Effects of Sea level Rise and Climate Variability on Ecosystem Services

of Tidal Marshes, South Atlantic Coast

US EPA STAR (Science to Achieve Results) Grant

Investigators: C Craft (PI, Indiana University, ccraft@indiana.edu), S Joye (Co-PI, University of

Georgia, mjoye@uga.edu), S Pennings (Co-PI, University of Houston,

spennings@uh.edu), D Park (Co-PI, Eco Modeling, dickpark@cableone.net),

J Ehman (Co-PI, Imagematters, jaehman@indiana.edu)

       

Project Summary:

            A conceptual model is proposed that describes how ecosystem services of tidal marshes vary along the salinity gradient and how climate change will alter the delivery of ecosystem services. Accelerated sea level rise is predicted to reduce the area of tidal marsh via submergence and conversion of tidal freshwater marsh to brackish & salt marsh. The result will be a reduction in ecosystem services of salt and brackish marshes along with an almost complete loss of services provided by tidal freshwater marshes. Predicted greater inter-annual variability of climate will lead to greater frequency of drought that reduces delivery of ecosystem services and freshwater pulsing which we predict will enhance delivery of ecosystem services.

        We will test the effects of rising sea level and greater inter-annual variability of climate on alteration of area and ecosystem services of tidal marshes in three estuaries, Altamaha, Satilla and Savannah Rivers, GA (Figure 1). Ecosystem services related to disturbance (shoreline protection) and gas regulation (CO2 & CH4 flux), soil formation (C sequestration), nutrient regulation (N, P retention), waste treatment (sediment deposition, denitrification), refugium and food (macrophytes & marsh nekton) will be measured in replicate salt, brackish and tidal freshwater marshes of each watershed. GIS in conjunction with the SLAMM model will be used to predict changes in marsh area resulting from submergence and habitat conversion. Overlay of ecosystem-level measurements will be used to predict how cumulative delivery of ecosystem services in each estuary will be altered in response to incremental (10 cm) increases in sea level. SLAMM also will be used to predict changes in shoreline protection potential of tidal marshes, commercial shrimp yields and the effects of dikes on delivery of ecosystem services. The results of the model will be scaled to the South Atlantic Coast (GA, SC) region. The effects of climate variability will be evaluated by analysis of climate (rainfall, temperature, salinity, freshwater discharge, average tide level) and ecosystem services data collected since 2000 from permanent plots of ten marshes of the GCE LTER study domain. Climate data for the region, including temperature, precipitation and river discharge extend back several decades and have been compiled by the GCE LTER program, allowing current patterns to be placed in historical context. Marsh vegetation, epifauna, accretion and sediment deposition data are collected biannually since 2000, through drought and average rainfall years.

        This work will (1) provide a basis to understand how ecosystem services vary among salt-, brackish- and tidal fresh-water marshes, (2) determine how sea level rise will alter marsh area and delivery of ecosystem services, (3) evaluate the effect of diking on delivery of ecosystem services and (4) elucidate how climate variability will affect temporal patterns of macrophytes, epifauna, sediment deposition and marsh accretion. A GIS-based model describing the effects of rising sea level on tidal marsh ecosystem services of river dominated estuaries will be produced that can be applied to comparable estuaries of the U.S.

      Figure 1.   Study region, including the southeast (GA, SC) coast, field sampling areas (Altamaha, Satilla, Savannah

      Rivers) and GIS map of tidal wetlands of the Altamaha River Estuary (GA).