Tracking and Assessing Oil Spill Toxicity to Aquatic Organisms: A Novel Approach

An in situ exposure and effects bioassay system was developed for assessing the toxicity of oil spills to aquatic organisms. The assessment tool combines components of 2 previously developed systems, the sediment ecotoxicity assessment ring (SEA Ring) and the drifting particle simulator. The integrated drifting exposure and effects assessment ring (DEEAR) is comprised of a Global Positioning System (GPS) float, a drifter drogue, the SEA Ring, and the Cyclops-7 fluorescent sensor. Polyethylene passive sampling devices (PED) were mounted for an additional means to characterize water quality conditions and exposures. The DEEAR is optimized for evaluating oil exposure and toxicity in the shallow surface mixing layer of marine waters. A short-term preliminary test was conducted in San Diego, California, USA, to verify the operation of the GPS tracking, the iridium communications, and the integrated SEA Ring exposure system. Further, a proof-of-concept demonstration was conducted offshore in the Santa Barbara Channel, where natural oil seeps produce surface slicks and sheens. Two DEEAR units were deployed for 24 h-one within the oil slick and one in an area outside observable slicks. An aerial drone provided tracking of the surface oil and optimal sites for deployment. The DEEAR proof-of-concept demonstrated integrated real-time tracking and characterization of oil exposures by grab samples, PED, and fluorescent sensors. Oil exposures were directly linked to toxic responses in fish and mysids. This novel integrated system shows promise for use in a variety of aquatic sites to more accurately determine in situ oil exposure and toxicity. Environ Toxicol Chem 2021;40:1452-1462. © 2021 SETAC.

Trophic Transfer of a Sediment-Associated Organophosphate Pesticide from Meiobenthos to Bottom Feeding Fish

Experiments were conducted to examine the dynamics of a sediment-associated pesticide azinphosmethyl (APM) using a sublethal benthic based trophic transfer model (meiobenthic copepods to juvenile fish). Two predominant pathways for contaminant transfer during feeding, prey ingestion and sediment ingestion, were examined to determine their relative contributions to APM transfer and subsequent effects on fish brain AChE inhibition. Experiments were conducted in 1993 and in 1994. Field collected benthic copepods were exposed to 14-C labeled APM, a potent acetylcholinesterase (AChE) inhibitor, in sediments for 96 h. APM burdens were measured in the copepods, and these contaminated copepods were fed to the juvenile fish predator Leiostomus xanthurus in uncomtaminated sediments. After gut clearance, fish were examined for brain AChE activity and APM residues in the liver, heart, gut, muscle, gill, and remains. Similar experiments were conducted in which meals of uncontaminated copepods were fed to spot in APM contaminated sediments, to determine the relative contribution of contaminated sediments to APM transfer. Copepods exposed to APM at a mean sediment concentration of 1223 ng/g dry weight accumulated APM at the level of 2.5 &mgr;g/g dry tissue. Brain AChE activity was significantly depressed (23%) in the 1993 fish fed one meal of contaminated copepods, however there was no significant decline in AChE activity in the fish tested during 1994. APM accumulation in fish feeding in contaminated sediments was generally greater than in fish feeding on contaminated prey. Significant accumulation was found in bodily remains, gills, gut, and muscle in fish that fed in contaminated sediments. No significant APM accumulation was found in fish fed the contaminated copepods.