OCE-PFP: Alkane-based metabolic coupling between phytoplankton and Marine Group II Euryarchaeota

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National Science Foundation
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Area/s of Research
Ecology and Evolution

Petroleum hydrocarbons enter the ocean via natural means—such as seepage from geologic strata—as well as from anthropogenic sources, such as industrial oil spills associated with extraction, transportation, and consumption of petroleum. Biogenic hydrocarbons (or cryptic microbial hydrocarbons) originate from phytoplankton (cyanobacteria and other microalgae) in the form of long-chain alkanes and alkenes, and are also released into the ocean in a massive and rapid cycle that greatly exceeds all other marine petroleum inputs. The lack of biological hydrocarbon accumulation in the ocean points to their efficient consumption by networks of microorganisms. However, there is currently a major knowledge gap regarding the fate of these compounds in the sunlit ocean where the majority of consumption occurs. This work seeks to lay a scientific foundation for understanding the production and biodegradation of biogenic hydrocarbons in contrasting oceanic environments, and to inform how biogenic alkane cycles play a role in structuring the ocean’s response to devastating marine oil spill disasters. The specific research proposed here derives from a combination of recent discoveries, namely the discovery of a pervasive biological hydrocarbon cycle in the ocean, described above, and the discovery that Marine Group II (MGII) Euryarchaeota broadly harbor the genomic capacity for hydrocarbon-degrading enzymatic machinery, specific genes which we directly observe abundant in nature. To explore the linkage between these observations, I have developed three testable hypotheses that focus on the uptake of biogenic alkanes by MGII, the extent to which MGII populations reflect ambient hydrocarbon supply, and whether MGII is capable of blooming when fed whole petroleum as substrate. This approach involves field studies conducted in tandem with a previously funded expedition, leverages access to natural oil seeps in the Pacific and Gulf of Mexico, ties-in to two local ocean time-series sampling programs (Plumes and Blooms and San Pedro Ocean Time Series), and incorporates laboratory studies centered on MGII dynamics in relation to biogenic alkanes. Toward broader impacts and educational opportunities, this research includes training of multiple undergraduate students over the entire duration of the project and will include field work on a previously funded expedition, laboratory experience with isotopic and microbial techniques, and participation in a major ocean sciences meeting.