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Batuwael, Anggi Wawan, e Dominggus Rumahlatu. "ASOSIASI GASTROPODA DENGAN TUMBUHAN LAMUN DI PERAIRAN PANTAI NEGERI TIOUW KECAMATAN SAPARUA KABUPATEN MALUKU TENGAH". Biopendix: Jurnal Biologi, Pendidikan dan Terapan 4, n. 2 (22 maggio 2019): 109–16. http://dx.doi.org/10.30598/biopendixvol4issue2page109-116.
Testo completoAbstract (sommario):
Background: Seagrasses are flowering plants (Angiosperms) that are able to adapt fully in waters with high salinity or live immersed in water. Seagrass has true rhizomes, leaves and roots like plants on land. Seagrasses usually form fields called seagrass beds, especially in tropical and sub-tropical regions. The existence of seagrasses is known to support fishing activities, shellfish communities and other invertebrate biota.
Method: This study is a descriptive study to reveal information about environmental characteristics, and associations of seagrasses with gastropods.
Results: The study found a class of gastropods, 10 species namely Strombus variabilis, Strombus microurceus, Nassariusl uridus, Nassarius dorsatus, Strombus urceus, Cypraea annulus, Strombus labiatus, Strombus marginatus, Neritas quamulata, Cypraeratigris. Of the seagrass plants found 4 species, namely Enhalus acoroides, Thalassia hemprichii, Halophila ovalis, Cymodocea rotundata. Association values ranged from 4.159-8.85 with positive and negative types. This means that both types of seagrass are often found together or not found together in each observation box.
Conclusion: There is a weak association between seagrass and gastropods in the coastal waters of Tiouw State. The association of gastropod types with seagrass species is found in 10 types of gastropods and 4 types of seagrasses in the waters of the Tiouw State coast
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Ierodiaconou, Daniel A., e Laurie J. B. Laurenson. "Estimates of Heterozostera tasmanica, Zostera muelleri and Ruppia megacarpa distribution and biomass in the Hopkins Estuary, western Victoria, by GIS". Australian Journal of Botany 50, n. 2 (2002): 215. http://dx.doi.org/10.1071/bt00093.
Testo completoAbstract (sommario):
Knowledge of the spatial arrangement of the seagrass distribution and biomass within the Hopkins Estuary is an essential step towards gaining an understanding of the functioning of the estuarine ecosystem. This study marks the first attempt to map seagrass distribution and model seagrass biomass and epiphyte biomass along depth gradients by the use of global positioning system (GPS) and geographical information system (GIS) technologies in the estuary. For mapping seagrass in small estuaries, ground-surveying the entire system is feasible. Three species of seagrasses, Heterozostera tasmanica (Martens ex Aschers), Zostera muelleri (Irmisch ex Aschers) and Ruppia megacarpa (Mason), were identified in the Hopkins Estuary. All beds investigated contained a mixed species relationship. Three harvest techniques were trialed in a pilot study, with the 25 × 25-cm quadrat statistically most appropriate. Biomass of seagrasses and epiphytes was found to vary significantly with depth, but not between sites. The average estimate of biomass for total seagrasses and their epiphytes in the estuary in January 2000 was 222.7 g m–2 (dry weight). Of the total biomass, 50.6% or 112.7 g m–2 (dry weight) was contributed by seagrasses and 49.4% of the biomass (110.0 g m–2) were epiphytes. Of the 50.6% of the total biomass represented by seagrasses, 39.3% (87.5 g m–2) were leaves and 11.3% (25.2 g m–2) were rhizomes. The total area of seagrasses present in the Hopkins Estuary was estimated to be 0.4 ± 0.005 km2, with the total area of the estuary estimated to be 1.6 ± 0.02 km2 (25% cover). The total standing crop of seagrasses and epiphytes in the Hopkins Estuary in January 2000 was estimated to be 102.3 ± 57 t in dry weight, 56% (56.9 ± 17 t, dry weight) seagrasses and 44% (45.4 ± 19 t, dry weight) epiphytes. Of the seagrass biomass, 39% (39.7 ± 13 t, dry weight) was contributed by leaves and 17% (17.3 ± 7 t, dry weight) by rhizomes.
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Short, Frederick T., e Sandy Wyllie-Echeverria. "Natural and human-induced disturbance of seagrasses". Environmental Conservation 23, n. 1 (marzo 1996): 17–27. http://dx.doi.org/10.1017/s0376892900038212.
Testo completoAbstract (sommario):
SummaryMany natural and human-induced events create disturbances in seagrasses throughout the world, but quantifying losses of habitat is only beginning. Over the last decade, 90000 ha of seagrass loss have been documented although the actual area lost is certainly greater. Seagrasses, an assemblage of marine flowering plant species, are valuable structural and functional components of coastal ecosystems and are currently experiencing worldwide decline. This group of plants is known to support a complex trophic food web and a detritus-based food chain, as well as to provide sediment and nutrient filtration, sediment stabilization, and breeding and nursery areas for finfish and shellfish.We define disturbance, natural or human-induced, as any event that measurably alters resources available to seagrasses so that a plant response is induced that results in degradation or loss. Applying this definition, we find a common thread in many seemingly unrelated seagrass investigations. We review reports of seagrass loss from both published and ‘grey’ literature and evaluate the types of disturbances that have caused seagrass decline and disappearance. Almost certainly more seagrass has been lost globally than has been documented or even observed, but the lack of comprehensive monitoring and seagrass. mapping makes an assessment of true loss of this resource impossible to determine.Natural disturbances that are most commonly responsible for seagrass loss include hurricanes, earthquakes, disease, and grazing by herbivores. Human activities most affecting seagrasses are those which alter water quality or clarity: nutrient and sediment loading from runoff and sewage disposal, dredging and filling, pollution, upland development, and certain fishing practices. Seagrasses depend on an adequate degree of water clarity to sustain productivity in their submerged environment. Although natural events have been responsible for both large-scale and local losses of seagrass habitat, our evaluation suggests that human population expansion is now the most serious cause of seagrass habitat loss, and specifically that increasing anthropogenic inputs to the coastal oceans are primarily responsible for the world-wide decline in seagrasses.
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Burkholder, Derek A., Michael R. Heithaus e James W. Fourqurean. "Feeding preferences of herbivores in a relatively pristine subtropical seagrass ecosystem". Marine and Freshwater Research 63, n. 11 (2012): 1051. http://dx.doi.org/10.1071/mf12029.
Testo completoAbstract (sommario):
Understanding forage choice of herbivores is important for predicting the potential impacts of changes in their abundance. Such studies, however, are rare in ecosystems with intact populations of both megagrazers (sirenians, sea turtles) and fish grazers. We used feeding assays and nutrient analyses of seagrasses to determine whether forage choice of grazers in Shark Bay, Australia, are influenced by the quality of seagrasses. We found significant interspecific variation in removal rates of seagrasses across three habitats (shallow seagrass bank interior, shallow seagrass bank edge, deep), but we did not detect variation in gazing intensity among habitats. In general, grazers were more likely to consume fast-growing species with lower carbon : nitrogen (C : N) and carbon : phosphorus (C : P) ratios, than the slower-growing species that are dominant in the bay. Grazer choices were not, however, correlated with nutrient content within the tropical seagrasses. Slow-growing temperate seagrasses that experienced lower herbivory provide greater habitat value as a refuge for fishes and may facilitate fish grazing on tropical species. Further studies are needed, however, to more fully resolve the factors influencing grazer foraging preferences and the possibility that grazers mediate indirect interactions among seagrass species.
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J. Lee Long, W., R. G. Coles e L. J. McKenzie. "Issues for seagrass conservation management in Queensland". Pacific Conservation Biology 5, n. 4 (1999): 321. http://dx.doi.org/10.1071/pc000321.
Testo completoAbstract (sommario):
Coastal, reef-associated and deepwater (> 15 m) seagrass habitats form a large and ecologically important community on the Queensland continental shelf. Broad-scale resource inventories of coastal seagrasses were completed in the 1980s and were used in marine park and fisheries zoning to protect some seagrasses. At least eleven of the fifteen known species in the region reach their latitudinal limits of distribution in Queensland and at least two Halophila species may be endemic to Queensland or northeastern Australia. The importance of seagrasses to Dugongs Dugong dugon, Green Turtles Chelonia mydas and commercially valuable prawn fisheries, will continue to strongly influence directions in seagrass research and conservation management in Queensland. Widespread loss of seagrasses following natural cyclone and flood events in some locations has had serious consequences to regional populations of Dugong. However, the impacts to Queensland fisheries are little studied. Agricultural land use practices may exacerbate the effects of natural catastrophic events, but the long-term impacts of nutrients, pesticides and sediment loads on Queensland seagrasses are also unknown. Most areas studied are nutrient limited and human impacts on seagrasses in Queensland are low to moderate, and could include increases in habitat since modern settlement. Most impacts are in southern, populated localities where shelter and water conditions ideal for productive seagrass habitat are often targets for port development, and are at the downstream end of heavily modified catchments. For Queensland to avoid losses experienced by other states, incremental increases in impacts associated with population and development pressure must be managed. Seagrass areas receive priority consideration in oil spill management within the Great Barrier Reef and coastal ports. Present fisheries legislation for marine plant protection, marine parks and area closures to trawl fishing help protect inshore seagrass prawn nursery and Dugong feeding habitat, but seagrasses in deep water do not yet receive any special zoning protection. Efficacy of the various Local, State and Commonwealth Acts and planning programmes for seagrass conservation is limited by the expanse and remoteness of Queensland's northern coast, but is improving through broad-based education programmes. Institutional support is sought to enable community groups to augment limited research and monitoring programmes with local "habitat watch" programmes. Research is helping to describe the responses of seagrass to natural and human impacts and to determine acceptable levels of changes in seagrass meadows and water quality conditions that may cause those changes. The management of loss and regeneration of sea grass is benefiting from new information collected on life histories and mechanisms of natural recovery in Queensland species. Maintenance of Queensland's seagrasses systems will depend on improved community awareness, regional and long-term planning and active changes in coastal land use to contain overall downstream impacts and stresses.
