The Benthic Microalgal Subsidy in Estuarine Ecosystems
James L. Pinckney, Erik Smith, Eilea Knotts, John Kupfer, Craig Plante
National Science Foundation
(grant # OCE 2241830)
2023 – 2026
Estuaries are nurseries that are critical habitat for many commercially and recreationally important species. The base of the food web in these systems is supplied by microalgal primary production in both the water column (phytoplankton) and the sediments (benthic microalgae). This project focuses on quantifying the contribution of benthic microalgae to total ecosystem primary production in the North Inlet Estuary, SC. Benthic microalgal production estimates along an elevational gradient (low to high tide region) are then used to assess responses to the impending sea level rise. The results have implications for wetlands valuation, carbon credits, trophodynamics, and carbon storage in estuarine ecosystems. This research is transformative in that it provides the first ever comprehensive measures of intertidal, ecosystem-level benthic microalgal contributions to total net primary production to evaluate the ecological importance of BMA for estuarine ecosystem processes and functions. The research results will likely restructure our understanding and current paradigms of energy flow and cycling processes in estuaries.
Our current understanding of ecosystem net primary production in southeastern estuaries is missing a fundamental component that may, in fact, provide as much as a third of the fixed C fueling the high biomass of upper trophic levels. The concept of a major benthic microalgal-based subsidy contradicts the traditional views that phytoplankton and detritus-based food webs are the only energy sources for most southeastern estuaries. This project quantitatively determines the relative BMA contribution by characterizing the spatiotemporal variability in BMA NPP to estimate the annual ecosystem-level contribution to total system NPP. The primary objective is the measurement of estuarine intertidal BMA NPP, biomass, community composition, and relevant environmental variables (nutrients, grain size, porosity, etc.) along fixed transects that span the intertidal elevational gradient from mean low water to mean high water and incorporate these results in a GIS DEM to calculate ecosystem-level BMA NPP. Furthermore, the GIS model predicts shifts in the magnitude and spatial distribution of BMA NPP resulting from various sea-level rise scenarios.