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Development of Models for Phytoplankton-Nutrient Responses in Support of Numeric Nutrient Criteria for Estuarine Water Quality

Principal Investigators

James Pinckney and Erik Smith, University of South Carolina Belle W. Baruch Institute for Marine and Coastal Sciences

Project Information

2018-2020 Healthy Coastal Ecosystems

Project Number: R/ER-49

Research Description

It is clear that water quality in tidal creeks differs between developed and undeveloped watersheds, particularly in headwater areas of the creek. Although prior studies of the impact of development on coastal ecosystems have focused on surface waters, hydrologic changes associated with development have the potential to affect groundwater as well. Groundwater delivery of nutrients in particular has the potential to be affected in both concentration and form of nutrients. Regionally and globally, fixed nitrogen (N) is usually the primary nutrient controlling or “limiting” estuarine and coastal primary production. Rapidly growing and diversifying anthropogenically-generated N compounds associated with agricultural, urban, and industrial expansion, have been identified as key “drivers” of accelerating planktonic primary production, or eutrophication, in N-sensitive waters. Fast-paced and widespread development, agricultural practices in the watershed, and an increasing human population in the coastal zone of SC have resulted in a general decline in water quality in estuaries. Concerns about this decline have led to the need to determine minimum nutrient criteria to ensure acceptable water quality conditions for both biota and recreational uses. Numeric nutrient criteria are established by state and federal management agencies to provide targets for pollutant reduction and maintenance of acceptable water quality in aquatic systems.

A major component of numeric nutrient criteria modeling is the understanding of the quantitative relationship between nutrient loading and phytoplankton productivity responses, in terms of both total biomass and community composition. Phytoplankton responses to excessive N loading result in a variety of negative impacts such as hypoxia, anoxia, fish kills, and harmful algal blooms. The research proposed here will use a quantitative empirical approach for predicting the magnitude of phytoplankton group-specific (i.e., diatoms, cyanobacteria, dinoflagellates, chlorophytes, etc.) responses to a range of nutrient loading conditions. The empirical models developed can be directly used by the S.C. Department of Health and Environmental Control to evaluate numeric nutrient criteria for this system under a variety of N addition/reduction scenarios. Thus, the proposed research will provide an independent tool for developing numeric nutrient criteria models with potential methodological applications to other river-dominated estuarine systems.

Contact for Questions

Dr. James Pinckney (