Artykuły w czasopismach na temat „Estuarine sediments”
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Spencer, K. L., i C. L. MacLeod. "Distribution and partitioning of heavy metals in estuarine sediment cores and implications for the use of sediment quality standards". Hydrology and Earth System Sciences 6, nr 6 (31.12.2002): 989–98. http://dx.doi.org/10.5194/hess-6-989-2002.
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Abstract. Total metal concentrations in surface sediments and historically contaminated sediments were determined in sediment cores collected from three estuaries (Thames, Medway and Blackwater) in south-east England. The partitioning behaviour of metals in these sediments was also determined using a sequential extraction scheme. These data were then compared with sediment quality values (SQVs) to determine the potential ecotoxicological risk to sediment dwelling organisms. When total metal concentrations in surface sediments are examined, no risk to biota in any of the estuaries is indicated. However, when historically contaminated sediments at depth are also considered, risks to biota are apparent and are greatest for the Thames, followed by the Medway and then the Blackwater. This suggests that regulatory authorities should examine vertical metal profiles, particularly in estuaries that are experiencing low sediment accumulation rates where historically contaminated sediments are in the shallow sub-surface zone and where erosion or dredging activities may take place. When metal partitioning characteristics are also considered, the risk to biota is comparable for the Medway and the Blackwater with the potentially bioavailable fraction presenting no ecotoxicological risk. Conversely, over 70% of metals are labile in the Thames Estuary sediments and toxic effects are probable. This suggests that the application of SQVs using total sediment metal concentrations may over- or under-estimate the risk to biota in geochemically dissimilar estuarine sediments. Keywords: sediment quality values, estuarine sediments, metal contamination, partitioning, sequential extraction
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Siddiqee, Mahbubul, Rebekah Henry, Rebecca Coulthard, Christelle Schang, Richard Williamson, Rhys Coleman, Graham Rooney, Ana Deletic i David McCarthy. "Salmonella enterica Serovar Typhimurium and Escherichia coli Survival in Estuarine Bank Sediments". International Journal of Environmental Research and Public Health 15, nr 11 (21.11.2018): 2597. http://dx.doi.org/10.3390/ijerph15112597.
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Estuarine bank sediments have the potential to support the survival and growth of fecal indicator organisms, including Escherichia coli. However, survival of fecal pathogens in estuarine sediments is not well researched and therefore remains a significant knowledge gap regarding public health risks in estuaries. In this study, simultaneous survival of Escherichia coli and a fecal pathogen, Salmonella enterica serovar Typhimurium, was studied for 21 days in estuarine bank sediment microcosms. Observed growth patterns for both organisms were comparable under four simulated scenarios; for continuous-desiccation, extended-desiccation, periodic-inundation, and continuous-inundation systems, logarithmic decay coefficients were 1.54/day, 1.51/day, 0.14/day, and 0.20/day, respectively, for E. coli, and 1.72/day, 1.64/day, 0.21/day, and 0.24/day for S. Typhimurium. Re-wetting of continuous-desiccated systems resulted in potential re-growth, suggesting survival under moisture-limited conditions. Key findings from this study include: (i) Bank sediments can potentially support human pathogens (S. Typhimurium), (ii) inundation levels influence the survival of fecal bacteria in estuarine bank sediments, and (iii) comparable survival rates of S. Typhimurium and E. coli implies the latter could be a reliable fecal indicator in urban estuaries. The results from this study will help select suitable monitoring and management strategies for safer recreational activities in urban estuaries.
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Wyness, Adam J., David M. Paterson, James E. V. Rimmer, Emma C. Defew, Marc I. Stutter i Lisa M. Avery. "Assessing Risk of E. coli Resuspension from Intertidal Estuarine Sediments: Implications for Water Quality". International Journal of Environmental Research and Public Health 16, nr 18 (5.09.2019): 3255. http://dx.doi.org/10.3390/ijerph16183255.
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Estuarine sediments are a reservoir for faecal bacteria, such as E. coli, where they reside at greater concentrations and for longer periods than in the overlying water. Faecal bacteria in sediments do not usually pose significant risk to human health until resuspended into the water column, where transmission routes to humans are facilitated. The erosion resistance and corresponding E. coli loading of intertidal estuarine sediments was monitored in two Scottish estuaries to identify sediments that posed a risk of resuspending large amounts of E. coli. In addition, models were constructed in an attempt to identify sediment characteristics leading to higher erosion resistance. Sediments that exhibited low erosion resistance and a high E. coli loading occurred in the upper- and mid-reaches of the estuaries where sediments had higher organic content and smaller particle sizes, and arose predominantly during winter and autumn, with some incidences during summer. Models using sediment characteristics explained 57.2% and 35.7% of sediment shear strength and surface stability variance respectively, with organic matter content and season being important factors for both. However large proportions of the variance remained unexplained. Sediments that posed a risk of resuspending high amounts of faecal bacteria could be characterised by season and sediment type, and this should be considered in the future modelling of bathing water quality.
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Nayak, Ganapati Narayan. "Changing Tropical Estuarine Sedimentary Environments with Time and Metals Contamination, Cest Coast of India". Journal of The Indian Association of Sedimentologists 38, nr 2 (31.12.2021): 63–78. http://dx.doi.org/10.51710/jias.v38i2.141.
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Estuaries are one of the major sub-environments of the coastal zone wherein freshwaters interact and mix with saline waters, and facilitate deposition of finer sediments, organic matter, and metals. Intertidal mudflat and mangrove sediment cores collected from estuaries along the central west coast of India were investigated for various sedimentological and geochemical parameters to understand the changes in the sedimentary depositional environments and various factors influencing the processes. Additionally, estuarine biota was examined to understand the bioaccumulation of metals with respect to bioavailability. The results indicated considerable changes in the depositional environments with time owing to sea-level changes; geomorphology of the estuaries; rainfall and river runoff; anthropogenic activities including construction of dams and bridges. The sediments in the estuaries are considerably polluted by metals and pose toxicity risks to the estuarine biota due to high metal bioavailability. Marine gastropods and mangrove plants act as prospective bio-indicators, and the bioremediation potential of mangroves for contaminated sediments was identified. Metal bioaccumulation in edible benthic biota can be harmful to the human health.
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Da Silva Santos, Isaac, i Marjorie Nolasco. "Modelagem de Fundo do Estuário do Serinhaém – Ba: Morfologia e Granulometria / Modeling of the bottom of Serinhaém’s estuary, BA: Morphology and Granulometry." Caderno de Geografia 27, nr 49 (2.05.2017): 247. http://dx.doi.org/10.5752/p.2318-2962.2017v27n49p247.
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<p>O presente estudo teve como objetivo elaborar um modelo de distribuição granulométrica e morfologia de fundo do Estuário do Serinhaém em Ituberá-BA. Os procedimentos metodológicos envolveram <em>à priori</em> coleta de sedimentos e dados de profundidade ao longo do estuário. As amostras de sedimentos foram tratadas para análise granulométrica segundo metodologia proposta por Suguio (1973), e posteriormente os dados de sedimento foram tabulados e modulados espacialmente, seguindo o mesmo procedimento que os dados de morfologia de fundo. Observou-se que o estuário do Serinhaém faz parte de um sistema estuarino maior que conflui à Baía de Camamu, cuja morfologia de fundo se destaca pela presença de “degraus”, onde a profundidade aumenta gradualmente em direção a sua foz, mantendo as maiores profundidades entre o centro e a margem norte do estuário. Sua granulometria é predominantemente arenosa com frações de sedimento cascalhosos na sua calha, e ao longo de todo ambiente é caracterizado por áreas de baixios, devido a acumulação de sedimentos.</p><p>O levantamento dessas informações é básico para subsidiar estudos ambientais e auxiliar o planejamento territorial e o manejo dessa área estuarina.</p><p><strong>Palavras–chave:</strong> Sedimentos; Ambientes Costeiros; Estuários; Morfologia de Fundo.</p><p><strong>Abstract </strong></p><p>The aim of this study was to build a model for particle size distribution and bottom morphology in Serinhaém´s estuary from Ituberá, BA. Methodological proceedings implicated a priori to collect sediments and depth data according to the methodology developed by Suguio (1973); after that, sediments data were tabulated and spatially modeled according to the same procedure taken for the data obtained for bottom morphology. It was observed that Serinhaém´s estuary is a part from largest estuarine system which converges in Camamu´s Bay, in whose bottom morphology are noted the presence of “steps”, gradually increasing the depth in direction to the river mouth and keeping the higher depths between the middle and north shore of the estuary. Particle size is basically sandy with gravel sediments in its riverbed and was observed, throughout the entire environment, the presence of shoals due to accumulation of sediments. These results are basic to support environmental studies and to help the territorial planning and management of this estuarine area.</p><p><strong>Keywords</strong>: garbage collectors, recycling, working conditions, Association.</p><p> </p>
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Newton, Gina M., i Brad D. Mitchell. "Egg dormancy in the Australian estuarine-endemic copepods Gippslandia estuarina and Sulcanus conflictus, with reference to dormancy of other estuarine fauna". Marine and Freshwater Research 50, nr 5 (1999): 441. http://dx.doi.org/10.1071/mf98161.
