Distribution and Bioavailability of Trace Metals in Shallow Sediments from Grand Lake, Oklahoma.

The Tri-State Mining District (TSMD) is a historic mining area containing the Tar Creek superfund site and is the source for sediment-bound metals in Grand Lake. Despite elevated concentrations of cadmium, lead, and zinc, no evidence of sediment toxicity has been observed during previous investigations; however, these studies were limited to lake transects with mostly deep-water sediments. The purpose of this study was to assess whether TSMD-specific sediment toxicity thresholds (STTs), developed for small streams and tributaries draining the TSMD, are predictive of biological effects within the greater lake body. Investigations focused on determining trace metal distribution within the northern reaches of Grand Lake, emphasizing shallow water areas (≤ 6-m depth), and the effects of sediment disturbance on trace metal bioavailability and toxicity to two freshwater invertebrates. No significant mortality or differences in growth occurred under natural or disturbed sediment conditions for either aquatic invertebrate despite using some sediments that exceeded both McDonald general sediment quality guidelines (SQGs) and TSMD-specific STTs. Although the simulated disturbance event (i.e., vigorously aerating sediments for 30 days before toxicity tests) was sufficient to increase trace metal water concentrations and detection frequencies, no changes in overall sediment load, bioavailability, or toxicity were observed following a 10-day exposure duration. These results suggest that TSMD-specific STTs could be used to evaluate Grand Lake sediments that could potentially be disturbed by boat traffic, wave action, and dredging associated with dock construction as opposed to the more conservative general-SQGs.