SS3.14 An Interdisciplinary Journey Towards Integrated Aquatic Sciences: Homage to Jacob Kalff
Date: Thursday, June 13, 2002
Time: 10:30:00 AM
Location: Saanich
Ross, P., Colorado School of Mines, Golden,CO 80401 USA, ,
DeLorenzo, M, , National Ocean Service, Charleston, SC, USA, ,
Henebry, M, , Illinois Environmental Protection Agency, Springfield, IL, ,
Single species toxicity tests may fail to predict complex effects on emergent ecosystem properties. Natural microbial communities have been collected on artificial substrates and used to study chronic effects of exposure to single chemicals and to contaminant mixtures. In freshwater studies, complex contaminant mixtures (sediment elutriates) inhibited respiration, colonization and species abundance, especially phototrophs, in laboratory tests. In-situ exposures at contaminated harbor sites gave similar results. In tidal creek (estuarine) studies the herbicide atrazine and its metabolite deethylatrazine, inhibited chlorophyll-a, phototrophic carbon assimilation, dissolved oxygen, and phototrophic biovolume at concentrations from 50 to 250 g/L, while bacterial abundance increased. The insecticide endosulfan, at 1 and 10 g/L, inhibited bacterial abundance, particularly cyanobacteria. The insecticide chlorpyrifos at 10 g/L reduced the numbers of heterotrophic ciliates and flagellates, which in turn increased bacterial abundance and decreased chlorophyll-a. Studies with selective inhibitors suggested a seasonal shift from microbial loop-type dynamics (summer) to a more linear trophic system (fall).