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Release of dissolved organic matter during oxic and anoxic decomposition of salt marsh cordgrass 总被引：1，自引：0，他引：1
Xu-Chen Wang Liannea Litz Robert F. Chen Wei Huang Peng Feng Mark A. Altabet 《Marine Chemistry》2007,105(3-4):309-321
Chromophoric dissolved organic matter (CDOM), as the light absorbing fraction of bulk dissolved organic matter (DOM), plays a number of important roles in the global and local biogeochemical cycling of dissolved organic carbon (DOC) and in controlling the optical properties of estuarine and coastal waters. Intertidal areas such as salt marshes can contribute significant amounts of the CDOM that is exported to the ocean, but the processes controlling this CDOM source are not well understood. In this study, we investigate the production of DOM and CDOM from the decomposition of two salt marsh cordgrasses, Spartina patens, a C4 grass, and Typha latifolia, a C3 grass, in well-controlled laboratory experiments. During the seven-week incubation period of the salt marsh grasses in oxic and anoxic seawater, changes in dissolved organic carbon (DOC) concentrations, dissolved nitrogen (DN) concentrations, stable carbon isotopic composition of DOC (DOC-δ13C), and CDOM fluorescence demonstrate a significant contribution of DOC and CDOM to estuarine waters from salt marsh plants, such as Spartina and Typha species. In the natural environment, however, the release processes of CDOM from different cordgrass species could be controlled largely by the in situ oxic and anoxic conditions present during degradation which affects both the production and decomposition of DOC and CDOM, as well as the optical properties of CDOM in estuarine and coastal waters. 相似文献
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Development and application of a remote sensing-based salinity prediction model for a large estuarine lake in the US Gulf of Mexico coast 总被引：1，自引：0，他引：1
Salinity in estuaries is highly variable due to river discharge, tidal motion, and winds. Information on the spatial and temporal changes in salinity can provide important ecological indications, but accurate monitoring of the space–time variability for a large estuary is often costly and time-consuming. This study applied remote sensing techniques to develop a salinity prediction model for Lake Pontchartrain, a large estuarine lake located in the Northern Gulf of Mexico, USA. “Ground truth” salinity was measured along two transects across the lake and near the shoreline. Water-leaving reflectance from the measurement locations was extracted from Landsat Thematic Mapper (TM) images pre-processed through “banding” noise reduction and radiometrical correction approaches. Ordinary least square and ridge regression methods were performed to identify model parameters and to determine relationships between salinity and reflectance. Salinity in the lake on eight dates was predicted with the developed model. Difference in salinity level and patterns, and impacts of Hurricanes Katrina and Rita on salinity were assessed with ANOVA and Fuzzy Similarity methods. The results showed that the model achieved a high power in prediction of the lake salinity (R2 = 0.89 and RMSE of validation = 0.27). Reflectance from TM bands 1, 2, and 4 was positively correlated to salinity levels and explained 1.9%, 20.3%, and 10.2% variance in salinity levels. Reflectance from bands 3 and 5 was negatively correlated to salinity and explained 34.1% and 31.2% variance. Under normal circumstances without the impacts of hurricanes, the lake salinity presented two patterns with average salinity level of 5.5 ppt. After Katrina’s landfall, the average was significantly increased by 1.1 ppt and the spatial patterns were altered. The pattern on 30 August 2005 was the most dissimilar one as compared to the two normal patterns, and then followed by the patterns on 9 and 25 October, and 7 September 2005. This study demonstrated that satellite remote sensing techniques can be applied to monitor salinity in coastal environments, and that freshwater discharge not only affects salinity levels and patterns under normal conditions but also is crucial for the return of salinity patterns to normal conditions after hurricane disturbance. 相似文献
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We deployed hydroponic eelgrass, Zostera marina L., to test its use as a sentinel accumulator and indicator of the source of water-borne lead (Pb) contamination in the marine environment. Eelgrass was deployed unrooted in the water column in the vicinity of the Portsmouth Naval Shipyard, located on Seavey Island in Portsmouth Harbor of New Hampshire and Maine, offshore from seepage sites near the Jamaica Island landfill (JIL). Deployed eelgrass, water samples from seepage sites, and sediment from the deployment sites were analyzed for Pb concentration and stable Pb isotopic composition. Isotopic composition was used to distinguish recent anthropogenic Pb inputs from background Pb in the estuary. Isotope ratios indicated that two groundwater seeps were a source of recent anthropogenic Pb (i.e. industrial Pb from the landfill) to Jamaica Cove. The eelgrass that showed the strongest presence of industrial Pb (having the lowest 206Pb/207Pb) was closest to a high volume seep that drained from the JIL and had a similar isotope signature as well as elevated Pb concentrations. These data confirm a source of water-borne industrial Pb in the estuary and show that eelgrass can function as a sentinel accumulator of Pb from anthropogenic sources. 相似文献
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Anupam Ghosh Sourav Saha Pratul Kumar Saraswati Santanu Banerjee Stuart Burley 《Marine and Petroleum Geology》2009,26(8):1592-1599
The Gulf of Cambay is a macro-tidal estuarine embayment lying in an active monsoon zone characterized by a high annual sediment load. The present study examines the distribution of foraminifera in the Narmada and Tapti estuaries of the Gulf in order to use these as analogues for the study of palaeo-macro-tidal estuarine environments and as a means of recording the extent of sea-level change in estuarine settings. Foraminifera are widely distributed in sand flats, mud flats and marshes at the mouths of the estuaries. The overall foraminiferal assemblage is low diversity, comprising epifaunal and infaunal taxa dominated by Ammonia, Murrayinella, Haynesina, Quinqueloculina, Nonion, Cibicides, Cibicidoides, Elphidium, Trochammina and Miliammina. The triserial planktonic foraminifer Gallitellia vivans, an indicator of stressed and up-welling areas, is also recorded in the intertidal sediments of the estuaries. These foraminifera are carried into estuaries up to 50 km up the river mouths by the strong tidal currents in the bay. Three biofacies are recognized: Trochammina–Miliammina biofacies (high marsh); Murrayinella-Haynesina biofacies (low marsh and mud flats) and Ammonia-Elphidium-Quinqueloculina biofacies (shallow marine). 相似文献
