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Journal articles on the topic 'Estuarine ecology'
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1
Kirby-Smith, William W., and Robert R. Stickney. "Estuarine Ecology." Ecology 66, no. 6 (December 1985): 1986. http://dx.doi.org/10.2307/2937398.
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Kirby-Smith, William W. "Estuarine Ecology." Ecology 66, no. 6 (December 1985): 1987–88. http://dx.doi.org/10.2307/2937399.
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Kirby-Smith, William W. "Estuarine Ecology." Ecology 66, no. 6 (December 1985): 1986. http://dx.doi.org/10.2307/2937397a.
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Baugh, Thomas M., J. W. Day, C. A. S. Hall, W. M. Kemp, A. Yáñez-Arancibia, and A. Yanez-Arancibia. "Estuarine Ecology." Estuaries 13, no. 1 (March 1990): 112. http://dx.doi.org/10.2307/1351438.
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Maitland, Peter S. "Estuarine ecology." Biological Conservation 56, no. 2 (1991): 242–43. http://dx.doi.org/10.1016/0006-3207(91)90021-z.
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Whitfield, Alan K. "Estuarine ecology." Marine Biology Research 9, no. 8 (October 2013): 815–16. http://dx.doi.org/10.1080/17451000.2013.789913.
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Guterstam, Björn. "Estuarine ecology." Ecological Economics 3, no. 2 (July 1991): 169–70. http://dx.doi.org/10.1016/0921-8009(91)90019-b.
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Boerner, Ralph E. J. "African Estuarine Ecology." Landscape Ecology 29, no. 4 (March 12, 2014): 761–62. http://dx.doi.org/10.1007/s10980-014-0005-3.
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Bernardino, Angelo Fraga, Paulo Roberto Pagliosa, Ronaldo Adriano Christofoletti, Francisco Barros, Sergio A. Netto, Pablo Muniz, and Paulo da Cunha Lana. "Benthic estuarine communities in Brazil: moving forward to long term studies to assess climate change impacts." Brazilian Journal of Oceanography 64, spe2 (2016): 81–96. http://dx.doi.org/10.1590/s1679-875920160849064sp2.
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Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships.
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Gallop, Shari L., Karin R. Bryan, David P. Hamilton, Melissa Foley, and John L. Largier. "ECOENGINEERING FRESHWATER FLOWS FOR ESTUARY HYDROLOGICAL STATE." Coastal Engineering Proceedings, no. 37 (September 1, 2023): 17. http://dx.doi.org/10.9753/icce.v37.management.17.
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The quantity, quality and timing of freshwater inflow into estuaries is critical to support estuarine ecosystem health. However, most estuaries are affected by upstream manipulation of freshwater inflows. Coinciding with the United Nations Decade of Restoration (2021–2030), there is great interest in re-creating functional estuarine ecosystems, including by modifying the physio-chemical characteristics with the premise that a functional ecosystem will follow (ecoengineering). To restore estuarine ecology, the physical processes of the system must first be conductive to supporting the re-establishment and sustenance of biota. These physical processes are generally under-monitored and often not used as a measure of restoration success. We explore ecoengineering to restore freshwater inflows to estuaries, focused on hydrological state. We use the Pressure—State—Response (PSR) framework to set the context for this review.
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Whitfield, AK. "Littoral habitats as major nursery areas for fish species in estuaries: a reinforcement of the reduced predation paradigm." Marine Ecology Progress Series 649 (September 10, 2020): 219–34. http://dx.doi.org/10.3354/meps13459.
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For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.
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Watts, Robyn J., and Michael S. Johnson. "Estuaries, lagoons and enclosed embayments: habitats that enhance population subdivision of inshore fishes." Marine and Freshwater Research 55, no. 7 (2004): 641. http://dx.doi.org/10.1071/mf04051.
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Several studies have suggested that estuaries, lagoons and enclosed embayments may offer special opportunities for local subdivision in marine species. We used data from published papers and unpublished theses to examine the effect of such water bodies on allozyme differentiation of seven species of inshore fishes in Western Australia. We included species that differ in their dispersal, and hence their intrinsic potential for gene flow. Over large distances, subdivision was generally greater among estuarine populations than among conspecific marine populations collected over similar distances. Over small distances, paired marine and estuarine samples were generally more divergent than pairs of marine samples separated by similar distances. For species with a low capability for dispersal, estuaries appear to add to the high levels of genetic subdivision that commonly result from other factors. Under special circumstances estuaries may also provide opportunities for genetic divergence in species with a high capability of dispersal that are rarely subdivided at a large geographical scale. These observations indicate that estuaries can increase the genetic subdivision of populations of inshore fishes, and that species that use both marine and estuarine habitats are likely to have greater genetic subdivision than those that are restricted to marine habitats.
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Huisman, Jeroen B. J., Henry J. Kuipers, Leopold A. J. Nagelkerke, Peter Paul Schollema, and Inge van der Knaap. "Estuarine-Specific Migration of Glass Eels in the Ems Estuary." Fishes 8, no. 8 (July 27, 2023): 392. http://dx.doi.org/10.3390/fishes8080392.
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Understanding recruitment of glass eels in estuaries is crucial for the conservation of the European eel (Anguilla anguilla). However, basic knowledge on estuarine-specific glass eel migration, including in estuarine harbours, is mostly lacking. Therefore, we studied glass eel migration in the Dutch–German Ems estuary and the harbour at Delfzijl (The Netherlands) and tagged glass eels with Visual Implant Elastomer tags (VIE tags). We released 2000 tagged glass eels into the Ems estuary itself and 1000 tagged glass eels into the tidal harbour at Delfzijl. At three estuarine locations, i.e., Delfzijl–Duurswold, Termunterzijl, and Nieuwe Statenzijl, glass eel collectors were strategically placed, each location being progressively situated further upstream in the Ems estuary. Most glass eels (nuntagged = 97,089, ntagged = 74) were caught at Nieuwe Statenzijl, although this location is much further upstream. Lower numbers of glass eels (nuntagged = 1856, n tagged = 31) were caught at Delfzijl–Duurswold and Termunterzijl (nuntagged = 1192, ntagged = 7). Glass eels arrived approximately a week earlier at Nieuwe Statenzijl than at the other two locations, and the migration speed of tagged glass eels was highest at Nieuwe Statenzijl (>2 km/day) and lower (<1 km/day) at Delfzijl–Duurswold. Our study highlights that migration and the resulting potential recruitment of glass eels in estuaries and harbours may vary considerably both spatially and temporally. Further research on estuarine-specific factors that influence glass eel migration, such as the (anthropogenically altered) tidal action and flow, will provide valuable information on what influences glass eel migration in estuaries.