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Omollo, Derrick, Virginia Wang’ondu, Michael Githaiga, Daniel Gorman e James Kairo. "The Contribution of Subtidal Seagrass Meadows to the Total Carbon Stocks of Gazi Bay, Kenya". Diversity 14, n. 8 (11 agosto 2022): 646. http://dx.doi.org/10.3390/d14080646.
Testo completoAbstract (sommario):
Seagrass beds occur globally in both intertidal and subtidal zones within shallow marine environments, such as bays and estuaries. These important ecosystems support fisheries production, attenuate strong wave energies, support human livelihoods and sequester large amounts of CO2 that may help mitigate the effects of climate change. At present, there is increased global interest in understanding how these ecosystems could help alleviate the challenges likely to face humanity and the environment into the future. Unlike other blue carbon ecosystems, i.e., mangroves and saltmarshes, seagrasses are less understood, especially regarding their contribution to the carbon dynamics. This is particularly true in regions with less attention and limited resources. Paucity of information is even more relevant for the subtidal meadows that are less accessible. In Kenya, much of the available information on seagrasses comes from Gazi Bay, where the focus has been on the extensive intertidal meadows. As is the case with other regions, there remains a paucity of information on subtidal meadows. This limits our understanding of the overall contribution of seagrasses in carbon capture and storage. This study provides the first assessment of the species composition and variation in carbon storage capacity of subtidal seagrass meadows within Gazi Bay. Nine seagrass species, comprising of Cymodocea rotundata, Cymodocea serrulata, Enhalus acoroides, Halodule uninervis, Halophila ovalis, Halophila stipulacea, Syringodium isoetifolium, Thalassia hemprichii, and Thalassodendron ciliatum, were found. Organic carbon stocks varied between species and pools, with the mean below ground vegetation carbon (bgc) stocks (5.1 ± 0.7 Mg Cha−1) being more than three times greater than above ground carbon (agc) stocks (0.5 ± 0.1 Mg Cha−1). Mean sediment organic carbon stock (sed Corg) of the subtidal seagrass beds was 113 ± 8 Mg Cha−1. Combining this new knowledge with existing data from the intertidal and mangrove fringed areas, we estimate the total seagrass ecosystem organic carbon stocks in the bay to be 196,721 Mg C, with the intertidal seagrasses storing about 119,790 Mg C (61%), followed by the subtidal seagrasses 55,742 Mg C (28%) and seagrasses in the mangrove fringed creeks storing 21,189 Mg C (11%). These findings are important in highlighting the need to protect subtidal seagrass meadows and for building a national and global data base on seagrass contribution to global carbon dynamics.
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Samper-Villarreal, Jimena. "Seagrasses in the Eastern Tropical Pacific: species, distribution ecology, blue carbon, and threats". Latin American Journal of Aquatic Research 52, n. 3 (30 giugno 2024): 336–49. http://dx.doi.org/10.3856/vol52-issue3-fulltext-3167.
Testo completoAbstract (sommario):
Eastern Tropical Pacific (ETP) seagrasses are composed of three genera and four species: Halophila baillonii, Halodule beaudettei, Halodule wrightii, and Ruppia maritima. These are colonizing seagrass species and meadows in the ETP can be ephemeral. Current seagrass distribution in this region remains unknown, with verified extant presence at a limited number of locations and mapping heavily reliant on historical reports. Suitable environmental conditions for seagrasses in the ETP consist of sheltered bays <10 m depth with fine sediment, 19-35 salinity, 26-32°C temperature, and water transparency of up to 10 m Secchi depth. In this region, seagrass organic carbon (OC) biomass pools (<0.2 Mg ha-1) have been reported from three locations, while sediment bulk density (<1.4 g mL-1) and OC (<24 Mg ha-1) have been reported from eight locations, all found on the Pacific coast of Costa Rica. Recent blue carbon reports from the ETP have not been included in global assessments to date. OC sequestration and sediment accumulation rates are currently unknown. Seagrasses provide key ecosystem services yet they are also threatened by anthropogenic and natural stressors. Seagrasses have already disappeared from two locations within the ETP, with restoration efforts currently underway on the northern Pacific coast of Costa Rica. This overview of our current understanding of seagrasses in the ETP and their services highlights the need for further research in this understudied region.
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Pollard, PC, e M. Greenway. "Photosynthetic characteristics of seagrasses (Cymodocea serrulata, Thalassia hemprichii and Zostera capricornia) in a low-light environment, with a comparison of leaf-marking and lacunal-gas measurements of productivity". Marine and Freshwater Research 44, n. 1 (1993): 127. http://dx.doi.org/10.1071/mf9930127.
Testo completoAbstract (sommario):
We describe the photosynthetic characteristics of three seagrasses and the relationship between their production and natural light intensities (photosynthesis-irradiance response, i.e. PI curves). Seagrass production (gross production minus shoot respiration) was measured in the field by the rate of gas release from the lacuna1 space of whole seagrass shoots and compared with net leaf production. Field work was carried out on the seagrasses Cymodocea serrulata (R. Br.) Aschers, and Magnus, Thalassia hemprichii (Ehrenb.) Aschers., and Zostera capricornia Aschers. in the turbid, warm waters of Cairns Harbour, Queensland, Australia. The photosynthetic efficiencies (the initial slope of the PI curves) of all of the seagrass species were 10 times greater than any previously measured for the same species in higher-light environments. The high compensating light intensities (80-92 �E m-2 s-1) showed that the plants have high respiration rates that were probably due to the high water temperatures (29-33�C) of the harbour. The seagrasses responded to small increases of light at low light intensities by rapidly reaching saturating light intensities, and the maximum rates of production were between 0.4 and 0.6 mg C h-1 shoot-1. The average period of exposure to saturating light intensity was 2 h day-1. One-quarter of the gross production was lost to plant respiration. The net productivity and respiration of all three seagrasses was calculated from this photoperiod. Net leaf production in situ compared well with the seagrass production estimates that were measured with the lacunal-gas technique. Most of the production appeared to be allocated to the above-ground tissue, a feature consistent with seagrasses growing in low-light and terrigenous sediments.
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Lavery, Paul. "Marine Management: Marine Conservation". Pacific Conservation Biology 5, n. 4 (1999): 240. http://dx.doi.org/10.1071/pc00240a.
Testo completoAbstract (sommario):
The research papers in this volume highlight some of the major issues in marine conservation and offer some exciting insights into future directions for research and management. It is particularly pleasing that the issue focuses on seagrasses, a component of marine biodiversity that is well recognized and with profound ecological significance, but has suffered widespread decline in its distribution over the past half century. The absence of any accurate inventory of seagrass resources makes it difficult to accurately assess the cumulative impact of human activity on them. However, the need to conserve seagrasses is well recognized and it is exciting to see the significant advances being made in bringing conservation biology techniques to seagrass research. The work of Waycott and Kenworthy (this issue) is clearly showing dramatic differences in the life-history strategies, genetic diversity and population structure of different seagrasses. It suggests that seagrasses are far from the homogenous organism that they seem to have been viewed as up until now. This also supports findings elsewhere which suggest that many of the classic paradigms regarding seagrass biology and ecology are based on inappropriate generalizations from a few species. For example, the work of Paling and others (in this issue) challenges the generally held view that we are unlikely to be able to transplant temperate species of seagrass back into disturbed areas.
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Hwang, Charnsmorn, Chih-Hua Chang, Michael Burch, Milena Fernandes e Tim Kildea. "Effects of Epiphytes and Depth on Seagrass Spectral Profiles: Case Study of Gulf St. Vincent, South Australia". International Journal of Environmental Research and Public Health 16, n. 15 (29 luglio 2019): 2701. http://dx.doi.org/10.3390/ijerph16152701.
Testo completoAbstract (sommario):
Seagrasses are a crucial indicator species of coastal marine ecosystems that provide substratum, shelter, and food for epiphytic algae, invertebrates, and fishes. More accurate mapping of seagrasses is essential for their survival as a long-lasting natural resource. Before reflectance spectra could properly be used as remote sensing endmembers, factors that may obscure the detection of reflectance signals must be assessed. The objectives in this study are to determine the influence of (1) epiphytes, (2) water depth, and (3) seagrass genus on the detection of reflectance spectral signals. The results show that epiphytes significantly dampen bottom-type reflectance throughout most of the visible light spectrum, excluding 670–679 nm; the depth does influence reflectance, with the detection of deeper seagrasses being easier, and as the depth increases, only Heterozostera increase in the exact “red edge” wavelength at which there is a rapid change in the near-infrared (NIR) spectrum. These findings helped improve the detection of seagrass endmembers during remote sensing, thereby helping protect the natural resource of seagrasses.
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Fraser, Matthew W., Gary A. Kendrick, Pauline F. Grierson, James W. Fourqurean, Mathew A. Vanderklift e Diana I. Walker. "Nutrient status of seagrasses cannot be inferred from system-scale distribution of phosphorus in Shark Bay, Western Australia". Marine and Freshwater Research 63, n. 11 (2012): 1015. http://dx.doi.org/10.1071/mf12026.
