More than 400,000 tons of petroleum hydrocarbons are released annually into the ocean, with human activities and natural seepage contributing comparable amounts. This quantity is dwarfed, according to recent work, by the production of 308,000,000 - 771,000,000 tons of hydrocarbons by cyanobacteria. While the ubiquity of hydrocarbons in the oceans has long-been attributed to a phytoplankton source, no study has considered the latent biogeochemical cycling of such biogenic hydrocarbons or the effects of this cycle.
This proposal seeks to lay a scientific foundation for understanding the distribution, partitioning, and cycling of biogenic hydrocarbons in the ocean. The hypotheses driving this proposal focus on the abundance and molecular diversity of biogenic hydrocarbons in relation to the cyanobacterial population; the extent to which volatilization to the atmosphere acts as a sink for biogenic hydrocarbons; and the rate at which hydrocarbons are produced by cyanobacteria and consumed by hydrocarbon-degrading bacteria.
The approach involves field studies conducted in tandem with a previously funded expedition, and laboratory studies centered on biogenic hydrocarbons produced by cyanobacteria. Field studies will capitalize on natural gradients in phytoplankton community structure that are hypothesized to control hydrocarbon composition and abundance and will include both survey components to understand the distribution of biogenic hydrocarbons and incubation components to quantify the rate of cycling. Laboratory studies will augment field studies by assessing hydrocarbon production and loss mechanisms under controlled laboratory conditions