Date of Award

Spring 4-30-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Christine Mutiti

Second Advisor

Dr. Samuel Mutiti

Third Advisor

Dr. David Weese

Abstract

Barrier islands have great ecological and economical importance and face a threat from increasing sea-level due to climate change. Erosion of existing freshwater lens and ocean inundation could greatly change freshwater availability on the island. This could have significant impacts on freshwater crayfish like Procambarus lunzi, which are complexly intertwined into the trophic food web of the island. This study’s goal was to investigate the salinity tolerance of this crayfish on Sapelo Island, Georgia, in an attempt to predict the possible effects and response to sea-level rise by this crayfish. Crayfish were wild-caught from the island in March, June, and September of 2019. A total of 172 crayfish were exposed to three treatments: freshwater, slow rise salinity, and fast rise. Salinity was increased by 3‰ each week in the fast rise group and increased at half that rate (1.5‰ each week) in the slow rise salinity group, while the freshwater group remained at 0‰ throughout the duration of the study. Treatments were observed for three different criteria: mortality, mass gain, and molting frequency. The study found that these crayfish can tolerate surprisingly high salinities, with an overall 50% mortality rate being reached only when salinity was raised to 39‰, greater than the salinity of sea water. However, mass gain did not seem to be an effective method for measuring stress, as crayfish in each group exhibited limited gains in overall body mass. Molting frequency showed a definitive tendency favoring molting in freshwater, although overall rates were too small to be significant. Overall, P. lunzi showed significant ability to survive in increased salinities; however much further investigation would be required to reach definitive conclusions, as the factors influencing P. lunzi’s survivability are nuanced and complex.

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