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Abstract
Suspended fine particulate matter (SFPM) is an important component of southeastern river food webs; however, variability in its quality has not previously been measured. A chironomid growth assay was used as an integrative measure of quality, SFPM was collected along the Little Tennessee River continuum. Quality of SFPM collected from the 7th order site was significantly higher than SFPM collected from the 5th order site. Traditional measures of quality (% lipids, % diatoms, calories, bacteria, % inorganic and N/C ratio) were not related to growth. Using the same methods, I measured the quality of SFPM collected from the Chattahoochee River which flows through metropolitan Atlanta, GA. Traditional measures of quality and total recoverable metal concentrations associated with SFPM were measured. Quality of SFPM was inversely related to urbanization but was not related to metal concentration. SFPM quality in the Chattahoochee River was less than in the Little Tennessee River.|I also examined the role of SFPM as a conduit for metals to macroinvertebrates. Three macroinvertebrate taxa (scraping mayflies,collecting/gathering midges and filtering caddisflies) were collected from four sites along the Chattahoochee River during four seasons. While the concentrations of metals (arsenic,copper,cadmium,lead and mercury) in macroinvertebrates were not different among sites,they were elevated compared to macroinvertebrate metal concentrations measured in other sites around the US. No other factor (diet,size,extent of exoskeleton,and sorbed and dissolved metal concentrations in the water column) was significantly related to tissue metal concentrations. Arsenic,copper,cadmium and mercury dynamics were also examined in the food web of the Chattahoochee. Cadmium and mercury biomagnified from SFPM to macroinvertebrates and arsenic and mercury biomagnifed from macroinvertebrates to fishes. Arsenic and mercury were positively related to ? 15N and were significantly related to each other, suggesting that they move in similar ways through the food web.|Currently only dissolved concentrations of metals are regulated in US surface waters and Georgia adopted this standard in 1998. Metals sorbed to SFPM are no longer regulated. The criteria change and adoption of clean techniques, resulted in 943 Georgia stream miles being no longer listed for metals violations. I recommend metals criteria based on tissue residue to more adequately protect biota.