Eric Febbo

The primary biodegradation of dispersed crude oil in the sea.

Dispersants are important tools for stimulating the biodegradation of large oil spills. They are essentially a bioremediation tool - aiming to stimulate the natural process of aerobic oil biodegradation by dispersing oil into micron-sized droplets that become so dilute in the water column that the natural levels of biologically available nitrogen, phosphorus and oxygen are sufficient for microbial growth. Many studies demonstrate the efficacy of dispersants in getting oil off the water surface. Here we show that biodegradation of dispersed oil is prompt and extensive when oil is present at the ppm levels expected from a successful application of dispersants - more than 80% of the hydrocarbons of lightly weathered Alaska North Slope crude oil were degraded in 60 d at 8 °C in unamended New Jersey (USA) seawater when the oil was present at 2.5 ppm by volume. The apparent halftime of the biodegradation of the hydrocarbons was 13.8 d in the absence of dispersant, and 11 d in the presence of Corexit 9500 - similar to rates extrapolated from the field in the Deepwater Horizon response.

TOXICITY OF PHYSICALLY AND CHEMICALLY DISPERSED OILS UNDER CONTINUOUS AND ENVIRONMENTALLY REALISTIC EXPOSURE CONDITIONS: APPLICABILITY TO DISPERSANT USE DECISIONS IN SPILL RESPONSE PLANNING

ABSTRACT As part of efforts to develop standardized testing protocols under the Chemical Response to Oil Spills Environmental Research Forum (CROSERF) and apply the results to real-world scenarios, three types of oils and two dispersants were tested in both continuous and short-term spiked exposures using the early life-stages of several marine organisms. Test species included embryo-larval stages of Pacific oyster (Crassostrea gigas), two marine mysids (Holmesimysis costata and Mysidopsis bahia), and two marine fishes (turbot, Scophthalmus maximus and inland silverside, Menidia beryllina). Oils were physically dispersed in seawater by vortex mixing in a flask and chemically dispersed using the same approach with COREXIT® 9527 or COREXIT® 9500 applied in a 10:1 oil-to-dispersant ratio to generate maximum exposure concentrations. Continuous exposure tests followed standard testing protocols for 96-hour or 48-hour duration, according to demands of the test species. Spiked exposures reflect continuous diluti...

Temporal patterns in the transcriptomic response of rainbow trout, Oncorhynchus mykiss, to crude oil

Time is often not characterized as a variable in ecotoxicogenomic studies. In this study, temporal changes in gene expression were determined during exposure to crude oil and a subsequent recovery period. Juvenile rainbow trout, Oncorhynchus mykiss, were exposed for 96 h to the water accommodated fractions of 0.4, 2 or 10 mgl(-1) crude oil loadings. Following 96 h of exposure, fish were transferred to recovery tanks. Gill and liver samples were collected after 24 and 96 h of exposure, and after 96 h of recovery for RNA extraction and microarray analysis. Fluorescently labeled cDNA was hybridized against matched controls, using salmonid cDNA arrays. Each exposure scenario generated unique patterns of altered gene expression. More genes responded to crude oil in the gill than in the liver. In the gill, 1137 genes had altered expression at 24 h, 2003 genes had altered expression levels at 96 h of exposure, yet by 96 h of recovery, no genes were significantly altered in expression. In the liver at 10 mgl(-1), only five genes were changed at 24 h, yet 192 genes had altered expression after 96 h recovery. At 2 mgl(-1) in the liver, many genes had altered regulation at all three time points. The 0.4 mgl(-1) loading also showed 289 genes upregulated at 24 h after exposure. The Gene Ontology terms associated with altered expression in the liver suggested that the processes of protein synthesis, xenobiotic metabolism, and oxidoreductase activity were altered. The concentration-responsive expression profile of cytochrome P450 1A, a biomarker for oil exposure, did not predict the majority of gene expression profiles in any tissue or dose, since direct relationships with dose were not observed for most genes. While the genes and their associated functions agree with known modes of toxic action for crude oil, the gene lists obtained do not match our previously published work, presumably due to array analysis procedures. These results demonstrate that changes in gene expression with time and dose may be complicated, and should be characterized in controlled laboratory settings before attempts are made to interpret responses in field-collected organisms. Further, processes for analyzing microarray data need to be developed such that standardized gene lists are developed, or that analysis does not rely on lists of significantly altered genes before arrays can be further evaluated as a monitoring tool.