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Tremblin, Clément M., Maria Holzmann, Justin H. Parker, Aleksey Sadekov, and David W. Haig. "Invasive Japanese foraminifera in a south-west Australian estuary." Marine and Freshwater Research 73, no. 3 (November 24, 2021): 328–42. http://dx.doi.org/10.1071/mf21254.
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An invasive foraminiferan is recorded for the first time in an Australian estuary. Trochammina hadai, originally described as endemic from Japan and subsequently found to be alien in coastal waters of California and Brazil, has been identified in estuarine sediment in the vicinity of Bunbury Port in Western Australia. Species determination is based on morphological, molecular and ecological similarities to the Japanese type. The species has not been recorded in other estuaries in Australia. Bunbury Port is a major exporter of woodchip to Japan and the introduction of T. hadai may have come from ballast water out of shallow-draught woodchip vessels. Small sediment samples of estuarine mud obtained at water depths of ~5 m contain abundant T. hadai (on average ~0.4 mm in adult diameter) that are easily recognised in microscopic view of the sediment surface by their bright reddish-brown colour. The collection of sediment samples from the estuarine floor and ballast water, and the examination of these for foraminifers, may provide a useful indicator in estuaries for the possible presence of other exotic species, particularly in the vicinity of ports.
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Wildish, David J., and Adriana E. Radulovici. "Amphipods in estuaries: the sibling species low salinity switch hypothesis." Zoosystematics and Evolution 96, no. 2 (November 19, 2020): 797–805. http://dx.doi.org/10.3897/zse.96.55896.
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A novel low salinity switch hypothesis is proposed to account for the speciation of an obligate estuarine (oligohaline) amphipod, Orchestia aestuarensis, from a closely-related one, Orchestia mediterranea, found in both estuarine and marine conditions (euryhaline). The underlying genetic mechanisms could involve: 1. A dimorphic allele, or linked set of alleles, carried by the euryhaline amphipod which controls the ability to breed in low salinity conditions in estuaries and which is selected for in these conditions, producing the oligohaline amphipod. 2. A genetically-assimilated gene or genes, controlling the ability to breed in low salinity conditions in estuaries, which is/are “switched on” by low salinity conditions. 3. Allopatric speciation from a euryhaline to an oligohaline amphipod species where low salinity conditions is the selective switch. It is possible that other estuarine, sibling, amphipod pairs have evolved by salinity switching. In the North Atlantic coastal region, this could include: Gammarus tigrinus/G. daiberi and G. salinus/G. zaddachi (Amphipoda, Gammaridae).
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Tittley, Ian. "Ecology of Freshwater and Estuarine Wetlands." Botanical Journal of the Linnean Society 155, no. 3 (November 2007): 447. http://dx.doi.org/10.1111/j.1095-8339.2007.00701.x.
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Huxham, Mark. "Ecology of Freshwater and Estuarine Wetlands." Freshwater Biology 53, no. 3 (March 2008): 635. http://dx.doi.org/10.1111/j.1365-2427.2007.01910.x.
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McLusky, Donald S. "Estuarine benthic ecology: A European perspective." Austral Ecology 24, no. 4 (August 1999): 302–11. http://dx.doi.org/10.1046/j.1442-9993.1999.00983.x.
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Guerin, William F., and Galen E. Jones. "Estuarine ecology of phenanthrene-degrading bacteria." Estuarine, Coastal and Shelf Science 29, no. 2 (August 1989): 115–30. http://dx.doi.org/10.1016/0272-7714(89)90002-4.
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Wei, Xi, Josette Garnier, Vincent Thieu, Paul Passy, Romain Le Gendre, Gilles Billen, Maia Akopian, and Goulven Gildas Laruelle. "Nutrient transport and transformation in macrotidal estuaries of the French Atlantic coast: a modeling approach using the Carbon-Generic Estuarine Model." Biogeosciences 19, no. 3 (February 15, 2022): 931–55. http://dx.doi.org/10.5194/bg-19-931-2022.
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Abstract. Estuaries are key reactive ecosystems along the land–ocean aquatic continuum, with significant ecological and economic value. However, they have been facing strong morphological management changes and increased nutrient and contaminant inputs, possibly leading to ecological problems such as coastal eutrophication. Therefore, it is necessary to quantify the import and export fluxes of the estuaries, their retention capacity, and estuarine eutrophication potential. The 1-D Carbon-Generic Estuary Model (C-GEM) was used to simulate the transient hydrodynamics, transport, and biogeochemistry for estuaries with different sizes and morphologies along the French Atlantic coast during the period 2014–2016 using readily available geometric, hydraulic, and biogeochemical data. These simulations allowed us to evaluate the budgets of the main nutrients (phosphorus – P; nitrogen – N; silica – Si) and total organic carbon (TOC), and their imbalance, providing insights into their eutrophication potential. Cumulated average annual fluxes to the Atlantic coast from the seven estuaries studied were 9.6 kt P yr−1, 259 kt N yr−1, 304 kt Si yr−1, and 145 kt C yr−1. Retention rates varied depending on the estuarine residence times, ranging from 0 %–27 % and 0 %–34 % to 2 %–39 % and 8 %–96 % for total phosphorus (TP), total nitrogen (TN), dissolved silica (DSi), and TOC, respectively. Large-scale estuaries had higher retention rates than medium and small estuaries, which we interpreted in terms of estuarine residence times. As shown by the indicator of eutrophication potential (ICEP), there might be a risk of coastal eutrophication, i.e., the development of non-siliceous algae that is potentially harmful to the systems studied due to the excess TN over DSi. This study also demonstrates the ability of our model to be applied with a similar setup to several estuarine systems characterized by different sizes, geometries, and riverine loads.
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Whitfield, A. "Predation on small juvenile fishes in shallow estuarine nursery areas: Reply to Baker & Sheaves (2021)." Marine Ecology Progress Series 662 (March 18, 2021): 209–14. http://dx.doi.org/10.3354/meps13678.
