration alongside a natural meadow located within a high-temperate marine embayment in Gåsö, Sweden. We combined continuous measurements of O2 fluxes using underwater eddy covariance with dissolved inorganic carbon (DIC) and O2 fluxes from benthic chambers during the productive season (July). Based on the ratio between O2 and DIC, we derived site-specific photosynthetic and respiratory quotients, enabling the conversion of eddy covariance fluxes to DIC. We assessed benthic diversity parameters as potential drivers of metabolic flux variability. We observed high rates of gross primary productivity (GPP) spanning −18 to −82 mmolDICm-2d-1, which increased progressively with meadow age. Community respiration (CR) mirrored the GPP trend, and all meadows were net heterotrophic (GPP < CR), with net community productivity (NCP) ranging from 16 to 28 mmolDICm-2d-1. While autotrophic biomass did not increase with meadow age, macrophyte diversity did, elucidating potential effects of niche complementarity among macrophytes on community metabolism. These findings provide valuable insights into how community composition and meadow development relate to ecosystem functioning, highlighting potential tradeoffs between carbon uptake and biodiversity.
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Mishra, AK, e D. Apte. "Ecological connectivity with mangroves influences tropical seagrass population longevity and meadow traits within an island ecosystem". Marine Ecology Progress Series 644 (25 giugno 2020): 47–63. http://dx.doi.org/10.3354/meps13349.
Testo completoAbstract (sommario):
Seagrass meadows around the Andaman Sea are globally significant, but declining rapidly. Assessment of the existing seagrass population dynamics is essential to facilitate effective conservation measures. We studied population dynamics of the seagrass Thalassia hemprichii at 3 locations in the Andaman and Nicobar Islands in the Andaman Sea. At each location, 2 sites were assessed, one with mangroves (MG) and another without mangroves (WMG). Quadrat and corer sampling techniques were used to collect seagrass and sediment samples. Reconstruction techniques were used to derive population dynamics of T. hemprichii. Sand fractions dominated (>90%) the T. hemprichii meadows, with silt comprising a higher percentage only at the MG sites. The density, biomass, productivity and horizontal meadow migration of T. hemprichii were higher at the MG sites. The number of leaves shoot-1, vertical rhizome (VR), VR internode length, number of VRs shoot-1 and vertical growth were higher at the WMG sites. T. hemprichii required less time to produce a single leaf at the MG sites than at the WMG sites. Plants associated with mangroves had 4 to 5 yr of longevity, with higher numbers of younger plants. Population growth rates were positive at all sites except at the WMG site of Burmanallah. Our results provide evidence that mangrove ecosystems have a positive impact on seagrass meadow traits and population dynamics. Therefore, it is crucial to focus on the ecological connectivity between seagrasses and associated coastal ecosystems, as it is pivotal to increase our understanding of the important link between coastal ecosystems and ecosystem functioning.
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Xu, Shaochun, Shuai Xu, Yi Zhou, Shidong Yue, Xiaomei Zhang, Ruiting Gu, Yu Zhang, Yongliang Qiao e Mingjie Liu. "Long-Term Changes in the Unique and Largest Seagrass Meadows in the Bohai Sea (China) Using Satellite (1974–2019) and Sonar Data: Implication for Conservation and Restoration". Remote Sensing 13, n. 5 (25 febbraio 2021): 856. http://dx.doi.org/10.3390/rs13050856.
Testo completoAbstract (sommario):
Seagrass meadows play critical roles in supporting a high level of biodiversity but are continuously threatened by human activities, such as sea reclamation. In this study, we reported on a large seagrass (Zostera marina L.) meadow in Caofeidian shoal harbor in the Bohai Sea of northern China. We evaluated the environmental impact of sea reclamation activities using Landsat imagery (1974–2019) by mapping seagrass meadow distribution changes. ISODATA was adopted for the unsupervised classification and mapping of seagrass beds. The error matrix developed using the in situ data obtained from acoustic surveys for Landsat 8OLI image classification was 87.20% accurate. The maps showed rapidly increasing changes in seagrass meadows as the amount of reclaimed land increased. Some seagrass meadows experienced large-scale changes, and sea reclamation has been suggested as the main factor responsible for habitat loss, which results from physical damage, excessive sedimentation, and increased turbidity caused by reclamation. In addition, habitat degradation may have resulted from three storm surges induced by typhoons in 1992–1998. Fortunately, land reclamation, forming an artificial “longshore bar”, buffers seagrass meadows from wave actions, providing relatively sheltered conditions, which has allowed a large habitat increase since 2012. These were the largest eelgrass meadows (3,217.32 ha), with a peripheral area of ~100 km2, in the Bohai Sea of northern China in 2019. However, the existing largest eelgrass beds in China are threatened by trawling, clam harvesting (especially clam sucking), channel dredging, and culture pond construction. Our work will help coastal managers monitor the environmental impacts of reclamation activities on seagrass meadows on a large spatio-temporal scale and will also provide information for seagrass restoration using artificial “longshore bars”.
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Gole, Swapnali, Sivakumar Kuppusamy, Himansu Das e Jeyaraj Antony Johnson. "Flowering and fruiting of Tape Seagrass Enhalus acoroides (L.f.) Royle from the Andaman Islands: observations from inflorescence buds to dehiscent fruits". Journal of Threatened Taxa 15, n. 1 (26 gennaio 2023): 22494–500. http://dx.doi.org/10.11609/jott.8163.15.1.22494-22500.
Testo completoAbstract (sommario):
Seagrass phenophases are crucial in understanding their reproductive biology but are seldom documented. We studied flowering and fruiting phenophases of Enhalus acoroides from a mixed-species intertidal seagrass meadow in Ritchie’s archipelago, Andaman Islands, India. The estimated mean densities of pistillate and staminate flowers were 16.0 ± 12.0/ m2 and 12.7 ± 7.3/ m2, respectively. We observed the bloom of free-floating male flowers (961.7 ± 360.4/ m2) during the spring low tides (at mean sea surface temperature ~30°C). Seagrass cover, shoot density, and canopy height of E. acoroides, along with flowering densities, showed a zonal variation within the sampled meadow. We report the first-time observations of several phenophases of E. acoroides, such as female inflorescence buds, male inflorescence, a bloom of released male flowers, pollination, and fertilized flowers from the Indian waters. We also report the prevailing threats to seagrass meadows, such as meadow scarring done by boat anchorage in the Andaman Islands.
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Unsworth, Richard K. F., Alex Higgs, Bettina Walter, Leanne C. Cullen-Unsworth, Isabella Inman e Benjamin L. Jones. "Canopy Accumulation: Are Seagrass Meadows a Sink of Microplastics?" Oceans 2, n. 1 (12 febbraio 2021): 162–78. http://dx.doi.org/10.3390/oceans2010010.
Testo completoAbstract (sommario):
A growing body of research is documenting the accumulation of microplastics within marine sediments around the world. The hydrodynamic influences of seagrasses in coastal environments are shown to increase sedimentation of finer particles and as a result there has been speculation that this attribute will lead to seagrass meadows acting as a site of elevated microplastic contamination. To date a range of localised studies have provided conflicting answers to this hypothesis. Seagrass meadows provide multiple ecosystem services including vital support roles for a range of fisheries; therefore, there are considerable human health implications for understanding their role as sinks of microplastics. This research investigated the abundance and diversity of microplastics present in temperate North Atlantic seagrass meadow sediments relative to unvegetated sediments and examined how they correlate with the meadow structure and the sediment type. We also placed this data in the context of the current knowledge of microplastics in seagrass sediments through a global meta-analysis of published data. Eight seagrass meadows and adjacent unvegetated sites around the UK were sampled to test for the abundance of microplastic particles in the sediment. Microplastics were found in 98% of the samples, with fibres making up 91.8% of all microplastics identified. Abundance was recorded to overall be 215 ± 163 microplastic particles (MP) kg−1 Dry Weight (DW) of sediment in seagrass and 221 ± 236 MP kg−1 DW of sediment in unvegetated habitats. There were no significant differences found between the number of MP with respect to vegetation. We report evidence of the almost ubiquitous contamination of seagrass sediments with microplastics both in the UK and globally but find that the contamination reflects a general build-up of microplastics in the wider environment rather than becoming concentrated within seagrass as an enhanced sink. Microplastic build up in sediments is hypothesised to be the result of local hydrodynamics and plastic sources rather than the result of elevated habitat level concentration. Although not of a higher abundance in seagrass, such contamination in seagrass is of cause for concern given the high dependency of many species of fish on these habitat types and the potential for plastics to move up the food chain.
