ACCESS NUMBER: 30951-16802

STUDY TITLE: Deepwater Program: Evaluating Sublethal Effects of Exposure to 

Petroleum Additives on Fishes Associated with Offshore Platforms

REPORT TITLE: Evaluating Sublethal Effects of Exposure to Petroleum Additives on 

Fishes Associated with Offshore Platforms

CONTRACT NUMBERS: 1435-01-99-CA-30951 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREAS: Western, Central, and Eastern Gulf of Mexico 

FISCAL YEAR OF PROJECT FUNDING: 1999 

COMPLETION DATE OF REPORT: December 2005 

COSTS: FY 1999 $314,729; CUMULATIVE PROJECT COST: $314,729 

PROJECT MANAGER: Donald M. Baltz 

AFFILIATION: Louisiana State University 

ADDRESS: Coastal Fisheries Institute, Louisiana State University, Baton Rouge, LA 

70803-7503 

PRINCIPAL INVESTIGATORS*: Donald M. Baltz, Edward J. Chesney, Matthew A. Tarr 

and Alan S. Kolok 

KEY WORDS: Sublethal effects, Swimming performance, Ethylene glycol, Methanol, 

LC50, Gulf of Mexico 

BACKGROUND: Recently, new technology has pushed petrochemical exploration into 

increasingly deeper water (>305 m) at increased risks to marine fauna. One risk is from 

chemical additives used to enhance deepwater production, such as ethylene glycol and 

methanol, which are used during the production and treatment of petroleum to prevent 

the formation of gas hydrates in deepwater wells and pipelines. Deepwater petroleum 

production requires that a number of additives, such as ethylene glycol and methanol, 

be transported and stored offshore in large quantities posing the risk of spills. Although 

these additives may not be highly toxic per se, it is important to evaluate and 

understand the risks to marine organisms, especially fishes that are often strongly 

associated with oil production facilities. 

OBJECTIVES: The objectives were to provide an estimate of the 24-h LC50, to identify 

sublethal exposure levels from which individuals could apparently recover after shortterm exposures expected in open marine systems, and to evaluate sublethal effects by 
ACCESS NUMBER: 30951-16802

comparing changes in individual swimming performance before and after exposure to 

ethylene glycol, methanol and their combination. 

DESCRIPTION: Juvenile Florida pompano Trachinotus carolinus were used in a series 

of controlled experiments to test the sublethal effects of 3.0% ethylene glycol (EG), 

1.07% methanol (MeOH) and a combination of the two chemicals (EG + MeOH) on 

swimming performance of individual fish. Florida pompano swimming performance was 

evaluated by comparing differences in pre- and post-exposure critical swimming speeds 

(Ucrit) for each individual to quantify sublethal effects. The experimental protocols 

included identical fasting, exposure, acclimation, and swimming experience for each 

group and required up to18 days for each experimental trial. An additional ethylene 

glycol exposure experiment was conducted on a second species, juvenile Atlantic 

spadefish Chaetodipterus faber.

SIGNIFICANT CONCLUSIONS: The results of the juvenile Florida pompano study 

showed that exposure to 1.07% methanol and 17 hr recovery did little to impair their 

swimming performance. Sublethal exposure to methanol had only a short-term effect 

on behavior but little effect on measured swimming performance. The lack of 

detectable levels of methanol in the plasma samples suggests that pompano completely 

metabolized methanol (probably into formaldehyde and formate products) during the ~ 

20-hr swimming and recovery process. In contrast, the mean percentage (±1 SE) of 

ethylene glycol still present in pompano plasma samples ~ 20 h after exposure was 

0.623 ± 0.04% (v/v). 

The reduction in swimming performance of juvenile Florida pompano (a 13.0% 

reduction) exposed to ethylene glycol was substantially higher than the reduction in 

performance of Atlantic spadefish (a 6.9% reduction). Spadefish may be more efficient 

at buffering against or removing the metabolite responsible (glycolic acid) for the toxic 

effects of ethylene glycol. 

Pompano exposed to the combination of ethylene glycol and methanol exhibited the 

most profound reduction in swimming performance. Fish that were exposed to the 

combination of ethylene glycol and methanol performed far worse than fish exposed to 

the single concentration of ethylene glycol. Methanol and ethylene glycol may become 

more toxic when fish are exposed to a combination of both chemicals. Similar joint 

action or additive interactions occur when toxicants have similar modes of action but act 

independently resulting in the toxicity of the mixture amounting to the sum of the 

toxicities of the individual toxicants present. Interactive action can be either synergistic 

(more than additive) or antagonistic (less than additive). These interactions occur when 

one toxicant alters the toxicity of another toxicant present. The results of the Florida 

pompano study showed that a synergistic interaction probably occurred after juveniles 

were exposed to the combination of ethylene glycol and methanol. 

Future studies should concentrate on accumulating more data on the sublethal and 

lethal effects of ethylene glycol, methanol, and other additives on a variety of species 

associated with deepwater oil and gas platforms (i.e., encrusting organisms, planktonic 
ACCESS NUMBER: 30951-16802

species, etc.). This would aid in developing a working model to better understand 

potential impacts on predator-prey interactions, chemical avoidance, behavior and 

feeding activity of fishes after exposure. Quantifying the sublethal and lethal effects of 

ethylene glycol and methanol at all trophic levels of the ecosystem would be a good first 

step in understanding the effects of deepwater oil development on fisheries in the 

northern Gulf of Mexico. 