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The key criticism by Baker & Sheaves (2021; Mar Ecol Prog Ser 662:205-208) of the Whitfield (2020; Mar Ecol Prog Ser 649:219-234) estuarine littoral predation paradigm review is that shallow water fish nursery habitats contain abundant predator assemblages which may create high predation pressure on the juvenile fish cohorts that occupy these areas. The primary arguments supporting Baker & Sheaves’ criticism arise from a series of papers published by them on piscivorous fish predation in certain tropical Australian estuaries. The counter-argument that shallow littoral areas in estuaries do indeed provide small juvenile fishes with refuge from small and large piscivorous fishes is provided by published papers from 4 different estuary types in South Africa, covering both subtropical and warm-temperate systems. Based on the overall published information, the argument for shallow (<1 m depth) estuarine waters providing major protection for newly settled juveniles appears to be weak in northern Australia but strong in South Africa. The global situation, as outlined in this response, is more supportive of low piscivorous predation in shallow nursery habitats, but further targeted research is needed before we can confirm that littoral estuarine waters are indeed a universal keystone attribute in this regard.
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Mai, Ana Cecilia Giacometti, and João Paes Vieira. "Review and consideration on habitat use, distribution and life history of Lycengraulis grossidens (Agassiz, 1829) (Actinopterygii, Clupeiformes, Engraulididae)." Biota Neotropica 13, no. 3 (September 2013): 121–30. http://dx.doi.org/10.1590/s1676-06032013000300015.
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In this paper, we present a summary of the current knowledge of Lycengraulis grossidens, a widely distributed coastal fish that occurs from Belize to Argentina. This species is abundant in estuaries along the Southwest Atlantic Coast and is important for recreational fishing, and as bycatch of shrimp fisheries. We compiled data available on taxonomy, phylogeny, ecology, fisheries and organized conceptually the life cycle of the species according to modern estuarine-use classification. Our review showed that along its geographic distribution and inside some particular environments (i.e., estuaries and costal lagoons) the species have been classified in a variety of ways in order to describe the remarkable complexity of habitat use that varies from freshwater resident, anadromous, marine migrant, estuarine resident, marine stragglers, catadromous to semi-catadromous. We conclude that L. grossidens is able to reproduce either in freshwater or estuarine water and postulate that it has a high plasticity in habitat use and life history, with migratory and resident contingents in the same local population. There seems to be a latitudinal change in migratory behavior of this species along the South America Coast, prevailing anadromous or semi-anadromous pattern at higher latitudes and marine migrants at the tropical northeast coast of Brazil.
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Henderson, Christopher J., Ben L. Gilby, Edward Stone, Hayden P. Borland, and Andrew D. Olds. "Seascape heterogeneity modifies estuarine fish assemblages in mangrove forests." ICES Journal of Marine Science 78, no. 3 (February 12, 2021): 1108–16. http://dx.doi.org/10.1093/icesjms/fsab022.
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Abstract Mangroves are a dominant structural habitat within tropical and subtropical estuaries that provide a number of ecosystem services, including habitat for a range of crustaceans and fish. However, mangroves are one of the most threatened estuarine habitats globally, having been severely reduced in extent, and replaced by urban structures. Here, we test for the effects of both natural (e.g. seagrass, rock and mangroves habitat extent, and connectivity) and human (e.g. extent of urban area) landscape variables on the number and type of fish inhabiting mangroves forests. We used remote underwater video stations to quantify fish assemblages within mangroves at 150 sites in 30 estuaries across Queensland, Australia. Fish community structure was best explained by the extent of mangroves and seagrasses within an estuary, the distance to the estuary mouth, and the size of the estuary and catchment. Moderate catchment size and proximity to the estuary mouth increased species richness and abundance of harvestable fish at individual mangrove sites. In order to maintain mangrove fish assemblages and the functions they provide, management initiatives should focus on maintaining natural estuarine seascapes that are located closer to the mouth of estuaries, in particular, focusing on estuaries that have lower levels of catchment urbanization.
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Moore-Maley, Benjamin L., Debby Ianson, and Susan E. Allen. "The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river." Biogeosciences 15, no. 12 (June 20, 2018): 3743–60. http://dx.doi.org/10.5194/bg-15-3743-2018.
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Abstract. Ocean acidification threatens to reduce pH and aragonite saturation state (ΩA) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and ΩA in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and ΩA to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500–1000 µmol kg−1) but relatively DIC-rich. Model results show that estuarine pH and ΩA are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine ΩA. When freshwater DIC : TA increases (beyond ∼ 1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season.
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Hockin, D. C., and R. S. K. Barnes. "Estuarine Biology." Journal of Applied Ecology 22, no. 2 (August 1985): 613. http://dx.doi.org/10.2307/2403207.
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Roast, S. D., R. S. Thompson, B. ,. J. Widdows, and M. B. Jones. "Mysids and environmental monitoring: a case for their use in estuaries." Marine and Freshwater Research 49, no. 8 (1998): 827. http://dx.doi.org/10.1071/mf97099.
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Mysids (Crustacea : Mysidacea) are ubiquitous members of the permanent, endemic hyperbenthic fauna of estuarine and other coastal ecosystems. They often occur in high numbers and their ecological importance, particularly their role in food chains as a link between the benthic and pelagic systems, is becoming increasingly apparent. In general, mysids are omnivores, feeding on detritus, zooplankton and phytoplankton, and they contribute up to 40% of the standing stock of omnivores in some systems. In estuaries, specific mysid faunas often occur in discrete zones, usually as a result of different salinity tolerances, although responses to turbidity and water flow also determine mysid distributions. Many mysids are particularly sensitive to chemical contaminants as illustrated by their relatively low 96-h LC50 values. Due to this sensitivity, the United States Environmental Protection Agency promotes the use of Americamysis ( Mysidopsis) bahia for laboratory toxicity testing; however, there is growing interest in the use of local, endemic species rather than the standard American mysid. At Plymouth, novel and sensitive techniques are being developed for assessing sublethal responses to toxicants by use of the northern European estuarine mysid Neomysis integer. This paper summarizes the ecological role of mysids in estuaries and describes their potential for use for estuarine environmental monitoring.
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Laruelle, Goulven Gildas, Nicolas Goossens, Sandra Arndt, Wei-Jun Cai, and Pierre Regnier. "Air–water CO<sub>2</sub> evasion from US East Coast estuaries." Biogeosciences 14, no. 9 (May 15, 2017): 2441–68. http://dx.doi.org/10.5194/bg-14-2441-2017.