Hepatic gene expression in rainbow trout (Oncorhynchus mykiss) exposed to different hydrocarbon mixtures

Traditional biomarkers for hydrocarbon exposure are not induced by all petroleum substances. The objective of this study was to determine if exposure to a crude oil and different refined oils would generate a common hydrocarbon-specific response in gene expression profiles that could be used as generic biomarkers of hydrocarbon exposure. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to the water accommodated fraction (WAF) of either kerosene, gas oil, heavy fuel oil, or crude oil for 96 h. Tissue was collected for RNA extraction and microarray analysis. Exposure to each WAF resulted in a different list of differentially regulated genes, with few genes in common across treatments. Exposure to crude oil WAF changed the expression of genes including cytochrome P4501A (CYP1A) and glutathione-S-transferase (GST) with known roles in detoxification pathways. These gene expression profiles were compared to others from previous experiments that used a diverse suite of toxicants. Clustering algorithms successfully identified gene expression profiles resulting from hydrocarbon exposure. These preliminary analyses highlight the difficulties of using single genes as diagnostic of petroleum hydrocarbon exposures. Further work is needed to determine if multivariate transcriptomic-based biomarkers may be a more effective tool than single gene studies for exposure monitoring of different oils.

Use of passive samplers for improving oil toxicity and spill effects assessment.

Methods that quantify dissolved hydrocarbons are needed to link oil exposures to toxicity. Solid phase microextraction (SPME) fibers can serve this purpose. If fibers are equilibrated with oiled water, dissolved hydrocarbons partition to and are concentrated on the fiber. The absorbed concentration (Cpolymer) can be quantified by thermal desorption using GC/FID. Further, given that the site of toxic action is hypothesized as biota lipid and partitioning of hydrocarbons to lipid and fibers is well correlated, Cpolymer is hypothesized to be a surrogate for toxicity prediction. To test this method, toxicity data for physically and chemically dispersed oils were generated for shrimp, Americamysis bahia, and compared to test exposures characterized by Cpolymer. Results indicated that Cpolymer reliably predicted toxicity across oils and dispersions. To illustrate field application, SPME results are reported for oil spills at the Ohmsett facility. SPME fibers provide a practical tool to improve characterization of oil exposures and predict effects in future lab and field studies.

Application of the target lipid model for deriving predicted no‐effect concentrations for wastewater organisms

The target lipid model (TLM) was applied to literature data from 10 microbial toxicity assays to provide a quantitative effects assessment framework for wastewater treatment plant organisms. For the nonpolar organic chemicals considered, linear relationships between the logarithm of the median effect concentrations (EC50) and log(K(OW)) conformed to the TLM for all endpoints with the exception of nitrification inhibition. Additional experimental data for the nitrification inhibition endpoint were generated for 16 narcotic chemicals using a procedure that allowed testing of volatile substances. Results obtained from the present study demonstrated that the nitrification inhibition endpoint was not adequately described by the TLM consistent with previous literature data. Acute to chronic ratios (ACRs) defined as the ratio of the EC50 to the 10% effect concentration (EC10) were available for two of the endpoints investigated and ranged from 1.1 to 2.3 for the Tetrahymena growth assay and from 2.4 to 24.1 for the nitrification inhibition endpoint. No inhibitory effects for any of the microbial endpoints investigated were observed for compounds with log(K(OW)) >5. The critical target lipid body burdens (C(L)(*)) were calculated for the nine microbial toxicity endpoints conforming to the TLM and ranged from 252 to 2,250 micromol/g octanol. The Microtox light inhibition (C(L)(*) = 252 micromol/g octanol) and Tetrahymena pyriformis growth (C(L)(*) = 254 micromol/g octanol) assays were found to be the most sensitive endpoints. The predicted no-effect concentration (PNEC) derived using the HC5 (hazardous concentration to 5% of test organisms) statistical extrapolation procedure was calculated using TLM parameters for substances with log(K(OW)) from 0 to 5. Results from this analysis demonstrate PNECs for narcotic compounds are protective of wastewater organisms excluding nitrifying bacteria. Further model improvement is needed if protection of nitrifying bacteria in wastewater treatment systems is required.

