Climate drivers of Spartina marsh production on the Georgia coast

Global climate changes are altering functioning of the earth’s ecosystems. Tidal saltmarshes are threatened by sea level rise and changes in weather patterns. In order to predict the consequences of climate change on coastal communities, we need to understand how climate drivers mediate ecosystem production. In case of the tidal marshes this understanding is currently ambiguous and geographically limited to the central and northern part of the Atlantic coast.

In 2000-2011 we conducted annual surveys of Spartina alterniflora biomass in tidal marshes of the coast of Georgia. Plant length was measured at permanent plots established near the creekbank and in the midmarsh zone at 9 sites located in the Altamaha river estuary. Data on plant length was converted into biomass using site specific regressions. Spartina alterniflora biomass, air temperature, precipitation, sea level and Altamaha river discharge were analyzed using multilevel modeling.

Spartina ANPP strongly varied between years. River discharge had stronger effects on creekbank than mid-marsh production. A weak  effect of sea level on midmarsh ANPP had been detected. The decrease in salinity in high discharge years was most likely the proximate driver of the increased production. Our results differ from analyses from tidal marshes of the central and northern part of the Atlantic coast which can be due to differences in climate or hydrology and/or reflect differences in statistical and sampling methodology.