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The presence of dormant life history stages was investigated for the zooplankton of an annually flooding salt-wedge estuary. Such stages are seen as a potential mechanism for population persistence following environmental adversity. Laboratory incubation experiments were conducted on estuarine sediments. As a result, dormant eggs in Australian estuarine-endemic copepods are reported for the first time. Nauplii of the dominant estuarine-endemic calanoids Gippslandia estuarina and Sulcanus conflictus commonly hatched from the sediments. Manipulation of the salinity and temperature of experimental media indicated that temperature was the more important hatching trigger for S. conflictus, and that both high salinity and high temperature were important for G. estuarina. Results of the incubation experiments, including those of ‘conversion’ experiments (i.e. from freshwater to saline conditions or low temperature to high temperature), help to elucidate the type of dormancy characteristic of each species; it appears that S. conflictus may have diapause eggs and G. estuarina may have quiescent eggs, although this is yet to be confirmed. Other estuarine fauna developed from the mud during the incubation experiments, most notably the harpacticoids Onychocamptus chathamensis, an ectinosomatid and Schizopera sp., and the medusa Australomedusa baylii. Ecological and evolutionary consequences of dormancy in these estuarine-endemic zooplankton are briefly discussed.
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Dowson, P. H., J. M. Bubb, T. P. Williams i J. N. Lester. "Degradation of Tributyltin in Freshwater and Estuarine Marina Sediments". Water Science and Technology 28, nr 8-9 (1.10.1993): 133–37. http://dx.doi.org/10.2166/wst.1993.0611.
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The degradation of tributyltin (TBT) in contaminated freshwater and estuarine sediments was investigated for a 330 day period under controlled laboratory conditions. Rates of TBT degradation at different depths were established using regression modelling and revealed TBT half lives ranging from 360-775 d in surficial sediments. There appeared to be little difference in degradation rates between freshwater and estuarine sediments, although a notable increase in TBT half life was evident in TBT spiked sediments. Degradation values suggest that TBT either debutylates to DBT and MBT in aerobic sediments or degrades to DBT which is subsequently desorbed to the overlying water. In anaerobic sediment the half life of TBT was not discernible and appeared to be in the order of tens of years. Biotic processes would seem to be the most important mechanisms for the decomposition of TBT in freshwater and estuarine sediments.
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De Oliveira, Allan De Oliveira. "CARACTERIZAÇÃO SEDIMENTAR E APLICAÇÃO DO DIAGRAMA DE PEJRUP PARA INTERPRETAÇÃO DA DINÂMICA EM UMA ENSEADA ESTUARINA NA LAGOA DOS PATOS/BRASIL / Sedimentary Characterization and Application of Pejrup Diagram to Interpret the Dinamics in a Small Cove of The Lagoa dos Patos/Brazil". Geographia Meridionalis 1, nr 2 (18.12.2015): 363. http://dx.doi.org/10.15210/gm.v1i2.6232.
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A partir da análise dos parâmetros estatísticos dos sedimentos de fundo de uma enseada estuarina e da aplicação do diagrama de Pejrup, foi possível caracterizar os processos dinâmicos e sedimentares que ocorrem em uma pequena enseada da Lagoa dos Patos. Os sedimentos que recobrem o fundo da área estudada são formados por areias finas a muito finas, com presença de material lamoso, preferencialmente silte, em direção à região central e margens da enseada. A hidrodinâmica da área é dominada pela circulação estuarina e correntes fluviais, bem como pela ação dos ventos que influenciam estas correntes. Esses fatores são responsáveis pelo transporte, redistribuição e deposição dos sedimentos na área de estudo.ABSTRACTFrom statistical parameters of the bottom morphology and of the application of the diagram of Pejrup it was possible to characterize the dynamic and sedimentary processes that occur in a small cove of the Lagoa dos Patos. The sediments that recover the bottom of the studied area are formed by fine to very fine sands, with the presence of muddy (silt) in the central region and marginal area. The hydrodynamic of the area is dominated by the estuarine circulation and fluvial currents as well, partly due the action of winds which influence these currents. These factors are responsible for the transport, redistribution and deposition of the sediments in the study area.Keywords: sedimentary characterization; hydrodinamics; estuarine cove.
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Simone, Michelle N., Kai G. Schulz, Joanne M. Oakes i Bradley D. Eyre. "Warming and ocean acidification may decrease estuarine dissolved organic carbon export to the ocean". Biogeosciences 18, nr 5 (16.03.2021): 1823–38. http://dx.doi.org/10.5194/bg-18-1823-2021.
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Abstract. Relative to their surface area, estuaries make a disproportionately large contribution of dissolved organic carbon (DOC) to the global carbon cycle, but it is unknown how this will change under a future climate. As such, the response of DOC fluxes from microbially dominated unvegetated sediments to individual and combined future climate stressors of temperature change (from Δ−3 to Δ+5 ∘C compared to ambient mean temperatures) and ocean acidification (OA, ∼ 2× current CO2 partial pressure, pCO2) was investigated ex situ. Warming alone increased sediment heterotrophy, resulting in a proportional increase in sediment DOC uptake; sediments became net sinks of DOC (3.5 to 8.8 mmol C m−2 d−1) at warmer temperatures (Δ+3 and Δ+5 ∘C, respectively). This temperature response changed under OA conditions, with sediments becoming more autotrophic and a greater sink of DOC (up to 4× greater than under current pCO2 conditions). This response was attributed to the stimulation of heterotrophic bacteria with the autochthonous production of labile organic matter by microphytobenthos. Extrapolating these results to the global area of unvegetated subtidal estuarine sediments, we find that the future climate of warming (Δ+3 ∘C) and OA may decrease estuarine export of DOC by ∼ 80 % (∼ 150 Tg C yr−1) and have a disproportionately large impact on the global DOC budget.
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Charry, Maria P., Vaughan Keesing, Mark Costello i Louis A. Tremblay. "Assessment of the ecotoxicity of urban estuarine sediment using benthic and pelagic copepod bioassays". PeerJ 6 (30.05.2018): e4936. http://dx.doi.org/10.7717/peerj.4936.
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Urban estuarine sediments are sinks to a range of contaminants of anthropogenic origin, and a key challenge is to characterize the risk of these compounds to receiving environments. In this study, the toxicity of urban estuarine sediments was tested using acute and chronic bioassays in the benthic harpacticoid Quinquelaophonte sp., and in the planktonic calanoid Gladioferens pectinatus, two New Zealand copepod species. The sediment samples from the estuary tributary sites significantly impacted reproduction in Quinquelaophonte sp. However, results from one of the estuary sites were not significantly different to those from the tributaries sites, suggesting that chemicals other than trace metals, polycyclic aromatic hydrocarbons and ammonia may be the causative stressors. Sediment elutriate samples had significant effects on reproductive endpoints in G. pectinatus, and on the induction of DNA damage in cells, as shown by the comet assay. The results indicate that sediment contamination at the Ahuriri Estuary has the potential to impact biological processes of benthic and pelagic organisms. The approach used provides a standardized methodology to assess the toxicity of estuarine sediments.
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Almeida, C. Marisa R., Iraide Sáez-Zamacona, Diogo M. Silva, Sabrina M. Rodrigues, Rúben Pereira i Sandra Ramos. "The Role of Estuarine Wetlands (Saltmarshes) in Sediment Microplastics Retention". Water 15, nr 7 (3.04.2023): 1382. http://dx.doi.org/10.3390/w15071382.
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Concerns regarding plastic pollution, especially microplastics, have increased, as they can be present in different environmental compartments, including estuarine areas and saltmarshes. Although saltmarshes are highly vulnerable to different human activities and pressures, they have the ability to trap/retain contaminants in their vegetated sediments. However, there is still little information regarding the role of saltmarshes in microplastic retention. Thus, the present study aims to investigate the capability of an estuarine saltmarsh to trap microplastics by comparing microplastic concentrations in vegetated (saltmarsh) and non-vegetated sediments. Microplastic content from sediment (vegetated and non-vegetated) samples collected at different sampling sites in Lima River estuary was estimated using previously optimised extraction protocols, and the observed particles were then characterised accordingly to their size, colour, shape, and polymer (by FTIR). Water samples were also collected and analysed for their microplastics content to complement MPs characterisation within the estuarine area. Microplastics were detected in all sediment samples, with fibres being the most common type of microplastic found, followed by fragments/particles. Overall, vegetated sediments, especially those of saltmarsh species Juncus maritimus, presented a higher number of plastic items. These results indicated that microplastics tend to be trapped in vegetated sediments, supporting the fact that saltmarshes have a significant influence on the transport, distribution, and accumulation of MPs in estuarine areas.
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Pailles, C., i PW Moody. "Effect of experimental conditions on phosphorus extracted from estuarine and marine sediments". Marine and Freshwater Research 46, nr 2 (1995): 435. http://dx.doi.org/10.1071/mf9950435.
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The effect of the ratio of sediment to extracting solution was determined on the amount of P extracted by the Bray-P1 extractant (0.03 M NH4F in 0.025 M HCl) from 10 estuarine and marine sediments. Phosphorus extracted from the sediments by the Colwell extractant (0.5 M NaHCO3 at pH 8.5) was also determined. Decreasing the ratio of sediment to Bray-P1 extractant from 1 :7 to 1 : 7000 caused a one-hundredfold increase in extractable P. The amount of Bray-P1 extractable P also decreased significantly (P < 0.001) as extraction pH increased, and extraction pH varied between sediments. Sediment CaCO3 content alone could not explain the increase in extracting solution pH (i.e. neutralization of the acid in the extracting solution) that occurred during the extraction period, and the surface area of the CaCO3 may be a factor in determining final extraction pH. Bray-P1 extractable P was not correlated with Colwell extractable P. Because of the effect of the sediments on Bray extractant pH, it is concluded that this extractant is inappropriate for determining the P status of estuarine and marine sediments. The effect of the ratio of sediment to extracting solution on extractable P has implications for determining the P status of suspended sediments. Extra keywords: Bray extractable P, Colwell extractable P
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Priji, V. S., R. Karuppasamy i G. Prasad. "Status of Microplastic Accumulation in Water and Sediments of Selected Estuarine Ecosystem of Southern Kerala, India". UTTAR PRADESH JOURNAL OF ZOOLOGY 44, nr 14 (15.07.2023): 6–16. http://dx.doi.org/10.56557/upjoz/2023/v44i143553.
