MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(MAC-1117-577621) Effects of physical/ chemical characteristics of formulated sediments on bioassay responses by Leptocheirus plumulosus to synthetic-based drilling muds.

MacGregor, III, R.¹, Morris, Hope¹, Slimp, Karla¹, Stone , Shantel¹, ¹ Halliburton Baroid / Bioassay Lab, Houston, TX, USA

ABSTRACT- The key objective of this study was to identify controllable parameters that might reduce test variability of the 4-day sediment toxicity bioassay of synthetic-based drilling muds (SBM) required for offshore drill cuttings discharge into the Gulf of Mexico. Within this test, parameters that may affect the results include, but are not limited to, SBM-sediment blending procedures, sediment composition and test organism health, size and weight. This study was designed to assess which sediment physical/ chemical characteristics might impact the variability of the SBM-sediment toxicity test responses. The study design focused on 3 basic formulated sediments. These sediments were distinguished by particle size distribution (PSD), percent water content, wet/ dry weight ratio, wet density and total carbon. The bioassays measured the percent survival, LC50, and dose-response quality of L. plumulosus to the synthetic-based drilling muds. These bioassay responses were evaluated by multi-variant analyses for correlations or relationships with the key physical/ chemical characteristics of the sediment types. These effects or correlations between sediment characteristics and bioassay response variability could be used to identify potential improvements in the application of this test as a regulatory tool.

Key words: Leptocheirus, formulated sediment, sediment bioassay