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STUDY TITLE: The Role of Zooplankton in the Distribution of Hydrocarbons 

REPORT TITLE: The Role of Copepods in the Distribution of Hydrocarbons: An Experimental Approach 

CONTRACT NUMBER: 1435-01-98-CA 30909; TASK ORDER (TO): 15171 

SPONSORING OCS REGION: Alaska 

APPLICABLE PLANNING AREA: Gulf of Alaska 

FISCAL YEAR OF PROJECT FUNDING: 1999 

COMPLETION DATE OF REPORT: December 2002 

COST: FY 1999: $20,286; CUMULATIVE PROJECT COST: $20,286 

PROJECT MANAGER: Thomas C. Shirley 

AFFILIATION: University of Alaska Fairbanks 

ADDRESS: Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska, Fairbanks, 

11120 Glacier Highway, Juneau, AK 99801 

PRINCIPAL INVESTIGATOR*: Thomas C. Shirley 

KEY WORDS: copepods, hydrocarbon distribution, bioaccumulation factors, photoenhanced toxicity 

BACKGROUND: 

Copepods may provide a significant pathway for the concentration and transfer of polyaromatic 

compounds (PAC) to higher trophic level consumers. PAC dissolved from weathered crude oil are more 

persistent in the environment and have much higher toxicity than lighter, more volatile fractions of crude 

oil. Because of their polarity, PAC tend to accumulate in bio-lipids. Subarctic copepod species can contain 

up to 80% of their body dry weight in lipids and have a high surface-area-to-volume ratio. Thus, PAC 

accumulation is rapid and bioaccumulation factors are in the order of 500–8000, depending upon species 

and lipid content. While direct toxic effects of oil on copepods have been reported in the order of 10 mg L–

1

, toxicity increases substantially in the presence of natural ultraviolet (UV) radiation. 

OBJECTIVES: 

Our goals were to evaluate the role of copepods in the distribution of hydrocarbons by: 1) investigating 

PAC uptake in tissue in relation to total lipid content in copepods, 2) assessing the synergistic effect of 

low PAC concentrations in exposure water and ambient levels of UV radiation, and 3) studying the effects 

of low level PAC exposure on copepod egg production. 

DESCRIPTION: 

A new continuous-flow PAC-exposure system was developed for copepod exposures. Field collected 

copepods were subjected to 24-h PAC exposures and tissue accumulation was determined by PAC 

analysis. In addition, lipid class composition and total lipid content were determined from parallel samples 

of copepods and a regression analysis of total lipid content and PAC accumulation was conducted. 

Phototoxicity of PAC was investigated by exposure of copepods at low PAC concentrations followed by 

exposure to ambient sunlight. Further experiments were conducted to address the relationship between 

PAC concentration in the exposure water, PAC concentration in copepod tissue and the duration of 

sunlight exposure. A comparison of egg production rates of oiled and unoiled female Calanus marshallae

copepods was not feasible within the scope of this study as revealed by preliminary experiments and a 

power analysis of the results. 
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SIGNIFICANT CONCLUSIONS: 

Copepods rapidly accumulated dissolved PAC from the surrounding water relative to their total lipid 

content. Thus, the lipid-rich subarctic copepods Calanus and Neocalanus are likely to play a significant 

role in the retention and distribution of PAC after oil spill events. Due to their importance as prey for many 

commercial fish species, including pink salmon and herring, copepods may introduce substantial amounts 

of accumulated PAC into the food web. A significant interaction of the effects of PAC concentration and 

UV exposure was documented at contamination levels likely to be encountered after an oil spill event or in 

areas with significant urban runoff. This interaction effect was also observed when the UVB bandwidth 

was excluded during sunlight exposure, indicating that UVA radiation had sufficient energy to cause 

phototoxicity. Locally-increased mortality due to photoenhanced toxicity could cause sedimentation of 

dead and dying copepods, therewith introducing PAC to the sediment and benthic detritus feeders. 

STUDY RESULTS: 

This work represented the first account of PAC accumulation in copepod tissue and bioaccumulation 

factors. Bioaccumulation of dissolved PAC from the surrounding water was correlated with the PAC 

concentration in the water and total lipid content of copepods. A significant interaction of effects of low 

PAC concentrations in the exposure water (2μg of total PAC L–1) and UV radiation in 4–8 h of ambient 

daylight was reported. In addition, discoloration of the lipid sac was observed in copepods that had been 

exposed to oil and UV, but not in copepods treated with oil only or UV only exposures. Phototoxicity was 

best correlated with the product of the exposure doses of light (intensity × duration) and PAC 

concentration in tissue. Our results clearly demonstrated that phototoxicity also occurred when the UVB 

bandwidth was excluded from the light spectrum, indicating that UVA radiation possessed sufficient 

energy to cause the observed mobility impairment and mortality in copepods. 