Testo completoAbstract (sommario):
Differences in phosphorus (P) availability can influence the ecology and physiology of seagrass communities; and are usually inferred from changes in the relative P content in seagrass leaves. Shark Bay is a subtropical marine embayment, with decreasing P concentrations in the water column and sediments from north to south across the entire embayment. We examined the P and nitrogen (N) content of seagrass leaves and P content of sediments across the Faure Sill and Wooramel delta region of Shark Bay, to determine whether the leaf content of seagrasses in Shark Bay also decreased from north to south over smaller spatial scales. Nutrient content of Amphibolis antarctica and Halodule uninervis were highly variable and were not strongly correlated with sediment P concentrations. Mean N : P ratios of seagrasses (<33.5) were not indicative of P limitation, as has been previously assumed for Shark Bay. We conclude that availability of P for uptake by seagrasses across Shark Bay may be highly localised and cannot be predicted from system-scale gradients (>100 km) of sedimentary P distributions. We suggest that P availability to seagrasses is more likely a complex function of differing nutrient inputs, rates of delivery to the plants and cycling rates.
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Unsworth, Richard K. F., Leanne C. Cullen-Unsworth, Benjamin L. H. Jones e Richard J. Lilley. "The planetary role of seagrass conservation". Science 377, n. 6606 (5 agosto 2022): 609–13. http://dx.doi.org/10.1126/science.abq6923.
Testo completoAbstract (sommario):
Seagrasses are remarkable plants that have adapted to live in a marine environment. They form extensive meadows found globally that bioengineer their local environments and preserve the coastal seascape. With the increasing realization of the planetary emergency that we face, there is growing interest in using seagrasses as a nature-based solution for greenhouse gas mitigation. However, seagrass sensitivity to stressors is acute, and in many places, the risk of loss and degradation persists. If the ecological state of seagrasses remains compromised, then their ability to contribute to nature-based solutions for the climate emergency and biodiversity crisis remains in doubt. We examine the major ecological role that seagrasses play and how rethinking their conservation is critical to understanding their part in fighting our planetary emergency.
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Seng, Nicholas, Samantha Lai, Jenny Fong, Muhammad Faiq Saleh, Clement Cheng, Zi Yu Cheok e Peter A. Todd. "Early evidence of microplastics on seagrass and macroalgae". Marine and Freshwater Research 71, n. 8 (2020): 922. http://dx.doi.org/10.1071/mf19177.
Testo completoAbstract (sommario):
Microplastic accumulation on marine macrophytes, such as macroalgae and seagrasses, is a potentially critical but overlooked pathway by which microplastics enter the marine food web. Despite the possible significance of this pathway, few studies have examined the presence of microplastics on macrophytes found in situ. We quantified the density of microplastics found on the surfaces of three species of intertidal seagrasses (Cymodocea rotundata, Cymodocea serrulata and Thalassia hemprichii) and two species of subtidal macroalgae (Padina sp. and Sargassum ilicifolium), and found significantly higher microplastic densities on seagrasses than on macroalgae. However, we found no relationships between microplastic density and epibiont cover in either seagrass or macroalgae. Our study has provided early evidence of microplastics on macrophyte surfaces in situ, being the first such evidence for macroalgae, and the second for seagrasses.
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Jones, Cynthia M. "Can we predict the future: juvenile finfish and their seagrass nurseries in the Chesapeake Bay". ICES Journal of Marine Science 71, n. 3 (4 settembre 2013): 681–88. http://dx.doi.org/10.1093/icesjms/fst142.
Testo completoAbstract (sommario):
Abstract The importance of estuarine seagrass beds as nurseries for juvenile fish has become a universal paradigm, especially for estuaries that are as important as the Chesapeake Bay. Yet, scientific tests of this hypothesis were equivocal depending on species, location, and metrics. Moreover, seagrasses themselves are under threat and one-third of seagrasses have disappeared worldwide with 65% of their losses occurring in estuaries. Although there have been extensive studies of seagrasses in the Chesapeake Bay, surprisingly few studies have quantified the relationship between seagrass as nurseries for finfish in the Bay. Of the few studies that have directly evaluated the use of seagrass nurseries, most have concentrated on single species or were of short duration. Few landscape-level or long-term studies have examined this relationship in the Bay or explored the potential effect of climate change. This review paper summarizes the seagrass habitat value as nurseries and presents recent juvenile fish studies that address the dearth of research at the long term and landscape level with an emphasis on the Chesapeake Bay. An important conclusion upon the review of these studies is that predicting the effects of climate change on fishery production remains uncertain.
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Han, Qiuying, Wenxue Che, Hui Zhao, Jiahui Ye, Wenxuan Zeng, Yufeng Luo, Xinzhu Bai, Muqiu Zhao e Yunfeng Shi. "Effects of Aquaculture and Thalassia testudinum on Sediment Organic Carbon in Xincun Bay, Hainan Island". Water 16, n. 2 (19 gennaio 2024): 338. http://dx.doi.org/10.3390/w16020338.
Testo completoAbstract (sommario):
Eutrophication due to aquaculture can cause the decline of seagrasses and impact their carbon storage capacity. This study explored the effects of aquaculture on the sediment organic carbon (SOC) in Thalassia testudinum seagrass beds using enzyme activity and microorganisms as indicators. Our results showed that the distance to aquaculture significantly increased the SOC and TN of sediments; the C/N ratio of sediments was reduced by the distance to aquaculture. Distance to aquaculture and seagrasses significantly impacted the δ13C of sediments, and their significant interactive effects on the δ13C of sediments were found. Distance to aquaculture and seagrasses had significantly interactive effects on the cellulase activity of sediments. Distance to aquaculture and seagrasses separately reduced the invertase activity of sediments. SOC in the seagrass bed was significantly positively impacted by cellulase activity and polyphenol oxidase activity in sediments. Firmicutes, Desulfobacterota and Chloroflexi were the dominant taxa in the S1 and S2 locations. From the S1 location to the S2 location, the relative abundances of Firmicutes and Desulfobacterota increased. The functional profiles of COG were relatively similar between the S1 and S2 locations. BugBase phenotype predictions indicated that the microbial phenotypes of all the seagrass sediment samples were dominated by anaerobic bacteria in terms of oxygen utilizing phenotypes. FAPROTAX functional predictions indicated that aquaculture affects functions associated with seagrass bed sediment bacteria, particularly those related to carbon and nitrogen cycling. This study can provide an important basis for understanding the response mechanism of global carbon sink changes to human activities such as aquaculture and supply more scientific data for promoting the conservation and management of seagrass beds.
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Namoua, Dilivia J., Adnan S. Wantasen, Khristin I. F. Kondoy, Rene Ch Kepel, Febry S. I. Menajang e Wilmy Pelle. "Carbon Absorption in Seagrasses in Tongkaina Coastal Waters, Bunaken District, Manado City, North Sulawesi". Jurnal Ilmiah PLATAX 10, n. 2 (30 settembre 2022): 433. http://dx.doi.org/10.35800/jip.v10i2.43485.
Testo completoAbstract (sommario):
This study was conducted to determine the types of seagrasses and calculate biomass and calculate how much carbon absorption in seagrasses was found in the location of Tongkaina Beach, Bunaken District, Manado City, North Sulawesi. The sampling procedure in the field is the method of cruising surveys. A cruising survey is a sample collection method that is carried out by walking through the coastal area of all seagrasses found. After the sampling at the site is completed, the sample in the inventory is then photographed. The samples that have been obtained are analyzed in the laboratory using the loss on ignition (LOI) method. The results of the study on Tongkaina coastal waters covering an area of 25,000 meters with a coastal length of ±500 meters, in an area parallel to the coastline as wide as ±50 meters towards the sea and six types of seagrasses were obtained, namely: Enhalus acoroides, Thalassia hemprichii, Syringodium isoetifolium, Cymodocea rotundata, Halodule uninervis, and Halodule pinifolia. The biomass in seagrasses found had an average value of 78.10% with the highest individual seagrass biomass found in seagrass type Enhalus acoroides with a biomass value of 87.23grams of dry weight (gbk)/individual and the lowest type of seagrass individual biomass value was found in seagrass type seagrass with a biomass value of 66.67grams of dry weight (gbk)/individual. The total carbon content calculated in the entire seagrass obtained was 46,0941gCKeywords: Tongkaina Beach; seagrasses; biomass; carbon absorptionAbstrakPenelitian ini dilakukan untuk mengetahui jenis-jenis lamun dan menghitung biomassa serta menghitung berapa serapan karbon pada lamun yang ditemukan dilokasi Perairan Pantai Tongkaina Kecamatan Bunaken Kota Manado Provinsi Sulawesi Utara. Prosedur pengambilan sampel di lapangan menggunakan metode survei jelajah. Survei jelajah adalah metode pengumpulan sampel yang di lakukan dengan cara menyusuri daerah pantai terhadap semua lamun yang ditemukan. Setelah pengambilan sampel di lokasi selesai, sampel di inventarisir kemudian difoto. Sampel yang telah diperoleh dianalisa di laboratorium dengan menggunakann metode loss on ignition (LOI). Hasil penelitian pada perairan pantai Tongkaina seluas 25.000 meter dengan panjang pantai ±500 meter sejajar garis pantai dan lebar ±50 meter ke arah laut. Ditemukan enam jenis lamun yaitu: Enhalus acoroides, Thalassia hemprichii, Syringodium isoetifolium, Cymodocea rotundata, Halodule uninervis dan Halodule pinifolia. Biomassa pada lamun yang ditemukan memiliki nilai rata-rata 78,53% dengan biomassa individu lamun tertinggi terdapat pada lamun jenis Enhalus acoroides dengan nilai biomassa mencapai 87,23gram berat kering (gbk)/individu dan nilai biomassa individu jenis lamun terendah terdapat pada lamun jenis Syringodium isoetifolium dengan nilai biomassa 66,67gram berat kering (gbk)/individu. Untuk total kandungan karbon yang dihitung pada keseluruhan lamun yang didapat sebesar 46,0941gC.Kata kunci: Pantai Tongkaina; Lamun; biomasa, serapan carbon
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Dilipan, Elangovan, Jutta Papenbrock e Thirunavakkarasu Thangaradjou. "Random amplified polymorphic DNA (RAPD) finger prints evidencing high genetic variability among marine angiosperms of India". Journal of the Marine Biological Association of the United Kingdom 97, n. 6 (19 maggio 2016): 1307–15. http://dx.doi.org/10.1017/s0025315416000631.
