The effects of salinity on leaf litter decomposition 

NSF fellow: Zach Gordon, Oglethorpe University

Mentor: Dr. Checo Colon-Gaud

The frequency and magnitude of coastal salinity intrusion events are expected to increase in coming years due to the combined effects of landscape modification and sea level rise. Salinization of coastal wetlands has the potential to decrease functional ecological integrity via community replacement. In this study, we exposed isopods (Caecidotea sp.) to varying salinity regimes (0-15 PSU) utilizing laboratory microcosm. The resulting effect on decomposition rates of leaf material as well as isopod growth and mortality were quantified. We found that increases in salinity led to a significant increase in isopod mortality with no individuals being exposed to 15 PSU water persisting for the exposure period (23 days). Additionally, increases in salinity led to decreases in the decomposition rate of detrital material with this being closely tied to the decrease in available decomposers present. In a negative control, tanks without isopods showed no difference in decomposition rate compared to those containing isopods. These findings demonstrate that salinization of freshwater aquatic habitats will lead to a decrease in overall ecosystem function and will likely lead to the replacement of less-tolerant freshwater species with brackish or marine equivalents. Additional studies regarding the responses of other decomposer groups, such as bacteria and fungi, to salinization are needed. This additional insight would allow a better understanding of the anticipated effects of salinity intrusion on the aquatic decomposer community.