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In the wake of the Deepwater Horizon (DWH) oil spill, a number of government agencies, academic institutions, consultants, and nonprofit organizations conducted lab- and field-based research to understand the toxic effects of the oil. Lab testing was performed with a variety of fish, birds, turtles, and vertebrate cell lines (as well as invertebrates); field biologists conducted observations on fish, birds, turtles, and marine mammals; and epidemiologists carried out observational studies in humans. Eight years after the spill, scientists and resource managers held a workshop to summarize the similarities and differences in the effects of DWH oil on vertebrate taxa and to identify remaining gaps in our understanding of oil toxicity in wildlife and humans, building upon the cross-taxonomic synthesis initiated during the Natural Resource Damage Assessment. Across the studies, consistency was found in the types of toxic response observed in the different organisms. Impairment of stress responses and adrenal gland function, cardiotoxicity, immune system dysfunction, disruption of blood cells and their function, effects on locomotion, and oxidative damage were observed across taxa. This consistency suggests conservation in the mechanisms of action and disease pathogenesis. From a toxicological perspective, a logical progression of impacts was noted: from molecular and cellular effects that manifest as organ dysfunction, to systemic effects that compromise fitness, growth, reproductive potential, and survival. From a clinical perspective, adverse health effects from DWH oil spill exposure formed a suite of signs/symptomatic responses that at the highest doses/concentrations resulted in multi-organ system failure.

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., (© 2021 SETAC.)

Hazardous site management in the United States includes remediation of contaminated environmental media and restoration of injured natural resources. Site remediation decisions are informed by ecological risk assessment (ERA), whereas restoration and compensation decisions are informed by the natural resource damage assessment (NRDA) process. Despite similarities in many of their data needs and the advantages of more closely linking their analyses, ERA and NRDA have been conducted largely independently of one another. This is the 4th in a series of papers reporting the results of a recent workshop that explored how ERA and NRDA data needs and assessment processes could be more closely linked. Our objective is to evaluate the technical underpinnings of recentmethods used to translate natural resource injuries into ecological service losses and to propose ways to enhance the usefulness of data obtained in ERAs to the NRDA process. Three aspects are addressed: 1) improving the linkage among ERA assessment endpoints and ecological services evaluated in the NRDA process, 2) enhancing ERA data collection and interpretation approaches to improve translation of ERA measurements in damage assessments, and 3) highlighting methods that can be used to aggregate service losses across contaminants and across natural resources. We propose that ERA and NRDA both would benefit by focusing ecological assessment endpoints on the ecosystem services that correspond most directly to restoration and damage compensation decisions, and we encourage development of generic ecosystem service assessment endpoints for application in hazardous site investigations. To facilitate their use in NRDA, ERA measurements should focus on natural resource species that affect the flow of ecosystem services most directly, should encompass levels of biological organization above organisms, and should be made with the use of experimental designs that support description of responses to contaminants as continuous (as opposed to discrete) variables. Application of a data quality objective process, involving input from ERA and NRDA practitioners and site decision makers alike, can facilitate identification of data collection and analysis approaches that will benefit both assessment processes. Because of their demonstrated relationships to a number of important ecosystem services, we recommend that measures of biodiversity be targeted as key measurement endpoints in ERA to support the translation between risk and service losses. Building from case studies of recent successes, suggestions are offered for aggregating service losses at sites involving combinations of chemicals and multiple natural resource groups. Recognizing that ERA and NRDA are conducted for different purposes, we conclude that their values to environmental decision making can be enhanced by more closely linking their data collection and analysis activities.

Aqueous, pore-water, and whole-sediment bioassays were conducted with meiobenthic copepods with different infaunal lifestyles to assess the acute and chronic toxicity of the organophosphorous pesticide azinphosmethyl (APM) and its bioaccumulation potential in sediments. Biota sediment accumulation factors were an order of magnitude higher for the deeper burrowing Amphiascus tenuiremis (26.6) than the epibenthic Microarthridion littorale (2.2). The female A. tenuiremis APM median lethal concentration (LC50; 3.6 microg/L) was twice the male LC50 (1.8 microg/L), in straight seawater exposures, and nearly 20% higher than males in whole-sediment exposures (540 vs 456 ng/g dry weight). Amphiascus tenuiremis were 17 times more sensitive to sediment-associated APM than M. littorale. In pore-water-only exposures, the adult mixed-sex A. tenuiremis LC50 (5.0 microg/L) was nearly twice the seawater mixed-sex LC50 (2.7 microg/L). Dissolved organic carbon in pore water was five times higher (20 mg/L) than in seawater-only exposures (4 mg/L). Differences in acute toxicity within exposure media were driven by species- and sex-specific differences in lipid content. Amphiascus tenuiremis likely experienced greater exposure to sediment-associated toxicants via longer periods of direct contact with pore water than M. littorale and, therefore, exhibited correspondingly higher bioaccumulation and acute toxicity. Copepod reproduction was significantly reduced (>60%) in 14-d sediment culture exposures at sublethal APM levels, suggesting that chronic field exposure to sediment-associated APM would result in sharp declines in copepod population growth.

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.