Testo completoAbstract (sommario):
In India 14 seagrass species can be found with monospecific genera (Enhalus, ThalassiaandSyringodium),Cymodoceawith two species andHalophilaandHalodulerepresented by more than two taxonomically complex species. Considering this, the present study was made to understand the level and pattern of genetic variability among these species collected from Tamilnadu coast, India. Random amplified polymorphic DNA (RAPD) analysis was used to evaluate the level of polymorphism existing between the species. Out of the 12 primers tested, 10 primers amplified 415 DNA fragments with an average of 41.5 fragments per primer. Of the total 415 amplified fragments only 123 (29.7%) were monomorphic and the remaining 292 (70.3%) were polymorphic for Indian seagrass species. Among the 10 primers used four are identified as the key primers capable of distinguishing all the Indian seagrasses with a high degree of polymorphism and bringing representative polymorphic alleles in all the tested seagrasses. From the present investigation, this study shows that the RAPD marker technique can be used not only as a tool to analyse genetic diversity but also to resolve the taxonomic uncertainties existing in the Indian seagrasses. The efficiency of these primers in bringing out the genetic polymorphism or homogeneity among different populations of theHalophilaandHalodulecomplex still has to be tested before recommending these primers as an identification tool for Indian seagrasses.
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van Wyk, Johanna W., Janine B. Adams e Sophie von der Heyden. "Conservation implications of herbicides on seagrasses: sublethal glyphosate exposure decreases fitness in the endangered Zostera capensis". PeerJ 10 (15 novembre 2022): e14295. http://dx.doi.org/10.7717/peerj.14295.
Testo completoAbstract (sommario):
Worldwide seagrass populations are in decline, calling for urgent measures in their conservation. Glyphosate is the most widely used herbicide globally, leading to increasing concern about its ecological impact, yet little is known about the prevalence or impact of glyphosate on seagrasses. In this study, we investigated the effect of sublethal glyphosate exposure on the endangered seagrass, Zostera capensis, to identify effects on growth, photosynthetic pigments and leaf morphology as measures of seagrass fitness. Seagrasses were exposed to a single dose of a commercial glyphosate formulation—ranging between 250 to 2,200 µg/L. After three weeks, the median leaf area decreased by up to 27%, with reductions of up to 31% in above ground biomass (p < 0.05). Photosynthetic pigment concentration showed no significant difference between groups. The observed effects on biomass and leaf area were seen at glyphosate levels below the regulatory limits set for surface water by several countries and may negatively affect the long-term resilience of this ecosystem engineer to additional stressors, such as those associated with climate change and anthropogenic pollution. As such, glyphosates and other herbicides that are washed into estuarine and marine ecosystems, pose a significant threat to the persistence of seagrasses and are important factors to consider in seagrass conservation, management and restoration efforts.
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Luong, Cao Van, Nguyen Manh Linh, Vu Manh Hung, Dam Duc Tien, Dau Van Thao e Tran Dinh Lan. "The status of seagrass communities in the Truong Sa archipelago". Tạp chí Khoa học và Công nghệ biển 20, n. 3 (1 ottobre 2020): 285–95. http://dx.doi.org/10.15625/1859-3097/20/3/15076.
Testo completoAbstract (sommario):
Seagrasses in Truong Sa archipelago have not been intensively studied and understood, even in some obviously progressive works recently published. It is essential to carry out much more researches to fill up understanding gaps of seagrasses in the area. In 2019, within the framework of the project coded KC09.29/16–20, two surveys were conducted for three selected islands (Truong Sa Lon, Thuyen Chai and Song Tu Tay) in the area, focusing on marine ecosystems including seagrass beds. Survey results in the selected islands show eight seagrass species (one new record), the estimated total distribution area of 1,190 ha, the total reserve of biomass reaching 7,417.2 tons.dry, equivalent to 11,432.8 tons.CO2.
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Naufal, Mohammed, e Gadi Padmavati. "Ethnobotany of three sea grass species from Port Blair, a step towards its conservation in Andaman Islands". Journal of Tropical Life Science 11, n. 1 (3 febbraio 2021): 11–16. http://dx.doi.org/10.11594/jtls.11.01.02.
Testo completoAbstract (sommario):
Ethno-phycology is the study of the relationships of human society to flora and its ecosystem. In the marine world, ethno-biology is a thriving area of research which have yielded valuable ethno-biological knowledge. The main goal of the present study was to understand the effect of abiotic factors as well as the natural and anthropogenic disturbances that shape seagrass community in Andaman Island and to reveal the knowledge of the local people, about the significance of seagrass habitat and its conservation. The qualitative study on distribution of seagrasses in Chidiyatapu (11° 29' 30" to 11° 30' 34" N and 92° 35' 10" to 92° 42' 30" E) was carried out during December2012 to February 2013. A total of three seagrass species such as Thalassia hempirichi (Ehrenberg) Ascherson, 1871, Halodule uninervis (R.Brown) J.D.Hooker 1858, Halophila ovalis (Forsskål) Ascherson 1882, where identified. Among them, T. hempirichi, and H. ovalis found in this study was reported to have the ethno-medicinal value from west coast of India. As a part of the study, the semi-structured survey was carried out among the local coastal people to analyse the Traditional Ecological Knowledge (TEK). The survey has revealed the unawareness of coastal residents about the medicinal, nutritional as well as conservational values of seagrasses. An effective implementation has to be taken to make them aware that seagrasses are fundamental components of healthy marine ecosystems and the local livelihoods that rely on them. The present findings provide the first report on the ethno-phycology of seagrasses from South Andaman Island.
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Copertino, Margareth S., Joel C. Creed, Marianna O. Lanari, Karine Magalhães, Kcrishna Barros, Paulo C. Lana, Laura Sordo e Paulo A. Horta. "Seagrass and Submerged Aquatic Vegetation (VAS) Habitats off the Coast of Brazil: state of knowledge, conservation and main threats". Brazilian Journal of Oceanography 64, spe2 (2016): 53–80. http://dx.doi.org/10.1590/s1679-875920161036064sp2.
Testo completoAbstract (sommario):
Abstract Seagrass meadows are among the most threatened ecosystems on earth, raising concerns about the equilibrium of coastal ecosystems and the sustainability of local fisheries. The present review evaluated the current status of the research on seagrasses and submerged aquatic vegetation (SAV) habitats off the coast of Brazil in terms of plant responses to environmental conditions, changes in distribution and abundance, and the possible role of climate change and variability. Despite an increase in the number of studies, the communication of the results is still relatively limited and is mainly addressed to a national or regional public; thus, South American seagrasses are rarely included or cited in global reviews and models. The scarcity of large-scale and long-term studies allowing the detection of changes in the structure, abundance and composition of seagrass habitats and associated species still hinders the investigation of such communities with respect to the potential effects of climate change. Seagrass meadows and SAV occur all along the Brazilian coast, with species distribution and abundance being strongly influenced by regional oceanography, coastal water masses, river runoff and coastal geomorphology. Based on these geomorphological, hydrological and ecological features, we characterised the distribution of seagrass habitats and abundances within the major coastal compartments. The current conservation status of Brazilian seagrasses and SAV is critical. The unsustainable exploitation and occupation of coastal areas and the multifold anthropogenic footprints left during the last 100 years led to the loss and degradation of shoreline habitats potentially suitable for seagrass occupation. Knowledge of the prevailing patterns and processes governing seagrass structure and functioning along the Brazilian coast is necessary for the global discussion on climate change. Our review is a first and much-needed step toward a more integrated and inclusive approach to understanding the diversity of coastal plant formations along the Southwestern Atlantic coast as well as a regional alert the projected or predicted effects of global changes on the goods and services provided by regional seagrasses and SAV.
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Siahaya, Chalvin Salmon, Prelly Marsell Jolanda Tuapattinaya e Stevin Melay. "DIVERSITY PHENETICS OF TYPES SEAGRASS IN VILLAGE POKA BEACH MALUKU BASED ON MORPHOMETRICS". RUMPHIUS Pattimura Biological Journal 4, n. 2 (29 settembre 2022): 062–66. http://dx.doi.org/10.30598/rumphiusv4i2p062-066.
