Temporal Variability in Ecological Stoichiometry and Material Exchange in a Tidally Dominated Estuary (North Inlet, South Carolina) and the Impact on Community Nutrient Status
Across the coastal zone, rates of carbon and nutrient exchange are defined by the spatiotemporal heterogeneity of individual estuarine systems. Elemental stoichiometry provides a mechanism for simplifying overlapping physical, chemical, and biological drivers into proxies that can be used to compare and monitor estuarine biogeochemistry. To this end, the seasonal and tidal variability of estuarine stoichiometry was examined over an annual cycle in North Inlet (NI), South Carolina. Surface samples for dissolved and particulate carbon (C), nitrogen (N), and phosphorus (P) were collected every 20 days (August 2014 to August 2015) over a semi-diurnal tidal cycle. Dissolved nutrient flux estimates of an individual tidal creek were also made. Overall, the results demonstrated the dominance of seasonal versus tidal forcing on water column C:N:P stoichiometry. This seasonal behavior mediated the relative exchange of N and P into and out of the tidal creek and influenced the nutrient status index (NSI) of NI plankton communities. These communities were largely N deficient with the magnitude of this deficiency impacted by assumptions of inorganic versus organic plankton P demand and nutrient supply. Persistent N deficiency appeared to help drive the net import of N, while temporary P surplus likely drives its seasonal export. Combined, these results indicate that material delivery must be considered on seasonal time frames, as net annual fluxes do not reflect the short-term deliveries of C and nutrients into nearshore ecosystems.
KeywordsStoichiometry Tidal exchange Nutrient status Salt marsh tidal creek NERRS
We give special thanks to Drs. Jay Pinckney and George Voulgaris for their helpful consultation regarding our statistical approaches and tidal exchange estimates. Additional thanks are given to Elise Van Mersche and Yuan Shen for thoughtful discussions and access to their respective bioassay and bioavailability data. We gratefully acknowledge the efforts of Tracy Buck in collecting and QA/QC’ing the meteorological and YSI water quality data. This is contribution #1852 to the Belle W. Baruch Institute for Marine and Coastal Sciences.
Portions of this work were supported by a National Oceanic and Atmospheric Administration operations grant to the North Inlet—Winyah Bay National Estuarine Research Reserve (Award # NA14NOS4200054). This work was additionally supported by the SPARC Graduate Research Grant program (Office of the Vice President for Research, University of South Carolina to DWB), the Kathryn D. Sullivan Earth and Marine Science Fellowship (S.C. Space Grant and Sea Grant Consortiums to DWB), and the Slocum-Lunz Foundation (to DWB).
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