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Some research assesses the spatial and temporal variations in microplastic pollution in specific ecosystems, such as the estuarine regions of Thiruvananthapuram and Kollam, taking into account its potential effects on the aquatic ecosystem and the lack of information on the abundances of microplastic in estuarine water and sediments. The estuarine environment has raised growing apprehensions over plastic waste smaller than 5 mm in diameter locally and globally. Microplastic pollution in water and sediments of Southern Kerala was monitored at regular intervals from February 2020 through January 2022. During the course of two years, seasonal samples of water and sediment were taken at 16 locations. Microplastics were sorted and labelled based on their material make-up, size, colour, and kind. Polypropylene (PP), polyethylene (PE), polystyrene (PS), and other polymers were found to make up the majority of the microplastics studied. Secondary microplastics with a length of less than 1 mm predominated in both the water and the sediment. Microplastics were more often seen in white, and analysis of the chemical makeup of the particles found in all of the samples revealed a predominance of polyamide. This study aims to conduct a thorough evaluation of microplastic pollution, including its origins and potential risks, in two environmental mediums such as estuarine water and sediments.
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Zhuang, Mei, Edmond Sanganyado, Liang Xu, Jianming Zhu, Ping Li i Wenhua Liu. "High Throughput Sediment DNA Sequencing Reveals Azo Dye Degrading Bacteria Inhabit Nearshore Sediments". Microorganisms 8, nr 2 (9.02.2020): 233. http://dx.doi.org/10.3390/microorganisms8020233.
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Estuaries and coastal environments are often regarded as a critical resource for the bioremediation of organic pollutants such as azo dyes due to their high abundance and diversity of extremophiles. Bioremediation through the activities of azoreductase, laccase, and other associated enzymes plays a critical role in the removal of azo dyes in built and natural environments. However, little is known about the biodegradation genes and azo dye degradation genes residing in sediments from coastal and estuarine environments. In this study, high-throughput sequencing (16S rRNA) of sediment DNA was used to explore the distribution of azo-dye degrading bacteria and their functional genes in estuaries and coastal environments. Unlike laccase genes, azoreductase (azoR), and naphthalene degrading genes were ubiquitous in the coastal and estuarine environments. The relative abundances of most functional genes were higher in the summer compared to winter at locations proximal to the mouths of the Hanjiang River and its distributaries. These results suggested inland river discharges influenced the occurrence and abundance of azo dye degrading genes in the nearshore environments. Furthermore, the azoR genes had a significant negative relationship with total organic carbon, Hg, and Cr (p < 0.05). This study provides critical insights into the biodegradation potential of indigenous microbial communities in nearshore environments and the influence of environmental factors on microbial structure, composition, and function which is essential for the development of technologies for bioremediation in azo dye contaminated sites.
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Simpson, Stuart L., Louisa Rochford i Gavin F. Birch. "Geochemical influences on metal partitioning in contaminated estuarine sediments". Marine and Freshwater Research 53, nr 1 (2002): 9. http://dx.doi.org/10.1071/mf01058.
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Stormwater runoff has resulted in heavy metal contamination throughout much of the Port Jackson estuary, Sydney, Australia. Metal partitioning was investigated in the benthic estuarine sediments of Iron Cove, an off-channel embayment of Port Jackson. Contamination was greatest near the stormwater canal, where sediments were anoxic and contained high concentrations of sulfide in the porewater. Away from the canal a layer of non-cohesive, sub-oxic surficial sediment containing high dissolved iron was found overlaying a more cohesive substratum. At all sites, porewater Cd, Cu, Ni, Pb and Zn were <2.5 g L–1, and negligible metal release was observed upon sediment resuspension. According to water quality guidelines, the ecological risk posed by dissolved metals from the Iron Cove sediments is low. Estimated fluxes of Cd, Cu, Ni, Pb and Zn from the sediments were calculated to be <0.2 mol m–2 day–1. The rapid oxidation then hydrolysis of iron(II) in porewaters caused a drop in pH and the formation of iron hydroxide precipitate. These processes may affect dissolved metal concentrations; hence, oxidation of samples must be avoided during sampling and extraction procedures. Sediment-bound zinc was the metal most easily mobilized.
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Li, Haifu, Lifeng Li, Fangli Su, Tieliang Wang i Peng Gao. "The Periodic Response of Tidal Flat Sediments to Runoff Variation of Upstream Main River: A Case Study in the Liaohe Estuary Wetland, China". Water 12, nr 1 (22.12.2019): 61. http://dx.doi.org/10.3390/w12010061.
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(1) Background: To reveal the intrinsic relationship between the tidal flat sediments in an estuary wetland and the runoff from the upstream river. This research was conducted in the tidal flats of the Liaohe estuary wetland. (2) Methods: The 137Cs and 210Pb dating technique was used to reconstruct the time correspondence between tidal flat sediments and runoff, and the periodic response was explored between the changes in the tidal flat sediments and runoff based on the spectrum analysis method. (3) Results: The average sedimentation rate in the tidal flat was 2.24 cm·year−1 during the past 50 years. The amount of fine sediment particles deposited on the estuary tidal flat was directly related to the amount of sediments transported by the river and inversely proportional to the ability of rivers to transport fine matter. The high frequency reproduction cycle of 14–15 years in the flood season flow and 5–6 years in the annual sediment discharge of the Liaohe River correspond to the high and low frequency reproduction cycles of the median size of sediments in Liaohe estuarine wetland tidal flats. (4) Conclusions: The research clarified the hydrological constraints of the action law between Liaohe River runoff and the estuarine sediments. The periodic response between Liaohe River runoff and the sediment was established.
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Bartoli, Marco, Sara Benelli, Monia Magri, Cristina Ribaudo, Paula Carpintero Moraes i Giuseppe Castaldelli. "Contrasting Effects of Bioturbation Studied in Intact and Reconstructed Estuarine Sediments". Water 12, nr 11 (7.11.2020): 3125. http://dx.doi.org/10.3390/w12113125.
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Macrofauna can produce contrasting biogeochemical effects in intact and reconstructed sediments. We measured benthic fluxes of oxygen, inorganic carbon, and nitrogen and denitrification rates in intact sediments dominated by a filter and a deposit feeder and in reconstructed sediments added with increasing densities of the same organisms. Measurements in reconstructed sediments were carried out 5 days after macrofauna addition. The degree of stimulation of the measured fluxes in the intact and reconstructed sediments was then compared. Results confirmed that high densities of bioturbating macrofauna produce profound effects on sediment biogeochemistry, enhancing benthic respiration and ammonium recycling by up to a factor of ~3 and ~9, respectively, as compared to control sediments. The deposit feeder also increased total denitrification by a factor of ~2, whereas the filter feeder activity did not stimulate nitrogen removal. Moreover, the effects of deposit feeders on benthic fluxes were significantly higher (e.g., on respiration and ammonium recycling) or different (e.g., on denitrification) when measured in intact and reconstructed sediments. In intact sediments, deposit feeders enhanced the denitrification coupled to nitrification and had no effects on the denitrification of water column nitrate, whereas in reconstructed sediments, the opposite was true. This may reflect active burrowing in reconstructed sediments and the long time needed for slow growing nitrifiers to develop within burrows. Results suggest that, in bioturbation studies, oversimplified experimental approaches and insufficient preincubation time might lead to wrong interpretation of the role of macrofauna in sediment biogeochemistry, far from that occurring in nature.
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Wang, Guoqiang, Tianjian Yang, Mengmeng Zhao, Ting Li, Cai Zhang, Qinghua Chen, Xinyue Wen i Lirong Dang. "Natural Nitrogen-Bearing and Phosphorus-Bearing Nanoparticles in Surface Sediments of the Pearl River Estuary, China: Implications for Nitrogen and Phosphorus Cycling in Estuarine and Coastal Ecosystems". Sustainability 15, nr 19 (27.09.2023): 14301. http://dx.doi.org/10.3390/su151914301.