19
Sierra, Joan Pau, Vicente Gracia, Xavier Castell, Manuel García-León, César Mösso e Jue Lin-Ye. "Potential of Transplanted Seagrass Meadows on Wave Attenuation in a Fetch-Limited Environment". Journal of Marine Science and Engineering 11, n. 6 (7 giugno 2023): 1186. http://dx.doi.org/10.3390/jmse11061186.
Testo completoAbstract (sommario):
In this paper, the effectiveness of transplanted (either created or restored) seagrass meadows as a coastal protection measure is assessed through a five-step methodology. The analysis is focused on a stretch of the Catalan coast (NW Mediterranean) which is a fetch-limited environment. The results show that even considering conservative values for the meadow parameters (plant diameter, meadow density and canopy height), significant reductions of the annual average wave heights reaching the beach may be obtained, reducing flooding and erosion risks. Therefore, the investment in the conservation and restauration of seagrass meadows for protecting coastal areas from erosion and flooding is a measure that must be considered, due to the multiple benefits that they provide including ecosystem services. In addition, the proposed methodology may be a useful tool for coastal managers to help them in the design of seagrass meadows for coastal protection.
20
Ondiviela, Bárbara, Lina Fernández, Araceli Puente, Gerardo García-Castrillo e José A. Juanes. "Characterization of a resilient seagrass meadow during a decline period". Scientia Marina 82, n. 1 (20 marzo 2018): 67. http://dx.doi.org/10.3989/scimar.04616.18a.
Testo completoAbstract (sommario):
Seagrasses are globally threatened ecosystems with essential ecological roles. An important limitation in seagrass conservation efforts is the poor understanding of resilient meadows. The present work studies a meadow, which maintained a large population of Zostera marina and Zostera noltei, during the decline of seagrasses in the Bay of Santander (from 1984 to 2000). The work examines resilience parameters related to the biological traits (biomass, density, length and width of the leaves) and to the associated benthic assemblages. The maturity of the meadow and the changing environmental conditions induced by the torrential regime of the Miera River, have likely improved the resistance to the periods of stress. The adaptation to these fluctuating conditions is reflected in a high seasonal and spatial variability in the biomass, density, morphological traits and benthic assemblages. These variations are related to the summer peaks in the PAR, the sea surface temperature and the freshwater influence along the discharge of the Miera River. This work provides the first seagrass data in Cantabria. The data are dated in the early 2000s and constitute a baseline study for the Bay of Biscay.
21
Barosin, Emily B., e Joseph D. Warren. "Diurnal measurements of sound attenuation (100 Hz—10 kHz) in a shallow (1-2 m), seagrass (Zostera marina) meadow are impacted by photosynthetic activity and water column height". Journal of the Acoustical Society of America 154, n. 4_supplement (1 ottobre 2023): A81. http://dx.doi.org/10.1121/10.0022868.
Testo completoAbstract (sommario):
Seagrass meadows are important habitats that provide a variety of ecosystem services. As the seagrasses photosynthesize, they fill their vascular tissues with oxygen which is also released as bubbles into the water column. Measurements of sound attenuation were made in August 2022 in a shallow (1–2 m water depth) Zostera marina meadow in Shinnecock Bay, New York. Sound sources included tones (100 Hz–2 kHz) transmitted over an 8hour period (0800–1600 local time) and a 10 kHz Fishtek pinger operating over a 3 day period. Hydrophones were placed in the seagrass meadow at ranges of 1, 3, and 7 m from the source to determine attenuation. Vertical profiles of temperature, salinity, and dissolved oxygen were measured at the study site during the 8 hour tonal source experiment, and solar irradiance and tide level for Shinnecock Bay were obtained for the 3 day study period. Peak to peak sound pressure levels varied by more than 31 dB over a diurnal period for the 10 kHz signals. Sound attenuation of lower frequency tones varied from 9 to 30 dB both with dissolved oxygen (a proxy for photosynthetic activity of the seagrass) as well as water column height.
22
Jerome, Thomas S., Megan Ballard, Kevin M. Lee, Colby W. Cushing, Kyle Capistrant-Fossa, Andrew R. McNeese, Preston S. Wilson e Kenneth H. Dunton. "Effective medium modeling of acoustic propagation in a seagrass meadow". Journal of the Acoustical Society of America 153, n. 3_supplement (1 marzo 2023): A62. http://dx.doi.org/10.1121/10.0018168.
Testo completoAbstract (sommario):
Seagrasses are foundation species in many coastal ecosystems, but these environments are declining globally due to climate change and other anthropogenic impacts. Ballard et al. [J. Acoust. Soc. Am. 147, 2020] established the efficacy of acoustic remote sensing techniques for seagrass monitoring by exploiting acoustic sensitivity to gas bubbles produced by photosynthesis and gas channels within the seagrass leaves. However, the effects of seagrass on acoustic propagation are not understood with sufficient quantitative detail, and an improved model describing propagation through a mixture of seagrass leaves, free gas bubbles, and seawater is needed to aid in integrating acoustic methods into conservation efforts. This talk provides an overview of developments in the modeling of acoustic propagation through a Thalassia testudinum meadow using a homogeneous effective medium approach to represent the seagrass leaves and seawater. The model accounts for the complex microstructure of seagrass leaves including the encapsulated gas channels and the elastic properties of the seagrass tissue. The model is intended for use in geoacoustic inference algorithms for the overall goal of providing estimates of seagrass productivity and biomass. Candidate effective medium models include 2D cylindrical seagrass leaves and a micromechanical model of a seagrass leaf cross-section. [Work supported by NSF.]
23
Hayes, Matthew A., Eva C. McClure, Paul H. York, Kristin I. Jinks, Michael A. Rasheed, Marcus Sheaves e Rod M. Connolly. "The Differential Importance of Deep and Shallow Seagrass to Nekton Assemblages of the Great Barrier Reef". Diversity 12, n. 8 (27 luglio 2020): 292. http://dx.doi.org/10.3390/d12080292.
Testo completoAbstract (sommario):
Seagrass meadows are an important habitat for a variety of animals, including ecologically and socioeconomically important species. Seagrass meadows are recognised as providing species with nursery grounds, and as a migratory pathway to adjacent habitats. Despite their recognised importance, little is known about the species assemblages that occupy seagrass meadows of different depths in the coastal zone. Understanding differences in the distribution of species in seagrass at different depths, and differences in species diversity, abundance, biomass, and size spectra, is important to fully appreciate both the ecological significance and economic importance of these seagrass meadows. Here, we assess differences in the assemblage characteristics of fish, crustacea, and cephalopods (collectively, nekton) between deep (>9 m; Halophila spinulosa dominant) and shallow water (<2 m; Halodule uninervis and/or Zostera muelleri dominant) seagrass meadows of the central Great Barrier Reef coast of Queensland, Australia. Nekton assemblage structure differed between deep and shallow seagrass. Deeper meadows were typified by juvenile emperors (e.g., Lethrinus genivittatus), hairfinned leatherjacket (Paramonacanthus japonicus) and rabbitfish (e.g., Siganus fuscescens) in both biomass per unit effort (BPUE) and catch per unit effort (CPUE), whereas shallow meadows were typified by the green tiger prawn (Penaeus semisulcatus) and pugnose ponyfish (Secutor insidiator) in both BPUE and CPUE. Both meadow depths were distinct in their nekton assemblage, particularly for socioeconomically important species, with 11 species unique to both shallow and deep meadows. However, both meadow depths also included juveniles of socioeconomically important species found in adjacent habitats as adults. The total nekton CPUE was not different between deep and shallow seagrass, but the BPUE and body mass of individual animals were greater in deep than shallow seagrass. Size spectra analysis indicated that in both deep and shallow meadows, smaller animals predominated, even more so than theoretically expected for size spectra. Our findings highlight the unique attributes of both shallow and deeper water seagrass meadows, and identify the distinct and critically important role of deep seagrass meadows within the Great Barrier Reef World Heritage Area (GBRWHA) as a habitat for small and juvenile species, including those of local fisheries value.
