You are here:
A Biological Condition Gradient Model for Historical Assessment of Estuarine Habitat Structure
Citation:
Shumchenia, E., Marguerite C. Pelletier, G. Cicchetti, S. Davies, Carol E. Pesch, C. Deacutis, AND M. Pryor. A Biological Condition Gradient Model for Historical Assessment of Estuarine Habitat Structure. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 55(1):143-158, (2015).
Impact/Purpose:
Coastal ecosystems are affected by ever increasing natural and human pressures. Because the physical, chemical, and biological characteristics unique to each ecosystem control the ways that biological resources respond to ecosystem stressors, we recommend a flexible and adaptable biological assessment method for estuaries. The biological condition gradient (BCG) approach is a scientific model of biological response to increasing anthropogenic stress that is comprehensive, ecosystem-based, and evaluates biological, physical and chemical conditions in order to effectively identify, communicate and prioritize management action. In this study we constructed the first estuarine BCG model that examines changes in habitat structure through time in a New England (U.S.) estuary (Greenwich Bay) with a long history of human influence. The Greenwich Bay habitat structure BCG identifies biological indicators and stressors that have been important to characterizing the ecosystem over time. This BCG contains a description of a “minimally disturbed” range of conditions for the ecosystem anchored by observations before 1850 AD, in addition to providing documentation of the ecosystem trajectory under increasing levels of stress. Stressor-response relationships were complex and rarely straightforward. This BCG showed that broad-scale stressors, such as storms and hydrodynamics, amplify the effects of human-derived stressors such as nutrients. A further observation was that the decline of eelgrass (Zostera marina) extent likely influenced the declines of shellfish and benthic habitat, showing that indicators are interdependent and that the overall ecology of this estuary is complex. We also document, for the first time in Narragansett Bay, the replacement of eelgrass by widgeongrass (Ruppia maritima) and discuss the implications of viewing this event as seagrass recovery. A BCG framework that relies on observed stressor-response relationships and anchors management, conservation and restoration goals in real-world conditions will be widely applicable for estuarine systems. Awareness of these concepts is extremely important for public support of management action and provides valuable information to managers seeking to reduce the influence of stressors and/or set restoration targets.
Description:
Coastal ecosystems are affected by ever increasing natural and human pressures. Because the physical, chemical, and biological characteristics unique to each ecosystem control the ways that biological resources respond to ecosystem stressors, we recommend a flexible and adaptable biological assessment method for estuaries. The biological condition gradient (BCG) approach is a scientific model of biological response to increasing anthropogenic stress that is comprehensive, ecosystem-based, and evaluates biological, physical and chemical conditions in order to effectively identify, communicate and prioritize management action. In this study we constructed the first estuarine BCG model that examines changes in habitat structure through time at the single-habitat scale in a New England (U.S.) estuary (Greenwich Bay) with a long history of human influence. We developed an approach to define a reference level, which we described as a “minimally disturbed” range of conditions for the ecosystem, anchored by observations before 1850 AD. Natural and anthropogenic stressors to this ecosystem over time were storms, hydrodynamics, water quality, temperature, sediment metals concentrations, and nutrients. We characterized the response of three biological indicators to these cumulative stressors: “seagrass extent”, “benthic habitats”, and “primary productivity and shellfish”. Although quantitative data were rare prior to 1950, we suggest that even qualitative descriptions of the biological indicators through time would provide useful information for defining condition levels. Stressor-response relationships were complex and rarely straightforward. This BCG showed that broad-scale stressors, such as storms and hydrodynamics, amplify the effects of human-derived stressors such as nutrients. A further observation was that the decline of eelgrass (Zostera marina) extent likely influenced the declines of shellfish and benthic habitat, showing that indicators are interdependent and that the overall ecology of this estuary is complex. We also document, for the first time in Narragansett Bay, the replacement of eelgrass by widgeongrass (Ruppia maritima) and discuss the implications of viewing this event as seagrass recovery. A BCG framework that relies on observed stressor-response relationships and anchors management, conservation and restoration goals in real-world conditions will be widely applicable for estuarine systems. Awareness of the ecological concepts described in this study would be extremely important for public support of management action and for informing managers who seek to reduce the influence of stressors and/or set restoration targets.