Testo completoAbstract (sommario):
This research aims to determine the phenetic diversity of seagrass species in the coastal waters of Poka Village based on morphometrics. This research is a type of descriptive research, in which morphometric measurements are carried out to determine the phenetic diversity of seagrass species. Meanwhile, for kinship relationships between seagrasses. Software is used past 4.0. The results of this research were that four types of seagrass were found, namely Thalasssia hemprichii, Enhalus acoroides, Halophila pinifolia and Halophila ovalis. This indicates that the Poka Village beach has a high phenetic diversity of seagrass species with varying morphometrics for each character and type, which is influenced by the type of substrate and environmental parameters. Seagrasses that are closely related, namely, Thalasssia hemprichii and Enhalus acoroides are in one monophyletic group (ingroup) and are very closely related. Likewise with Halodule pinifolia and Halophila ovalis.
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Coles, RG, WJ Lee Long, RA Watson e KJ Derbyshire. "Distribution of seagrasses, and their fish and penaeid prawn communities, in Cairns harbour, a tropical estuary, Northern Queensland, Australia". Marine and Freshwater Research 44, n. 1 (1993): 193. http://dx.doi.org/10.1071/mf9930193.
Testo completoAbstract (sommario):
From aerial photography (July 1987) and diving surveys (February 1988), 876 ha of seagrasses (eight species) were mapped in Cairns Harbour, tropical north-eastern Queensland. Zostera capricorni was the most common seagrass species and had the greatest biomass at 79 g m-2 dry weight of stems and leaves and 180 g m-2 dry weight of roots and rhizomes. The maximum shoot density found was 4798 shoots m-2 of Halodule pinifolia, the second most common species. Seagrasses were found only between 0.5 and 5.0 m below mean sea level. Zostera capricorni was found at the shallowest depths, Halodule pinifolia at the deepest depths. Twenty species of penaeid prawns, nine of which are marketed commercially, were sampled from the seagrass beds. Abundances of prawns of commercial species were significantly greater on seagrass-covered substrata than on nonvegetated substrata. Overall, 5614 mostly small or juvenile fish, representing 134 taxa, were sampled from seagrasses in Cairns Harbour. The most numerous fish species were a goby, Yongeichthys criniger, and a pony fish, Leiognathus splendens. Only 15 species were highly valued as recreational fish, and only 11 species were highly valued as commercial fish. Of the fish species, five (4%) were highly valued species of both groups. The density of fish on the seagrass beds was estimated to be 8809 fish ha-1.
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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.
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Wardono, Suko, Elland Yupa Sobhytta, I. Gusti Ngurah Agung Dhananjaya, Rodo Lasniroha, Yuniarti Karina Pumpun, Mochammad Miftakhul Mashuda, Dewa Gde Tri Bodhi Saputra e Permana Yudiarso. "Association Analysis of Seagrass Coverage and Human Activities in Nusa Lembongan". Jurnal Biodjati 7, n. 2 (30 novembre 2022): 247–58. http://dx.doi.org/10.15575/biodjati.v7i2.20307.
Testo completoAbstract (sommario):
Nusa Lembongan has high marine biodiversity, including seagrass. Seagrass is a plant that lives submerged in a marine or estuary water that functions as a nursery ground, trapping sediment, and beach protector, so it is important to know the condition of seagrass coverage, especially in Nusa Lembongan for managing the Nusa Penida Marine Protected Area. This study aimed to understand the condition of seagrass coverage and the factors influencing the existence of its ecosystem in Nusa Lembongan. According to reslut in two stations, it was found that six of the twelve types of seagrasses in Indonesia, namely Enhalus acoroides, Thalassia hemprichii, Cymodocea serrulata, Cymodocea rotundata, Halodule pinifolia, and Halophila ovalis. From the two stations (LMB01 and LMB02), the total seagrass coverage was 38.10±30.98% or the medium category. The seagrass communities in the station areas were generally formed by 3 types of seagrasses; Thalassia hemprichii, Cymodocea serrulata, and Cymodocea rotundata. LMB02 has higher seagrass coverage than LMB01. The seagrass coverage is inversely proportional to the intensity of human activity.
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Sidi Cheikh, Mohamed Ahmed, Salomão Bandeira, Seydouba Soumah, Gnilane Diouf, Elisabeth Mayé Diouf, Omar Sanneh, Noelo Cardoso et al. "Seagrasses of West Africa: New Discoveries, Distribution Limits and Prospects for Management". Diversity 15, n. 1 (21 dicembre 2022): 5. http://dx.doi.org/10.3390/d15010005.
Testo completoAbstract (sommario):
The onset of a major seagrass initiative in West Africa enabled important seagrass discoveries in several countries, in one of the least documented seagrass regions in the world. Four seagrass species occur in western Africa, Cymodocea nodosa, Halodule wrightii, Ruppia maritima and Zostera noltei. An area of about 62,108 ha of seagrasses was documented in the studied region comprising seven countries: Mauritania, Senegal, The Gambia, Guinea Bissau, Guinea, Sierra Leone and Cabo Verde. Extensive meadows of Zostera noltei were recorded for the first time at Saloum Delta, Senegal, which represents the new southernmost distribution limit of this species. This paper also describes the seagrass morphology for some study areas and explores the main stressors to seagrasses as well as conservation initiatives to protect these newly documented meadows in West Africa. The produced information and maps serve as a starting point for researchers and managers to monitor temporal and spatial changes in the meadows’ extent, health and condition as an efficient management tool.
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Emmclan, Lau Sheng Hann, Muta Harah Zakaria, Shiamala Devi Ramaiya, Ikhsan Natrah e Japar Sidik Bujang. "Morphological and biochemical responses of tropical seagrasses (Family: Hydrocharitaceae) under colonization of the macroalgae Ulva reticulata Forsskål". PeerJ 10 (18 gennaio 2022): e12821. http://dx.doi.org/10.7717/peerj.12821.
Testo completoAbstract (sommario):
Background Coastal land development has deteriorated the habitat and water quality for seagrass growth and causes the proliferation of opportunist macroalgae that can potentially affect them physically and biochemically. The present study investigates the morphological and biochemical responses of seagrass from the Hydrocharitaceae family under the macroalgal bloom of Ulva reticulata, induced by land reclamation activities for constructing artificial islands. Methods Five seagrass species, Enhalus acoroides, Thalassia hemprichii, Halophila ovalis, Halophila major, and Halophila spinulosa were collected at an Ulva reticulata-colonized site (MA) shoal and a non-Ulva reticulata-colonized site (MC) shoal at Sungai Pulai estuary, Johor, Malaysia. Morphometry of shoots comprising leaf length (LL), leaf width (LW), leaf sheath length (LSL), leaflet length (LTL), leaflet width (LTW), petiole length (PL), space between intra-marginal veins (IV) of leaf, cross vein angle (CVA) of leaf, number of the cross vein (NOC), number of the leaf (NOL) and number of the leaflet (NOLT) were measured on fresh seagrass specimens. Moreover, in-situ water quality and water nutrient content were also recorded. Seagrass extracts in methanol were assessed for total phenolic content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radical cation scavenging activity (ABTS), and ferric reducing antioxidant power (FRAP). Results Seagrasses in the U. reticulata-colonized site (MA) had significantly higher (t-test, p < 0.05) leaf dimensions compared to those at the non-U. reticulata colonized site (MC). Simple broad-leaved seagrass of H. major and H. ovalis were highly sensitive to the colonization of U. reticulata, which resulted in higher morphometric variation (t-test, p < 0.05) including LL, PL, LW, and IV. Concerning the biochemical properties, all the seagrasses at MA recorded significantly higher (t-test, p < 0.05) TPC, TFC, and ABTS and lower DPPH and FRAP activities compared to those at MC. Hydrocharitaceae seagrass experience positive changes in leaf morphology features and metabolite contents when shaded by U. reticulata. Researching the synergistic effect of anthropogenic nutrient loads on the interaction between seagrasses and macroalgae can provide valuable information to decrease the negative effect of macroalgae blooms on seagrasses in the tropical meadow.
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Beer, Sven, Mats Bjork, Frida Hellblom e Lennart Axelsson. "Inorganic carbon utilization in marine angiosperms (seagrasses)". Functional Plant Biology 29, n. 3 (2002): 349. http://dx.doi.org/10.1071/pp01185.
Testo completoAbstract (sommario):
The mechanisms by which marine angiosperms, or seagrasses, utilize external inorganic carbon (Ci) include, in addition to uptake of CO2 formed spontaneously from HCO3–: (i) extracellular carbonic anhydrasemediated conversion of HCO3– to CO2 at normal seawater pH, or in acid zones created by H+ extrusion, and (ii) H+-driven utilization (direct uptake?) of HCO3–. The latter mechanism was recently indicated for Zostera marina, Halophila stipulaceaand Ruppia maritima, and manifested itself as a sensitivity of photosynthesis to buffers, as well as a relative insensitivity to acetazolamide under buffer-free conditions, especially at high pH. Seagrasses have until recently been viewed as having Ci utilization systems that are less ‘efficient’ than macroalgae, and this has, for example, led to the thought that future rises in atmospheric and thus dissolved CO2 would have a stronger effect on seagrasses than on macroalgae. However, most of the experiments leading to such conclusions were carried out in the laboratory on detached leaves, and buffers were used to keep HCO3–/CO2 ratios stable during Ci additions. The revelation that seagrass photosynthesis is sensitive to buffers as well as to physical perturbations, has led to new experiments in which initial pH values are set by appropriate HCO3–/CO32–ratios, and/or O2 measurements on leaf pieces are replaced with pulse amplitude-modulated fluorometry on whole, attached leaves, often in situ. Under such conditions, the photosynthetic responses of seagrasses to Ci match those obtained for macroalgae. Thus, the paradigm of ‘inefficient’ Ci utilization by seagrasses as compared with macroalgae may no longer be valid. Consequently, it seems that the generally observed high productivity of seagrass beds may have its background in very efficient, H+-driven, means of HCO3– utilization.