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Abstract. This study presents the first regional-scale assessment of estuarine CO2 evasion along the US East Coast (25–45° N). The focus is on 42 tidal estuaries, which together drain a catchment of 697 000 km2 or 76 % of the total area within this latitudinal band. The approach is based on the Carbon–Generic Estuary Model (C-GEM) that allows the simulation of hydrodynamics, transport, and biogeochemistry for a wide range of estuarine systems using readily available geometric parameters and global databases of seasonal climatic, hydraulic, and riverine biogeochemical information. Our simulations, performed using conditions representative of the year 2000, suggest that, together, US East Coast estuaries emit 1.9 Tg C yr−1 in the form of CO2, which corresponds to about 40 % of the carbon inputs from rivers, marshes, and mangroves. Carbon removal within estuaries results from a combination of physical (outgassing of supersaturated riverine waters) and biogeochemical processes (net heterotrophy and nitrification). The CO2 evasion and its underlying drivers show important variations across individual systems, but reveal a clear latitudinal pattern characterized by a decrease in the relative importance of physical over biogeochemical processes along a north–south gradient. Finally, the results reveal that the ratio of estuarine surface area to the river discharge, S∕Q (which has a scale of per meter discharged water per year), could be used as a predictor of the estuarine carbon processing in future regional- and global-scale assessments.
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Lonthair, Joshua, Rasmus Ern, and Andrew J. Esbaugh. "The early life stages of an estuarine fish, the red drum (Sciaenops ocellatus), are tolerant to high pCO2." ICES Journal of Marine Science 74, no. 4 (January 8, 2017): 1042–50. http://dx.doi.org/10.1093/icesjms/fsw225.
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Ocean acidification (OA) and other climate change induced environmental alterations are resulting in unprecedented rates of environmental deterioration. This environmental change is generally thought to be too fast for adaptation using typical evolutionary processes, and thus sensitivity may be dependent on the presence of existing tolerant genotypes and species. Estuaries undergo natural pCO2 fluctuations over a variety of time scales, and levels regularly exceed the predicted end of the century values. Interestingly, estuarine fish species have been overlooked in reference to the impacts of OA. Here, we use the estuarine red drum (Sciaenops ocellatus) as a model to explore the hypothesis that early life stages of estuarine species have intrinsic tolerance to elevated pCO2. Our sensitivity endpoints included: survival, growth, yolk consumption, heart rate, and scototaxis. Survival was significantly decreased when exposed to 1300 μatm and 3000 μatm, and coincided with a significant increase in heart rate at the 3000 μatm exposure. However, these effects were less pronounced than the findings of previous studies on other marine fish species. Yolk depletion rate and standard length were not significantly affected by pCO2. Scototaxis behaviour was also not significantly affected by exposure to elevated levels of pCO2 under both acute and acclimated exposure scenarios. Overall, these results support the hypothesis that estuarine life history and habitat usage may play a critical role in determining sensitivity of fish species to OA. Furthermore, estuarine species may provide present-day insight into the physiological and ecological foundation of OA tolerance.
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Magalhães, Wagner F., and Francisco Barros. "Structural and functional approaches to describe polychaete assemblages: ecological implications for estuarine ecosystems." Marine and Freshwater Research 62, no. 8 (2011): 918. http://dx.doi.org/10.1071/mf10277.
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Polychaete assemblages are of special interest when studying dynamic environments such as estuaries because of their high plasticity in life strategies to cope with environmental variability. We tested the hypothesis that polychaete feeding guilds would be more related to environmental characteristics than to taxonomic composition. Polychaetes were sampled on two different occasions along three tropical estuarine systems in north-eastern Brazil. Different polychaete taxa replaced one another along the entire salinity gradient and the overall pattern from high- to low-salinity regions was from high species and feeding-guild diversities to dominance by a single species or a feeding group. We suggest that the relationships between structure and function of polychaete assemblages might provide a measure of the resilience of estuarine conditions; estuaries with a high redundancy in the trophic role of polychaetes might recover faster from disturbance and retain more natural ecological functions than those estuaries with low or no redundancy, because more species would have the capacity to expand their niches to compensate for the loss of neighbouring species. Integrative approaches allying species composition to their trophic role need to be thoroughly investigated to help understand such complex temporal and spatial organisation of benthic assemblages in estuaries.
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Henderson, Christopher J., Ben L. Gilby, Thomas A. Schlacher, Rod M. Connolly, Marcus Sheaves, Nicole Flint, Hayden P. Borland, and Andrew D. Olds. "Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes." ICES Journal of Marine Science 76, no. 4 (February 4, 2019): 1052–61. http://dx.doi.org/10.1093/icesjms/fsz007.
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Abstract Coastal seascapes are composed of a diversity of habitats that are linked in space and time by the movement of organisms. The context and configuration of coastal ecosystems shapes many important properties of animal assemblages, but potential seascape effects of natural and artificial habitats on nearby habitats are typically considered in isolation. We test whether, and how, the seascape context of natural and urban habitats modified fish assemblages across estuaries. Fish were sampled with underwater videos in five habitat types (mangroves, rock bars, log snags, unvegetated sediments, armoured shorelines) in 17 estuaries in eastern Australia. Different habitats supported distinct fish assemblages, but the spatial context of mangroves and armoured shorelines had pervasive ecological effects that extended across entire estuaries. In most estuarine habitats, fish diversity and abundance was greatest when they were in close proximity of mangroves, and decreased due to the proximity of armoured shorelines. Many cities are centred on estuaries, and urban expansion is often associated with the fragmentation of mangrove forests. Our findings emphasize that these transformations of urban estuarine landscapes are likely to propagate to broader ecological impacts detectable in multiple habitats beyond mangrove forests.
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Ramos, S., C. B. Paris, and M. M. Angélico. "Larval fish dispersal along an estuarine–ocean gradient." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 9 (September 2017): 1462–73. http://dx.doi.org/10.1139/cjfas-2016-0325.