24
Gallagher, John B., Chee Hoe Chuan, Tzuen-Kiat Yap e Wydia Farhain Fredelina Dona. "Carbon stocks of coastal seagrass in Southeast Asia may be far lower than anticipated when accounting for black carbon". Biology Letters 15, n. 5 (8 maggio 2019): 20180745. http://dx.doi.org/10.1098/rsbl.2018.0745.
Testo completoAbstract (sommario):
Valuing sedimentary ‘blue carbon’ stocks of seagrass meadows requires exclusion of allochthonous recalcitrant forms of carbon, such as black carbon (BC). Regression models constructed across a Southeast Asian tropical estuary predicted that carbon stocks within the sandy meadows of coastal embayments would support a modest but not insignificant amount of BC. We tested the prediction across three coastal meadows of the same region: one patchy meadow located close to a major urban centre and two continuous meadows contained in separate open embayments of a rural marine park; all differed in fetch and species. The BC/total organic carbon (TOC) fractions in the urban and rural meadows with small canopies were more than double the predicted amounts, 28 ± 1.6% and 36 ± 1.5% (±95% confidence intervals), respectively. The fraction in the rural large-canopy meadow remained comparable to the other two meadows, 26 ± 4.9% (±95% confidence intervals) but was half the amount predicted, likely owing to confounding of the model. The relatively high BC/TOC fractions were explained by variability across sites of BC atmospheric supply, an increase in loss of seagrass litter close to the exposed edges of meadows and sediment resuspension across the dispersed patchy meadow.
25
Langdon, Mark W., Eric I. Paling e Mike Van Keulen. "The development of urchin barrens in seagrass meadows at Luscombe Bay, Western Australia from 1985 to 2004." Pacific Conservation Biology 17, n. 1 (2011): 48. http://dx.doi.org/10.1071/pc110048.
Testo completoAbstract (sommario):
Herbivore grazing is a well-documented cause of habitat decline in terrestrial systems, but marine examples from seagrass meadows are rare. Here we present evidence that isolated urchin grazing events have caused further localized losses to seagrass meadows already degraded by eutrophication or other anthropogenic disturbances. By 1992 a substantial scar in Posidonia meadows at Luscombe Bay in Cockburn Sound, Western Australia, had been caused by grazing urchins. When seagrass transplants were placed at the site more than a decade later most were grazed and did not survive. GIS analyses on imagery from 1985 to 2004 indicated that rapid seagrass meadow decline coincided with the presence of an unusually large aggregation of the grazing urchin Heliocidaris erythrogramma. Evidence of some seagrass recovery after 1993 was also apparent after the manual removal of the urchins in late 1992. Restoration efforts in seagrass meadows should consider the potential for grazing damage, as is commonplace in terrestrial systems.
26
Laia, Dominikus Yoeli Wilson, Ganang Wibisono, Eddy Handoko, Gita Endang Palufi, Fajar Kurniawan, Syofyan Roni e Muhammad Alrizky Ratno Budiarto. "Seagrass Meadow Distribution Mapping in the Coastal Lagoon of Buan Island, Anambas". Jurnal Kelautan Tropis 26, n. 3 (27 ottobre 2023): 554–64. http://dx.doi.org/10.14710/jkt.v26i3.20450.
Testo completoAbstract (sommario):
Seagrasses are vital monocotyledonous marine flowering plants that serve as essential food sources for megaherbivores, contribute significantly to organic carbon production, and offer a multitude of crucial ecosystem services. Preserving seagrass habitats is of utmost importance, but the lack of comprehensive spatial data poses challenges to conservation efforts. The Anambas Islands, consisting of 255 small islands in the Natuna Sea, the southern part of the South China Sea, exemplify the scarcity of seagrass data, with the current distribution map only covering the Central and East Siantan region. In this study, our aim was to map the Buan coastal lagoon, where previous visual interpretation of Google Earth imagery suggested the presence of seagrasses. To achieve this, we carried out a drone survey and collected field data to classify and map the substrate types in the study area. The field survey documented four species in the location: T. hemprichii, E. acoroides, H. ovalis and S. isoetifolium, thereby expanding the known seagrass species in Anambas to nine. By employing a pixel-based classification of orthophotos, we achieved a promising overall accuracy of 69.5%. Our findings demonstrated that imageries from the Google Earth platform are viable alternatives for identifying seagrass meadows and can be utilized to support seagrass mapping efforts. This discovery offers valuable support for future seagrass mapping initiatives, especially at a local scale. Ultimately, our study contributes to the broader understanding of seagrass distribution in the Anambas Islands, and emphasizes the importance of further exploration to support conservation efforts in the seagrass ecosystem.
27
Maabuat, Pience Veralyn, Agustina Monalisa Tangapo e Beivy Jonathan Kolondam. "Distribution of Seagrass in North Sulawesi: A Review". International Journal of Research and Review 10, n. 9 (15 settembre 2023): 157–61. http://dx.doi.org/10.52403/ijrr.20230917.
Testo completoAbstract (sommario):
Seagrasses are crucial coastal ecosystems that provide a multitude of ecological and economic benefits. The distribution of seagrass meadows plays a pivotal role in maintaining marine biodiversity, supporting fisheries, and contributing to carbon sequestration. Seagrass meadow ecosystems are important in the coastal environment. This ecosystem functions ecologically in the water as a habitat for various species of marine life, and has the ability to bind soil and sediment and dampen waves so that it helps protect the coast from erosion and storms. Seagrass ecosystems play a role in nutrient circulation, carbon storage, and play an important role in climate change mitigation. In addition, these ecosystems can potentially serve as a source of antioxidant compounds and bioindicators of aquatic environmental health. The coast of North Sulawesi has the potential for the existence of this ecosystem so it is necessary to assess the potential of seagrasses that are important in the coast of North Sulawesi Province. There are reportedly 10 seagrass species that have been identified in coastal North Sulawesi, consisting of Hydrocharitaceae and Cymodoceaceae families, namely Enhalus acoroides, Thalassia hemprichii, Halophila ovalis, Syringodium isoetifolium, Halodule uninervis, Cymodocea serrulata, Cymodocea rotundata, Thalassodendron ciliatum, Halophila spinulosa, and Halodule Pinifolia. Keywords: Seagrass, North Sulawesi, Bioindicator, ecosystem
28
Astudillo-Gutierrez, Carlos, Iván Cáceres Rabionet, Vicente Gracia Garcia, Joan Pau Sierra Pedrico e Agustín Sánchez-Arcilla Conejo. "Study of Velocity Changes Induced by Posidonia oceanica Surrogate and Sediment Transport Implications". Journal of Marine Science and Engineering 12, n. 4 (27 marzo 2024): 569. http://dx.doi.org/10.3390/jmse12040569.