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Ahmad-Kamil, E. I., R. Ramli, S. A. Jaaman, J. Bali e J. R. Al-Obaidi. "The Effects of Water Parameters on Monthly Seagrass Percentage Cover in Lawas, East Malaysia". Scientific World Journal 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/892746.
Testo completoAbstract (sommario):
Seagrass is a valuable marine ecosystem engineer. However, seagrass population is declining worldwide. The lack of seagrass research in Malaysia raises questions about the status of seagrasses in the country. The seagrasses in Lawas, which is part of the coral-mangrove-seagrass complex, have never been studied in detail. In this study, we examine whether monthly changes of seagrass population in Lawas occurred. Data on estimates of seagrass percentage cover and water physicochemical parameters (pH, turbidity, salinity, temperature, and dissolved oxygen) were measured at 84 sampling stations established within the study area from June 2009 to May 2010. Meteorological data such as total rainfall, air temperature, and Southern Oscillation Index were also investigated. Our results showed that (i) the monthly changes of seagrass percentage cover are significant, (ii) the changes correlated significantly with turbidity measurements, and (iii) weather changes affected the seagrass populations. Our study indicates seagrass percentage increased during the El-Nino period. These results suggest that natural disturbances such as weather changes affect seagrass populations. Evaluation of land usage and measurements of other water physicochemical parameters (such as heavy metal, pesticides, and nutrients) should be considered to assess the health of seagrass ecosystem at the study area.
30
van Katwijk, Marieke M., e Brigitta I. van Tussenbroek. "Facultative Annual Life Cycles in Seagrasses". Plants 12, n. 10 (16 maggio 2023): 2002. http://dx.doi.org/10.3390/plants12102002.
Testo completoAbstract (sommario):
Plant species usually have either annual or perennial life cycles, but facultative annual species have annual or perennial populations depending on their environment. In terrestrial angiosperms, facultative annual species are rare, with wild rice being one of the few examples. Our review shows that in marine angiosperms (seagrasses) facultative annual species are more common: six (of 63) seagrass species are facultative annual. It concerns Zostera marina, Z. japonica, Halophila decipiens, H. beccarii, Ruppia maritima, and R. spiralis. The annual populations generally produce five times more seeds than their conspecific perennial populations. Facultative annual seagrass species occur worldwide. Populations of seagrasses are commonly perennial, but the facultative annual species had annual populations when exposed to desiccation, anoxia-related factors, shading, or heat stress. A system-wide ‘experiment’ (closure of two out of three connected estuaries for large-scale coastal protection works) showed that the initial annual Z. marina population could shift to a perennial life cycle within 5 years, depending on environmental circumstances. We discuss potential mechanisms and implications for plant culture. Further exploration of flexible life histories in plant species, and seagrasses in particular, may aid in answering questions about trade-offs between vegetative and sexual reproduction, and preprogrammed senescence.
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Bongga, Marthen, Calvyn F. A. Sondak, Deisle RH Kumampung, Kakaskasen A. Roeroe, Sandra Olivia Tilaar e Joudy Sangari. "KAJIAN KONDISI KESEHATAN PADANG LAMUN DI PERAIRAN MOKUPA KECAMATAN TOMBARIRI KABUPATEN MINAHASA". JURNAL PESISIR DAN LAUT TROPIS 9, n. 3 (4 ottobre 2021): 44. http://dx.doi.org/10.35800/jplt.9.3.2021.36519.
Testo completoAbstract (sommario):
Seagrass ecosystems services in the coastal waters are included as primary producers, nutrient recycler, bottom stabilizers, sediment traps, and erosion barriers. Gleaning fisheries in seagrass bed in Mokupa waters could cause damage on seagrass, that can be marked by changes in seagrass cover. The purposes of this study were to identify the types of seagrasses and to determine the health condition of seagrass bed ecosystem in Mokupa waters. The research method used in this study is quadrat transect method. Data collection was carried out by laid three transects (100 m) with distance between each transect was 50 m. A square frame (50×50 cm2) which is divided into 4 squares is placed on the right side of the transect, with 10 m distance between frame. This study found four types of seagrasses, namely Enhalus acoroides, Thalassia hemprichii, Halodule pinifolia and Halophila ovalis. E. acoroides have the highest percentage cover (16.19%) followed byT. hemprichii (6.91%), H. pinifolia (4.50%) and H. ovalis (1.56%) respectively. Seagrass cover in the study area is considered medium (26-50%) while the health condition was poor (29.25%).
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Jason G. Tuang-tuang. "Thriving Seagrasses in Rocky Sandy Substrate in Tinabilan, Northwest Leyte, Philippines". East Asian Journal of Multidisciplinary Research 1, n. 9 (29 ottobre 2022): 1881–86. http://dx.doi.org/10.55927/eajmr.v1i9.1258.
Testo completoAbstract (sommario):
The coastline of Palompon, Leyte has endowed with rich seagrass abundance and diversity which supports the well-established Siganid industry. Baseline information on the cover and species composition were gathered using the transect-quadrat method. Results showed that there were four (4) species of seagrasses identified in the coastal area of Tinabilan, Palompon, Leyte. Cymodocea rotundata and Thalassia hemprichii were observed in all the sampling stations. The average percentage cover of seagrasses was 8.36% which revealed in poor condition. However, the poor percentage cover condition can be associated with the topography and environmental factors in the area which is observed to have been dominated with rocky-sandy substrate and high temperature which possibly affects negatively the biological processes of the seagrass species.
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Muhaemin, Moh, Mohammad Fadhil Priambodo, Oktora Susanti e Eko Efendi. "THE INITIAL ECHINODERMS COMMUNITY STRUCTURE IN SEAGRASS BED OF MARINE TOURISM AREA: MAHITAM ISLAND AND KETAPANG BEACH, LAMPUNG". AQUASAINS 12, n. 1 (7 novembre 2023): 1422. http://dx.doi.org/10.23960/aqs.v12i1.p1422-1434.
Testo completoAbstract (sommario):
Lampung is one of national marine tourism destination. Seagrass is one of fragile coastal ecosystem and it is a habitat and feeding ground for a number of Echinoderms species. Echinodermata are nutrient recyclers that will in turn provide benefits to the seagrass ecosystem. This research aimed to assess the community structure of Echinoderms and seagrass as well as the relationship between Echinoderms abundance, seagrass densities, and water quality in Mahitam Island and Ketapang Beach. Observations were conducted at 7 stations, namely 3 stations on Ketapang Beach and 4 stations on Mahitam Island. Observations included the type and number of echinoderms, as well as the type, number of individuals, and number of seagrasses stands. Habitat quality that was observed were included water quality such as temperature, salinity, pH, DO (dissolved oxygen), current speed, brightness, and TOM (total organic matter) and also observed substrate type at each station. The result elucidated nine species of echinoderms and 4 species of seagrasses were found in both study sites. The average value of Echinoderms diversity index in Mahitam Island and Ketapang Beach was low. The uniformity index of Echinoderms in Mahitam Island was medium and Ketapang Beach was low. The dominance index of Echinoderms on Mahitam Island was categorized as low and Ketapang Beach was considered high. There was a domination of an Echinoderms species in some stations. The association between Echinoderms abundance, seagrass density and habitat quality in both locations showed a positive relationship and was influenced by the habitat quality parameters of seagrasses.
34
Udy, James W., e William C. Dennison. "Physiological responses of seagrasses used to identify anthropogenic nutrient inputs". Marine and Freshwater Research 48, n. 7 (1997): 605. http://dx.doi.org/10.1071/mf97001.
Testo completoAbstract (sommario):
Fertilization experiments have established that seagrass growth in Moreton Bay can be limited by the supply of both N and P. In the present study, morphological and physiological characteristics (canopy height, shoot density, biomass, growth, tissue nutrient content, amino acid concentrations and δ15N ratios) of Zostera capricorni Aschers. in Moreton Bay, close to and distant from nutrient sources, were compared. Z. capricorni at the four sites close to nutrient sources (sewage, septic or prawn-farm effluent, or river discharge), had physiological characteristics representative of high nutrient availability and at the five sites distant from nutrient sources had physiological characteristics representative of low nutrient availability. Differences in sediment nutrient concentrations (NH4+ and PO43- ), seagrass morphology and growth were not related to proximity to nutrient sources. However, the nutrient content of the seagrasses and their amino acid concentrations were consistently higher at sites close to a nutrient source. The amino acids glutamine and asparagine were the most responsive to elevated nutrient availability, and δ15N values of seagrasses reflected the source of N rather than the nutrient load. These results demonstrate that physiological characteristics of seagrasses can be used to identify the nutrient load and source affecting marine ecosystems.
35
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.
36
Farid, M. A., S. Rasidi e M. P. Patria. "THE COMMUNITY STRUCTURE OF SEAGRASS IN ENGGANO ISLANDS, BENGKULU". Marine Research in Indonesia 33, n. 1 (30 giugno 2008): 7–10. http://dx.doi.org/10.14203/mri.v33i1.501.