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The present study investigated the larval fish dispersal along an estuarine–ocean gradient to explore connectivity between ocean and estuaries. During spring 2009, a combined ocean–estuarine survey was conducted along the Lima estuarine salinity gradient and in two transects off the adjacent coast (northwestern Iberian Peninsula), until the 100 m isobaths. Salinity, total particulate matter, particulate organic matter, total dissolved carbon, and dissolved organic carbon reached higher values at the ocean, and chlorophyll a and nutrients increased at the estuary. From the total 56 taxa identified, 14 were present along the gradient, including estuarine species (ES), marine stragglers (MS), and migrants (MM). Canonical correspondence analysis showed that species were separated along the gradient according to their ecological functional classification. MM associated with high salinity were separated from ES correlated with lower salinities and high chlorophyll a concentrations of inner estuary. Flounder (Platichthys flesus) showed a typical spatial gradient of MM, with abundance increasing from the ocean towards inner estuary. The dispersal of larvae along the Lima estuarine–ocean gradient was indicative of connectivity between habitats, emphasizing the need to consider this feature in management plans, mainly for species exploited by commercial fisheries.
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Hirst, Alastair J. "Broad-scale environmental gradients among estuarine benthic macrofaunal assemblages of south-eastern Australia: implications for monitoring estuaries." Marine and Freshwater Research 55, no. 1 (2004): 79. http://dx.doi.org/10.1071/mf03011.
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The importance of abiotic factors in explaining patterns of estuarine benthic macrofaunal community structure was examined on a broad spatial scale across south-eastern Australia. Macrofaunal communities were surveyed using an Ekman grab and a modified epibenthic sled (dredge) at each sampling site: data for 24 environmental variables were also collected. Twenty-eight estuaries were sampled on a single occasion during late summer at three stratified locations within each estuary (upper, mid and lower). Macrofaunal community composition was best explained by a common environmental gradient summarising variation in both salinity and longitude. Hence, although the distribution of macrofaunal taxa can be clearly linked to changes in salinity, the geographical position of the sites along an east–west axis, rather than a generalised down-stream gradient, appears to best explain the data. This association was primarily linked to broad-scale changes in estuarine morphology across the geographical range of this survey. A sediment-based environmental gradient among grab samples, but not dredge samples, reflected the largely infaunal nature of the grab samples. In general, the present survey did not support the classification of estuarine assemblages on the basis of a range of physical parameters but, instead, emphasised the continuity of estuarine benthic macrofaunal community structure on a broad spatial scale.
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Lill, Adrian W. T., Aparna Lal, and Gerard P. Closs. "Life history and reproduction of two abundant mysids (Mysidacea: Mysidae) in an intermittently open New Zealand estuary." Marine and Freshwater Research 61, no. 6 (2010): 633. http://dx.doi.org/10.1071/mf09085.
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Mysids typically form a large proportion of the hyperbenthic faunal biomass in estuaries and are central to the functioning of estuarine food webs. The population dynamics, annual life histories and reproductive effort of two common temperate estuarine mysids, Tenagomysis chiltoni and T. novae-zealandiae, are described in the intermittently open Kaikorai Lagoon, New Zealand. Mysids were sampled by night, monthly from September 2003 to September 2004. Both species completed their life cycles in the lagoon. There was an apparent spatial separation of breeding populations, with T. chiltoni prevalent in the upper lagoon and T. novae-zealandiae dominating the lower lagoon. Densities were lowest in late winter and peaked in late summer/early autumn for both species. Both species exhibited multivoltine life cycles, with breeding peaks occurring in October 2003, December 2003 and February/March 2004 for T. novae-zealandiae, and October/November 2003 and February/March 2004 for T. chiltoni. Breeding strategy for both species varied over the year with the adult size, brood size and the reproductive effort of both T. novae-zealandiae and T. chiltoni all being highest in spring. The life histories of both T. novae-zealandiae and T. chiltoni in the Kaikorai Lagoon are comparable to life histories described for other temperate estuarine mysid species in large open estuaries, and were not significantly modified to cope with the unpredictable demands of life in an intermittent estuary.
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Sedberry, George R. "Tropical Estuarine Fishes—Ecology, Exploitation and Conservation." Copeia 2001, no. 3 (August 2001): 880–83. http://dx.doi.org/10.1643/0045-8511(2001)001[0880:]2.0.co;2.
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Ducrotoy, J. P., and M. Elliott. "Recent developments in estuarine ecology and management." Marine Pollution Bulletin 53, no. 1-4 (January 2006): 1–4. http://dx.doi.org/10.1016/j.marpolbul.2006.02.001.
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Elliott, M., and A. K. Whitfield. "Challenging paradigms in estuarine ecology and management." Estuarine, Coastal and Shelf Science 94, no. 4 (October 2011): 306–14. http://dx.doi.org/10.1016/j.ecss.2011.06.016.
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Hodgkin, Ernest P., and Patrick Hesp. "Estuaries to salt lakes: Holocene transformation of the estuarine ecosystems of south-western Australia." Marine and Freshwater Research 49, no. 3 (1998): 183. http://dx.doi.org/10.1071/mf96109.
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When the estuaries of south-western Australia were first flooded by the Holocene marine transgression about 7000 years before present (BP), most were enclosed by limestone barrier dunes. Coastal sand drift built bars and flood-tide deltas in the narrow entrances, but until about 3500 years BP the estuaries remained tidal-dominated systems with a diverse marine–estuarine fauna. Now the bars/deltas so obstruct the small tides that estuary water is fresh in winter and marine to hypersaline in summer; the estuaries are river-flow-dominated systems and the ecosystems are characterised by a restricted euryhaline estuarine biota. Some estuaries are still permanently open, their bars/deltas never close, and some are seasonally open, their bars open with river flow in winter and close in summer. Other estuaries are normally closed, their bars remain closed for several years and break with episodic flood flow, or are permanently closed coastal salt lakes with bars that never or rarely break: they can become grossly hypersaline and may dry up altogether. An hypothesis to explain this Holocene transformation of the estuaries attributes it principally to sedimentary processes in an environment where river flow is highly seasonal, tides are microtidal, there was a fall in sea level, and there are differences in the volume and periodicity of flow and the degree of shelter to the entrances from the prevailing south-west winds and swell.
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Beard, Jason M., Natalie A. Moltschaniwskyj, Christine M. Crawford, John A. E. Gibson, and D. Jeff Ross. "Using macrofaunal communities to inform estuarine classification." Marine and Freshwater Research 70, no. 3 (2019): 371. http://dx.doi.org/10.1071/mf17372.
