Collaborative Research: The Role of Microbial Food Webs in Carbon Fluxes and Shelf-Basin Exchange in the Arctic Ocean

University Of Delaware, Newark DE

Investigators

Abstract

The Shelf-Basin Interaction (SBI) program and other large, multi-disciplinary projects have recently completed field work to examine carbon cycling in the Arctic Ocean. These programs included measurements of microbial standing stocks and production because of the fundamental importance of microbes in structuring marine food webs and in modulating fluxes of inorganic and organic carbon in the oceans. It has been hypothesized that heterotrophic bacteria and the rest of the microbial loop process less primary production in high latitude oceans than in most oceanic regimes because perennially cold water inhibits microbial activity. Some of the data from the SBI program indicate that the flux of carbon through the microbial loop is lower in the western Arctic than in warmer marine systems, whereas other data indicate organic carbon degradation exceeds rates of primary production. These observations have major implications for our understanding of carbon export and exchange between productive shelf waters and organic carbon-poor basins of the Arctic. However, several unresolved issues remain about the validity and interpretation of the data, the generality of the SBI findings, and the impact of microbial processes on the Arctic carbon system. To address these issues, this effort will examine the following questions: 1. What is the structure of energy flow through the microbial loop in various regions of the Arctic Ocean? All data on microbes and related biogeochemical parameters from SBI and other Arctic studies will be analyzed in order to compose a pan-Arctic synthesis and to identify possible linkages between regions of the Arctic Ocean ecosystem. 2. What is the impact of microbial activity on the carbon system in the western Arctic? Microbial rates will be compared with rates of net community production and DOM export as estimated from temporal and spatial variations in DIC and DOC in the western Arctic. 3. What is the role of transport in decoupling the production and degradation of organic matter in the Arctic Ocean? An explicit, three dimensional model of Arctic Ocean circulation and biogeochemistry will be used to evaluate the role of transport in the spatial and temporal decoupling of production and respiration. This work will help maximize use of the datasets collected by SBI and other programs, of which much has not been thoroughly analyzed and synthesized. In addition, the data synthesis and modeling efforts will provide a framework in which to consider how climate change may affect carbon fluxes and food web dynamics in the Arctic. This synthesis will be an essential mile post for gauging the trajectory of potential changes in this important ecosystem.