Marine heterotrophic bacteria perform a key role in the global carbon cycle by remineralizing organic carbon and nutrients. The kinetics of remineralization helps set the distribution and residence time of carbon in the ocean, and little is known about how the ecology of bacteria regulates these processes. Here we ask the question: how does heterogeneity in the distribution of organic matter and bacteria on the microscale influence remineralization processes? We study this question theoretically, beginning with models of individual bacteria which search the environment for resource patches and which are parametrized by traits. Utilizing theory from polymer physics, we develop a model of the fractionation of organic polymers between dissolved and gel phases, and study the how interaction of our bacteria with this heterogeneous nutrient source influences both the trait distribution and the kinetics of remineralization.
Results/Conclusions
We find that the number of different types of organic matter plays a key role in the evolution of the trait distribution: increasing diversity leads to an evolutionary bifurcation between a population of small, non-motile bacteria to one of fast-swimming, large bacteria which colonize particles. When we introduce public goods dynamics, we recover the broad features of the observed trait distribution. This scenario would imply that the decomposition of organic polymers takes place primarily in the gel phase, and we explore the implications of this for age-size distribution of organic carbon in the ocean.