Most of the biomass, productivity, and overall metabolism in the ocean are due to microbes, including bacteria, single-celled algae and protozoa. Oxygen depletion, harmful blooms, and other ocean ills are all attributable to these smallest members of the plankton. Their production and processing of organic matter, however, form the basis of the ocean's food web and thus determine the amount of food humans can harvest from the sea. Due to their small size, it is more difficult to assess the biological diversity of microbes than it is for larger organisms, such as the ocean's fish and mammal populations, yet because of their high abundance and dominance of ocean metabolism it is critical that we are able to measure microbial diversity and to understand how it changes over different time and space scales in response to changes in the environment. This project will make an important step forward in helping us to understand microbial biodiversity and set a baseline for changes that are expected in coming decades. In carrying out this research, undergraduate and graduate students as well as post-doctoral scholars will obtain training in the latest sequencing and data-processing technologies, an important goal for maintaining US leadership in biotechnology.
This project will use DNA-based methods to measure microbial diversity in the coastal ocean, employing the deep-sequencing technology to sample hundreds of thousands of microbial species simultaneously. To enable the deepest possible sampling, it will focus on a single group of microbes, the ciliates, using them as a model for similar microbes. Previous use of such methods has revealed a common pattern in which a small group of common ciliate species is accompanied by a very large group of rare ones. Because the new sequencing technologies provide so much information about microbial communities from each sample, this project will be able to evaluate how both the common and rare parts of the community (the latter is often referred to as the "rare biosphere") change with seasons, distance from shore, climate zone, etc. The technical goals for this project are to evaluate how ciliate diversity varies over time and space in the ocean, to evaluate environmental factors, both abiotic and biotic, that drive this variation, and to perform experiments under controlled conditions to test hypotheses about the relationship between diversity and these factors.
