Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98%) of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity. 1. Introduction It is now estimated that 780 million litres of oil entered the Gulf of Mexico waters in the months following the sinking of the Deepwater Horizon platform on April 22, 2010 [1], affecting an area of over 75 000？km2 (Figure 1). After 7 months of clean up activity, it was considered that approximately 41% of the oil had evaporated, dissolved, or dispersed by natural means, 33% was captured, chemically dispersed, burned, or skimmed during remediation efforts, and 26% remained as a potential hazard [1]. British Petroleum’s (BP) principle remediation effort used up to 3 000 000 litres of the dispersant Corexit (EC9500A and EC9527A), much of which was injected at 1500？m depth, to disperse the spill and reduce the amount reaching the surface [2]. Application of dispersants is controversial and in some environments has been shown to inhibit the activity of hydrocarbon-degrading bacteria [3], the primary mechanism by which oil eventually leaves the ecosystem. Figure 1: NASA’s Terra satellite image of the Gulf of Mexico oil spill (light grey area) on May 17th, 2010, at 12:40？PM. The point marks the site of the Deepwater Horizon drilling platform that sank on April 20th, 2010 (source
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