PARENT SESSION
IP01 - Sediment Quality Guidelines
Chair: Pawlisz, Andrew1, 1 The Cadmus Group, Ottawa, ON
8:00 AM to 12:00 PM - Sunday, 17 November 2002
Room Room 150 G
(IP09) Density as a potential confounding factor in sediment toxicity tests: Management Implications.
Orr, Thomas*,1, Meister, Scott1, Halbrook, Richard1, 1 Cooperative Wildlife Research Labratory, Southern Illinois University, Carbondale, Illinois
ABSTRACT- The amphipod Hyalella azteca is widely used in standardized sediment toxicity testing. Endpoints described in these methods include survival, growth, and reproduction after varying periods of sediment exposure. Growth has been shown to be a more sensitive indicator than survival, and better in predicting possible toxic effects of contaminated sediment to invertebrates. However, there has not been a thorough investigation to determine if the number of individuals surviving in each replicate may influence growth (i.e. density dependence). Density effects are most likely due to competition for resources. A sediment with high organic matter is likely to reduce competition and therefore reduce density effects. The objectives of this study were to determine if amphipod density and organic matter content lead to growth differences. Sediment was collected from the top 5 cm of Little Crab Orchard Creek, Carbondale, IL using a stainless steel handtrowl. Subsamples were taken to determine particle size distribution and organic matter content. Half of the remaining sediment was unaltered and served as the low organic treatment and the other half was amended with humus to serve as the high organic treatment. Amphipods were placed in replicate jars containing 100 mL of sediment and 150 mL of overlying water in groups of 2, 4, 6, 8, and 10 to simulated possible survival outcomes and in groups of 20 to observe what may happen when the system was exacerbated. Amphipods were recovered after 28 d and preserved in 8% sugar formalin for growth determination. Preliminary results indicate a general decrease in growth as density increases for the low organic matter treatment. The initial results of this study indicate that density is a confounding factor in sediment toxicity tests and should be taken into consideration in future management decisions.
Key words: Toxicity, Sediment, Amphipod, Hyalella azteca