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Worldwide, geomorphological classifications of estuaries are often used to guide the design of monitoring programs and management strategies. However, if classifications do not reflect biotic patterns, the effectiveness of monitoring and management is potentially reduced. In this study, we consider the effectiveness of one classification scheme in describing biotic patterns by examining and comparing spatial variation of macrofaunal assemblages and their relationship with the environment in 12 estuaries of 2 geomorphological types (mesotidal river dominated and permanently open barrier estuaries). Estuaries were sampled at three locations (upper, mid and lower) for macroinvertebrates and environmental characteristics. Differences in macrofaunal assemblages occurred between the estuary types at the lower and mid locations, but not the upper. Similarities in the upper locations were related to sediment, whereas at the mid and lower locations differences were linked to salinity, dissolved oxygen concentrations and seagrass area. Within estuaries, location effects were definitive and unique within each estuary type, correlating to changes in sediment particle size, nitrogen concentration, microphytobenthos and percentage organic carbon. These results suggest that estuarine classification based on physical attributes alone does have the potential to capture important biological attributes if the biological scales of variability within these systems are well understood.
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Denis, Jérémy, Mario Lepage, Marie-Christine Gruselle, and Rachid Amara. "The Influence of Natural and Anthropogenic Environmental Pressures on European Eel Abundances in French Estuaries." Fishes 9, no. 2 (January 23, 2024): 44. http://dx.doi.org/10.3390/fishes9020044.
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The aim of this study was to investigate the influence of environmental characteristics and anthropogenic pressures on the abundance of estuarine European eels (Anguilla anguilla L.) during their continental growth phase. European eels were collected with fyke nets from spring to autumn in twenty-nine estuaries along the French English Channel and the Atlantic coast. Eel abundance (catch per unit effort, CPUE) was assessed for all eels and by size class for small (total length < 300 mm), intermediate (≥300 to <450 mm), and large (≥450 mm) eels. The environmental characteristics of the French estuaries were described by twelve descriptor variables, mainly related to hydro-morphological and sedimentary factors. Based on principal component analysis and hierarchical clustering analysis, estuary size was identified as the main explanatory variable and used to compare eel abundance. Eel abundance differed significantly according to estuary size, with higher abundances observed in small estuaries (7.22 to 13.00 ind. fyke nets 24 h−1) compared to large estuaries (0.13 to 0.71 ind. fyke nets 24 h−1). Spatial variation in eel abundance was correlated with differences in estuary size for all eel size classes. The influence of anthropogenic pressures on eel abundance was assessed by nine anthropogenic estuarine pressure indicators. The results indicate that high values of the anthropogenic pressure indicators were correlated with low eel abundance. This study highlights that large French estuaries subject to stronger anthropogenic pressures were less favourable habitats than small estuaries with less anthropogenic pressure.
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MAGRIS, R. A., and L. F. LOUREIRO FERNANDES. "Diversity and distribution of assemblages of estuarine decapod larvae (Crustacea: Decapoda: Anomura, Brachyura) in tropical southeastern Brazil." Zootaxa 2758, no. 1 (February 7, 2011): 26. http://dx.doi.org/10.11646/zootaxa.2758.1.2.
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Decapod larvae assemblages were studied in the tropical estuaries off southeastern Brazil (Piraquê-açú and Piraquê-mirim rivers estuaries). A total of 32 taxa of decapod larvae were recorded. Brachyuran larvae dominated in Piraquê-açú estuary, with 62% of the relative abundance, and 49% in Piraquê-mirim estuary. Mean larvae concentrations ranged from 17.2 m -3 at Piraquê-mirim (August 2003) to 221.1 m -3 at Piraquê-açú (April 2003). The assemblage of larvae in both estuaries was diverse, especially at Piraquê-mirim, which showed higher ecological stability. The high spatial heterogeneity of the Piraquê-açú and Piraquê-mirim estuarine system resulted in the division of the assemblage into two well-defined groups (truly estuarine and euryhaline). Salinity spatial gradient was a key factor in the structure and distribution of larvae.
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Newton, GM. "Estuarine Ichthyoplankton Ecology in Relation to Hydrology and Zooplankton Dynamics in salt-wedge Estuary." Marine and Freshwater Research 47, no. 2 (1996): 99. http://dx.doi.org/10.1071/mf9960099.
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The ichthyoplankton assemblage of the Hopkins River estuary, Victoria, was dominated by estuarine taxa that included demersal (goby, gudgeon) and pelagic (black bream, estuary perch, anchovy) species. The two seasonal peaks in fish larvae abundance were related to (1) the spring/summer zooplankton increase that occurred after flooding of the estuary and was comprised predominantly of copepod nauplii, thereby providing a good prey field for very young fish larvae, and (2) the autumn zooplankton maxima, which would provide a wide selection of copepod stages and meroplankton and promote dietary partitioning and flexibility among older larval stages. The two peaks in fish larvae abundance occurred well before and well after the attainment of maximum water temperature in the estuary. Goby, gudgeon, estuary perch and anchovy larvae were in the plankton over an extended period coinciding with the more stable conditions of salt-wedge presence and maximum zooplankton densities. The spawning of black bream and anchovies in the estuary was clearly related to physical conditions, such as salinity and water temperature, and habitat-although spawning of both species also occurred at times of high concentrations of potential prey organisms for their larvae. Adults of all the above fish species appear to have evolved spawning strategies that are adapted to the average hydrological and biological conditions in the estuary that would lead to the enhanced survival of their larvae. With the exception of the black bream, it appears that a ubiquitous and prolonged rather than a synchronous and confined spawning strategy is more widely used by estuarine-spawning fishes in the Hopkins River estuary. This type of spawning strategy, combined with the generally high density of food available to fish larvae in estuaries, suggests that the match-mismatch hypothesis of Cushing may be less relevant in the estuarine than in the marine environment.
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Mills, Courtenay E., Wade L. Hadwen, and Jane M. Hughes. "Looking through glassfish: marine genetic structure in an estuarine species." Marine and Freshwater Research 59, no. 7 (2008): 627. http://dx.doi.org/10.1071/mf07215.
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Through the use of mitochondrial DNA (ATP8 gene), the prediction of intermediate genetic structuring was investigated in two species of estuarine glassfish (Ambassis marianus and Ambassis jacksoniensis) (Perciformes : Ambassidae) to determine the possibility of a generalised ‘estuarine’ genetic structure. Individuals were collected from estuaries in eastern Australia between Tin Can Bay (Queensland) in the north and Kempsey (New South Wales) in the south. Analysis of the haplotype frequencies found in this region suggested panmictic populations with star-like phylogenies with extremely high levels of genetic diversity, but with no correlation between geographic distance and genetic distance. Non-significant FST and ΦST suggested extensive dispersal among estuaries. However, Tajima’s D and Fu’s FS values suggest ‘mutation–genetic drift equilibrium’ has not been reached, and that population expansions occurring 262 000 (A. marianus) and 300 000 (A. jacksoniensis) years ago may obscure any phylogeographic structuring or isolation by distance. The finding of panmixia was contrary to the prediction of genetic structuring intermediate between that of marine fish (shallowly structured) and freshwater fish (highly structured), suggesting high dispersal capabilities in these species.