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Eutrophication creates multiple environmental problems, threatening the ecological security and sustainability of estuarine and coastal ecosystems worldwide. Key nutrients of concern are nitrogen (N) and phosphorus (P), which are the main controls in eutrophication. Considering that sediments are inseparable sinks of N and P, concern has grown regarding the forms in which N and P occur in the surface sediments of estuaries and coastal areas. Nonetheless, studies on the natural N-bearing or P-bearing nanoparticles in estuarine and coastal sediments have rarely been reported. Herein, the surface sediments (0–5 cm) of the Pearl River Estuary in China were collected and subjected to analysis. Using high-resolution transmission electron microscopy (HR-TEM) analysis, numerous natural N-bearing and P-bearing nanoparticles were observed. The results revealed that there are some differences in the occurrence forms of N and P in nanoparticles, suggesting that N and P could be adsorbed by nanoparticles of minerals such as hematite, goethite, muscovite, anorthite and quartz in estuarine and coastal environments, and further form N-bearing and P-bearing nanoparticles. These nanoparticles contained small amounts of N (1.52–3.73 wt%) and P (0.22–1.12 wt%), and were mainly single crystal or polycrystalline in form, with sizes ranging from 10 nm × 50 nm to 250 nm × 400 nm. In addition, P was shown to exist in the form of Ca and Fe phosphate nanoparticles in the estuarine sediments. The Ca and Fe phosphate nanoparticles had higher phosphorus content (5.02–9.97 wt%), mainly amorphous, with sizes ranging from 50 nm × 120 nm to 250 nm × 400 nm. Moreover, N-bearing and P-bearing nanoparticles could influence the migration, precipitation and release processes of N and P, and play a certain role in the N-cycling and P-cycling of estuarine and coastal ecosystems. Furthermore, we explored the role of N-bearing and P-bearing nanoparticles in the N-cycling and P-cycling in estuarine and coastal ecosystems. Thus, this study could provide new ideas for water environment management and other related research fields.
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Rainbow, P. S., B. D. Smith i M. C. Casado-Martinez. "Biodynamic modelling of the bioaccumulation of arsenic by the polychaete Nereis diversicolor". Environmental Chemistry 8, nr 1 (2011): 1. http://dx.doi.org/10.1071/en10089.
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Environmental context Models that explain the uptake and bioaccumulation of an element in an aquatic ecosystem are valuable for predicting its potential ecotoxicity in coastal areas. Arsenic is a toxic element that is strongly adsorbed to sediments, offering a potential risk to deposit-feeding invertebrates, and ultimately to consumers higher up coastal food chains. This study uses biodynamic modelling to predict the uptake and accumulation of arsenic from water and sediment in a deposit-feeding polychaete worm that is a major source of food to fish and wading birds in estuaries. Abstract Arsenic (AsV) uptake and bioaccumulation from water and ingested sediment by the deposit-feeding polychaete Nereis diversicolor has been investigated using biodynamic modelling. Worms accumulated As from solution linearly at dissolved concentrations from 2 to 20 µg L–1 (uptake rate constant 0.057 l g–1 day–1 at 10°C, 16-psu salinity), and the As assimilation efficiency from ingested sediment was 28.9%. Efflux rate constants of As taken up from water and ingested sediment were 0.0488 and 0.0464 day–1 and did not differ significantly. Sediment As concentrations, ranging from very high to low, were measured at eight estuarine sites, and the model predicted accumulated As concentrations in resident N. diversicolor. Comparisons of predicted against independently measured As concentrations in locally collected worms showed that the model generally performed well, highlighting the potential of biodynamic modelling in predicting the uptake and therefore ecotoxicity of As in estuarine sediments.
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Meadows, P. S., i A. Tufail. "Bioturbation, microbial activity and sediment properties in an estuarine ecosystem". Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 90 (1986): 129–42. http://dx.doi.org/10.1017/s0269727000004930.
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SynopsisMacrobenthic bioturbation and microbial activity can have major ecological effects on present day marine sediments some of which are also seen in the fossil record. The coastal and estuarine sediments in the Clyde Estuary area are described. They contain very high densities of benthic macroorganisms and microorganisms. These organisms have dramatic effects on the physical and chemical properties of sediments, and field and laboratory studies have shown that many geotechnical and geochemical properties of sediments are dictated by them. The effects can be on a microscale of a few millimetres horizontally or vertically (micro-spatial variation), or can have large scale consequences over hundreds of metres (macro-spatial variation).Sediment stability (shear strength and critical erosion velocity), permeability and particle sedimentation are all altered by macro-invertebrate bioturbation or microbial activity, and many chemical properties such as Eh and pH may be influenced in a similar manner.Biological activity may therefore play a major role in modifying sediment geotechnics and early sediment diagenesis. It also has direct relevance to the siting of man-made structures on the sea-bed and to sediment stability and transport in estuaries.In situseeding experiments may lead to biological control and manipulation of these most important field phenomena.
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Lupker, Maarten, Christian France-Lanord i Bruno Lartiges. "Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes". Earth Surface Dynamics 4, nr 3 (12.08.2016): 675–84. http://dx.doi.org/10.5194/esurf-4-675-2016.
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Abstract. Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga–Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga–Brahmaputra is estimated ca. 6.5 meq 100 g−1. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28 × 109 mol yr−1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga–Brahmaputra is responsible for an additional Ca2+ flux of 23 × 109 mol yr−1, while ca. 27 × 109 mol yr−1 of Na+, 8 × 109 mol yr−1 of Mg2+ and 4 × 109 mol yr−1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na+ flux, 8 % of the dissolved K+ flux and 4 % of the Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment–seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and its main effect is the sequestration of a significant fraction of the riverine Na flux to the oceans. The limited exchange fluxes of the Ganga–Brahmaputra relate to the lower than average CEC of its sediment load that do not counterbalance the high sediment flux to the oceans. This can be attributed to the nature of Himalayan river sediment such as low proportion of clays and organic matter.
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Li, C., CE Reimers i JW Chapman. "Microbiome analyses and presence of cable bacteria in the burrow sediment of Upogebia pugettensis". Marine Ecology Progress Series 648 (27.08.2020): 79–94. http://dx.doi.org/10.3354/meps13421.
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We utilized methods of sediment cultivation, catalyzed reporter deposition-fluorescence in situ hybridization, scanning electron microscopy, and 16s rRNA gene sequencing to investigate the presence of novel filamentous cable bacteria (CB) in estuarine sediments bioturbated by the mud shrimp Upogebia pugettensis Dana and also to test for trophic connections between the shrimp, a commensal bivalve (Neaeromya rugifera), and the sediment. Agglutinated sediments from the linings of shrimp burrows exhibited higher abundances of CB compared to surrounding suboxic and anoxic sediments. Furthermore, CB abundance and activity increased in these sediments when they were incubated under oxygenated seawater. Through core microbiome analysis, we found that the microbiomes of the shrimp and bivalve shared 181 taxa with the sediment bacterial community, and that these shared taxa represented 17.9% of all reads. Therefore, bacterial biomass in the burrow sediment lining is likely a major food source for both the shrimp and the bivalve. The biogeochemical conditions created by shrimp burrows and other irrigators may help promote the growth of CB and select for other dominant members of the bacterial community, particularly a variety of members of the Proteobacteria. These associations give new understanding to the ecology of a burrowing crustacean that is common, but in decline, throughout intertidal mudflats of Northeastern Pacific estuaries.
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Li, Xiaojun, Yanping Zhao, Guoxiang Wang, Ruiming Han, Xinyi Dang, Zhuoran Li, Jiafeng Ren i Chenxi Gao. "Sedimentary nitrogen fractions and source assignment from different inflows to a receiving lake". Water Supply 20, nr 5 (25.05.2020): 1950–64. http://dx.doi.org/10.2166/ws.2020.106.
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Abstract The spatial distribution of the sediment nitrogen in ten typical estuaries of Lake Taihu was determined. A simple quantitative estimation model and principal component analysis (PCA) method were applied to find the source and major factors of estuarine sediment nitrogen loading. The average concentrations of total nitrogen (TN), organic nitrogen (Org-N), ammonium nitrogen and nitrate-nitrogen in the sediments of the ten estuaries were 1315.5, 1220.1, 82.53 and 6.45 mg/kg, with the organic fraction dominating. Results showed a significant difference for the TN concentration in sediments of different estuaries, which was mainly caused by geographical location, land use type and vegetation restoration measures. An important result was that sediment nitrogen in 80% of the estuaries was mainly originated from autochthonous algae and presettled organic matter, although there has been continuous pollution input from inflow rivers. The source estimation results found that the autochthonous aquaculture excretion, algae and hydrophyte debris and buried biodetritus accounted for 58.9% of the total nitrogen loading, which dominated the nitrogen sources compared with the pollution input. In addition, the PCA method was used to find that phosphorus loading and redox conditions were the major limiting factors affecting the distribution of inorganic and , respectively.
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Hasan, Ozren, Natalia Smrkulj, Slobodan Miko, Dea Brunović, Nikolina Ilijanić i Martina Šparica Miko. "Integrated Reconstruction of Late Quaternary Geomorphology and Sediment Dynamics of Prokljan Lake and Krka River Estuary, Croatia". Remote Sensing 15, nr 10 (16.05.2023): 2588. http://dx.doi.org/10.3390/rs15102588.
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The upper part of the Krka River estuary and Prokljan Lake are a specific example of a well-stratified estuarine environment in a submerged river canyon. Here, we reconstructed the geomorphological evolution of the area and classified the data gathered in the study, integrating multibeam echosounder data, backscatter echosounder data, side-scan sonar morpho-bathymetric surveys, and acoustic sub-bottom profiling, with the addition of ground-truthing and sediment analyses. This led to the successful classification of the bottom sediments using the object-based image analysis method. Additional inputs to the multibeam echosounder data improved the segmentation of the seafloor classification, geology, and morphology of the surveyed area. This study uncovered and precisely defined distinct geomorphological features, specifically submerged tufa barriers and carbonate mounds active during the Holocene warm periods, analogous to recent tufa barriers that still exist and grow in the upstream part of the Krka River. Fine-grained sediments, classified as estuarine sediments, hold more organic carbon than coarse-grained sediments sampled on barriers. A good correlation of organic carbon with silt sediments allowed the construction of a prediction map for marine sedimentary carbon in this estuarine/lake environment using multibeam echosounder data. Our findings highlight the importance of additional inputs to multibeam echosounder data to achieve the most accurate results.
