Planktonic Communities in Bratina Island Melt-Water Ponds: Linking Environment to Community Dynamics

One of the fundamental challenges in biology today is to understand how organisms respond and evolve in relation to changing environments. Antarctica offers access to one of the most physically and chemically demanding environments on earth inhabited by microorganisms. Antarctic limnetic ecosystems, in particular, can experience large fluctuations in temperature and light regimes, and sustain steep chemical gradients, which greatly impact the physiology and life history strategies of the organisms that reside there. These systems provide an extraordinary and tractable opportunity to examine metabolic function and the adaptations that allow microbial communities to thrive under these extreme conditions. Yet, after decades of research we still know little about the microbial biodiversity and processes in Antarctic ecosystems and environmental factors that structure them.

A layer of rocky debris and sediments covers the undulating surface of the McMurdo Ice Shelf (MIS) near to Bratina Island (Victoria Land, Antarctica). In the depressions of this unusual ice shelf, meltwater accumulates to form a system of ponds each with a unique chemical signature. The equilibrium between water supply and evaporation results in a range of pond salinities from fresh water to hypersaline. Individual ponds can be highly stratified with steep gradients in conductivity and oxygen concentrations in the lower strata of the water column. With the lack of complex food webs, the dynamics (community structure and physiology) of the microbial populations in ponds of the MIS throughout the summer months can be directly correlated to the extreme chemical and physical structure of the environment.

This research will use a suite of modern genetic approaches matched with geochemistry to investigate how gene function and adaptation control the community structure and ecosystem dynamics of the MIS pond microbial communities in relation to well-established intense geochemical gradients. Specifically, the goals of this project are to: 1) gain a better understanding of diversity and spatial variability of microbial populations in relation to the extreme physicochemical characteristics of their environment from mid-summer until the final freeze, and 2) investigate microbial community-level gene expression involved in specific metabolisms and adaptations to these highly stratified environments.

I intend to formulate and develop a model of how the microbial communities of the ponds are structured in response to their environment, how they function within that environment and what drives the community composition and structure.