STUDY PRODUCTS: 

Duesterloh, S. 2000. Part 1: Copepod reproduction in culture experiments, and Part 2: Synergistic 

effects of oil and ultraviolet radiation (UV) on copepods. Seminar summarizing research results 

presented at the Juneau Center School of Fisheries and Ocean Sciences public seminar series, 

December 2000, Juneau. 

Duesterloh, S. 2001. Photoenhanced toxicity of Alaskan North Slope crude oil to copepods. Presentation 

at the American Fisheries Society Student Chapter, November 2001, Juneau. 

Duesterloh, S. 2001. Photoenhanced toxicity of Alaskan North Slope crude oil to copepods. Presentation 

at the American Fisheries Society Alaska Chapter, November 2001, Sitka. 

Duesterloh, S. 2002. An experimental approach to investigate seasonal differences in the role of 

zooplankton in the distribution of hydrocarbons. University of Alaska Coastal Marine Institute Annual 

Research Review, February 2002, Fairbanks. 

Duesterloh, S. 2002. The role of copepods in the distribution of hydrocarbons. Seminar summarizing 

research progress at the Juneau Center School of Fisheries and Ocean Sciences public seminar 

series. February 2002, Juneau. 

Duesterloh, S. 2002. The role of copepods in the distribution of hydrocarbons: An experimental 

approach. Seminar in partial fulfillment of dissertation requirements presented at the Juneau Center 

School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, October 2002, Juneau. 

Duesterloh, S. 2002. The role of copepods in the distribution of hydrocarbons: An experimental 

approach. Ph.D. Dissertation, University of Alaska Fairbanks, 182 p. 

Duesterloh, S., and T.C. Shirley. 2001. An experimental approach to investigate seasonal differences in 

the role of zooplankton in the distribution of hydrocarbons. University of Alaska Coastal Marine 

Institute Annual Research Review, February 2001, Fairbanks. 

Duesterloh, S., and T.C. Shirley. 2003. The Role of Copepods in the Distribution of Hydrocarbons: An 

Experimental Approach. Final Report. OCS Study MMS 2004-034, University of Alaska Coastal 

Marine Institute, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region, 53 p. 

Duesterloh, S., J.W. Short and M.G. Barron. 2002. Photoenhanced toxicity of weathered Alaska North 

Slope crude oil to the calanoid copepods Calanus marshallae and Metridia okhotensis. Environmental 

Science and Technology 36(18):3953–3959. 
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Shirley, T.C. 2001. An experimental approach to investigate seasonal differences in the role of 

zooplankton in the distribution of hydrocarbons. Seminar summarizing research progress at Minerals 

Management Service office. April 2001, Anchorage. 

Shirley, T.C. 2001. An experimental approach to investigate seasonal differences in the role of 

zooplankton in the distribution of hydrocarbons. Seminar to the National Science Foundation 

Research Experience for Undergraduates Symposium. June 2001, Juneau. 

Shirley, T.C. 2002. An experimental approach to investigate seasonal differences in the role of 

zooplankton in the distribution of hydrocarbons. Seminar summarizing research progress at Minerals 

Management Service office. April 2002, Anchorage. 

Shirley T.C., and S. Duesterloh. 2000. The role of zooplankton in the distribution of hydrocarbons, 

p. 77. In University of Alaska Coastal Marine Institute Annual Report No. 6. OCS Study MMS 

2000-046, University of Alaska Fairbanks and USDOI, MMS, Alaska OCS Region. 

Shirley T.C., and S. Duesterloh. 2000. An experimental approach to investigate seasonal differences in 

the role of zooplankton in the distribution of hydrocarbons, p. 51–54. In University of Alaska Coastal 

Marine Institute Annual Report No. 7. OCS Study MMS 2000-070, University of Alaska Fairbanks and 

USDOI, MMS, Alaska OCS Region. 

Shirley T.C., and S. Duesterloh. 2002. An experimental approach to investigate seasonal differences in 

the role of zooplankton in the distribution of hydrocarbons, p. 39–47. In University of Alaska Coastal 

Marine Institute Annual Report No. 8. OCS Study MMS 2002-001, University of Alaska Fairbanks and 

USDOI, MMS, Alaska OCS Region. 

Shirley T.C., and S. Duesterloh. 2003. An experimental approach to investigate seasonal differences in 

the role of zooplankton in the distribution of hydrocarbons, p. 7–11. In University of Alaska Coastal 

Marine Institute Annual Report No. 9. OCS Study MMS 2003-003, University of Alaska Fairbanks and 

USDOI, MMS, Alaska OCS Region. 

Shirley T.C., and S. Duesterloh. 2004. An experimental approach to investigate seasonal differences in 

the role of zooplankton in the distribution of hydrocarbons, p. 7. In University of Alaska Coastal 

Marine Institute Annual Report No. 10. OCS Study MMS 2004-002, University of Alaska Fairbanks 

and USDOI, MMS, Alaska OCS Region. 

*P.I.’s affiliation may be different than that listed for Project Manager. 
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Map of the Gulf of Alaska study region