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Defew, E. C., T. J. Tolhurst i D. M. Paterson. "Site-specific features influence sediment stability of intertidal flats". Hydrology and Earth System Sciences 6, nr 6 (31.12.2002): 971–82. http://dx.doi.org/10.5194/hess-6-971-2002.
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Abstract. The factors that influence the sediment stability and the transport of estuarine mudflats are not yet fully understood but knowledge of them is essential in coastal engineering applications and pollution ecology studies. The suggestion that variation in predictive models of sediment stability might be due to site-specific characteristics is investigated using data from four estuarine mudflats (Eden Estuary, Scotland, the Biezelingsche Ham, Zandkreek, and Molenplaat mudflats in The Netherlands). These estuaries differ in their environmental conditions, macrofaunal species composition and local features (e.g. Enteromorpha mats, migratory biofilms). Stable and unstable sediments were compared, and mean chlorophyll-a concentrations and granulometry of the sediments were significantly different between the two groups. Step-wise multiple linear regressions were applied to the sediment stability data of all sites to establish the influences on erosion threshold of microphytobenthic biomass, water content, granulometry, organic carbon content and the abundance of dominant macrofaunal species. The stability of each site was influenced by different factors. Sediment stability of the Eden Estuary was affected by the Enteromorpha bloom; Biezelingsche Ham was influenced by the highly migratory nature of the diatom biofilms and the abundance of Corophium volutator; the polychaete worm Arenicola marina had a net negative effect on sediment stability of the Zandkreek; and the Molenplaat was influenced by microphytobenthic biomass. This research highlights the need for site-specific calibration of models and suggests that a universal proxy parameter for sediment stability is unlikely to be obtained. Keywords: sediment stability; erosion threshold; cohesive strength meter; microphytobenthos; Enteromorpha spp.
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Lubis, Ali Arman. "Instrumental Neutron Activation Analysis (INAA) of Cisadane Estuarine Sediments". Jurnal Natur Indonesia 10, nr 1 (4.05.2018): 58. http://dx.doi.org/10.31258/jnat.10.1.58-65.
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Nuclear analytical technique instrumental neutron activation analysis was employed for the multielemental analysis of sediments collected from Cisadane estuary. This analytical technique provides concentration of 20 elementswhich consist of heavy metals and rare earth elements simultaneously. Two sediments cores were collected using core sampler for determining the distribution of all elements in the depth profiles of sediments. Sediment cores were subdivided into 2 cm increment, dried and sent to reactor for irradiation using thermal flux of ?1013 neutrons.cm-2.s-1 for 20 minutes in Research Reactor Siwabessy, National Nuclear Energy Agency (BATAN), Serpong. Irradiated samples were measured using a multichannel analyzer (MCA) gamma spectrometer coupled with high purity germanium detector. Analysis of particle size was done since uptake of heavy metals by sediments is particle-size dependent. The results are presented and discussed.
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Moles, N. R., S. M. Betz, A. J. McCready i P. J. Murphy. "Replacement and authigenic mineralogy of metal contaminants in stream and estuarine sediments at Newtownards, Northern Ireland". Mineralogical Magazine 67, nr 2 (kwiecień 2003): 305–24. http://dx.doi.org/10.1180/0026461036720103.
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Tidal mudflats are locally enriched in heavy metals at the head of Strangford Lough in Northern Ireland, where drainage from the hinterland enters the sea lough via a tidal canal in an urban area. To characterize the metallic contaminants and investigate their provenance, heavy particles separated from stream, canal and estuarine sediments were analysed by electron microprobe and laser Raman microspectroscopic methods. Potential metal sources are mineralization in the catchment area and industrial or domestic pollution. Anthropogenic particles include metallic grains, alloys and compounds of Pb, Zn, Cu, Fe, Cr and Sn. Alteration of metallic particles includes de-zincification of brass in freshwater sediment and replacement of Cu wire by covellite in brackish to marine sediment. Mobility of Cu, Fe and S in canal and estuarine sediments is indicated by the authigenic growth of framboidal Fe sulphide on oxide substrates and of chalcopyrite rims on covellite. Intricate colloform and platy crystalline textures suggest a cyclical deposition of covellite and chalcopyrite under conditions of varying redox and salinity. Lead and Cr mobility in the contaminated estuarine sediment is shown by the authigenic formation on Pb-rich substrates of heterogeneous Pb- and Cr-rich sulphate-phosphate compounds and Pb-oxychlorides.
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Pita, Ana Laura, Luis Giménez, Noelia Kandratavicius, Pablo Muniz i Natalia Venturini. "Benthic trophic status of aquatic transitional environments with distinct morphological and dynamic characteristics on the south-western Atlantic coast". Marine and Freshwater Research 68, nr 11 (2017): 2028. http://dx.doi.org/10.1071/mf16284.
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The benthic trophic status of Uruguayan coastal estuarine habitats (permanently open estuaries and open or closed coastal lagoons) was evaluated, twice in 1 year and at different spatial scales, using the amount and biochemical composition of the sedimentary organic matter. Nested hierarchical ANOVAs were applied to evaluate differences at the habitat level, among sites for each type of estuarine habitat (three estuaries and three lagoons) and between sectors located at different distances from the sea (inner v. outer sectors). Morphological and hydrodynamic differences between the two types of habitats explained site-to-site variations in eutrophic conditions in the open or closed coastal lagoons and meso-oligotrophic conditions in permanently open estuaries. These differences followed the patterns found for sediment grain size, with inner sectors (lower-energy areas) favouring the accumulation of finer sediments and higher amounts of degraded–detrital organic matter. In autumn, biochemical parameters indicated the dominance of aged and more degraded organic matter, with both types of habitats having a low nutritional value no matter which sector was considered. By contrast, in spring, biochemical composition showed the prevalence of fresh and more labile sedimentary organic matter with a high food value, especially in the outer sectors.
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Cesar, Augusto, Camilo Dias Seabra Pereira, Aldo Ramos Santos, Denis Moledo de Sousa Abessa, Nuria Fernández, Rodrigo Brasil Choueri i Tomaz Angel DelValls. "Ecotoxicological assessment of sediments from the Santos and São Vicente estuarine system- Brazil". Brazilian Journal of Oceanography 54, nr 1 (marzec 2006): 55–63. http://dx.doi.org/10.1590/s1679-87592006000100005.
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Sediments represent an important repository of pollutants and a source of contamination for the aquatic food web. Toxicity tests using amphipods as test-organisms have been employed in the assessment of marine and estuarine sediments, together with chemical analyses. The present work aimed to evaluate the quality of sediments from six stations situated in the Santos and São Vicente Estuarine and Harbour System (São Paulo - Brazil) using acute whole sediment toxicity tests with amphipods (Tiburonella viscana) and chemical analyses of metals, PCB's, and PAH's. Other sediment parameters, such as organic carbon and grain size distribution were also analysed. Higher contamination levels were observed in the internal portion of the estuary, where Santos harbour and the industrial zone are located. The toxicity tests showed significant adverse results for most of the samples tested, and the sediments from the internal portion of the estuary presented the highest toxicity. The principal component analyses (PCA) indicated a close relationship between sediment contamination and toxicity. Positive correlation of these factors in the samples studied was used to establish the ranges of the chemical concentrations associated with adverse effects. Such ranges allowed the estimation of preliminary effect threshold values for sediment contamination, by means of multivariate analysis. These suggested values are: Cu, 69.0; Pb, 17.4; Zn, 73.3 (mg.kg-1); PAHs, 0.5 (mg.kg-1) and PCBs, 0.1 (µg.kg-1).
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Gomes, Vando J. C., Nils E. Asp, Eduardo Siegle, José Diego Gomes, Ariane M. M. Silva, Andrea S. Ogston i Charles A. Nittrouer. "Suspended-Sediment Distribution Patterns in Tide-Dominated Estuaries on the Eastern Amazon Coast: Geomorphic Controls of Turbidity-Maxima Formation". Water 13, nr 11 (1.06.2021): 1568. http://dx.doi.org/10.3390/w13111568.
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In tide-dominated estuaries, maximum-turbidity zones (MTZs) are common and prominent features, characterized by a peak in suspended-sediment concentration (SSC) associated with estuarine processes. The Brazilian Amazon coast includes many estuaries, experiencing macrotidal conditions. MTZs are expected to occur and are crucial for sediment delivery to the longest continuous mangrove belt of the world. The area is under influence of the Amazon River plume (ARP), the main SSC source, as local rivers do not deliver substantial sediment supply. To assess the processes that allow the ARP to supply sediment to the estuaries and mangrove belt along the Amazon coast, the results from previous individual studies within five Amazon estuaries (Mocajuba, Taperaçu, Caeté, Urumajó and Gurupi) were compared with regards to SSC, salinity, morphology and tidal propagation. This comparison reinforces that these estuaries are subject to similar regional climate and tidal variations, but that their dynamics differ in terms of distance from the Amazon River mouth, importance of the local river sediment source, and morphology of the estuarine setting. The Urumajó, Caeté and Gurupi are hypersynchronous estuaries where perennial, classic MTZs are observed with SSC > 1 g·L−1. This type of estuary results in transport convergence and MTZ formation, which are suggested to be the main processes promoting mud accumulation in the Amazonian estuaries and therefore the main means of mud entrapment in the mangrove belt. The Mocajuba and the Taperaçu estuaries showed synchronous and hyposynchronous processes, respectively, and do not present classic MTZs. In these cases, the proximity to the ARP for the Mocajuba and highly connected tidal channels for the Taperaçu estuary, assure substantial mud supply into these estuaries. This study shows the strong dependence of the estuaries and mangrove belt on sediment supply from the ARP, helping to understand the fate of Amazon River sediments and providing insights into the mechanisms providing sediment to estuaries and mangroves around the world, especially under the influence of big rivers.