Testo completoAbstract (sommario):
The community structure of seagrass in Enggano Islands has been studied in August 2004. The aim of the study was to assess the seagrass community including species composition, density, and distribution pattern. The study was executed using transect quadrat methods, where seagrasses were counted in quadrats of 50 cm2. The result showed that the Enggano Islands seagrasses consist of seven species Enhalus acoroides, Halophila ovalis, Thallasia hemprichii, Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis, and Syringodium isoetifolium. The highest density occurred in Dua Island dominated by Thallasia hemprichii (363.3 shoots m-2), while the lowest density occurred in Merbau Island dominated by Enhalus acoroides (0.4 shoot m-2). The highest diversity index (HB) occurred in Kiape Bay (1.446) and the lowest in Merbau Island (0.634). In general, seagrass community in Enggano Islands was dominated by Thallasia hemprichii. All species has clumped distribution pattern (Id > 1).
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Zabarte-Maeztu, Iñigo, Fleur E. Matheson, Merilyn Manley-Harris, Robert J. Davies-Colley, Megan Oliver e Ian Hawes. "Effects of Fine Sediment on Seagrass Meadows: A Case Study of Zostera muelleri in Pāuatahanui Inlet, New Zealand". Journal of Marine Science and Engineering 8, n. 9 (21 agosto 2020): 645. http://dx.doi.org/10.3390/jmse8090645.
Testo completoAbstract (sommario):
Seagrass meadows are vulnerable to fine sediment (mud) pollution, with impacts usually attributed to reduction in submerged light. Here we tested two non-exclusive hypotheses, that mud particles (<63 µm) impact seagrasses through both (1) the light climate and (2) changes in substrate physico-chemistry. We tested these hypotheses in Pāuatahanui Inlet, New Zealand, by comparing seagrass presence, abundance, and health, together with light climate and substrate physico-chemistry at contrasting habitats where (1) seagrass used to thrive but no longer grows (historical seagrass), (2) seagrass still persists (existing seagrass) and (3) seagrass has been present recently, but not currently (potential seagrass). Historical seagrass substrate had significantly higher mud (35% average), bulk density (1.5 g cm−3), porewater ammonium concentration (65 µM), and a more reduced redox profile (negative redox at only 2 cm soil depth) as well as a lower light availability when submerged compared to other habitats, while total daily light exposure differed little between habitats. This suggests that failure of seagrass to recolonize historical seagrass habitat reflects substrate muddiness and consequent unfavorable rhizosphere conditions. Our results provide evidence for the multi-stressor effects of fine sediment on seagrasses, with substrate suitability for seagrass being detrimentally affected even where light exposure seems sufficient.
38
Menez, Ernani G., e Ronald C. Phillips. "Seagrasses". Smithsonian Contributions to the Marine Sciences, n. 34 (1988): 1–104. http://dx.doi.org/10.5479/si.01960768.34.
Testo completo
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Watson, RA, RG Coles e WJ Lee Long. "Simulation estimates of annual yield and landed value for commercial penaeid prawns from a tropical seagrass habitat, Northern Queensland, Australia". Marine and Freshwater Research 44, n. 1 (1993): 211. http://dx.doi.org/10.1071/mf9930211.
Testo completoAbstract (sommario):
Concern over the loss of seagrass habitat has prompted examination of the value of the production of commercial prawns from such habitat. Cairns Harbour in tropical northern Queensland has 876 ha of mixed seagrasses, dominated by Zostera capricorni and Halodule pinifolia, that support a multispecies commercial penaeid prawn fishery offshore. Densities of juvenile commercial prawns estimated from seagrass surveys were used to project estimates of annual yield and landed value, using a deterministic simulation model employing lunar-period time steps. Estimates of the potential total annual yield from Cairns Harbour seagrasses for the three major commercial prawn species (Penaeus esculentus, P. semisulcatus and Metapenaeus endeavouri) were 178 t (range 81-316 t) year-1 with a landed value of $A1.2 million (range $0.6 million to $2.2 million) year-1.
40
Akbar, Nebuchadnezzar, Arfa Buamona, Irmalita Tahir, Abdurrachman Baksir, Rustam Effendi e Firdaut Ismail. "Epiphytic Community Base Depth of the Sea on Seagrass Leaves in Maitara Island, North Maluku Province". JURNAL SUMBERDAYA AKUATIK INDOPASIFIK 4, n. 1 (14 maggio 2020): 33. http://dx.doi.org/10.46252/jsai-fpik-unipa.2020.vol.4.no.1.81.
Testo completoAbstract (sommario):
Seagrasses are habitat of various types of sea animals, including association epiphytic in rhizoma, leave and steam. Research about community structure microepiphytic based on depth and ecology index, important as community conditions information. The goal research for ecology index analysis microepiphytic based on depth sea and seagrasses community condition. Sample collections epiphytic on seagrass leave used 1x1 meters quadrant based on depth. Epiphytic sample cutted and scraped in leave surface, than into to bottles sample contain 70% alcohol. The research method used line trasect 50 meters toward sea. The result founded 23 genus epiphytic with biodiversity medium, low dominance and high uniformity.
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Ramesh, Chatragadda, e Raju Mohanraju. "Seagrass Ecosystems of Andaman and Nicobar Islands: Status and Future Perspective". Environmental and Earth Sciences Research Journal 7, n. 4 (31 dicembre 2020): 169–74. http://dx.doi.org/10.18280/eesrj.070407.
Testo completoAbstract (sommario):
Seagrasses are unique marine flowering plants that play an important ecological role by yielding primary production and carbon sequestration to the marine environment. Seagrass ecosystems are rich in organic matter, supporting the growth of bio-medically important epi and endophytic microorganisms and harbor rich marine biodiversity. They are an essential food source for endangered Andaman state animal Dugongs. Seagrasses are very sensitive to water quality changes, and therefore they serve as ecological bio-indicators for environmental changes. The benthic components in and around the seagrass beds support a significant food chain for other Micro and organisms apart from fishery resources. The epiphytic bacterial communities of the leaf blades support the sustenance against the diseases. Recent reports have shown that the loss of seagrass beds in tropical and temperate regions emphasizes the depletion of these resources, and proper management of seagrass is urgent. The decline of seagrass will impact primary production, biodiversity, and adjacent ecosystems, such as reefs. Therefore, restoring the seagrass meadows could be possible with effective implementing management programs, including seagrass meadows in marine protected areas, restoration projects, seagrass transplantation, implementation of legislative rules, monitoring coastal water quality and human activities in the coastal zone. Lacunas on the seagrass ecosystem management in Andaman & Nicobar Islands are addressed.
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Mascarinas, Honey Jane, e Otadoy Julie B. "Seagrass Diversity and Distribution in Maribojoc Bay, Bohol, Philippines". American Journal of Environment and Climate 1, n. 1 (3 maggio 2022): 12–19. http://dx.doi.org/10.54536/ajec.v1i1.217.
Testo completoAbstract (sommario):
Seagrasses are major parts of coastal and marine biodiversity. Unfortunately, these aquatic plants and their ecological values are virtually unknown to many Filipinos. This study assessed the seagrasses in Maribojoc Bay, particularly in the coastal areas of the three municipalities, namely Maribojoc, Dauis, Panglao, and the City of Tagbilaran. Ecological assessments were conducted to determine the composition, abundance, distribution, percent cover, diversity, dominance, and evenness of seagrass species. Eight sampling sites were surveyed from October to December 2020. Seven seagrass species were identified, with Thalassia hemprichii as the most abundant (52.79%). There was a significant difference (p>0.05) in seagrass species relative abundance. The Shannon diversity index implies low diversity (H’=1.40) of seagrass species. High dominance (2.98) and low evenness (0.72) were attributed to the high abundance of T. hemprichii in the seagrass beds. The seagrass coverage was characterized by patchy and continuous meadows, with percentage cover ranging from 17.45% (poor) – 60% (good). Maribojoc Bay had a seagrass percentage cover of 38.65%, which can be classified under “fair” conditions. Seagrass community structure implies sparse coverage and low diversity, probably due to the deterioration of once-continuous meadows. However, further studies concerning seagrass communities are recommended in order to implement rehabilitation program or improve current management in Maribojoc Bay.
43
Irawan, Andri, e Noorsalam R. Nganro. "DISTRIBUTION OF SEAGRASSES IN INNER AMBON BAY". Jurnal Ilmu dan Teknologi Kelautan Tropis 8, n. 1 (11 novembre 2016): 99–114. http://dx.doi.org/10.29244/jitkt.v8i1.12499.
Testo completoAbstract (sommario):
ABSTRACTExcessive sedimentation in Inner Ambon Bay (IAB) is alleged to cause the degradation of seagrass ve-getation in the area. To get a clearer picture about the matter, we conducted a field study in October 2010 - January 2011 to describe the distribution and density of seagrass at several locations in IAB with different conditions of sedimentation levels. Data were collected using transects perpendicular to the coastline along the seagrass vegetation. The results showed that there were six species of seagrass which were spreaded unevenly. At the locations with high sedimentation, we found the formation of monospecies seagrass vegetation. Conversely, at the locations with low sedimentation, we found the formation of multispecies seagrass vegetation. The distribution and abundance of each species was related to the differences of seagrasses ability to grow in a certain environment and the compe-titiveness among them. Keywords: sedimentation, distribution, seagrass, Inner Ambon Bay
44
Rein, Thu. "Seagrass surveys in Shwe Thaung Yan coastal areas, the southern part of Rakhine Coastal Region, Myanmar: biodiversity, coverage and biomass". Journal of Aquaculture & Marine Biology 8, n. 3 (2019): 105–12. http://dx.doi.org/10.15406/jamb.2019.08.00248.
