Nutrient and Carbon Dynamics in Coastal Ponds
Stormwater ponds, especially detention ponds, are a prevalent feature of the coastal zone in South Carolina. While these ponds are effective at minimizing localized flooding, they are often ineffective at sequestering the high nutrient loadings associated with residential area runoff. Despite reports that stormwater ponds commonly exhibit signs of eutrophication (high nutrient concentrations, phytoplankton blooms, and fish kills resulting from oxygen depletion), research examining how stormwater ponds respond, as integrated ecosystems, to nutrient enrichment is currently lacking. Further, high algal production in these ponds, in addition to fueling bottom water depletion within ponds, may represent a significant source of highly labile organic matter available for export to the downstream marine environment. The purpose of this study, conducted in several residential stormwater ponds within the North Inlet watershed, is therefore to quantify the relationship between nutrient input, net ecosystem metabolism (gross primary production and total ecosystem respiration), organic matter export and dissolved oxygen dynamics in representative residential stormwater detention ponds. Results from this study will provide homeowners and resource managers with information to better manage coastal stormwater ponds so as to maximize the value of ponds as aesthetic amenities while minimizing the impacts of pond discharges on coastal water quality conditions.
Long-term Composition and Abundance of Estuarine Macrofauna
Routine monitoring of dominant estuarine macrofauna in North Inlet began in the early 1980s with funding from a National Science Foundation’s Long-Term Ecological Research grant. This monitoring was continued by the Reserve beginning in 1993. The on-going goals of this program are to quantify the long-term composition and abundance of estuarine macrofauna with the Reserve in order to characterize and understand short-term variability and long-term changes in both resident and transient estuarine species. Researchers and resource managers use this reference data from a relatively pristine estuary for comparisons with anthropogenically-impacted estuarine sites. There are three components to the Reserve’s fauna monitoring program:
Precipitation Chemistry Monitoring
In partnership with the South Carolina Department of Health and Environmental Control, the Reserve initiated participation in the National Atmospheric Deposition Program (NADP) in January of 2002. A wet deposition collector is situated on the pier at Oyster Landing adjacent to the long-term weather, water quality and nutrient monitoring sites. Precipitation is collected weekly (every Tuesday) according to NADP/National Trends Network (NTN) protocols and sent to the NADP Central Analytical Laboratory, where it is analyzed for pH, sulfate, nitrate, ammonium, chloride, and base cations (calcium, magnesium, potassium and sodium). North Inlet NADP data can be obtained at the NADP website.
Salt Marsh Emergent Vegetation Response to Sea Level Rise
The long-term goal of this project is to assess the effects of rising sea level on the spatial dynamics of salt marsh vegetation communities of North Inlet. This information is critical to predicting the ability of marsh communities to migrate inland in the face of accelerated rates of sea level rise due to global warming. Previous studies have shown annual net aboveground production of Spartina alterniflora, the dominant emergent vegetation in North Inlet, to be positively correlated with annual anomalies in mean sea level. However, the effects of interannual variation and long-term change in sea level on the spatial dynamics of salt marsh macrophyte communities, particularly the high-marsh communities, remain unclear. Thus, this project specifically seeks to address how the spatial structure of the salt marsh vegetation community (species composition, stem density, canopy height, and above-ground biomass) varies along an elevation gradient, from creek bank to upland edge, in response to changes in tidal height and flooding frequency due to sea level rise. Data on sediment deposition and net accretion rates, sediment characteristics (organic content and bulk density), and porewater chemistry (salinity, nutrients, and sulfide concentrations) are also collected along each transect to quantify the interactions between sediment accretion rates, pore-water chemistry and vegetation community dynamics along the elevation gradient as a function of the frequency and duration of tidal inundation.
Microbial Heterotrophy in Tidal Creeks
This study seeks to quantify how microbial metabolism in tidal creek waters responds to variability in the magnitude and form of salt marsh exports over tidal, seasonal, and interannual time scales, and the consequences this has on organic matter export to the coastal ocean. The focus is on tidal creeks as they represent the conduits for organic matter exchange between salt marshes and the coastal ocean. They are also areas of substantial net heterotrophy (total respiration > in situ primary production), which is fueled by organic matter produced by the adjacent marshes. Routine sampling is conducted on both ebbing and flooding tides at the Oyster Landing site in conjunction with the NERR 20-day water chemistry monitoring program. Microbial metabolic responses are determined by quantifying rates of microbial production (3H leucine incorporation rate) and respiration (in vitro O2 consumption rates) in both whole water and size-fractionated samples. Information from this study is improving our understanding of carbon flow through salt marsh estuaries, why tidal creeks are naturally low in dissolved oxygen, and how organic matter exchange between salt marshes and the coastal ocean may respond to long-term changes associated with predicted climate alterations and sea level rise.