Principal Investigator: Kevin H. Barnes (University of Georgia)
Principal Investigator: Byron J. Freeman (University of Georgia)
Sponsor: GWRI
Start Date: 1996-04-01; Completion Date: 1996-04-01;
Keywords: suspended sediment, NTU, TSS, fish, biodiversity
Description:
Excessive sedimentation and high levels of turbidity threaten the native fish species of Georgia by destroying habitat and by impairing fish feeding and spawning. To propose water quality standards for suspended sediments that would be protective of Georgia’s diverse freshwater fish fauna (283 spp.), we have searched existing records of suspended sediment concentrations (measured as turbidity in NTUs) and fish collections taken throughout rivers and streams in Georgia. We focused our attention on rivers and streams above the fall line, where the greatest number of threatened fish species are found and where excessive sedimentation is the greatest problem. We searched 36 years of water quality data and over 20,000 records of fish collections in Georgia. Only 0 – 8% of the sediment sampling stations in four major river basins in this part of the state (Mobile, Apalachicola-Chattahoochee-Flint, Altamaha, and Tennessee) have contemporaneous fish and sediment data. Hence we conclude that adequate measures of suspended sediment are lacking in areas of high fish diversity, and therefore field work in representative basins is needed to test the proposed relationships between suspended sediments and fish diversity that we developed from this very limited data base.We analyzed the existing fish and sediment data by examining the percentage of suspended sediment samples that exceed 25, 50, and 100 NTU and by comparing the feeding and spawning guilds of fishes at sites with different exceedence characteristics. We then used these data to hypothesize suspended sediment regimes that would be protective of the native fish assemblages. Based on fish and sediment data from Yellow River and Falling Creek, we hypothesize that in the Piedmont physiographic province, native fishes would be protected if random monthly samples of turbidity never exceed 100 NTU, if less than 5% of samples exceed 50 NTU, and if less than 20% of samples exceed 25 NTU. Based on fish and sediment data from three sites in the Conasauga River, we hypothesize that in the Ridge and Valley physiographic province, native fishes would be protected if monthly random samples of turbidity never exceed 25 NTU. These more stringent standards appear necessary because of the nature of the sediments in this physiographic province and because of the vulnerability of the fishes in this region to sedimentation. These hypotheses require field testing.