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THE DISTRIBUTION OF MACROINVERTEBRATES ON SAPELO ISLAND, GA

Abstract

Sapelo Island is one of Georgia’s barrier islands that is almost completely owned and managed by the state. The island has vast amounts of salt marshes and tidal drainages that are inhabited by aquatic organisms. Salt marshes support large macroinvertebrate biodiversity, with the southeastern coast having the highest number of known crayfish species in the United States. The goal of this research was to study the distribution, presence and diversity of macroinvertebrates on Sapelo Island, Georgia, and correlate this distribution to the salinity (conductivity) and nitrate distribution and concentrations. Macroinvertebrates were collected using D-framed nets following the Georgia Adopt-A-Stream’s sampling protocols. A YSI multi-parameter instrument and a LabQuest Pro were used in the field to measure physical and chemical water parameters (temperature, pH, dissolved oxygen, conductivity, total dissolved solids). Nitrate concentrations were measured using an ISE nitrate-specific probe from Vernier LLC. Water and soil samples were collected and transported to the lab where salinity and nitrate concentrations were re-measured. Specific conductance values in surface waters ranged from 0.2 to 44 mS/cm while nitrate ranged from 1 to 60 ppm. The surface water bodies generally have very low macroinvertebrate diversity. These preliminary results showed strong negative correlations between salinity and the presence of crayfish and oval water beetles. Crayfish and oval water beetles on Sapelo Island appear to prefer low salinity waters (fresh and brackish water), which also coincided with low nitrate concentrations. Further spatial and temporal distributions and correlations are being carried out. These preliminary results imply that as global temperatures rise and seawater floods barrier islands, there will be a loss of habitats for some of the species of macroinvertebrates.

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