Testo completoAbstract (sommario):
An analysis of the interactions between wave-induced velocities and seagrass meadows has been conducted based on the large-scale CIEM wave flume data. Incident irregular wave trains act on an initial 1:15 sand beach profile with measurement stations from the offshore of a surrogate meadow until the outer breaking zone, after crossing the seagrass meadow. The analysis considers variability and peaks of velocities, together with their skewness and asymmetry, to determine the effects of the seagrass meadow on the near bed sediment transport. Velocity variability was characterized by the standard deviation, and the greatest changes were found in the area right behind the meadow. In this zone, the negative peak velocities decreased by up to 20.3%, and the positive peak velocities increased by up to 11.7%. For more onshore positions, the negative and positive peak velocities similarly decreased and increased in most of the studied stations. A progressive increase in skewness as the waves passed through the meadow, together with a slight decrease in asymmetry, was observed and associated with the meadow effect. Moving shoreward along the profile, the values of skewness and asymmetry increased progressively relative to the position of the main sandbar. The megaripple-like bedforms appeared earlier when the meadow was present due to the higher skewness, showing a belated development in the layout without the meadow, when skewness increased further offshore due to the proximity of the breaker sandbar. To assess the sediment transport capacity of a submerged meadow, the SANTOSS formula was applied, showing that in front of the meadow, there was a higher sediment transport capacity, whereas behind the meadow, that capacity could be reduced by up to 41.3%. In addition, this formula was able to produce a suitable estimate of sediment transport across the profile, although it could not properly estimate the sediment volumes associated with the bedforms generated in the profile.
29
Jarvis, JC, SA McKenna e MA Rahseed. "Seagrass seed bank spatial structure and function following a large-scale decline". Marine Ecology Progress Series 665 (29 aprile 2021): 75–87. http://dx.doi.org/10.3354/meps13668.
Testo completoAbstract (sommario):
We examined the spatial structure (distribution, density) and function (viability) of the seagrass sediment seed bank, the storage of viable propagules (e.g. seeds, tubers, diaspores) in the sediment over time,in the northern Great Barrier Reef World Heritage Area in Cairns, Queensland, following a large-scale decline in seagrass area. A spatially explicit seagrass seed bank analysis was paired with a long-term annual assessment of seagrass distribution to assess seed bank spatial patterns and their relationship with the recovery and presence of seagrass, and water depth. Four years post-decline, the seed bank contained Zostera muelleri, Halodule uninervis, Halophila ovalis and Cymodocea serrulata seeds. Seed banks reflected adjacent meadow community composition; however, the density of seeds for all recorded species was significantly lower than analogous seagrass populations, indicating a reduction in the capacity for recovery from the seed bank. A spatial structure existed in both the total (viable + non-viable) and viable seed bank, and distance between seed clusters ranged from 50-550 m depending on species and seed type. Observed patterns in clustering may be explained by variation in water depth and the past distribution of seagrass in these meadows. These results demonstrate that the distribution of seagrass seeds within the seed bank, which directly influences the natural recovery of seagrass communities, is not uniform across species and may result in patchy recovery of the meadows. Therefore, the resilience provided by the seed bank in seagrass communities should not be viewed as a static level of insurance for the entire meadow, but rather as dynamic and species-specific, with variability over both space and time.
30
Verduin, Jennifer J., E. I. Paling, M. van Keulen e Lotte E. Rivers. "Recovery of Donor Meadows ofPosidonia sinuosaandPosidonia australisContributes to Sustainable Seagrass Transplantation". International Journal of Ecology 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/837317.
Testo completoAbstract (sommario):
Donor meadow recovery is important in deciding whether removal of material from natural seagrass meadows is a sustainable activity. Thus an investigation into meadow regrowth was undertaken as part of a large-scale seagrass rehabilitation effort in Cockburn Sound, Western Australia. Several plug extraction configurations were examined inPosidonia sinuosaandPosidonia australismeadows to monitor shoot growth into plug scars. No significant differences in shoot growth between extraction configurations were observed, and both species increased their shoot numbers over two years, withP. sinuosashowing a significantly better recovery rate thanP. australis.P. sinuosashoot recovery into extracted areas was2.2±0.1shoots over 24 months, similar to shoot changes in controls (2.3 shoots over the same period).P. australisshoot recovery for each configuration was 0.8 ± 0.3 shoots in 24 months compared with 1.5 shoots in the controls. Based on the number of regrowing shoots, the predicted recovery time of a meadow is estimated at 4 years forP. sinuosaand three years forP. australis. Different plug extraction configurations do not appear to affect meadow recovery, and it can be concluded that established meadows of both species are sustainable providers of planting units for rehabilitation measures.
31
York, Paul H., Peter I. Macreadie e Michael A. Rasheed. "Blue Carbon stocks of Great Barrier Reef deep-water seagrasses". Biology Letters 14, n. 12 (dicembre 2018): 20180529. http://dx.doi.org/10.1098/rsbl.2018.0529.
Testo completoAbstract (sommario):
Shallow-water seagrasses capture and store globally significant quantities of organic carbon (OC), often referred to as ‘Blue Carbon’; however, data are lacking on the importance of deep-water (greater than 15 m) seagrasses as Blue Carbon sinks. We compared OC stocks from deep-, mid- and shallow-water seagrasses at Lizard Island within the Great Barrier Reef (GBR) lagoon. We found deep-water seagrass ( Halophila species) contained similar levels of OC to shallow-water species (e.g. Halodule uninervis ) (0.64 ± 0.08% and 0.9 ± 0.1 mg C cm −3 , 0.87 ± 0.19% and 1.3 ± 0.3 mg C cm −3 , respectively), despite being much sparser and smaller in stature. Deep-water seagrass sediments contained significantly higher levels (approx. ninefold) of OC than surrounding bare areas. Inorganic carbon (CaCO 3 ) levels were relatively high in deep-water seagrass sediments (8.2 ± 0.4%) and, if precipitated from epiphytes within the meadow, could offset the potential CO 2 -sink capacity of these meadows. The δ 13 C signatures of sediment samples varied among depths and habitats (−10.9 and −17.0), reflecting contributions from autochthonous and allochthonous sources. If the OC stocks reported in this study are similar to deep-water Halophila meadows elsewhere within the GBR lagoon (total area 31 000 km 2 ), then OC bound within this system is roughly estimated at 27.4 million tonnes.
32
Sordo, Laura, e Paulo Lana. "Temporal variations of Halodule wrightii meadows and associated fauna near their southern distribution limit in the southwestern Atlantic". Botanica Marina 63, n. 3 (25 giugno 2020): 215–28. http://dx.doi.org/10.1515/bot-2018-0106.
Testo completoAbstract (sommario):
AbstractHalodule wrightii meadows in Southern Brazil have been regressing in an unsheltered area of the subtropical Paranaguá Bay, near their southern limit in the SW Atlantic, since 2006. To identify early indicators of regression events, we assessed variations in plant and macrobenthic structure in two local meadows under unsheltered and protected conditions. Differences between sites increased after an epiphytic overgrowth of the alga Hincksia mitchelliae at the unsheltered site. Seagrass growth was suppressed and the numbers of burrowing and opportunistic benthic species increased with the increase of algal biomass. In the protected meadow, seagrass biomass and number of leaves changed seasonally, but macrobenthic abundance and species richness remained stable. Ecosystem changes were evident when the unsheltered meadow was already collapsing. The number of leaves per shoot, the horizontal internode length, the abundance and structure of the macrofaunal associations, and the host-epiphyte surface interactions, were the first variables to reflect the early stages of seagrass regression. Our results suggest that the persistence of H. wrightii meadows at their southern distribution limit in the SW Atlantic will be affected by local hydrodynamics and their ability to compete with ephemeral macroalgal species under stress conditions.
33
Garcias-Bonet, Neus, Marco Fusi, Muhammad Ali, Dario R. Shaw, Pascal E. Saikaly, Daniele Daffonchio e Carlos M. Duarte. "High denitrification and anaerobic ammonium oxidation contributes to net nitrogen loss in a seagrass ecosystem in the central Red Sea". Biogeosciences 15, n. 23 (11 dicembre 2018): 7333–46. http://dx.doi.org/10.5194/bg-15-7333-2018.
