Collaborative Research: Fragmentation of Marine Snow by Swimming Macrozooplankton

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9906827Alldredge Processes which alter the sizes and abundances of large, rapidly sinking detrital particles, known as marine snow, in the ocean can dramatically impact the flux of carbon and its availability to various components of the pelagic ecosystem. Consumption by animals, bacterial decomposition, solubilization, and disaggregation by physical mixing and current shear have all been proposed as processes by which large particles are consumed or transformed into smaller more slowly sinking forms. However, recent compelling evidence from both the lab and the field indicates that the vertically migrating krill, Euphausia pacifica, fragments marine snow in the water column through its swimming activities alone. Moreover, these impacts are significantly and positively correlated with euphausiid abundance. Preliminary laboratory observations verify that the shear stresses created by the appendages of these large macrozooplankton as they cruise near aggregates breaks the marine snow into more numerous, but smaller, and more slowly sinking particles. The investigators will verify and quantify this new process and evaluate the significance of animal fragmentation relative to other particle generating and consuming processes in nature. This research will generate the first quantitative information on the role of macrozooplankton swimming on the dynamics of large particles in the water column, revealing new links between biogeochemical processes and animal behavior. It will increase our understanding of the role of zooplankton biology in particle dynamics, carbon cycling and small-scale physics in the ocean. Data generated by this study may help explain the exponential loss of sinking carbon with depth seen in most areas of the ocean, as well as previously reported diel patterns in particulate flux.