The ecological energies of growth,respiration and assimilation in the intertidal American oyster Crassostrea virginica

Seasonal variations in the growth, respiration and assimilation of the intertidal oyster Crassostrea virginica (Gmelin) of different sizes were determined. The instantaneous growth rates for intertidal oysters decreased with increasing size and with lower temperatures. Q₁₀ values computed from instantaneous growth rates were approximately 2 during the warm growing season, but were higher in the colder months. Oxygen consumption increased with temperature and body size. A model was developed to predict oxygen consumption at any environmental temperature from 10° to 30°C for oysters ranging in weight from 0.1 to 100.0 g. Q₁₀ values computed from oxygen-consumption rates decreased with increasing temperature and increasing body size. Intertidal oysters utilize a large proportion of their assimilated energy in growth.Supported by a Belle W. Baruch Fellowship in Marine Ecology.     

Evaluation of ecological network analysis: Validation of output

Ecological network analysis (ENA) is a modeling approach increasingly being used to evaluate food webs and provide an ecosystem-based approach to resource management. Unfortunately, validation of ENA output is rarely performed. This study represents part of a larger effort to critically evaluate ENA. Here we validate ENA output using stable isotope analysis (SIA), and where validation is not met, determine the effects of modifying trophic networks to reflect validation.     

Ecological network analyses and their use for establishing reference domain in functional assessment of an estuary

We developed a framework to use ecological network analysis for functional assessment of large aquatic ecosystems in the context of ecosystem-based management. We established a reference domain for the Neuse River Estuary, North Carolina, USA, from changes over time. Four reference network models of the trophic structure of the estuary during early and late summers of 1997 and 1998 were constructed and analyzed. The estuary has experienced various symptoms of eutrophication during the past 20 years, including summer-time hypoxia and fish kills. The networks were used to quantify indices of nominal trophic dynamics and their variation. The ratio of biomass of nekton to that of macrobenthos, derived from network construction, was used to index severity of eutrophication and to promote accessibility of ecological network analysis to environmental management. The ratio increased from early to late summer, and network metrics demonstrated a variety of responses in association with that change. Some variables from network analysis, especially related to consumers, reflected some but not all of this change. Others reflected the most severe increase in the ratio in late summer 1997 when hypoxia was most extensive. We evaluated uncertainty and the modulating effects of hierarchy by comparing variation of input biomasses with integrative response variables. Relative variation in input variables was generally greater than that of the integrative response variables as predicted by hierarchy theory. Ecological network analysis has previously served as support for ecosystem-based management of large aquatic systems with some success. However, its use can be enhanced by making it more accessible to environmental managers and policy makers. Ways to do this include promoting simple metrics from network construction and explicitly associating network analysis to concepts familiar to the management community, such as functional assessment and reference.     

A simulation model of estuarine subsystem coupling and carbon exchange with the sea. II. North Inlet model structure,output and validation

A first-stage verified model of carbon/energy flux through the North Inlet (South Carolina) marsh—estuarine ecosystem is presented. The time series output for model compartments and overall septem carbon flow are compared with observed data collected over the past five to ten years. Results indicate that the model is stable and can broadly reproduce some of the major trends of a salt marsh—estuarine system. Further avenues of research are suggested.     

Pollution of water in Africa: a review of contaminants and fish as biomonitors and analytical methodologies—the case of Senegal

Environmental Science and Pollution Research - Environmental pollution is one of the major problems facing human health, ecosystems, and biodiversity. This is particularly the case for water...