Testo completoAbstract (sommario):
Abstract. Nitrogen loads in coastal areas have increased dramatically, with detrimental consequences for coastal ecosystems. Shallow sediments and seagrass meadows are hotspots for denitrification, favoring N loss. However, atmospheric dinitrogen (N2) fixation has been reported to support seagrass growth. Therefore, the role of coastal marine systems dominated by seagrasses in the net N2 flux remains unclear. Here, we measured denitrification, anaerobic ammonium oxidation (anammox), and N2 fixation in a tropical seagrass (Enhalus acoroides) meadow and the adjacent bare sediment in a coastal lagoon in the central Red Sea. We detected high annual mean rates of denitrification (34.9±10.3 and 31.6±8.9 mg N m−2 d−1) and anammox (12.4±3.4 and 19.8±4.4 mg N m−2 d−1) in vegetated and bare sediments. The annual mean N loss was higher (between 8 and 63-fold) than the N2 fixed (annual mean = 5.9±0.2 and 0.8±0.3 mg N m−2 d−1) in the meadow and bare sediment, leading to a net flux of N2 from sediments to the atmosphere. Despite the importance of this coastal lagoon in removing N from the system, N2 fixation can contribute substantially to seagrass growth since N2 fixation rates found here could contribute up to 36 % of plant N requirements. In vegetated sediments, anammox rates decreased with increasing organic matter (OM) content, while N2 fixation increased with OM content. Denitrification and anammox increased linearly with temperature, while N2 fixation showed a maximum at intermediate temperatures. Therefore, the forecasted warming could further increase the N2 flux from sediments to the atmosphere, potentially impacting seagrass productivity and their capacity to mitigate climate change but also enhancing their potential N removal.
34
BARROS, KCRISHNA V. S., e CRISTINA A. ROCHA-BARREIRA. "Responses of the molluscan fauna to environmental variations in a Halodule wrightii Ascherson ecosystem from Northeastern Brazil". Anais da Academia Brasileira de Ciências 85, n. 4 (10 ottobre 2013): 1397–410. http://dx.doi.org/10.1590/0001-37652013101212.
Testo completoAbstract (sommario):
ABSTRACT This study observed the spatial and temporal distributions of molluscs in a Halodule wrightii meadow, verifying if they respond satisfactorily to seasonal changes in this seagrass ecosystem. Twenty-four species were identified. Chitons were rare, bivalves had greater number of species (11), followed by gastropods (9) which were also the most abundant class (73%). All classes were more abundant in the belowground. The most common species was Tricolia affinis, especially in aboveground. The occurrence of some species in both strata or out of the expected stratum may have been influenced by shallow layer of the sediment considered in this study, hydrodynamic, and low biomass of the studied meadow. According to univariate and multivariate analyses, despite of molluscan descriptors had been related to variables associated with rainfall, the seagrasses had an important role on the seasonal and vertical variations of the molluscan fauna. The biomass of the epiphyte Hypnea musciformis was correlated to temporal variations of the species from aboveground, indicating its secondary role for this community. The molluscs were sensible to environmental variations, and also reflected seasonal changes of the seagrass, showing that damages on these meadows reflect even at lower levels of the marine food web.
35
Kusnadi, Agus, La Ode Alifatri, Ardian Nurrasyid Chamidy, Asep Rasyidin e Sobirin Sobirin. "Evaluating the seagrass ecological condition and habitat extent in Karimunjawa National Park, Jepara Indonesia". Jurnal Kelautan Tropis 27, n. 1 (3 gennaio 2024): 161–69. http://dx.doi.org/10.14710/jkt.v27i1.20637.
Testo completoAbstract (sommario):
In the coastal ecosystem, seagrass meadows play a vital role in delivering ecosystem services such as provision, control, and support. However, this ecosystem is one of the most threatened in the coastal environment, and it has been degraded as a result of anthropogenic disturbance and rapid environmental changes. Furthermore, the extent of the seagrass meadows is unknown, and the health of the meadows is unmonitored and unrecorded. There is little information on the current state of the seagrass extent and health conditions in Karimunjawa National Park. We evaluate the abundance, states, and health conditions of the seagrass meadows based on the ecological quality index in Karimunjawa National Park, Jepara, Indonesia. This district has a vast extent of seagrass meadows but has been affected by the expansion of the industrial/tourism area within the region. This study aimed to assess the seagrass current condition based on the ecological quality index. The result showed that the total seagrass extent area in Karimunjawa National Park was 969,15 ha where seven species were found in this area, including Enhalus acoroides, Thalassia hemprichii, Cymodocea rotundata, Cymodocea serrulate, Halodule pinifolia, Halophila ovalis and Halodule uninervis. Seagrass meadow coverages were moderate and categorized as less healthy. The seagrass ecological quality index value was 0.66 which indicated that the seagrass condition in Karimunjawa National Park was moderate. Ecological factors that affect the seagrass state are epiphyte cover and macroalgal cover.
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Ballard, Megan S., Kevin M. Lee, Andrew R. McNeese, Gabriel R. Venegas, Abdullah F. Rahman, Matthew C. Zeh e Preston S. Wilson. "Ecosystem monitoring of a seagrass meadow using wideband acoustic measurements". Journal of the Acoustical Society of America 150, n. 4 (ottobre 2021): A351. http://dx.doi.org/10.1121/10.0008557.
Testo completoAbstract (sommario):
Seagrasses are sentinel species whose sensitivity to changing water conditions makes it an indicator for sea level rise and climate change. The biological processes and physical characteristics associated with seagrass are known to affect acoustic propagation due to gas bodies contained within the seagrass tissue as well as photosynthesis-driven bubble production that results in free gas in the water. In this work, acoustical methods are applied to assess the health of seagrass meadows using a ray-based model that includes losses due to the dispersion, absorption and scattering of sound related to the gas bodies in the seagrass tissue and free bubbles in the water. The approach is applied to data collected in the Lower Laguna Madre where the seabed was covered by a dense growth of Thalassia testudinum. During the experiment, a piezoelectric source transmitted frequency-modulated chirps (0.1 to 100 kHz) over a four-day period. At the peak of photosynthesis-driven bubble production in the late afternoon, an additional decrease in the received level of more than 10 dB was observed. The volume fraction of gas present in the environment is estimated through acoustic modeling and related to seagrass biomass and photosynthesis. [Work supported by ARL IR&D and ONR.]
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Krause, Johannes R., Alejandro Hinojosa-Corona, Andrew B. Gray e Elizabeth Burke Watson. "Emerging Sensor Platforms Allow for Seagrass Extent Mapping in a Turbid Estuary and from the Meadow to Ecosystem Scale". Remote Sensing 13, n. 18 (15 settembre 2021): 3681. http://dx.doi.org/10.3390/rs13183681.
Testo completoAbstract (sommario):
Seagrass meadows are globally important habitats, protecting shorelines, providing nursery areas for fish, and sequestering carbon. However, both anthropogenic and natural environmental stressors have led to a worldwide reduction seagrass habitats. For purposes of management and restoration, it is essential to produce accurate maps of seagrass meadows over a variety of spatial scales, resolutions, and at temporal frequencies ranging from months to years. Satellite remote sensing has been successfully employed to produce maps of seagrass in the past, but turbid waters and difficulty in obtaining low-tide scenes pose persistent challenges. This study builds on an increased availability of affordable high temporal frequency imaging platforms, using seasonal unmanned aerial vehicle (UAV) surveys of seagrass extent at the meadow scale, to inform machine learning classifications of satellite imagery of a 40 km2 bay. We find that object-based image analysis is suitable to detect seasonal trends in seagrass extent from UAV imagery and find that trends vary between individual meadows at our study site Bahía de San Quintín, Baja California, México, during our study period in 2019. We further suggest that compositing multiple satellite imagery classifications into a seagrass probability map allows for an estimation of seagrass extent in turbid waters and report that in 2019, seagrass covered 2324 ha of Bahía de San Quintín, indicating a recovery from losses reported for previous decades.
