Project: Microbial interactions on particulate organic matter: from community structure to function

NSF Award Abstract:
For marine bacteria the ocean is a vast desert punctuated by hotspots of nutrients originating from fragments of animal and algal tissue rich in organic carbon. Marine bacteria colonize and consume these hotspots, turning them into dissolved nutrients and releasing CO2 to the atmosphere. This process has tremendous implications for the global carbon cycle, but its dynamics and efficiency are fully determined by poorly understood ecological processes that unfold at the scale of those microscopic hotspots. The research aims to identify and quantify those micro-scale ecological processes, in particular with respect to how interactions between species of marine bacteria on nutrient hotspots impact the dynamics and efficiency of carbon turnover in the ocean. To this end, this project will use novel techniques to cultivate marine bacteria that live on nutrient hotspots and to measure their interspecies interactions as well as their effect on ecosystem function. This project will directly train two undergraduate students and one PhD. student. The findings of this project will be communicated to a broad audience via a series of podcasts focused on how the complex life of microbes at micro-scales impact biogeochemical cycles. These will be developed by undergraduate and graduate students at MIT.

The main hypothesis behind this research is that microbial interactions, frequently occurring on nutrient hotspots, have a significant impact on the rate of organic matter turnover, thereby affecting the global carbon cycle. To test this idea, model marine particles composed of biopolymers frequently found in marine environments will be used as scaffolds for natural microbial communities. This technique will allow the researchers to study community dynamics and function in a controlled and quantitative fashion. This work will identify the main ecological species active in the particle-attached communities as well as their functional roles during particle consumption. The research will also determine how interactions between bacteria in the community impact the degradation rate and the efficiency with which organic matter is turned into biomass, CO2 and other forms of dissolved carbon that diffuse into the water column.