Marine Algal Sensitivity to Source and Weathered Oils

Area of Science:

• Marine Biology
• Ecotoxicology
• Environmental Chemistry

Background:

• The 2010 Deepwater Horizon oil spill impacted Gulf of Mexico ecosystems.
• Assessing the toxicity of crude oil and dispersants on primary producers is crucial.

Purpose of the Study:

• To evaluate the toxicity of Deepwater Horizon oil and Corexit 9500 on key algal species.
• To characterize the sensitivity of different microalgae and macroalgae to oil exposure.

Main Methods:

• Toxicity tests were conducted on five algal species using water-accommodated fractions (WAFs) and chemically enhanced (CE) WAFs.
• Exposure media were analyzed for hydrocarbons; toxicity was determined by growth rate inhibition (EC50).
• Physically dispersed and weathered oil samples were tested.

Main Results:

• Isochrysis galbana exhibited the highest sensitivity, with significant growth inhibition across all tested conditions.
• Ectocarpus siliculosus and Dunaliella tertiolecta showed minimal impact from WAFs and CEWAFs.
• Physically dispersed source oils were generally more toxic than weathered oils.

Conclusions:

• Algal species exhibit differential sensitivity to oil spills and dispersant toxicity.
• Chronic toxic units effectively predicted observed algal growth inhibitions.
• Understanding species-specific responses is vital for ecological risk assessment post-spill.