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Ballard, Megan, Kevin M. Lee, Kyle Capistrant-Fossa, Preston S. Wilson, Andrew R. McNeese e Kenneth H. Dunton. "Long-term monitoring of a seagrass meadow using wideband acoustic measurements". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A149. http://dx.doi.org/10.1121/10.0010932.
Testo completoAbstract (sommario):
Seagrasses are sentinel species whose sensitivity to changing water conditions makes them an indicator for sea level rise and climate change. The biological processes and physical characteristics associated with seagrass are known to affect acoustic propagation due to gas bodies contained within the seagrass tissue as well as photosynthesis-driven bubble production that results in free gas bubbles in the water. In this work, acoustical methods are applied to monitor seagrass biomass and gas ebullition with an autonomous field-deployed system using broadband acoustic measurements. Supporting environmental measurements including water temperature and salinity, dissolved oxygen, and photosynthetically active radiation (PAR) were also collected and used to interpret the acoustic data. A ray-based propagation model that includes losses due to the dispersion, absorption, and scattering of sound is applied to relate the measured acoustic signals to the gas bodies in the seagrass tissue and free bubbles in the water. This talk will present preliminary results from the first six months of a year-long deployment of the acoustic system in a dense seagrass meadow dominated by Thalassia testudinum (turtle grass) in Corpus Christi Bay, Texas (Gulf of Mexico). [Work supported by NSF.]
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Tis'in, Musayyadah, Rohani Ambo-Rappe, Supriadi Supriadi e Ahmad Faizal. "Decadal Remote Sensing Analysis of Seagrass Changes in Palu Bay, Central Sulawesi". Indonesian Journal of Geography 55, n. 2 (18 agosto 2023): 291. http://dx.doi.org/10.22146/ijg.78701.
Testo completoAbstract (sommario):
Seagrass meadows provide a variety of material, non-material and regulatory coastal ecosystem service; however, as the distribution of seagrass beds changes over time due to both anthropogenic activities and natural factors, it is important to monitor changes in seagrass condition. Seagrass meadows in Palu Bay are threatened by activities such as coastal development and land reclamation. Additionally, the bay was hit by a significant tsunami in 2018, which could have impacted ecosystems in the bay, including seagrass meadows. The aim of this study was to detect changes in seagrass extent and distribution over a 10-year period from 2012 to 2022 and changes in land use over approximately a decade (2010 and 2021) through the use of remote sensing technology. Changes in eagrass meadow areal extent were analyzed using data from a 2012 Landsat 7 Satellite Data Acquisition and a 2022 Landsat 8 Satellite Data Acquisition. Water column correction was implemented using the Lyzenga Algorithm. The results showed a significant decrease in the area of seagrass meadows around the coastal area of Palu Bay. Seagrass meadows in 2012 and 2022 covered 127.08 Ha and 87.79 Ha, respectively, indicating a decrease in extent of 43.29 Ha. As the accuracy of the satellite data classification results was 80%, the results are considered acceptable. Anthropogenic activities (mainly mining and construction related) are strongly suspected as the main drivers of this decline, while earthquake and tsunami events likely aggravated the degradation of coastal ecosystems in Palu Bay, including seagrass meadows.
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Barrón, C., E. T. Apostolaki e C. M. Duarte. "Dissolved organic carbon release by marine macrophytes". Biogeosciences Discussions 9, n. 2 (3 febbraio 2012): 1529–55. http://dx.doi.org/10.5194/bgd-9-1529-2012.
Testo completoAbstract (sommario):
Abstract. Estimates of dissolved organic carbon (DOC) release by marine macrophyte communities (seagrass meadows and macroalgal beds) were obtained experimentally using in situ benthic chambers. The effect of light availability on DOC release by macrophyte communities was examined in two communities both by comparing net DOC release under light and dark, and by examining the response of net DOC release to longer-term (days) experimental shading of the communities. All most 85% of the seagrass communities and almost all of macroalgal communities examined acted as net sources of DOC. There was a weak tendency for higher DOC fluxes under light than under dark conditions in seagrass meadow. There is no relationship between net DOC fluxes and gross primary production (GPP) and net community production (NCP), however, this relationship is positive between net DOC fluxes and community respiration. Net DOC fluxes were not affected by shading of a T. testudinum community in Florida for 5 days, however, shading of a mixed seagrass meadow in the Philippines led to a significant reduction on the net DOC release when shading was maintained for 6 days compared to only 2 days of shading. Based on published and unpublished results we also estimate the global net DOC production by marine macrophytes. The estimated global net DOC flux, and hence export, from marine macrophyte is about 0.197 ± 0.015 Pg C yr−1 or 0.212 ± 0.016 Pg C yr−1 depending if net DOC flux by seagrass meadows was estimated by taking into account the low or high global seagrass area, respectively.
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Hidayah, Nur, Siti Aishah Tahirin, Mohammad Fairoz e Mohammad Rozaimi. "Carbon stock and ?13C data of sediment samples collected from a tropical seagrass meadow in Malaysia". Plant Science Today 6, n. 2 (10 aprile 2019): 132–36. http://dx.doi.org/10.14719/pst.2019.6.2.489.
Testo completoAbstract (sommario):
Seagrass ecosystems are considered as major blue carbon sinks, thus contributing directly to the mitigation of climate change by storing carbon in their habitats. However, empirical data for carbon stocks in Malaysia seagrass meadow sediment remain unreported in a standardised format. This paper presents data on organic (OC) and inorganic carbon (IC) stocks, and stable isotope signatures of carbon (?13C) in bulk seagrass sediments collected from Sungai Pulai estuary (Johor, Malaysia). Within this estuary, seagrasses form shoals at Tanjung Adang and Merambong. Organic carbon and ?13C values in bulk sediment were analysed by an elemental analyser and a continuous flow isotope-ratio mass spectrometer, respectively, while sediment IC data was derived from loss-on-ignition calculations of sample mass differences. The data from these samples are presented as downcore profile of OC (values range at 0.14% to 2.49%), IC (0.16% to 5.29%), ?13C values of organic matter (-27.9‰ to -20.4‰), and cumulative carbon stocks (1.03-3.39 kg OC m-2 and 0.76-2.84 kg IC m-2) in the top 30 cm of sediments. This dataset is applicable for regional and local blue carbon studies, which would allow insights into carbon sink and carbon cycling capacity, in addition to gaining insights into the provenances of carbon stored in seagrass meadows.
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Tualangi, Jehezkiel Timotius, Jety K. Rangan, Joudy R. R. Sangari, Ari B. Rondonuwu, Gaspar D. Manu e Khristin I. F. Kondoy. "Gastropod community structure on seagrass beds in Bahoi Village, North Minahasa". Jurnal Ilmiah PLATAX 11, n. 2 (24 giugno 2023): 369–76. http://dx.doi.org/10.35800/jip.v11i2.48307.
Testo completoAbstract (sommario):
The village of Bahoi has a vast expanse of seagrass meadows of approximately 16.50 Ha, located between mangrove and coral reef ecosystems. This study aims to inventory the gastropod species in the seagrass meadow of Bahoi village waters and to determine the gastropod community structure through analysis of species density, relative density, species diversity index, and dominance index. The method used was a transect line method along 50 meters and a 1x1m quadrat pulled towards the sea, repeated three times during low tide. A total of 117 individuals were found, belonging to 26 species (11 families and 17 genera) of gastropods in the seagrass meadow of Bahoi village coastal waters. Based on the results, the highest density value was 1.10 ind/m2 with a relative density of 28.20%. Based on the analysis, the dominance index (D) of gastropods in the seagrass meadow of Bahoi village coastal waters was low, with values of D = 0.019 to 0.041, indicating that there was no specific species dominance in the seagrass meadow of Bahoi village coastal waters. This has an effect on the diversity index with a value of H' = 2.51, which is categorized as moderate. These results show that the diversity of gastropod species in the seagrass meadow of Bahoi village waters is quite diverse due to the absence of specific gastropod species dominance.