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Amano, Koji, i Takehiko Fukushima. "On the Longitudinal and Vertical Changes in Lake Estuarine Sediments". Water Science and Technology 20, nr 6-7 (1.06.1988): 143–53. http://dx.doi.org/10.2166/wst.1988.0198.
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In order to obtain environmental information about lake water and watersheds, the vertical and longitudinal distributions of physical and chemical properties in lake sediments were investigated. The concentrations of several substances (e.g., nutrients, metals, and chemicals) in the sediments were determined at fifty sampling sites in sixteen shallow lakes in Japan. The vertical profiles of particle size, particle organic carbon, particle organic nitrogen, total phosphorus, some metals (Ti, Mn, Fe, Zn, and Cu), and LAS were analysed. Various sediment properties, such as the sedimentation conditions and the redox conditions, were related to the vertical profiles observed, and traces of historical changes in the water and watersheds were found in the sediments. Longitudinal changes in the sediments between the mouths of the rivers and the deepest points of the lakes were clearly observed, and it was expected that these changes would correlate with one of the estuarine characteristics since they reflect the spatial variation in average composition of the particulate matter and in the average water quality. Some significant relationships between the lake sediments and the lake or watershed type were observed, indicating the possibility that lake sediments may be one of the most important indices for understanding lake environments.
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Dubar, Michel, i Edward J. Anthony. "Holocene Environmental Change and River-Mouth Sedimentation in the Baie des Anges, French Riviera". Quaternary Research 43, nr 3 (maj 1995): 329–43. http://dx.doi.org/10.1006/qres.1995.1039.
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AbstractRiver mouths on the steep, high-relief coast of the French Riviera exhibit thick sequences of Holocene marine, estuarine, deltaic, and river channel-floodplain sediments that overlie basal fluvial Pleistocene gravel. Gravel is uncommon in most of the early to middle Holocene aggradational-progradational marine, estuarine, deltaic sediments, despite an ample supply from rock units in the steep adjoining uplands. River-mouth gravel is common only in late Holocene river channels and in barrier beaches perched on finer-grained nearshore sediments. Neither downslope grain-size fining on alluvial fans nor sediment stacking patterns during sea-level (base-level) rise readily account for the lack of early to middle Holocene gravel in the river-mouth sediment wedges. Holocene sea-level rise led to the storage of fine-grained sediments in shallow marine, estuarine, and deltaic environments in the present coastal zone. We infer that humid temperate conditions, a dense forest cover, landscape stabilization, and a regular quiescent river flow regime associated with the Atlantic climatic optimum limited gravel supply in the adjoining catchments and gravel entrainment downstream during the early Holocene. Sea-level stabilization in the middle and late Holocene coincided with a marked change in bioclimatic conditions toward the present Mediterranean-type regime, which is characterized by a less dense forest cover, soil erosion, and episodic catastrophic floods. The late Holocene was thus a time of downstream bedload channel aggradation, fine-grained floodplain and paludal sedimentation, and seaward flushing of clasts leading to the formation and consolidation of the gravel barrier beaches that bound the rivermouths and embayments.
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Mariano, Dante Luís Silva, i Francisco Barros. "Intertidal benthic macrofaunal assemblages: changes in structure along entire tropical estuarine salinity gradients". Journal of the Marine Biological Association of the United Kingdom 95, nr 1 (15.11.2014): 5–15. http://dx.doi.org/10.1017/s002531541400126x.
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Spatial variation in the structure of macrobenthic assemblages on intertidal flats is known to be related to different environmental variables. Most of the studies have observed that along the estuarine gradient, salinity is the most important variable driving the patterns of the macrobenthic assemblages. However, the great majority of studies have been done on single estuarine systems in temperate regions. We investigated the relationship between the macrobenthic assemblages in intertidal habitats and the environmental variables along three tropical estuaries. From lower to upper estuarine regions we sampled benthic macrofauna, salinity and sediments. The structure of the benthic assemblages was primarily related to salinity. There was a decrease in the number of taxa from the upper to the lower estuarine regions, indicating important deviation from Remane's model of estuarine diversity. There were important similarities of taxa abundance along different estuarine salinity gradients which can be properly tested in other tropical and temperate regions. We advocate that in order to adopt general and robust management practices it is essential to identify broad patterns and general rules governing estuarine systems.
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Marsden, Islay D., i Carol H. T. Wong. "Effects of sediment copper on a tube-dwelling estuarine amphipod, Paracorophium excavatum". Marine and Freshwater Research 52, nr 7 (2001): 1007. http://dx.doi.org/10.1071/mf00139.
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Amphipods, Paracorophium excavatum, were exposed for 10 days to copper-spiked sediments in the concentration range 3–84 µg g –1 dry wt of sediment. Percent emergence was low, ranging from 0.18% to 2.1%, but increased with exposure time and with copper concentration. Amphipod mortality increased with exposure time and sediment copper concentration, following a linear relationship; the Cu 10-day LC 50 value was 55 µg g –1 . Mortality was <5% in the control (natural) sediment containing 3µg g–1 copper. >85% of surviving amphipods reburied themselves within 1 h, and therefore this behaviour was not a good discriminator for potentially toxic sediments. The concentration of copper within the whole-body tissues of P. excavatum (µg Cu g –1 ) was mostly independent of dry body weight within the range 0.12–0.37 mg. Average copper concentrations within the tissues ranged from 169 to 490 µg Cu g –1 , with higher variability in amphipods exposed to sediment copper concentrations of 16 and 32 µg g –1 . Amphipod tissue copper concentration increased with sediment copper concentration. It was concluded that P. excavatum is a suitable indicator species for use in ecotoxicological tests for potentially toxic marine and estuarine sediments.
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Duarte, Bernardo, Edite Manjate i Isabel Caçador. "Baseline Survey on the Accumulation of Microdebris in the Intertidal Sediments of a Reference Estuarine System (Mira Estuary, Portugal)". Oceans 1, nr 2 (30.04.2020): 47–55. http://dx.doi.org/10.3390/oceans1020005.
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Microdebris are nowadays a new emerging threat to marine ecosystems. Estuarine systems are considered sinks of contaminants, retaining these in their sediments. Nevertheless, baseline studies are essential, especially in reference estuarine systems such as the Mira Estuary, in order to establish reference conditions for other ecosystem assessment studies. Microdebris were extracted by density separation with saturated NaCl from sediment samples collected at the bare intertidal area of the lower sector of the Mira Estuary. Sediment vertical profiles showed a high abundance of microdebris, dominated by spherical and fibre-like microdebris, but also presenting metallic and uncategorized items. It was possible to observe that microdebris accumulation had its maximum concentration at a depth of 10 cm, indicating a recent increase in its usage and prevalence on this estuarine system. Comparing the item density from this work with previous studies on other aquatic ecosystems, it was found that the sediments analysed here present a very high concentration of microdebris. Although the Mira Estuary has been considered as a reference condition for the classical chemical contaminant descriptors considered in the Water Framework Directive, the data here presented indicate that this concept should be revisited adding microdebris contamination.
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Garzanti, Eduardo, Giovanni Vezzoli, Sergio Andò, Mara Limonta, Laura Borromeo i Christian France-Lanord. "Provenance of Bengal Shelf Sediments: 2. Petrology and Geochemistry of Sand". Minerals 9, nr 10 (19.10.2019): 642. http://dx.doi.org/10.3390/min9100642.
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The Bangladesh lowlands are traversed by the largest sediment flux on the planet. Detritus generated mostly in Himalayan highlands and conveyed through the Ganga–Brahmaputra rivers and Meghna estuary reaches the Bay of Bengal, where it forms a composite deltaic system. This study integrates the vast existing database on Ganga–Brahmaputra sediments of all grain sizes from clay to sand with new petrographic, mineralogical, and geochemical data on estuarine and shallow-marine sands. A large spectrum of compositional signatures was used to: (i) assess the relative supply of the Ganga and Brahmaputra rivers to estuarine and shelfal sediments; (ii) define the compositional variability of estuarine sediments and the impact exerted by hydraulic sorting and climate-related chemical weathering on provenance signals; (iii) define the compositional variability of shelf sediments and the potential hydrodynamic segregation of fast-settling heavy minerals in coastal environments and of slow-settling platy micas on low-energy outer-shelf floors; (iv) consider the potential additional mud supply from the western subaerial part of the delta formerly built by the Ganga River; and (v) draw a preliminary mineralogical comparison between fluvio-deltaic sediments and turbidites of the Bengal–Nicobar deep-sea fan, thus tracing sediment dispersal across the huge sedimentary system extending from Tibet to the equatorial Indian Ocean. All investigated mineralogical and geochemical parameters, as well as Sr and Nd isotope ratios and clay–mineral assemblages, showed a clear prevalence in sediment supply from the Brahmaputra (60–70%) over the Ganga (30–40%). Heavy-mineral suites and Sr and Nd isotope fingerprints of Bengal shelf sediments are nearly identical to those of the Brahmaputra River and Meghna estuary, also because the Brahmaputra carries almost twice as many Ca-plagioclase grains and heavy minerals including epidote than the Ganga, and these minerals control the large majority of the Sr and Nd budgets. The experience gained in modern settings can be directly extrapolated only to the recent past, because sediments older than the late Pleistocene and buried more than a few hundred meters begin to lose less durable ferromagnesian minerals by selective chemical dissolution, which makes quantitative estimates progressively less robust in more deeply buried older strata.
