Impacts of Eddies on Zooplankton Community Structure and Biogeochemical Cycling in the Open Ocean

College Of William & Mary Virginia Institute Of Marine Science, Gloucester Point VA

Investigators

Abstract

The distribution of plankton in relation to the physical structure of the water column results in patchiness, which can significantly impact biogeochemical cycling and production of higher trophic levels. The currents, fronts and eddies that comprise the oceanic mesoscale, sometimes referred to as the internal weather of the sea, are highly energetic and ubiquitous features of ocean circulation. Dynamical consequences of these phenomena include perturbation of the chemical and biological environment that can dramatically impact biogeochemical cycling in the ocean. Recent evidence suggests that mesoscale eddies are an important nutrient transport mechanism in the oligotrophic subtropical gyres, and that they are important in controlling the structure and productivity of marine planktonic communities. This study is an intensive field study of mesozooplankton community structure associated with mesoscale eddies to compliment a recently funded NSF project, Impacts of Eddies and Mixing on Biogeochemical Cycling in the Open Ocean: Regulation by a Complex Biological System. Given the integral role zooplankton play in food webs and flux of material out of the surface waters, this study expects to find that zooplankton contribute significantly to the overall trophic energy transfer and flux in this system. This complimentary study will address the following questions: 1. How do the specific physical/ chemical/ biological characteristics of mesoscale eddy features affect the spatial and temporal distribution of mesozooplankton? 2. How do eddies affect the vertical migration behavior of mesozooplankton at the population and/or individual level? 3. How do eddies affect the physiology (body condition) of mesozooplankton at the population and/or individual level? 4. How do differences in mesozooplankton dynamics within or outside eddy features affect vertical flux of carbon and associated bio-elements? Measurements of zooplankton biomass, species composition, diel vertical migration behavior, body condition, and contribution to vertical flux will be simultaneous with other ongoing physical, chemical, and biological measurements within a series of existing cruises. The goals are to advance our understanding of the complex interactions between physics and biology in eddies, and to elucidate the role mesoscale features play in structuring zooplankton communities and influencing biogeochemical cycling. Ultimately, this natural perturbation experiment could provide critical information about how the ocean has responded to environmental changes in the past, and how it might do so in the future. Broader impacts of the study include a benefit to society by infusing ocean science education into both graduate and K-12 education, as well as informing the general public. This project will coordinate education and outreach activities with the existing eddy program. This includes the support of a young investigator at the beginning of his career, curriculum development and enhancement, development of content for public lectures and web-based curriculum for science teachers, and participation in real-time web casts of cruise activities.