Marine microbes are the engines that drive the cycling of carbon and nutrients in the oceans. They are responsible for approximately half of all photosynthesis on the planet and drive the ‘biological pump’, which transfers organic carbon from the surface to the deep ocean. The Levine Lab seeks to understand the mechanisms through which climate variability influences microbial systems and to identify how microbial systems in turn impact climate (ecosystem-to-climate feedback loops). We are developing innovative, interdisciplinary numerical models that provide new insight into how dynamics occurring at the scale of individual microbes impact large-scale ecosystem processes such as rates of global carbon cycling.

Microbial Evolution in the Ocean

One of the grand challenges in Biological Oceanography is to understand how microbes will evolve in response to anthropogenically driven changes in climate and the implication for biogeochemical cycling, ecosystem structure, and food web dynamics. We are combining evolutionary theory with biogeochemical models to gain new insight into how microbes, in particular phytoplankton, might evolve in a warmer ocean. We have several projects focused on generating hypotheses about the types of trait changes that might result from adaptation under multi-stressor selective pressure, constraining the relevant timescales for marine phytoplankton adaptation, and understanding of the implications of phytoplankton adaptation for carbon cycling and ecosystem dynamics.

Microbial Ecosystem Dynamics and Global Change

Heterotrophic microbes play a fundamental role in ocean carbon cycling. However, we still have a limited understanding of how shifts in climate will impact heterotrophic microbial communities, the consequences of these shifts for rates of biogeochemical cycling, and the potential for climate feedbacks. We have several ongoing projects aimed at developing numerical models that explicitly represent dynamic, diverse microbial communities and their impact on ocean carbon cycling. This includes developing a mechanistic understanding of the turnover time of dissolved organic matter and the vertical flux of particulate organic matter in the ocean. We are also working to define heterotrophic microbial functional groups within a biogeochemical model specifically focusing on trade-offs between different traits.

Life in a Dynamic Ocean

The oceans are inherently variable on many different temporal and spatial scales. This variability plays a fundamental role in driving biogeochemical cycles and ecosystem dynamics. We have several ongoing projects focused on understanding the impact of fine-scale environmental variability on marine microbial communities.