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Rocha, Gustavo Rodrigues da, i Helenice Vital. "MORPHOLOGICAL CHARACTERIZATION OF THE POTENGI RIVER ESTUARINE SYSTEM, NATAL (BRAZIL)". Revista Brasileira de Geofísica 33, nr 1 (1.03.2015): 141. http://dx.doi.org/10.22564/rbgf.v33i1.649.
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ABSTRACT. This study mapped the Potengi estuary riverbed (Natal-RN), located in northeastern Brazil, using high-resolution geophysics (single beam and side-scan sonar) associated with sediment samples. The imaging of subaqueous features allowed to identify the bedforms and submerged rocky outcrops. Four main groups of bedforms were identified: large 2-D and 3-D dunes, ripples and flat bottom, as well as rocky outcrops. Rocky outcrops were correlated to Barreiras Formation and beachrocks. The estuarine channel is filled mainly by Holocene sandy sediments in the main channel ranging from well-sorted to sorted grains, and silty sediments in the river margins. The integration and analysis of these results contribute to a better understanding of tropical estuaries.Keywords: high-resolution geophysics, bathymetry, side scan sonar, bed forms.RESUMO. Este estudo teve como principal objetivo o mapeamento do substrato do estuário do Rio Potengi (Natal-RN), localizado no Nordeste do Brasil, utilizando geofísica de alta resolução (dados batimétricos monofeixe e sonográficos) associada à amostragem de sedimentos. O imageamento das feições subaquáticas permitiu a identificação das formas de leito, bem como de afloramentos rochosos submersos. Foram identificados quatro grupos principais de formas de leito: dunas 2D e 3D de grande porte, ripples e fundo plano, além de afloramentos rochosos. Quanto à composição dos sedimentos holocênicos que preenchem o rio, estes são predominantemente arenosos (canal principal), variando de selecionados a bem selecionados, por vezes siltosos (margens do rio). Os resultados obtidos contribuem para uma melhor compreensão dos estuários tropicais.Palavras-chave: geofísica de alta resolução, batimetria, imageamento sonográfico, formas de leito.
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Ezcurra, E., E. Barrios, P. Ezcurra, A. Ezcurra, S. Vanderplank, O. Vidal, L. Villanueva-Almanza i O. Aburto-Oropeza. "A natural experiment reveals the impact of hydroelectric dams on the estuaries of tropical rivers". Science Advances 5, nr 3 (marzec 2019): eaau9875. http://dx.doi.org/10.1126/sciadv.aau9875.
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We tested how sediment trapping by hydroelectric dams affects tropical estuaries by comparing two dammed and two undammed rivers on Mexico’s Pacific coast. We found that dams demonstrably affected the stability and productivity of the estuaries. The two rivers dammed for hydroelectricity had a rapid coastal recession (between 7.9 and 21.5 ha year−1) in what should otherwise be an accretional coastline. The economic consequences of this dam-induced coastal erosion include loss of habitat for fisheries, loss of coastal protection, release of carbon sequestered in coastal sediments, loss of biodiversity, and the decline of estuarine livelihoods. We estimate that the cost of the environmental damages a dam can cause in the lower part of basin almost doubles the purported benefits of emission reductions from hydroelectric generation.
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Jeng, Hueiwang C., Ryan Sinclair, Rebecca Daniels i Andrew J. Englande. "Survival ofEnterococci facalisin estuarine sediments". International Journal of Environmental Studies 62, nr 3 (czerwiec 2005): 283–91. http://dx.doi.org/10.1080/0020723042000275132.
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Beller, H. R., i B. R. T. Simoneit. "Hexachlorophene distributions in estuarine sediments". Bulletin of Environmental Contamination and Toxicology 41, nr 4-6 (październik 1988): 645–50. http://dx.doi.org/10.1007/bf02021013.
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Hsieh, Tung-Chou, Yan Ding, Keh-Chia Yeh i Ren-Kai Jhong. "Investigation of Morphological Changes in the Tamsui River Estuary Using an Integrated Coastal and Estuarine Processes Model". Water 12, nr 4 (10.04.2020): 1084. http://dx.doi.org/10.3390/w12041084.
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This study is to investigate morphological changes in the Tamsui River Estuary in Taiwan driven by multiple physical processes, such as river flows, tides, waves, and storm surges, and then to study the impacts of sediment flushing operated at the Shihmen reservoir upstream on the river estuary. An integrated coastal and estuarine processes model (CCHE2D-Coast) (Center for Computational Hydroscience and Engineering Two-Dimensional-Coast) was validated by simulating these physical processes in the estuary driven by three historical typhoons in 2008. The site-specifically validated model was then applied to simulate morphological changes in the estuary in response to reservoir sediment flush scenarios from the upstream. For the impact assessment of sediment flushing, a synthetic hydrological event was designed by including a historical typhoon and a typical monsoon. It was found that during the typhoon, the sediments will be mostly deposited in the estuarine river reach of Tamsui and the Wazihwei sandy beach. During the monsoon period, most of the sediments tend to be deposited in the second fishing port of Tamsui, the northern breakwater, and the estuary, while the Wazihwei sandy beach in the river mouth would be scoured by backflow. Simulations of the complex flow fields and morphological changes will facilitate the best practice of sediment management in the coastal and estuarine regions.
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Mangas-Suarez, Mario, Efren Garcia-Ordiales, Julio Antonio Pérez, Rodrigo Álvarez, Alberto Villa, Almudena Ordoñez i Nieves Roqueñí. "Enrichment of Metals in the Sediments of an Industrially Impacted Estuary: Geochemistry, Dispersion and Environmental Considerations". Applied Sciences 12, nr 21 (30.10.2022): 10998. http://dx.doi.org/10.3390/app122110998.
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The city of Avilés is one of the most industrialized cities in the north of Spain and, accordingly, its estuary and coastal area have been subjected to great anthropic impacts in the last 100 years. This research attempts to establish a preliminary scenario of the geochemical and environmental status of both coastal and estuarine sediments in this area. For this study, a total of 96 sediment samples were collected, processed and analyzed to quantify the granulometric distribution of the sediments, as well as their concentrations of organic carbon and main metal(oids) that may cause an environmental risk. The results show that the estuarine sediments present important concentrations of Cd, Hg, Pb and Zn that allow them to be clearly differentiated from the coastal sediments; this information, along with the sedimentology, implies that the estuary acts as a sink of pollution and not as source to the coastal area. Inside the estuary, the high levels of contamination produce a significant potential ecological risk due to contaminant transfers to other environmental compartments and to the biota. Although direct discharges of industrial effluents have been gradually eliminated, the current state of the sediment requires the implementation of measures that are more consistent than natural regeneration in order to ensure low risk levels for the ecosystem.
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Elliott, M., i A. H. Griffiths. "Mercury Contamination in Components of an Estuarine Ecosystem". Water Science and Technology 18, nr 4-5 (1.04.1986): 161–70. http://dx.doi.org/10.2166/wst.1986.0192.
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Tne Forth Estuary, Scotland, has received a discharge containing mercury for several decades. This study describes the ecological effects of that discharge as contamination in many components of the ecosystem and attempts to quantify the standing mass of Hg within those components. The contaminated area is contrasted with a less-contaminated area, 19km downstream, and shown to have significantly greater Hg levels in most components (sediments, plankton, infauna, epi-fauna, macroalgae and fish). The standing mass of Hg in the biota is 1% of that in the non-biotic components (sediments, suspended material and soluble phase); sediments alone contain 97% of that standing mass. The critical pathways in this system are (i) the sediment-infauna-estuarine demersal fish and wading birds, and (ii) suspended material-mussels-oystercatchers. Therefore, the top consumers in each of these are most at risk from increased contamination. However, in assessing the biological effects of increased contamination, there was no change at the contaminated area in fecundity in the viviparous estuarine demersal fish, Zoarces viviparus.
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Birch, Gavin F., i Marco A. Olmos. "Sediment-bound heavy metals as indicators of human influence and biological risk in coastal water bodies". ICES Journal of Marine Science 65, nr 8 (15.09.2008): 1407–13. http://dx.doi.org/10.1093/icesjms/fsn139.
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AbstractBirch, G. F., and Olmos, M. A. 2008. Sediment-bound heavy metals as indicators of human influence and biological risk in coastal water bodies. – ICES Journal of Marine Science, 65: 1407–1413. Currently, many institutions are conducting or planning large, regional-scale ecosystem assessments of estuarine health. A full, integrated assessment of these environments requires a large suite of biological, physical, and chemical indicators, including sedimentary chemistry, ecotoxicology, benthic community structure, and bioaccumulation. This commitment is beyond the capacity of most organizations, and a simpler approach is required to accommodate limited financial resources. A case is made for the use of sedimentary heavy metals as an easy and inexpensive indicator. The advantages are that sediments identify the “pristine” condition and give baseline information against which future management strategies may be benchmarked, and that they differentiate solely human-induced change from natural variation. Sediment indicators in depositional environments are also less dynamic than those associated with water and biota. Our objective is to demonstrate that sediment-bound heavy metals data provide the spatial extent and magnitude of chemical change, as well as the risk of biological stress attributable to contamination in estuarine ecosystems. An assessment of this scheme involving seven New South Wales (Australia) estuaries suggests that sedimentary heavy-metal indicators used in a weight-of-evidence approach, with data collected during the recent Australian National Land and Water Resources Audit, enhances estuarine condition assessment.
