Date of Award

5-2003

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography

Advisor

Peter A. Jumars

Second Committee Member

Gary M. King

Third Committee Member

Allen R. Place

Abstract

This work characterized the size of lipoidal colloids in benthic invertebrates' guts, using contact angle dilutions and imaging the fluorescence of the hydrophobic probe Nile Red. Deposit feeders and Nereis virens ingesting sediment were found to have micelles rather than emulsions in the gut. Gut fluids from Arenicola manna (a deposit-feeding polychaete) readily formed emulsions when incubated with mussel meat (Mytilus edulis; 80 g-mussel L"-gut fluid), suggesting that micelles form due to a paucity of emulsifying lipids in the gut. Lipid tracer contained in emulsion droplets was twice as likely to be captured by sediment than was tracer in micelles. Solubilizate interactions among binary mixtures of nutritional and contaminant lipids occurred in gut fluids with micelles or high protein concentrations. In Arenicola marina gut fluid, benzo(a)pyrene (BaP) enhanced the solubilization of hexadecane (491% of single compound) and palmitic acid (130%), but hindered solubilization of cholesterol (83%). Addition of cholesterol, phenanthrene, lecithin, and hexadecanol modified BaP solubilization (137% 154%, 140%, and 232%, respectively, of BaP's concentration when alone). Micellar gut fluids are much better than seawater at releasing polycyclic aromatic hydrocarbons (PAH) associated with anthropogenic particles. A. marina gut fluids dissolved significant concentrations of PAH from two tire treads, two diesel soots, and the urban particulate matter (SRM 1649). PAH in fly ashes and coal dusts were unavailable. Potential digestive exposure to PAH from these samples is much greater than that predicted to be available from these materials using equilibrium partitioning theory (EqP). These impacts of digestive micelles make commonly used models of PAH bioavailability based upon sediment-water distribution, e.g., equilibrium partitioning theory, less accurate. A cocktail of commercially available compounds designed to mimic A. marina gut fluids was developed. Sodium taurocholate, a vertebrate bile salt, was found to be an excellent mimic for lipid solubilization; 13.0 rnM sodium taurocholate and 5.0 g L-' bovine serum albumin in artificial seawater released 12 PAH from four different contaminated sediments to similar extent as A. marina gut fluid (critical micelle dilution of 15%, protein content of 42.0 g L-'). Ratios of release between cocktail and gut fluid ranged between 0.5 and 2.0 for 40 of 48 PAH-sediment combinations.

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