Use of Brine Shrimp (Artemia) In Dispersant Toxicity Tests: Some Caveats1

ABSTRACT Several Latin American countries currently use Artemia to evaluate the aquatic toxicity of dispersants. Test methods used to evaluate dispersant toxicity to Artemia are not uniform. The study reported here demonstrates how varying Artemia test conditions can significantly affect toxicity results for the dispersant Corexit® 9500. The type of seawater used in Artemia toxicity tests affects 48 hour LC50 values for Corexit 9500 (lethal concentration for 50% of test organisms). Nominal LC50 values ranged from 35 to 147 ppm when natural seawater was used. Nominal LC50 values ranged from 29 to 39 ppm when a synthetic seawater prepared from Crystal Sea® Marinemix was used. Greater toxicity was observed when synthetic (reconstituted) seawater was prepared according to the U. S. Environmental Protection Agency (USEPA, 1987) Artemia dispersant test guideline. Observed nominal LC50 values ranged from 8.4 to 14 ppm. Age of the Artemia nauplii is another test variable that can significantly affect toxicity res...

Integration of a Geospatial Framework With a Suite of Numerical Models for Operational, Environmental and Regulatory Aspects of Cooling Water Usage

Use of complex mathematical models and geospatial information systems (GIS) has traditionally been a mutually exclusive process. Spatial and temporal modeling is performed using a suite of well-established numerical models for a particular domain or area of interest (AOI) and outputs are produced for the same domain framework. GIS, on the other hand, allows integration for managing, storage, analyzing, connecting to perihyls, output (ie. hardcopy, softcopy) map and image products along with visualizing data for interpretation in two dimensions (2D) and three dimensions (3D) from many sources and different formats. A GIS system can include; marine data: biota, sediment types, water quality, hydrodynamic data, and ecological sensitivity information, in addition to atmospheric meteorological data. The ability to project and integrate results from numerical models in a GIS system could potentially be a powerful spatial decision support system (SDSS) for operational aspects of coastal and offshore industrial activities to support environmental management and for regulatory reporting requirements. The system would incorporate a web-based computing infrastructure where geospatial data can be accessible to many users with access controls set by data owners that are appropriate to needs. The vision is the implementation of integrated diverse multi-scale, multi-disciplinary spatial data with analytical and numerical models for environmental and industrial management. The initial SDSS developed in this stage of work integrates the physical and logical components of the modeling system into a GIS framework such that seamless interaction and functionality amongst existing GIS data sets and cooling water dispersion model scenarios can be further analyzed and visualized in a spatial format. The system will also have the flexibility to incorporate additional datasets, analytical or numerical models, and other decision making tools in the future. Such systems can assist users such as plant managers (adaptive management), emergency response teams (response planning and action) and policy advisors (impact assessment and planning). The recent emergence, although still in a nascent stage, of web-based, spatial referencing GIS tools show promise in many key aspects of environmental and operational management, research and public policy, including data storage, analysis, and decision making. Systems such as the SDSS developed in this work can help facilitate the use of these emerging technologies.

Aquatic Toxicity Testing Using Arctic Species: Some Considerations

Abstract There is increased interest in using Arctic species for aquatic toxicity testing. A limited number of test substances and Arctic species have been evaluated. There are some differences between Arctic and temperate aquatic species. Arctic aquatic species have lower metabolic rates. Therefore, they may accumulate contaminants more slowly compared to temperate species, but their relatively higher lipid content may result in a greater uptake of lipophilic contaminants. It has been suggested that Arctic aquatic species with their reduced total energy usage, may have less energy available for detoxification and depuration of contaminants. The early life stages of Arctic species have longer developmental times that may result in longer periods of increased sensitivity. Developmental stages rather than exposure periods need to be compared between temperate and Arctic species. Arctic species have longer acute response times but have similar ultimate responses compared with temperate species. Similar porti...

Spreading Agents Provide a New Oil Spill Response Option

ABSTRACT This paper describes research on a new approach to oil spill response that utilizes a silicone-based spreading agent to cause thick oil slicks to spread to extremely thin sheens. The incre...