STUDY RESULTS: Ethylene glycol toxicity tests on juvenile Florida pompano and 

subsequent probit analysis identified the LC50 as 5.63% (volume per volume) at 30 

practical salinity units and 25°C. Behavioral observations of treatment and control 

groups during 24-h exposures and 15-h recovery trials showed that 2.1% ethylene 

glycol was the lowest concentration at which individuals displayed lethargic behavior 

relative to controls after 24 h. Fish exposed to concentrations of 3.1% or less became 

lethargic or distressed relative to controls, but showed signs of recovery after 15 h in 

clean seawater. The mean (± SE) Ucrit of juveniles (23.1±4.73 g) was evaluated before 

and after exposure to a 3.0% concentration. The mean Ucrit declined significantly by 

13.5% (P<0.0002) from 95.9 ±2.37 cm/s in pre-exposure trials to 83.0 ±3.45 cm/s in 

post-exposure trials. Exposure to ethylene glycol did not impact all individuals to the 

same degree, and smaller fish experienced a greater percent reduction in swim 

performance (%R) than did larger individuals (%R = - 53.5 + [1.7 x Body Mass], R2 = 

0.3148, df = 13, P<0.0295). We also evaluated the toxicity and sublethal effects of 

methanol on the swimming performance of juvenile Florida pompano. A 24-h static 

exposure identified the LC50 of methanol as 1.28% (volume per volume, % v/v) at 30 

practical salinity units and 25°C. The mean (± SE) Ucrit of juveniles (20.5 ± 4.59 g) was 

evaluated before and after exposure to a 1.07% concentration of methanol and showed 

that Ucrit was significantly reduced (P < 0.0002) from 90.1 ± 1.35 cm/s to 84.2 ± 1.36 

cm/s in post-exposure trials. Following exposure and a 17-h recovery period in clean 

seawater, the mean 6.5% decline in performance of the methanol treatment group 

contrasted sharply with a mean increase of 4.0% in the control group, indicating that 

conditioning and/or training effects were significantly surpassed by the negative 

sublethal effects of methanol exposure. In a combination experiment (i.e., Control, EG, 

MeOH and EG + MeOH) on juvenile Florida pompano swimming performance, single 

exposures to ethylene glycol and the combination of ethylene glycol and methanol 

significantly reduced Ucrit by 13.0 and 42.0%, respectively. In this experiment, no 

detectable differences in Ucrit were found for Florida pompano exposed to methanol or 

for the controls. Juvenile Atlantic spadefish were used to test the single effects of 3.0% 

ethylene glycol on swimming performance of individuals using the same protocol 

developed for pompano. Treatment fish experienced a 6.9% reduction in Ucrit compared 

to pre-exposure swimming performance and a 17.9% reduction compared to the 

controls. The reduced ability of Florida pompano and Atlantic spadefish to sustain high 

prolonged and burst performance levels, even after a 17 hr recovery from exposure 

could affect their ability to avoid predators and feed effectively. 

STUDY PRODUCTS: 1999. Kay, M.E. (poster presenter) with D.M. Baltz, E.J. 

Chesney, M.A. Tarr, and A.S. Kolok. Toxicity and Sublethal Effects of Ethylene Glycol 
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to Juvenile Florida Pompano (Trachinotus carolinus). Presented at the 52nd Annual 

Meeting of the Gulf and Caribbean Fisheries Institute, Key West, Florida, 1-5 November 

1999. 

2000. Kay, M.E. Swimming performance of juvenile Florida pompano, Trachinotus 

carolinus, exposed to ethylene glycol. Masters Thesis. Louisiana State University, 

Baton Rouge. 42 pp. 

2000. Kay, M.E. (presenter), D.M. Baltz, E.J. Chesney, M.A. Tarr, and A.S. 

Kolok.Swimming performance of juvenile Florida pompano exposed to ethylene glycol. 

Presented at Gulf of Mexico Fish and Fisheries; Bringing Together New and Recent 

Research, October 24-26, 2000. 

2002. Hymel, M.K., D.M. Baltz, E.J. Chesney, M.A. Tarr and A.S. Kolok. Swimming 

performance of juvenile Florida pompano exposed to ethylene glycol. Pages 169-181 in 

McKay M., J. Nides, and D. Vigil (eds), Proceedings: Gulf of Mexico Fish and Fisheries: 

Bringing Together New and Recent Research, October 2000. U. S. Dept. of the Interior, 

Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS 

Study MMS 2002-004. 674 pp.

2002. Hymel, M.K., D.M. Baltz, E.J. Chesney, M.A. Tarr and A. S. Kolok. Swimming 

performance of juvenile Florida pompano exposed to ethylene glycol. Transactions of 

the American Fisheries Society 131:1152-1163. 

2005. Stead, M.A. Swimming Performance of Juvenile Florida Pompano (Trachinotus 

carolinus) and Atlantic Spadefish (Chaetodipterus faber) Exposed to Sublethal 

Concentrations of Ethylene Glycol and Methanol: Individual and Synergistic Effects. 

Masters Thesis. Louisiana State University, Baton Rouge. 64 pp.

2005. Baltz, D.M., E.J. Chesney, M. A. Tarr, A. S. Kolok, and M. J. Bradley. Swimming 

performance of juvenile Florida pompano exposed to methanol. Transaction of the 

American Fisheries Society 134: 730-740. 

2005. Stead, M.A.., D.M. Baltz, E. J. Chesney, M. A. Tarr, A. S. Kolok, and B. D. Marx. 

Swimming Performance of Juvenile Florida Pompano Exposed to Ethylene Glycol and 

Methanol: Synergistic Effects. Transaction of the American Fisheries Society 134: 1438-

1447. 

2005. Baltz, D.M. and E.J. Chesney. CD-ROM, Evaluating Sublethal Effects of 

Exposure to Petroleum Additives on Fishes Associated with Offshore Platforms. U.S. 

Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 

New Orleans, LA. OCS Study MMS 2005-054. 76 pp. 

*P.I.'s affiliation may be different than that listed for Project Managers.