Barnegat Bay nutrient inference model
Creators: name: Potapova, Marina
name: Desianti, Nina
name: Velinsky, David
name: Mead, Jerry
Publisher: name: No Publisher Supplied
Year: 2013

description: There is an on-going discussion on whether eutrophication is causing algal blooms and increased macrophyte growth, which are presumably causing documented secondary detrimental side effects (i.e., anoxia, loss of submerged aquatic vegetation, increase in jelly fish, decreases in fish and crab population, etc) in the Barnegat Bay, New Jersey. The discussion revolves around the fact that Barnegat Bay has historically been poorly drained, and that what we may see as current eutrophication effects is only a part of natural conditions exacerbated by current nitrogen loading (i.e., with some of the negative affects coming from other stressors such as increased boat and jet ski traffic, bulkhead increases, loss of freshwater flows due to regionalization of upstream river sewerage treatment plants and loss through MUA ocean outfall, etc).The New Jersey Department of Environmental Protection (NJDEP) is evaluating the appropriate indices to be used to measure the ecosystem health of New Jersey's shallow, lagoonal estuaries or coastal bays. These would include bays such as Great Bay, Great Egg Harbor Bay, Absecon Bay, Ludlam Bay and Barnegat Bay. The federal government (USEPA and NOAA) has already developed a suite of indicators (e.g., EPA's National Coastal Assessment Report 2005 and NOAA's National Estuarine Eutrophication Assessment update) and has applied them to NJ's coastal bays with mixed results, especially as state level management tools, due to both geographic scale issues and the inability of the USEPA and NOAA metrics to identify proximate sources and causes of impairments.Further information is needed for NJDEP to develop water quality management tools; this study is designed to directly assist NJDEP in the development and/or enhancement of its nutrient criteria. There is growing consensus that the traditional macroinvertebrate indices used in EPA's EMAP and National Coastal Assessment may not be adequate to fully characterize the ecosystem health of shallow lagoonal estuaries such as those along the New Jersey coast. Together with macroinvertebrates, diatoms, which are microscopic siliceous algae, are commonly used as indicators of environmental conditions in aquatic ecosystems. Diatoms are widely used to monitor ecosystem health in freshwater ecosystems, but investigations have been started to develop diatom-based environmental indicators in coastal systems, too. The main objective of this proposal was to determine whether surface sediment diatom assemblages may be used as indicators of ecosystem health in Barnegat Bay. This was accomplished by constructing a calibration set of diatom and water-quality data from the Barnegat Bay and the adjacent Great Bay and by quantifying responses of diatoms to environmental parameters of interest, first of all, nutrients. An additional objective of this study was an assessment of the responses of diatom assemblages to land-use.Surface sediment samples were collected from 100 sites across tidal wetland, embayment and offshore areas in Barnegat Bay. Water-quality characteristics, such as salinity, pH, nutrients in water and sediments, total suspended solids, turbidity and chlorophyll A content were measured in the field and laboratory. Land-use characteristics, such as percentage of land in the “developed”, “agricultural”, “forest”, or “wetland” categories was quantified using GIS methods. A rich diatom flora consisting of 402 species was found. The diatom assemblages were dominated by a few small-celled Cyclotella species, such as C. choctawhatcheeana and C. atomus, several species of Chaetoceros, Amphora, Cocconeis, Fallacia, Navicula, Planothidium, Thalassiosira, and Opephora. Diatom assemblages were highly diverse: the Shannon Diversity Index ranged from 2.3 to 4.2 with a mean of 3.5.Multivariate statistical analyses were conducted to evaluate the relationships between diatom distribution and environmental variables. The major gradient in the composition of diatom assemblages corresponded to the north-south gradient of land-use, salinity and other associated environmental variables. The second most important gradient in diatom species data was between the marsh sites and open-water sites and correlated with water depth. The strongest diatom response was to salinity, which is expected in an estuarine environment. Other environmental parameters that had statistically significant effect on the composition of diatom assemblages i were Depth, Dissolved Oxygen, Turbidity, Chlorophyll A, Total Dissolved Phosphorus, Particulate Phosphorus, Total Phosphorus, Nitrate+Nitrite, Ammonia, Total Inorganic Nitrogen, Sediment Organic Carbon, Sediment Total Nitrogen, Sediment Total Phosphorus, and land-use characteristicsInference models were constructed for those environmental parameters that were found to exert significant influence of the diatom assemblage composition. The models with the highest predictive power were those for Salinity, Total Dissolved Phosphorus, and Chlorophyll A. The inference models for Salinity may be useful for historical reconstruction of sea-level rise and other events related to climate change. Total Dissolved Phosphorus models, although highly statistically significant, may reflect a natural gradient of this compound related to salinity. Since an increased chlorophyll A level is a symptom of eutrophication and the chlorophyll gradient positively correlates with watersheds development, Chlorophyll A inference models seem to be most promising for reconstruction history of eutrophication in Barnegat Bay and adjacent areas. Diatom species optima and tolerances calculated for all models will be useful for environmental assessments in lagoonal estuaries in New Jersey.This initial study demonstrated that surface sediment diatom assemblages are sensitive to a number of water and sediment chemistry parameters, and can be used to track eutrophication in its diverse manifestations, such as elevated nutrients and algal blooms. This is the first study that investigated in detail composition of benthic diatom assemblages in New Jersey lagoonal estuaries and quantified responses of individual diatom species to a number of environmental factors. This information may be further analyzed to develop even more robust diatom indicators and lessons learned from this project should be used to design further studies of responses of benthic communities to environmental stress in coastal areas.