Implications for monitoring: study designs and interpretation of results

Abstract

This work was conducted in the Gulf of Mexico. From the Abstract: A Sediment Quality Triad approach was used to integrate concurrently obtained toxicological, sediment contaminant, and benthic ecological data from GOOMEX in a test of coherence of responses. The biological community responded to contaminants by increases in the ratio of “the more tolerant taxon” to “the more sensitive taxon”: the nematode to harpacticoid copepod ratio for meiofauna and the polychaete to amphipod ratio for macrofauna. Meiofaunal total abundance declined near platforms whereas macrofaunal total abundance increased — probably because of organic enrichment near platforms. A second approach used small-scale spatial heterogeneity of response as evidence of impact. Cd, Ba, ChemPC1 (first principal component of contaminant information), and the nematode to harpacticoid ratio had significant heterogeneity of variance among distances from platform, with higher variances near platforms. The pattern for Cd and ChemPC1 suggests that the impact may extend out to 200 m. We argue that differing objectives which are often demanded of the same study are often in conflict (e.g., generalization about environmental impact of similar platforms has different design requirements than description of spatial pattern of impact around each platform). Therefore, requiring that a study accomplish both objectives leads to compromises and a suboptimal design for both.