| The Mobile/Tensaw Delta is one of the largest deltas in the United States, comprising 2/3 of the state of Alabama and portions of Georgia, Mississippi and Tennessee. An integrated physical, chemical and biological assessment of streams in this area was conducted in 27 streams. Surface water and sediment samples were collected at each stream and analyzed for inorganic and organic contaminants, namely heavy metals and PCBs. No PCBs were present in the water column. The concentration of metals (Cu, Cd, Pb) in the sediment were well below threshold effect concentrations. The concentration of metals in the water was above values calculated for the highest level of long term exposure without detrimental effects. The benthic community structure was used to predict groupings based upon sediment metal concentrations. Boyeria, Gomphus and Dubiraphia were the main species in identifying stream groups. Metal concentrations were also detected in the dragonfly larvae Progomphus obscurus. |