Keywords: Bahoi, Seagrass Meadow, Gastropods, Community Structure.
Abstrak
Desa Bahoi memiliki luas hamparan padang lamun ± 16.50 Ha yang berada di antara ekosistem mangrove dan ekosistem terumbu karang. Penelitian ini bertujuan untuk melakukan inventarisasi jenis-jenis gastropoda di hamparan lamun perairan Desa Bahoi, dan mengetahui struktur komunitas gastropoda melalui analisis kepadatan spesies, kepadatan relatif, indeks keanekaragaman spesies, dan indeks dominasi. Metode yang digunakan adalah metode transek garis sepanjang 50 meter dan kuadrat berukuran 1×1m yang ditarik ke arah laut, dan dilakukan ulangan sebanyak 3 kali pada saat air surut.Ditemukan 117 individu yang termasuk ke dalam 26 spesies (11 famili dan 17 genera) gastropoda di hamparan padang lamun perairan pantai desa Bahoi. Berdasarkan hasil penelitian, nilai kepadatan tertinggi sebesar 1,10 ind/m2 dengan kepadatan relatif 28,20%. Berdasarkan hasil analisis, Indeks Dominansi (D) gastropoda di hamparan lamun perairan pantai desa Bahoi tergolong rendah, dengan nilai D=0,019 sampai dengan 0,041 menunjukkan bahwa tidak terdapat dominasi spesies tertentu di hamparan padang lamun perairan pantai desa Bahoi. Hal ini berpengaruh terhadap Indeks Keanekaragaman dengan nilai H’=2,51 sehingga berada pada kategori sedang. Hasil tersebut menunjukkan bahwa keanekaragaman jenis gastropoda di hamparan lamun perairan pantai desa Bahoi cukup beragam dikarenakan tidak adanya dominasi spesies gastropoda tertentu.
Kata kunci: Bahoi, Padang Lamun, Gastropoda, Struktur Komunitas
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Serrano, Oscar, Aurora M. Ricart, Paul S. Lavery, Miguel Angel Mateo, Ariane Arias-Ortiz, Pere Masque, Mohammad Rozaimi, Andy Steven e Carlos M. Duarte. "Key biogeochemical factors affecting soil carbon storage in <i>Posidonia</i> meadows". Biogeosciences 13, n. 15 (15 agosto 2016): 4581–94. http://dx.doi.org/10.5194/bg-13-4581-2016.
Testo completoAbstract (sommario):
Abstract. Biotic and abiotic factors influence the accumulation of organic carbon (Corg) in seagrass ecosystems. We surveyed Posidonia sinuosa meadows growing in different water depths to assess the variability in the sources, stocks and accumulation rates of Corg. We show that over the last 500 years, P. sinuosa meadows closer to the upper limit of distribution (at 2–4 m depth) accumulated 3- to 4-fold higher Corg stocks (averaging 6.3 kg Corg m−2) at 3- to 4-fold higher rates (12.8 g Corg m−2 yr−1) compared to meadows closer to the deep limits of distribution (at 6–8 m depth; 1.8 kg Corg m−2 and 3.6 g Corg m−2 yr−1). In shallower meadows, Corg stocks were mostly derived from seagrass detritus (88 % in average) compared to meadows closer to the deep limit of distribution (45 % on average). In addition, soil accumulation rates and fine-grained sediment content (< 0.125 mm) in shallower meadows (2.0 mm yr−1 and 9 %, respectively) were approximately 2-fold higher than in deeper meadows (1.2 mm yr−1 and 5 %, respectively). The Corg stocks and accumulation rates accumulated over the last 500 years in bare sediments (0.6 kg Corg m−2 and 1.2 g Corg m−2 yr−1) were 3- to 11-fold lower than in P. sinuosa meadows, while fine-grained sediment content (1 %) and seagrass detritus contribution to the Corg pool (20 %) were 8- and 3-fold lower than in Posidonia meadows, respectively. The patterns found support the hypothesis that Corg storage in seagrass soils is influenced by interactions of biological (e.g., meadow productivity, cover and density), chemical (e.g., recalcitrance of Corg stocks) and physical (e.g., hydrodynamic energy and soil accumulation rates) factors within the meadow. We conclude that there is a need to improve global estimates of seagrass carbon storage accounting for biogeochemical factors driving variability within habitats.
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Serrano, O., A. M. Ricart, P. S. Lavery, M. A. Mateo, A. Arias-Ortiz, P. Masque, A. Steven e C. M. Duarte. "Key biogeochemical factors affecting soil carbon storage in <i>Posidonia</i> meadows". Biogeosciences Discussions 12, n. 22 (27 novembre 2015): 18913–44. http://dx.doi.org/10.5194/bgd-12-18913-2015.
Testo completoAbstract (sommario):
Abstract. Biotic and abiotic factors influence the accumulation of organic carbon (Corg) in seagrass ecosystems. We surveyed Posidonia sinuosa meadows growing in different water depths to assess the variability in the sources, stocks and accumulation rates of Corg. We show that over the last 500 years, P. sinuosa meadows closer to the upper limit of distribution (at 2–4 m depth) accumulated 3 to 4-fold higher Corg stocks (averaging 6.3 kg Corg m−2) at 3 to 4-fold higher rates (12.8 g Corg m−2 yr−1) compared to meadows closer to the deep limits of distribution (at 6–8 m depth; 1.8 kg Corg m−2 and 3.6 g Corg m−2 yr−1). In shallower meadows, Corg stores were mostly derived from seagrass detritus (88 % in average) compared to meadows closer to the deep limit of distribution (45 % on average). Also, sediment accumulation rates and fine-grained sediment content (< 0.125 mm) in shallower meadows (2.0 mm yr−1 and 9 %, respectively) were approximately 2-fold higher than in deeper meadows (1.2 mm yr−1 and 5 %, respectively). The Corg stocks and accumulation rates accumulated over the last 500 years in bare sediments (0.6 kg Corg m−2 and 1.2 g Corg m−2 yr−1) were 3 to 11-fold lower than in P. sinuosa meadows, while fine-grained sediment content (1 %) and seagrass detritus contribution to the Corg pool (20 %) were 8 and 3-fold lower than in Posidonia meadows, respectively. The patterns found support the hypotheses that Corg storage in seagrass soils is influenced by interactions of biological (e.g. meadow productivity, cover and density), chemical (e.g. recalcitrance of Corg stocks) and physical (e.g. hydrodynamic energy and sediment accumulation rates) factors within the meadow. We conclude that there is a need to improve global estimates of seagrass carbon storage accounting for biogeochemical factors driving variability within habitats.
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Dolbeth, Marina, Dimítri de Araújo Costa, Manuel Meyer, José Alberto Gonçalves e Ana Bio. "Characterisation and Dynamics of an Emerging Seagrass Meadow". Remote Sensing 15, n. 16 (19 agosto 2023): 4086. http://dx.doi.org/10.3390/rs15164086.
