Impacts of photo-oxidized dispersed oil on Phaeodactylum tricornutum

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 in the presence of dispersants on the growth and photo-physiology of oil and dispersant resistant pennate diatom Phaeodactylum tricornutum. We exposed P. tricornutum to two different dilutions of dispersed oil and dispersed photo-oxidized oil and monitored their growth rates and photo-physiological parameters such as photosynthetic efficiency (Fv/Fm), electron transport rates between photosystem II and I (rETRmax), and light harvesting ability (α). Growth rates were unaffected when exposed to dispersed oil and dispersed photo-oxidized oil. Analysis of various photo-physiological parameters revealed no significant differences between any treatments, except for lower rETRmax values in photo-oxidized dispersed oil treatment on the very first day of exposure. Further research are underway to determine the mechanisms behind the resistant nature of P. tricornutum.

深水地平线漏油事件向墨西哥湾泄漏了1.3亿加仑原油，随后相关方施用了140万加仑的化学分散剂，以期将原油分散至水体层并促进原油的生物降解。原油光氧化是一种可使浮油发生氧化的自然过程。尽管学界已针对原油对浮游植物的毒性开展了大量研究，但光氧化原油的生态效应，尤其是其与分散剂联合作用时的影响，实际上仍未明确。不同浮游植物对原油与分散剂暴露的敏感性存在差异。本研究聚焦于抗原油及分散剂的羽纹硅藻——三角褐指藻（Phaeodactylum tricornutum），探究了分散剂存在条件下，光氧化原油对其生长及光生理特性的影响。我们将三角褐指藻分别暴露于两种不同稀释梯度的分散原油与分散光氧化原油体系中，并监测其生长速率，以及光合效率（Fv/Fm）、光系统II与I间的电子传递速率（rETRmax）、光捕获能力（α）等光生理参数。结果显示，暴露于分散原油与分散光氧化原油环境中时，三角褐指藻的生长速率未受显著影响。对各类光生理参数的分析表明，除暴露首日光氧化分散原油处理组的rETRmax值更低外，其余各处理组间均无显著差异。目前，我们正开展进一步研究，以阐明三角褐指藻抗逆特性背后的作用机制。