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E.E. van Soelen E.I. Lammertsma H. Cremer T.H. Donders F. Sangiorgi G.R. Brooks R.A. Larson J.S. Sinninghe Damsté F. Wagner-Cremer G.J. Reichart 《Estuarine, Coastal and Shelf Science》2010
A suite of organic geochemical, micropaleontological and palynological proxies was applied to sediments from Southwest Florida, to study the Holocene environmental changes associated with sea-level rise. Sediments were recovered from Hillsborough Bay, part of Tampa Bay, and studied using biomarkers, pollen, organic-walled dinoflagellate cysts and diatoms. Analyses show that the site flooded around 7.5 ka as a consequence of Holocene transgression, progressively turning a fresh/brackish marl-marsh into a shallow, restricted marine environment. Immediately after the marine transgression started, limited water circulation and high amounts of runoff caused stratification of the water column. A shift in dinocysts and diatom assemblages to more marine species, increasing concentrations of marine biomarkers and a shift in the Diol Index indicate increasing salinity between 7.5 ka and the present, which is likely a consequence of progressing sea-level rise. Reconstructed sea surface temperatures for the past 4 kyrs are between 25 and 26 ° C, and indicate stable temperatures during the Late Holocene. A sharp increase in sedimentation rate in the top ∼50 cm of the core is attributed to human impact. The results are in agreement with parallel studies from the area, but this study further refines the environmental reconstructions having the advantage of simultaneously investigating changes in the terrestrial and marine environment. 相似文献
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Susana Mendes Ma Jos Fernndez-Gmez Paula Resende Mrio Jorge Pereira Ma Purificacin Galindo-Villardn Ulisses Miranda Azeiteiro 《Estuarine, Coastal and Shelf Science》2009,84(4):637-644
This study examines the spatio-temporal structure of diatom assemblages in a temperate estuary (Ria de Aveiro, Western Portugal). Eighteen monthly surveys were conducted, from January 2002 to June 2003, at three sampling sites (at both high and low tide) along the estuarine salinity gradient. The relationship of diatom assemblages and environmental variables was analysed using the STATICO method, which has been designed for the simultaneous analysis of paired ecological tables. This method allowed examination of the stable part of the environment-diatom relationship, and also the variations of this relationship through time. The interstructure factor map showed that the relationship between the 11 environmental variables and the abundance of the 231 diatom species considered was strongest in the months May and September 2002 and January, February and May 2003. The stable part of the species–environment relationships mainly consisted of a combined phosphate, chlorophyll a and salinity gradient linked to a freshwater-marine species gradient. A more pronounced gradient was observed in January, February and May 2003. Diatom assemblages showed clear longitudinal patterns due to the presence of both marine and freshwater components. May and September 2002 had the least structured gradients with marine-estuarine species appearing in the freshwater side of the gradient. The most complete gradient in February 2003 could be considered, in terms of bio-ecological categories, as the most structured period of the year, with a combination of strong marine influence in the lower zone and freshwater influence in the upper. The best-structured gradients were during periods of a diatom bloom. Stable diatom assemblages (with a strong structure and a good fit between the diatoms and environment) are described and characterized. This study shows the efficiency of the STATICO analysis. The inclusion of space-time data analysis tools in ecological studies may therefore improve the knowledge of the dynamics of species–environmental assemblages. 相似文献
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Temporal and spatial variations in Synechococcus abundance were investigated over an annual cycle (February'10–January'11) along a salinity gradient (0–35) in the tropical Zuari estuary, influenced by south-west monsoons. Synechococcus exhibited salinity preferences with phycoerythrin-rich cells at salinities >2 (Synechococcus-PEI), >20 (Synechococcus-PEII) and <1 (Synechococcus-PEIII) whereas phycocyanin-rich (Synechococcus-PC) dominant at lower salinities. Downstream stratification during monsoon caused Synechococcus group segregation in the surface and near-bottom waters. During monsoon-break and non-monsoon period stabilized waters, increased salinity, temperature, solar radiation and low rainfall favored high Synechococcus abundance whereas unstable waters, increased turbidity and low solar radiation during active monsoon lowered abundance. SYN-PC positively co-related with nitrate and phosphate and SYN-PEI with phosphate. Synechococcus contribution to phytoplankton carbon biomass ranged from 9 to 29%. In monsoonal estuaries, rainfall intensity regulates freshwater runoff which modulates the estuarine environment, creating temporal–spatial niche segregation of Synechococcus groups thereby serving as indicator organisms of the estuarine hydrodynamics. 相似文献
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John F. Paul Jane L. Copeland Michael Charpentier Peter V. August Jeffrey W. Hollister 《Marine Geodesy》2013,36(1-2):63-72
Geographic information systems (GIS) tools are now considered integral in estuarine monitoring and assessment research. A synopsis is presented of our estuarine applications of GIS in the Northeast region of the U.S. The applications discussed cover sample site selection, support for field sampling activities, quality assurance of data, spatial display of geographic referenced information, quantitative spatial analysis of data, and communication of results. 相似文献