Testo completoAbstract (sommario):
Seagrasses are habitat-forming species that support biodiversity and a wide range of associated ecosystem services, from blue carbon capture to providing nursery areas for a variety of organisms. Their decline has been documented worldwide and is attributed to human impacts ranging from habitat loss and eutrophication to the effects of climate change. However, recent recovery trends have also been documented due to reductions in stressors, passive and active restoration, and even changes in environmental conditions owing to local management. In this study, we document for the first time the occurrence of Zostera noltei in the downstream area of the River Minho Estuary. This occurrence was unexpected given the hydrological conditions of the estuary, characterised by dredging and siltation. We reconstructed the occurrence and historical distribution of seagrass beds, and showed that they have existed in the region for more than a decade. The current distribution area was mapped using high-resolution multispectral remote sensing techniques, and in situ photoquadrats to complement the remote sensing information with an evaluation of the seagrass cover. A current seagrass area of 0.81 ha was found with an average cover of 70%. However, the Minho Estuary continues to be strongly affected by sediment deposition, which may affect the seagrass population in the long term. Continued surveys are recommended to confirm the long-term trend of colonisation of this important habitat, which ultimately provides so many benefits to coastal ecosystems and humankind.
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Stankovic, Milica, Naruemon Tantipisanuh e Anchana Prathep. "Carbon storage in seagrass ecosystems along the Andaman coast of Thailand". Botanica Marina 61, n. 5 (25 settembre 2018): 429–40. http://dx.doi.org/10.1515/bot-2017-0101.
Testo completoAbstract (sommario):
Abstract Seagrass ecosystems are important contributors to mitigation of climate change, since they are responsible for large carbon sinks. However, there is limited knowledge regarding the importance of variability of carbon storage in various ecosystems. In this study, we estimated carbon storage in several structurally different seagrass meadows along the west coast of Thailand and determined whether degree of exposure, human disturbance, and meadow type influenced carbon storage within these meadows. Carbon content within the living vegetation was on average 3±2.7 Mg ha−1, whilst average storage of carbon in the sediment was 122±35.3 Mg ha−1. Meadow type and disturbance had a significant influence on total carbon storage in the ecosystem, while the degree of exposure of the bay did not show great differences. Uniform meadows had a higher average total carbon storage than mixed meadows (133±36.2 and 110±41.3 Mg ha−1, respectively). Undisturbed meadows had a higher average total carbon storage than disturbed ones (140±36.5 and 103±34.8 Mg ha−1, respectively). The results obtained contribute to our understanding of carbon storage on an ecosystem scale and can provide a baseline for proper management, conservation, and climate change studies in the region.
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Paulo, Diogo, Onno Diekmann, Ana Alexandra Ramos, Filipe Alberto e Ester Alvares Serrão. "Sexual reproduction vs. clonal propagation in the recovery of a seagrass meadow after an extreme weather event". Scientia Marina 83, n. 4 (3 dicembre 2019): 357. http://dx.doi.org/10.3989/scimar.04843.06a.
Testo completoAbstract (sommario):
Marine flowering plants can reproduce sexually and clonally, and the relative contribution of these two modes can be dependent on the environmental conditions. Zostera marina, a seagrass widely distributed in the northern hemisphere, can form annual and perennial meadows with different proportions of sexual versus clonal propagation depending on the environmental disturbance regime. We study the hypothesis that the contribution of sexual propagation varies during the recovery of a seagrass meadow. In this case study, we compare the proportion of sexual versus clonal propagation of a perennial Z. marina meadow before its disappearance due to winter storms and after recovery. Before disturbance, genotypic diversity was high, indicating frequent sexual reproduction events likely to create an abundant seed bank. Seedling germination allowed the population to recover after the extreme disturbance. As months passed, seedlings became rare and finally absent, giving place to adult shoots. In an advanced stage of colonization, the shoots colonized the area by vegetative growth, which lowered the genotypic diversity. Despite this reduction over time, the genotypic diversity of the new meadow is still high, demonstrating the importance of sexual reproduction in meadow recovery and persistence.
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Kletou, Demetris, Periklis Kleitou, Ioannis Savva, Martin J. Attrill, Stephanos Charalambous, Alexis Loucaides e Jason M. Hall-Spencer. "Seagrass of Vasiliko Bay, Eastern Mediterranean: Lost Cause or Priority Conservation Habitat?" Journal of Marine Science and Engineering 8, n. 9 (16 settembre 2020): 717. http://dx.doi.org/10.3390/jmse8090717.
Testo completoAbstract (sommario):
Mediterranean coasts are affected by multiple mounting pressures. In Cyprus, marine fish farming has grown rapidly in the past decade and is concentrated in the west side of Vasiliko Bay. The east coast of this bay has ports, a power station, a desalination unit, a cement factory, a major new oil terminal, and gas storage facilities. The bay is earmarked to create the largest hydrocarbon processing, storing, and transport facility in the region. Here, we assess the status of Posidonia oceanica habitat in an understudied region at the upper thermal, and eastern limit, of this Mediterranean endemic seagrass. An extensive ancient seagrass meadow was revealed, covering about 200 ha across 10 km of coastline, over soft substrata at ca 10–30 m depth, and over hard substrata at ca 0–6 m depth. Seagrass shoot density and leaf surface area decreased, both with increasing depth and with proximity to industrial developments; part of the meadow had been destroyed by dredging to build a jetty. Close to fish farms the seagrass had higher epiphytic biomass as well as lower leaf number, mass, and surface area, all of which indicate adverse effects of eutrophication and increased turbidity. Despite these multiple stressors, most of the meadow was in good ecological status, with some of the highest shoot densities ever reported. Furthermore, iconic species like sea turtles, monk seals, and dolphins were seen during sampling. Posidonia oceanica meadows off Cyprus are among the most valuable in the Mediterranean due to their tolerance of high seawater temperatures. Managers of future coastal developments in the region will need to adhere to European legislation and international conventions designed to secure the socioeconomic benefits of seagrass beds.
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de Iongh, H. H., B. Bierhuizen e B. van Orden. "Observations on the behaviour of the dugong (Dugong dugon Müller, 1776) from waters of the Lease Islands, eastern Indonesia". Contributions to Zoology 67, n. 1 (1997): 71–77. http://dx.doi.org/10.1163/18759866-06701003.
Testo completoAbstract (sommario):
A small population of dugongs was discovered in coastal waters of the Lease islands in eastern Indonesia. Studies on behaviour and feeding ecology revealed information on the interaction with seagrass meadows, modes of surfacing and submergence times and behaviour in the presence of scuba divers. Regular concentrated feeding was observed in a grazing sward at a subtidal monospecific Halophila ovalis meadow, confirming earlier observations of regular recropping by dugongs of grazing swards, covered by monospecific Halodule uninervis, inside an intertidal multi-species meadow.
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Bramante, James F., Suryati M. Ali, Alan D. Ziegler e Tsai M. Sin. "Decadal biomass and area changes in a multi-species meadow in Singapore: application of multi-resolution satellite imagery". Botanica Marina 61, n. 3 (27 giugno 2018): 289–304. http://dx.doi.org/10.1515/bot-2017-0064.
Testo completoAbstract (sommario):
Abstract Due to the dearth of information regarding current and changing health of seagrass habitat in the Indo-Pacific region, prior research into global trends of seagrass habitat health has included little data from this region, even though it contains the highest abundance and species diversity of seagrass globally. This study evaluates the suitability of four satellite sensors [Worldview-2 (WV2), Advanced Land Imager (ALI), Enhanced Thematic Mapper+ (ETM+), Operational Land Imager (OLI)] for determining trends in seagrass habitat extent over the past decade in Singapore’s largest seagrass meadow, and thus contributes incrementally to the data available for regional or global analyses of seagrass habitat health. Using all four sensors, we find that seagrass bed extent at Pulau Semakau, Singapore, declined 37% from 2001 to 2015 at an average rate of 3.9% year−1. Using very high spatial resolution satellite images, we calculate that, although bed extent decreased 18% from April 2011 to June 2013, median meadow biomass increased, indicating that complex meadow dynamics may be mediating seagrass response to anthropogenic and environmental pressures. From a technological perspective, we find that, despite their lower spatial resolution, freely available satellite images can be used to measure the extent of a narrow, multi-species seagrass bed and to determine decadal trends reliably.