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FOOD WEB AND COMMUNITY COMPOSITION CHANGES IN RESPONSE TO NUTRIENT LOADING IN FRESHWATER AND MARINE COASTAL SYSTEMS (ESTUARIES AND COASTAL WETLANDS)
Impact/Purpose:
The States and EPA Regions will use the products of this research when setting ecologically relevant nutrient criteria for estuaries, in support of 305b reporting and TMDL development. Development and evaluation standardized methods and indices that can be used to measure food web responses to nutrient loading also will lead to the development of appropriate monitoring protocols. Secondary objectives of the research are to assess the use of food web analyses to improve our ability to predict changes in submerged aquatic vegetation as a result of nutrient loading and to better predict the probability of hypoxic events. This will lead to a method for classifying coastal embayments by their sensitivity to changes in nutrient loading.
Description:
Our research will investigate the mechanisms by which increased loading of nutrients to coastal waters alters the structure and dynamics of food webs, resulting in declines in populations of ecologically and commercially important organisms. Research across NHEERL Divisions will focus on the effects of nutrients on primary production and the cascading interactions with ecologically dominant organisms (such as ecosystem engineering species and predators) and critical food web processes (such as, benthic-pelagic nutrient exchange, fate and transformation of primary production). This research will have three critical elements to quantify food web responses to nutrient enrichment: 1) characterizing changes in community structure of higher trophic-level species (including, changes in populations of ecologically important species, benthic and pelagic community structure, and abundance of commercially important fishery species); 2) characterizing changes in ecosystem processes (including, energy and nutrient fluxes among trophic components of food webs, efficiency of transforming primary production into ecologically and commercially important species, and fate of excess primary production); and 3) characterizing changes in food web structure and function (including, developing food web models, measuring network properties of food webs, and developing ecologically relevant and stressor-sensitive metrics). The main components of the research include literature review, directed process studies (nutrient-loading responses of individual components of food webs), comparative field studies (comparison of food webs in impacted and non-impacted embayments), integrative models (network models of food web structure and dynamics; classification of sensitive embayments), and synthesis (evaluation of quantitative measures of food web responses to nutrient loading).