The Role of Sarcodine-Algal Symbiotic Associations in Upper Ocean Carbon and Nitrogen Cycles

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The three classes of symbiont-bearing sarcodines (acantharia, polycystine radiolaria and foraminifera) are a conspicuous component of upper ocean communities. Most of the previous research on the ecology of these taxa has been concentrated on a single species or limited group of species. Dr. Caron and colleagues will simultaneously examine the ecological role of the entire assemblage of these three protozoa. Their research examines two hypotheses: 1. In nutrient-poor oceanic environments, the symbiont primary production in the entire population of acantharia, polycystine radiolaria and foraminifera will represent a significant fraction of the total primary production and will dominate the production by large cells (operationally defined as cells larger than 74um). 2. Sarcodines will be a disproportionately important component of sinking material from the euphotic zone compared with their suspended biomass. Symbiont production rates of the entire population of symbiont-bearing sarcodines are determined through a combination of large volume and diver-collected production measurements to evaluate the importance of this production relative to total primary production. The significance of these planktonic protists for the vertical flux of material is estimated by the concurrent measurement of both the stocks of sarcodines and the rate of sinking export. These measurements are coordinated with the GOFS Time-Series Study at Bermuda (participation in two cruises per year), which enables the investigators to view their results from a large, seasonal perspective.