Benz(a)anthracene in benthic marine environments : bioavailability, metabolism, and physiological effects on the polychaete Neries virens

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1985

This research was supported by the DOE/BLM contract DE-AC02-77EV04256 A007 and interagency agreement AA550-IA7-20 to J.W. Farringtonand J.M. Tea 1; NOAA contract 83-ABD-00012 to J.M. Tea 1; OIP support toJ.M. Teal and the~author; and support to the author from the Andrew W.Mellon Foundation through the CRL; the NWF/API Environmental ConservationFe 110wship Program, Sigma Xi, and the WHOI/MIT Joint Program inOceanography.

The fate of [14C- 121 benz(a)anthracene (BA) was followed in benthicmicrocosm experiments in the presence and absence of the polychaeteNereis virens. In concert with chemical analysis of BA and itsmetabolites in all components of the system, physiological andbiochemical effects of exposure on Nereis were investigated. BA wasintroduced in three ways: already sorbed to the entire sedimentreservoir; directly into the water column; or incorporated into agelatin-based diet. Experiments ran from 4 to 25 days. Activity of BAand BA metabolic products was followed in sediments, worm tissue, and inthe water column. 14CO2 activity in the water column was also measured.Growth, oxygen consumption, ammonia excretion, adenylate nucleotidepools, and mixed function oxygenase activity of the worms were alsomonitored.The presence of worms and the mode of introduction had significanteffects on the fate of BA in this system. In experiments with sedimentsuniformly labeled with BA, worms increased flux of BA from the sediment,and after nine days, their presence lead to increased rates of microbialmineralization of BA to CO2. In experiments where BA was added directlyto the water column, worms mixed BA into the sediment, but had no neteffect on removal of BA in the sediment to the water column. BA added tothe water column and deposited at the sediment-water interface was moreavailable for uptake by worms, microbial mineralization to CO2, andremoval to the water column than BA sorbed to bulk sediments. Regardlessof mode of introduction, worms were able to accumulate BA. However,bioavailability of BA previously sorbed to sediments was less than BAadded to the water column and allowed to settle at the sediment-waterinterface. Of the three modes of introduction studied, BA ingested in ageletin-based diet was most available for accumulation by Nereis.Length of exposure and mode of introduction had significant effectson accumulation and metabolism of BA by Nereis. Of total activityaccumulated, the proportion remaining as parent compound decreased withtime, and was inversely correlated with relative efficiency foraccumulation. The relative amounts of different metabolic products werealso affected by time and mode of exposure. In all experiments, mostactivity recovered from worms was present as metabolic products with only2 to 23% remaining as parent compound. A significant portion (from 33 to51%) of total activity was not extractable, indicating incorportationinto macromolecular components.Physiological and biochemical effects of BA exposure on Nereis wereminimal. Subtle alterations in adenylate nucleotide pools were observedafter 6 days in experiments with either sediment-sorbed BA or BA addeddirectly to the water column. After 25 days of exposure to sediment-sorbedBA, worms showed increased rates of oxygen consumption and ammoniaexcretion. No significant changes in growth or activity of the mixedfunction oxygenase system were observed.These experiments demonstrated: (1) that the presence of a largeburrowing polychaete can have significant effects on the fate of PAH inthe benthos; (2) that source can have significant effects on both fate andmetabolism of PAH in the benthos; (3) that Nereis virens is capable ofaccumulating and metabolizing BA from the sediment, water column, oringested food; and (4) that incorporation into cellular macromolecules is amajor fate of accumulated BA.