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81.
Carbon balance in a salt marsh: Interactions of diffusive export, tidal deposition and rainfall-caused erosion 总被引:1,自引:0,他引:1
Alice G. Chalmers Richard G. Wiegert Paul L. Wolf 《Estuarine, Coastal and Shelf Science》1985,21(6):757-771
Studies of the concentrations of particulate and dissolved organic carbon in the Duplin River, of the tidal exchange of POC and DOC in the marsh, of the standing stock and movement of Spartina alterniflora wrack in the Duplin, and of the removal of carbon from the surface of the marsh by rain were conducted at Sapelo Island, Georgia in order to test three hypotheses about export of carbon from the Duplin River watershed. We found that the gradients in POC and DOC concentrations are such that carbon is being transported down the Duplin River throughout the year, although in smaller quantities than previously believed. In contrast, almost all tidal exchanges within the marsh result in deposition of carbon. Most of this deposited carbon is subsequently eroded as a result of rain falling on the exposed marsh surface, and is washed back into the tidal creeks. This cycle of deposition and erosion is a possible mechanism keeping POC in the thin aerobic surface layer of the marsh, thus increasing its availability to detritivores and aerobic microbes. The standing stock of wrack is only a fraction of the S. alterniflora produced each year, and its export is a negligible term in the carbon balance equation. 相似文献
82.
The acute toxicity of bromochlorinated estuarine water (ca. 20%) was determined for several estuarine organisms. The most sensitive species were oysters (Crassostrea virginica, larvae and juveniles) and copepods (Acartia tonsa) with 48-h LC50's of 0·10 to 0·21 mg BrCl/litre. Palaemonetes pugio was most tolerant with a 96-h LC50 of 0·70 mg BrCl/litre. The fish species tested (Menidia menidia, Brevoortia tyrannus and Leiostomus xanthurus) all had a 96-h LC50 of 0·21–0·23 mg BrCl/litre.The BrCl toxicity data are compared with Cl2 toxicity data for the same species. When the LC50's are expressed as equivalents per litre, BrCl is found to be two to four times less toxic than Cl2. The ranking of species in terms of sensitivity is the same for both disinfectants.Some data are provided concerning the decay rates of BrCl and Cl2 in estuarine water. BrCl was found to decay more rapidly than Cl2 at higher ammonia levels (0·25 mg NH4-N/litre). The question of chemical speciation is discussed with particular reference to the differential toxicities. 相似文献
83.
A code of practice for ocean mining has been developed by the International Marine Minerals Society. The code provides general guiding Principles for development of marine mineral resources and delineates Operating Guidelines for application, as appropriate, at specific mining sites. In total 11 operating guidelines are provided to serve as benchmarks for industry and targets for regulatory agencies and other stakeholders. They include the following commitments: •To sustainable development, •To environmentally responsible corporate ethics, •To the development of effective community partnership, •To implementation of environmental risk management, •To the integration of environmental management into all phases of development, •To the establishment of corporate environmental performance targets, •To timely environmental improvements and upgrading, •To responsible rehabilitation of operations sites and decommissioning of facilities, and •To accurate and timely, reporting and documentation, archiving, and performance review. 相似文献
84.
Seaward-dipping strata of carbonate-cemented shell debris located along the coast of Siesta Key on the Gulf Coast of the Florida peninsula have long been interpreted to be beachrock equivalent in age to the Pleistocene Anastasia Formation (Stage 5e) of the east coast of Florida. Detailed examination of thin sections along with radiometric dating and isotopic analyses demonstrates clearly that this is a Holocene deposit that is not beachrock but was lithified in a meteoric environment. Whole rock dates, dates from shells only, and from cement only demonstrate that these beach deposits were in place by at least 1800 yr BP and might have been there as long ago as 4300 yr BP. This means that some type of barrier island was in place at that time. Previous investigations have depicted Siesta Key as having a maximum age of 3000 yr with these deposits being located about 2 km landward of the beach deposits. This suggests that the beach deposits might have been the site of the original position of Siesta Key. These data also indicate that sea level must have been near its present position at the time that these foreshore beach deposits were deposited; sometime between 1800 and 4300 yr ago. This scenario indicates that sea level along this coastal reach probably reached its present level at least about 2000 yr ago. 相似文献
85.
