The effect of oil and weathered oil along with nitrogen and carbon supplementation on natural phytoplankton community composition, growth and physiology

The Deepwater Horizon oil spill spilled 130 million gallons of oil into the Gulf of Mexico. This was followed by an application of 1.4 million gallons of chemical dispersants in an effort to disperse the oil into the water column and promote the biodegradation of oil. Photooxidation of oil is a natural process that causes oxygenation of an oil slick. Although the toxicity of oil on phytoplankton has been extensively studied, the effects of photo-oxidized oil, especially in combination with dispersants is virtually unknown. Phytoplankton vary in their sensitivities to oil and dispersant exposure. Here, we study the effects of photo-oxidized oil on the growth and photo-physiology of the natural phytoplankton community. We also looked at the effects of nutrient amendments as both C and N on the above-mentioned treatment. Several parameters such as EOE (estimated oil equivalent), ETRmax- maximum electron transport rate, and relative fluorescence (Fv/Fm) were measured.