Testo completoAbstract (sommario):
Studies on percent cover and biomass of seagrasses from Shwe Thaung Yan coastal areas (Inn Din Gyi, Kyauk Nagar and Phoe Htaung Gyaing), the Southern parts of Rakhine Coastal Region, were carried out between March and August, 2018. A total of 8 species of seagrasses, namely Syringodiumisoetifolium (Ascherson) Danty, Halodulepinifolia (Miki) den Hartog, Haloduleuninervis (Forsskal) Ascherson, Cymodocearotundata Ehrenberg et Hemprich ex Ascherson, C. serrulata (R. Brown) Ascherson et Magnus, Thalassiahemprichii(Ehrenberg) Ascherson, Halophila major (Zoll.) Miquel and Enhalusacoroides (Linnaeus f.) Royle, were recorded in three study sites. Seagrass meadow in this study showed seasonal variations in both percent cover and biomass. Total seagrass coverage and biomass were higher in the dry season than in the monsoon season. Total seagrass coverage ranged between 8% and 75% in Phoe Htaung Gyaing, between 10% and 42% in Kyauk Nagar, and between 15% and 43% in Inn Din Gyi. Total seagrass mean biomass was 50.2413-259.846gdry.wtm-2 in Phoe Htaung Gyaing, 63.0194 -321.535gdry.wtm-2 in Kyauk Nagar, and 98.6819-416.237gdry.wtm-2 in Inn Din Gyi.
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Thorhaug, Anitra, e Jeffry Marcus. "EFFECTS OF DISPERSANT AND OIL ON SUBTROPICAL AND TROPICAL SEAGRASSES". International Oil Spill Conference Proceedings 1985, n. 1 (1 febbraio 1985): 497–501. http://dx.doi.org/10.7901/2169-3358-1985-1-497.
Testo completoAbstract (sommario):
ABSTRACT Preliminary experiments, using the subtropical/tropical coastal and estuarine seagrasses Thalassia testudinum, Halodule wrightii, and Syringodium filiforme, were carried out to examine the effects of dispersants. Experiments exposed seagrasses in vitro to concentrations of Louisiana crude oil ranging from 7.5 to 500 milliliters (mL) in 105 mL seawater at exposure times of 5 to 100 hours (seagrass not in contact with oil slick). In other experiments, the seagrasses were exposed to the dispersant Corexit 9527, which was combined with the oil in a ratio of 1 part dispersant to 10 parts oil with dispersant concentrations ranging from 0.75 to 50 mL in 105 mL seawater (dispersant plus oil forming a cloud of the substance in contact with seagrasses). The oil or oil with dispersant treatment was removed from the seagrasses after the designated exposure periods. Thereafter, the seagrasses were monitored for 14 days. Blade length was measured as a factor of growth. Thalassia showed the greatest tolerance to dispersant plus oil of the three species tested. It was not substantially affected by any oil concentration alone; however, when exposed to oil and dispersant, growth significantly decreased with concentrations of 125 mL oil and 12.5 mL dispersant in 105 mL seawater at longer periods of exposure (100 hours), and also at much decreased exposure times (5 hours) for 500 mL oil and 50 mL dispersant in 105 mL sea water. Syringodium and Halodule were generally less tolerant than Thalassia, particularly to oil. For example, at 75 mL oil/105 mL sea water and an exposure of 100 hours, growth decreased significantly and mortality increased to 53 percent. Growth and mortality of Syringodium and Halodule were further affected by the addition of dispersant.
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Ghandourah, Mohamed, Usama W. Hawas, Lamia T. Abou El-Kassem, Munir Bamkhrama e Hanan A. A. Taie. "Antioxidant and Antitumor Metabolites of Saudi Red Sea Seagrasses Halodule uninervis and Thalassia hemprichii". Letters in Organic Chemistry 16, n. 1 (4 dicembre 2018): 50–58. http://dx.doi.org/10.2174/1570178615666180525110832.
Testo completoAbstract (sommario):
The present study aimed to investigate the chemical constituents, and antioxidants and antitumor activities of the seagrasses Halodule uninervis and Thalassia hemprichii. Seventeen compounds were isolated from both seagrasses, and identified as flavonoids, phenolic acids, nitrogen compound, steroids and fatty acids. Their structures were established by spectral analysis (UV, MS, and 1D- and 2D-NMR) and chemical investigation (for glycosides). The total metabolites of each seagrass and the isolated flavonoids tested in different in vitro assays (DPPH, ABTS, FRAP, Fe2+ chelating, reducing power, and Ehrlich ascites carcinoma cell line) showed significant antioxidant and antitumor activities. H. uninervis extract revealed good antioxidant activities compared to water and butanol extracts of T. hemprichii, while quercetin 3-O-β-glucoside from H. uninervis revealed potent antioxidant activity at concentration of 25µg/ml. Moreover, the seagrasses extracts were displayed mild antitumor activity against Ehrlich ascites carcinoma cells in mice with less undesirable side effects compared to vincristine as a drug control.
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Hirst, A. J., K. Giri, D. Ball e R. S. Lee. "Determination of the physical drivers of Zostera seagrass distribution using a spatial autoregressive lag model". Marine and Freshwater Research 68, n. 9 (2017): 1752. http://dx.doi.org/10.1071/mf16252.
Testo completoAbstract (sommario):
Seagrass mapping has become a key tool in understanding the causes of change in seagrass habitats. The present study demonstrates a method for examining relationships between seagrass habitat polygons and environmental data generated by hydrodynamic, wave, catchment and dispersion models. Seagrass abundance data are highly spatially autocorrelated and this effect was corrected using a spatially simultaneous autoregressive lag model (SSARLM). The physical processes that determine the spatial distribution of seagrass in Port Phillip Bay, Australia, were investigated by examining the links between seagrass distribution and abundance and broadscale hydrodynamic (waves, currents), physical (light, depth, salinity and temperature) and catchment (nutrient and suspended sediment concentrations) processes. The SSARLM indicated that the distribution of Zostera spp. meadows is principally constrained by two physical thresholds, namely, wave height or exposure and light. The former excludes seagrasses from colonising wave-exposed coastlines, whereas the latter directly determines the depth profile of seagrasses through its influence on light availability. In total, 95% of all seagrass occurred within grid cells with a mean significant wave height of <0.38m and a mean percentage irradiance of >33% surface levels. By comparison, variation in water quality, represented by variables such as modelled total nitrogen, suspended solids or salinity, had little influence on seagrass distribution.
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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.]
49
Roem, Muhamad, Retno Setianingrum e Encik Weliyadi. "ASSOCIATION BETWEEN ECHINOID AND SEAGRASS COMMUNITY IN DERAWAN ISLAND WATERS". Journal of Aquatropica Asia 7, n. 2 (1 dicembre 2022): 104–16. http://dx.doi.org/10.33019/joaa.v7i2.3608.
Testo completoAbstract (sommario):
Sea urchins a biota that is often associated with seagrasses were often found in seagrass beds. The objectives of this research were to discover the condition of sea urchins and seagrass, such as diversity, uniformity, dominance in sea urchins, density, and cover on seagrass, and related to variables in this research. This research was conducted on Derawan Island. The research method that was used is a 5m x 5m (sea urchin) quadrate and 0.5m x 0.5m (seagrass) placed intentionally on 2 stations with a total of 30 quadrats. The results found 3 species of sea urchins and 4 species of seagrass. At station 1 abundance of sea urchins is 2.94 individual/m2 whereas at station 2 is 0,28 individual/m2. At station 1 seagrass density 117,33 shoot/m2 whereas station 2 is 120,13 shoot/m2. Seagrass cover at station 1 is 58,75% and at station 2 is 60,28%. The dominant sea urchin species is Diadema setosum with the following diversity values H'=0,36, E=0,3, and C=0.81. There was no significant difference between variables at each station except temperature (0.020<0.05) and DO (0.027<0.05). Variables that were correlated with sea urchins in the seagrass ecosystem are nitrate, salinity, phosphate, temperature, and pH. The association with seagrasses in Derawan Island is positive.
50
Lanuru, Mahatma, Rohani Ambo-Rappe, Khairul Amri e Susan L. Williams. "Hydrodynamics in Indo-Pacific seagrasses with a focus on short canopies". Botanica Marina 61, n. 1 (26 gennaio 2018): 1–8. http://dx.doi.org/10.1515/bot-2017-0037.
Testo completoAbstract (sommario):
Abstract Seagrass hydrodynamic regimes are important to understand and also to guide seagrass restoration, which is of great interest in Indonesia because of environmental threats to the exceptionally high seagrass species richness. Hydrodynamic regimes influence the physical stability of seagrass beds, sedimentation rates, and the advection of nutrients and food to seagrasses and associated organisms. In a flume, we determined the effect of canopies of Cymodocea rotundata, Enhalus acoroides, Halodule uninervis, Syringodium isoetifolium and Thalassia hemprichii on water velocity, turbulence, turbulence intensity and shear velocity. The taller canopies of Enhalus and Cymodocea slowed water flow, but the shorter canopies (<5 cm) had little effect. Seagrasses did not influence turbulence and turbulence intensity (turbulence normalized to mean velocity) but they reduced shear velocity U*. Our results indicate that Enhalus is a good candidate for transplantation in terms of reducing mean water flow and shear velocities, but that Halodule should also be considered as it also reduced shear velocities and it spreads quickly after transplantation. Our results extend the understanding of seagrass-hydrodynamic relationships to include very short canopies, unlike the taller canopies studied to date.