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Murray, Taryn S., Paul D. Cowley, Rhett H. Bennett, and Amber-Robyn Childs. "Fish on the move: connectivity of an estuary-dependent fishery species evaluated using a large-scale acoustic telemetry array." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 11 (November 2018): 2038–52. http://dx.doi.org/10.1139/cjfas-2017-0361.
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Connectivity — movements of animals between and among numerous habitats — and the factors (rhythmic cycles and environmental variables) influencing connectivity of juvenile Lichia amia (Teleostei: Carangidae) were assessed in complementary acoustic telemetry studies in two geographically separated estuaries (620 km apart) in South Africa. The studies were conducted within a nationwide array of acoustic receivers moored in estuaries and coastal waters. Tagged fish in both the Kowie (n = 21) and Goukou (n = 17) estuaries displayed high levels of multiple habitat connectivity, with 81% and 76% visiting nearby marine and estuarine environments, respectively. The presence of tagged L. amia within the tagging estuaries was significantly influenced by river and sea temperature (Kowie) and river inflow and moon phase (Goukou). Tidal phase, time of day, and season were found to significantly influence marine excursions undertaken by Kowie- and Goukou-tagged fish. Our study provides an assessment of connectivity among multiple estuarine, port, and marine habitats, relating those movements to rhythmic cycles and environmental variables, and highlights the benefits of tracking animals using an extensive acoustic receiver array that spans multiple habitats.
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Acha, Eduardo M., Hermes Mianzan, Carlos A. Lasta, and Raúl A. Guerrero. "Estuarine spawning of the whitemouth croaker Micropogonias furnieri (Pisces : Sciaenidae), in the Río de la Plata, Argentina." Marine and Freshwater Research 50, no. 1 (1999): 57. http://dx.doi.org/10.1071/mf98045.
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Most fishes that take advantage of the high productivity of estuaries exhibit offshore spawning, produce great numbers of small pelagic eggs and recruit to estuaries as larvae or juveniles. The reproductive pattern of Micropogonias furnieri (a planktonic egg spawner) in the Río de la Plata estuary (36°S,56°W) differs from this. Biological sampling and oceanographic data showed that the spawning area covers a narrow band across the river between Montevideo (34°50´8S,56°10´W) and Punta Piedras (35°25´S,57°10´W) at depths ranging from 6 to 8 m. This area is characterized by strong haloclines, reaching 21.5 units m-1. M. furnieri eggs were present only below the halocline, in salinities of 9.7–27.3, and at 18.5–20.2°C. Spawning occurred in the innermost part of the estuary, near the upstream edge of the salinity wedge and coinciding with the turbidity maximum (up to 150 mg L-1). The regular spawning of pelagic eggs has been reported in estuaries of southern Africa and Australia characterized by intermittent landlocking. The present results show that a large estuary may also provide the opportunity for successful spawning of pelagic eggs. Resumen. La mayoría de los peces que aprovechan la alta productividad de los estuarios efectúan sus desoves en el océano, producen gran cantidad de pequeños huevos pelágicos, y se reclutan a los estuarios como larvas o juveniles. El patrón reproductivo de Micropogonias furnieri (un desovante de huevos planctónicos) en el Río de la Plata (36°S,56°W), resulta diferente. Muestreos biológicos y datos oceanográficos demuestran que su área de desove cubre una estrecha franja a través del río, entre Montevideo (34°50´S,56°10´W) y Punta Piedras (35°25´S,57°10´W), en profundidades de 6 a 8 m. Esta área se caracteriza por fuertes haloclinas, de hasta 21.5 unidades m-1. Los huevos de M. furnieri se encuentran sólo debajo de la haloclina, en salinidades de 9.7 a 27.3, y temperaturas de 18.5° a 20.2°C. El desove tiene lugar en la parte más interna del estuario, cerca del límite río arriba de la cuña salina, y en coincidencia con el máximo de turbidez (hasta 150 mg L-1). En estuarios del sur de Africa y Australia, caracterizados por el cierre intermitente de su boca, ha sido reportado el desove regular de huevos planctónicos. Nuestros resultados demuestran que un gran estuario también puede proveer la oportunidad para el desove exitoso de huevos planctónicos.
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Hood, W. Gregory. "Landscape allometry: from tidal channel hydraulic geometry to benthic ecology." Canadian Journal of Fisheries and Aquatic Sciences 59, no. 8 (August 1, 2002): 1418–27. http://dx.doi.org/10.1139/f02-109.
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The use of hydraulic geometry and other geomorphic indices has been recommended for habitat restoration and creation of estuarine tidal channels. Although such an approach provides design guidance for tidal channel form, it does not provide guidance for the ecological consequences of channel form. This study investigates the potential linkage of the scaling of tidal channel form with ecological patterns and processes in estuarine tidal channels of the lower Chehalis River, Washington, U.S.A. Ebb tide surface velocity was related to channel size, as was exit time and export probability of tiny drogues, which mimic floating allochthonous detritus. Consequently, the amount of organic material in channel sediments scaled negatively with channel size as did the abundance of benthic surface deposit feeders. These observations suggest that the highest concentrations of fish feeding in estuarine tidal channels may be in smaller channels or in the smaller and more distal portions of large channels. Scaling of ecological patterns and processes with tidal channel size may be an example of a more general ecological scaling with landscape form, i.e., landscape allometry.
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Taylor, CB, JA Nyman, and MK La Peyre. "Nekton community dynamics within active and inactive deltas in a major river estuary: potential implications for altered hydrology regimes." Aquatic Biology 31 (February 24, 2022): 1–18. http://dx.doi.org/10.3354/ab00748.