The concentrations of a number of trace metals (Co, Ni, Cu, Zn, Ag, Cd and Hg) have been determined in sediments from cores collected in the Southampton Water region. Measurements of total hydrocarbons were also made on several of the cores. Markedly elevated concentrations of copper, up to 362 μg/g dry wt, were found in sediments which were collected close to the discharge points of oil refinery outfalls and which also showed concentrations of total hydrocarbons considerably greater than the background levels for the estuary. The results of selective chemical extractions showed that much of the copper was present in the non-lattice fraction of the sediment. Although the concentrations of Co, Ni, Zn and Cd were significantly correlated with those of copper in the core showing the highest concentrations of this element, these metals were not enhanced in comparison with the levels found in several other parts of the estuary. Variations in concentrations of metals in sediments throughout the estuary were not correlated with differences in organic carbon content. 相似文献
86.
87.
88.
Histopathological biomarkers in estuarine fish species for the assessment of biological effects of contaminants 总被引:1,自引:0,他引:1
Stentiford GD Longshaw M Lyons BP Jones G Green M Feist SW 《Marine environmental research》2003,55(2):137-159
The increasing emphasis on the assessment and monitoring of estuarine ecosystems has highlighted the need to deploy appropriate biological indices for these locations. Fish diseases and histopathology, with a broad range of causes, are increasingly being used as indicators of environmental stress since they provide a definite biological end-point of historical exposure. This study reports on the histopathological alterations observed in selected organs and tissues of three species of estuarine fish (Platichthys flesus, Pomatoschistus minutus and Zoarces viviparus), captured from four British estuaries (the Tyne, Tees, Mersey and Alde), differently impacted by contaminants, including PAHs. A biannual sampling regime was used to identify the important seasonal variations that occur in terms of the observed biological effects. Inflammatory lesions and hepatocellular fibrillar inclusions attained their highest prevalence in P. flesus captured from the Tyne, Tees and Mersey. The presence of pre-neoplastic and neoplastic toxicopathic lesions was highest in P. flesus captured from these sites, when compared to fish from the Aide reference site. In particular, the prevalence of hepatic foci of cellular alteration (up to 43.3%) and hepatocellular adenoma (up to 10%) were highest in P. flesus captured from the Mersey estuary. Intersex (ovotestis) was only recorded in male P.flesus captured from the Mersey estuary (up to 8.3%) and from male Z. viviparous captured from the Tyne estuary (25%). Pathologies associated with the gill and the kidney were also most prevalent in fish captured from the Tyne, Tees and Mersey estuaries. This study has successfully applied histopathology to an estuarine monitoring program, both for the recording of toxicopathic lesions in the liver and other organs, and for the detection of the endpoint of endocrine disruption, intersex. As such, it provides a powerful integrative tool for the assessment of biological effects of contaminants in these environments. 相似文献
89.
Richard B. Olsen 《Ocean Engineering》1987,14(6)
Empirical orthogonal function (EOF) analysis is used in conjunction with Markov chains to generate simultaneous current time series at several depths with a random walk model. Duration statistics and probability distributions for EOF modes obtained from real data are used to generate transition probability matrices for the random walk model. New time series of EOF modes are generated, and then combined to produce current time series. The technique has been tested on data from Haltenbanken. Statistical properties of real and simulated time series were compared. Results indicate that the model is acceptable as a tool in simulating current time series to be used in offshore operation models. 相似文献
90.
To improve resolution of seismic-reflection profiles in continental slope water depths of 900 to 1500 m, a single hydrophone
was towed about 150 m off the bottom to receive reflected signals from a surface-towed sparker sound source. That deep-towed
hydrophone data show that valleys which appear V-shaped in records from a surface-towed hydrophone are flat-bottomed, and
that subbottom reflections from an erosional unconformity can be much better resolved. The data produced by this technique
are very hepful when used in conjunction with records from conventional surface-towed seismic-profiling equipment. 相似文献