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Feldman, Howard R., Christopher G. Maples, Allen W. Archer, Ronald R. West i Erik P. Kvale. "An estuarine model for Pennsylvanian Lagerstätten". Paleontological Society Special Publications 6 (1992): 95. http://dx.doi.org/10.1017/s2475262200006559.
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Estuaries were important sites of deposition throughout most of the Pennsylvanian in the Midcontinent. Modern estuaries typically occur within flooded river valleys where marine and fresh waters mix. Characteristic estuarine circulation results in locally high rates of deposition of muddy sediment that can lead to good preservation of fossils. Several Pennsylvanian conservat-Lagerstätten are best interpreted as having formed within ancient estuaries. Three types of estuarine deposits have been identified. Type 1 estuarine systems are large-scale transgressive systems that start with fluvial sands overlying an erosional surface. This is overlain successively by middle-estuarine laminated mudstone, and finally marine mudstone and shale. Well-preserved fossils occur in laminated mudstones and siltstones. This sequence may include within in it type 3 estuarine Lagerstätten. An example is the Douglas Group (Missourian, Kansas).Type 2 estuarine Lagerstätten consist of thin estuarine deposits confined to narrow paleochannels. This includes the Garnett (Missourian, Kansas) and Hamilton (Virgilian, Kansas) deposits, both of which contain articulated vertebrates and well-preserved plants. Both channels are filled with mixed siliciclastic and carbonate sediments. Fine grained facies from which the best fossils are recovered in both contain evidence of tidal deposition, although tidal rhythmicity is best developed in the Hamilton channel. Plant assemblages in both are dominated by the conifer Walchia, probably indicating a relatively dry climate.Type 3 estuarine Lagerstätten consist of thick gray-shale wedges that overlie coals. The best-known example is the Francis Creek Shale (Desmoinesian, Illinois). A relatively wet climate is indicated by abundant fern and seed-fern foliage. Laminations in shale facies commonly show well-developed tidal rhythmicity. A typical stratigraphic succession starts with laminated shale overlying coal. This grades upwards into flaser and lenticular bedding to ripple and then large-scale cross-bedded sandstone. Upright trees rooted in the coal indicate rapid burial. Well-preserved fossils are recovered from early-diagenetic siderite concretions from the laminated shale.Preservation of fossils is best in laminated mudstones deposited in middle-estuarine environments where conditions are ideal for good preservation. In all cases so far studied the zones of best preservation are well laminated and have sparse (if any) burrows and sessile benthic fossils. Most of the well-preserved organisms are terrestrial, nektonic, or at least mobile. Brackish and fluctuating salinities restricted scavenging and burrowing organisms that may scatter skeletons. High turbidity and deposition rate may have further discouraged many organisms. Matching bedding rhythmicity with tidal cycles allows calculation of depositional rates of 1 cm or more of compacted sediment per 2-week neap-spring tidal cycle. This is consistent with the high rates of deposition known from modern tidal environments. High depositional rates assured that any organism that fell to the sea floor was buried in a few hours to a few days. Once buried anoxic conditions established around decaying carcasses may have led to early mineralization.
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Reeves, A. D., i J. A. Chudek. "Application of nuclear magnetic resonance imaging (MRI) to migration studies of oil-related residues in estuarine sediments (Tay Estuary)". Water Science and Technology 38, nr 11 (1.12.1998): 187–92. http://dx.doi.org/10.2166/wst.1998.0466.
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The tendency for selected organic compounds to sorb to sediments has been investigated extensively. These studies, however, have not permitted the ‘observation’ or measurement of advection/diffusion processes and the breakdown of organics within sediments. MRI is a multidimensional technique allowing the position of nuclei (most commonly protons) to be charted within a volume. We introduce MRI as a means of monitoring movement of oil within a series of estuarine sediments, thus offering a method of assessing the harming potential of oils in nearshore environments. Results presented in terms of the % change of oil distribution within a sediment sample, show the great potential of MRI in studying protonated contaminants in sediments.
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Logan, Brendan, Kathryn H. Taffs i Laura Cunningham. "Applying paleolimnological techniques in estuaries: a cautionary case study from Moreton Bay, Australia". Marine and Freshwater Research 61, nr 9 (2010): 1039. http://dx.doi.org/10.1071/mf09277.
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Paleoecological techniques are useful tools to identify restoration targets and natural variability for natural resource management programs. However, despite recent advances, caution is required when employing paleoecological techniques in estuaries, due to their dynamic nature relative to lake environments where these techniques were pioneered. This study used a novel combination of chronological, diatom, geochemical and isotopic data to assess the effectiveness of using these techniques in estuaries, and to develop an understanding of environmental changes within Moreton Bay, an open estuarine environment in subtropical east Australia. Results indicated mixed success, with 210Pb results indicating only background unsupported 210Pb levels, 14C results indicating sediment deposition from mixed sources, no diatom preservation and inconsistencies between geochemical and isotope proxies. Evidence did exist that the Moreton Bay sediments have been derived from different sources over the past 10 000 years. However, isotope records were not able to identify the likely sources of these sediments. Problems with diatom preservation were most probably due to the high salinity and temperatures associated with subtropical open embayment estuaries. Future studies attempting to identify environmental histories of estuaries should incorporate river-influenced locations rather than marine-dominated sites to ensure better diatom preservation and more definitive geochemical signals.
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Corbett, D. R. "Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary". Biogeosciences Discussions 7, nr 2 (16.04.2010): 2767–98. http://dx.doi.org/10.5194/bgd-7-2767-2010.
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Abstract. For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research studies initiated in the past several years have addressed the complex nutrient cycles in this system. Most of this research, however, is concerned with the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or wind-generated waves, may have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low. This study focused on the potential change in porewater and bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH4+ advective flux (resuspended) was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH4+ and PO43− indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.
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Corbett, D. R. "Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary". Biogeosciences 7, nr 10 (26.10.2010): 3289–300. http://dx.doi.org/10.5194/bg-7-3289-2010.
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Abstract. For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research initiated in the past several years have addressed the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, tides, or winds, may also have a significant effect on the flux of nutrients in an estuarine system These processes can result in the advective transport of sediment porewater, rich with nitrogen, phosphorus and carbon, into the water column. Thus, estimates of nutrient and carbon inputs from the sediments may be too low. This study focused on the potential change in bottom water nutrient concentrations associated with measured resuspension events. Previous research used short-lived radionuclides and meteorological data to characterize the sediment dynamics of the benthic system of the estuary. These techniques in conjunction with the presented porewater inventories allowed evaluation of the depth to which sediments have been disturbed and the advective flux of nutrients to the water column. The largest removal episode occurred in the lower NRE as the result of a wind event and was estimated that the top 2.2 cm of sediment and corresponding porewater were removed. NH4+ advective flux (resuspended) was 2 to 6 times greater than simply diffusion. Phosphate fluxes were estimated to be 15 times greater than the benthic diffusive flux. Bottom water conditions with elevated NH4+ and PO43− indicate that nutrients stored in the sediments continue to play an important role in overall water quality and this study suggests that the advective flux of nutrients to the water column is critical to understand estuarine nutrient cycling.
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Watson, Elizabeth Burke, Alejandro Hinojosa-Corona, Johannes R. Krause, Juan Carlos Herguera, Julianna McDonnell, Karen Raquel Villegas Villegas Manríquez, Michelle E. Gannon i Andrew B. Gray. "Lagoon Biogeochemical Processing is Reflected in Spatial Patterns of Sediment Stable Isotopic Ratios". Journal of Marine Science and Engineering 8, nr 11 (3.11.2020): 874. http://dx.doi.org/10.3390/jmse8110874.
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The spatial analysis of biota, particulate organic matter, and sediments for stable isotopes of carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) have proved useful for identifying patterns in productivity, nutrient pollution, and relationships between biological and physiochemical variables at the local and global scales. Yet such approaches are rarely applied to studies of lagoon or estuarine metabolism. Focusing on Bahía San Quintín, a heterotrophic seagrass-dominated lagoon on the Pacific coast of Baja California, México, we report on spatial patterns in surficial sediment CNS stable isotopic ratios as tracers of lagoon biogeochemical function. Stable nitrogen isotopes highlighted potential spatial variability in the balance between denitrification and nitrogen-fixation within the lagoon and identified an association between elevated δ15N levels and oyster culture, suggesting that oyster presence may be enhancing N2 production. Spatial patterns in δ34S covaried with sediment particle size, underlining the importance of sediment texture in determining the depth of sub-oxic-anoxic redox zones. Sediment carbon stable isotope ratios highlighted the lack of incorporation of seagrass carbon into seagrass meadow sediments, thus emphasizing the importance of phytoplankton or microphytobenthos for carbon accumulation in seagrass meadows. This report highlights the value of sediment isotopic values in corroborating spatial patterns in estuarine metabolism or macronutrient processing identified from chamber or flux-based studies. Stable isotope mapping can provide a useful addition to assessment of estuarine metabolism, or act as a stand-alone tool for generating hypotheses, identifying the influence of spatial gradients, and/or suggesting prime locations for investigation of microbial abundance or function.