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High fisheries production within estuaries is associated with coastal upwelling, tidal mixing, and land-based runoff facing increasing impacts from climate and human activities. Active river deltas receive large riverine inflows compared to inactive river deltas, providing contrasting estuaries to compare impacts of river inflow on estuarine nekton. We quantified nekton assemblages and stable isotopes (δ13C, δ15N) of commercially important blue crab Callinectes sapidus Rathbun, 1896 within an active and inactive delta in coastal Louisiana to explore the impacts of differing riverine inflow. Crustaceans dominated estuarine assemblages, differing only by season and not delta type, with summer and fall supporting highest densities. Fish density and assemblages differed by the interaction of season and delta due to differences during the 2019 record high spring river inflow. During this period, the active delta supported reduced fish densities and richness compared to the inactive delta. Nekton densities across deltas and seasons reflect a combination of species life history characteristics and habitat conditions. The high spring river discharge in 2019 impacted habitat availability (reduced presence of submerged aquatic vegetation), water conditions (decreased temperature and salinity), and potentially displaced nekton to unsampled habitat areas (i.e. interior marsh surface) within the active delta. While differences in nekton density and assemblages were only evident during the high spring river discharge, δ15N values of blue crabs were approximately 1.5 times higher in the active delta, potentially indicating more terrestrial influence. Understanding how altered inflow impacts environmental variables supporting estuarine nekton production remains critical for supporting management within these hydrologically managed regions.
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Lourenço, Pedro M., José A. Alves, Teresa Catry, and José P. Granadeiro. "Foraging ecology of sanderlings Calidris alba wintering in estuarine and non-estuarine intertidal areas." Journal of Sea Research 104 (October 2015): 33–40. http://dx.doi.org/10.1016/j.seares.2015.06.013.
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Pickens, BA, JC Taylor, MD Campbell, and WB Driggers. "Offshore snapper and shark distributions are predicted by prey and area of nearby estuarine environments in the Gulf of Mexico, USA." Marine Ecology Progress Series 682 (January 20, 2022): 169–89. http://dx.doi.org/10.3354/meps13925.
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Seascape ecology has demonstrated that marine fishes are associated with multiscale habitat characteristics; however, most species distribution models focus on only a few predictors (e.g. depth, temperature), and this limits knowledge of essential fish habitat characteristics. Our objectives were to (1) determine habitat associations of offshore predatory marine fishes using a comprehensive suite of predictors, including area of nearby estuarine environments, (2) assess variable influence, and (3) model the spatial distribution of selected fishes in the families Carcharhinidae and Lutjanidae. We hypothesized that the concept of coastal outwelling would be evidenced by species associations with areas of nearby estuarine environments, and prey abundance would correlate with predator distributions. Species distribution models were developed for 2 snapper and 3 shark species in the northern Gulf of Mexico, USA. We used 34 multiscale predictors to evaluate how fish probability of presence or catch per unit effort (CPUE) were associated with oceanography, geography, substrate, area of nearby wetlands and estuaries, and prey abundance. Boosted regression trees, a machine-learning technique, modeled the most influential variables and predicted distributions. Model validation showed an overall accuracy of 79-86%, and CPUE models explained >40% of model deviance. Oceanographic variables, particularly mixed layer depth, were most influential and most frequently selected. As hypothesized, predatory fish distributions were predicted by prey abundances, and shark distributions were predicted by area of nearby coastal wetlands and estuaries. Our findings suggest that spatial models can provide novel insights into prey associations and linkages of marine species with nearby wetlands and estuaries.
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Matich, Philip, Robert J. Nowicki, Jonathan Davis, John A. Mohan, Jeffrey D. Plumlee, Bradley A. Strickland, Thomas C. TinHan, R. J. David Wells, and Mark Fisher. "Does proximity to freshwater refuge affect the size structure of an estuarine predator (Carcharhinus leucas) in the north-western Gulf of Mexico?" Marine and Freshwater Research 71, no. 11 (2020): 1501. http://dx.doi.org/10.1071/mf19346.
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The life histories of estuarine species are often adapted to the environmental variability they experience. However, estuaries are increasingly vulnerable to natural and anthropogenic changes, necessitating an understanding of how shifting conditions affect the survival, behaviour and population structure of estuarine-dependent animals. In this study we used data from fisheries-independent surveys collected across six estuaries with variable salinity regimes in Texas, USA, from 1975 to 2016 to investigate the role sources of freshwater inflow play in shaping juvenile bull shark Carcharhinus leucas size structure. High frequencies of co-occurrence with similarly sized conspecifics (59% of capture events) suggest bull sharks segregated within Texan estuaries based on body size. Bull shark sizes increased with distance to the nearest source of freshwater inflow, although effect sizes were small and access to freshwater habitats may be more important in shaping size-dependent distribution patterns. River mouths were disproportionately used by smaller juveniles (<90-cm total length, TL) and avoided by larger juveniles (>135cm TL). However, the use of river mouths decreased in estuaries characterised by limited freshwater inflow and greater variability in salinities at river mouths, highlighting geographic differences in the functions these habitats provide as potential environmental and predator refugia. Young-of-the-year (i.e. age-0) sharks also increased their use of river mouths throughout the 40-year study period, revealing the growing importance of river mouths as potential nursery habitats.
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Moens, Tom, and Magda Vincx. "Observations on the Feeding Ecology of Estuarine Nematodes." Journal of the Marine Biological Association of the United Kingdom 77, no. 1 (February 1997): 211–27. http://dx.doi.org/10.1017/s0025315400033889.
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Observations on living estuarine nematodes show that previous feeding type classifications do not accurately represent the trophic structure of an intertidal mudflat in the Westerschelde Estuary (Netherlands). A new scheme with six major nematode feeding guilds is proposed: (1) microvores; (2) ciliate feeders; and (3) deposit feeders sensu stricto are all nematodes without a distinct buccal armature. In the first two groups bacteria and protozoa, respectively are the major particulate food sources, while other items are included in the diet of the third. The three other categories are recognized among the nematodes with a buccal armature: (4) epigrowth feeders; (5) facultative predators; and (6) predators. Diatoms and other microalgae are an important particulate food for many epigrowth feeders. The importance of bacteria as a food source for these nematodes remains poorly documented. A strictly or mainly predatory behaviour has been described for only few species from the study area. Several nematodes, however, are facultative predators. The predatory strategy of Calyptronema maxweberi, as described in this paper, suggests the use of a paralysing or lethal secretion in prey capture, which, to our knowledge, is the first report for aquatic nematodes. Furthermore, the importance of sources other than particulate food in free-living aquatic nematodes is stressed. Our observations show that many aquatic nematodes are in fact opportunistic feeders, which may change feeding strategies in response to available food.