Particulate amino acids in the sea: Effects of primary productivity and biological decomposition

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Abstract
We measured the flux of amino acids associated with sinking particles collected by sediment traps at two Pacific Ocean sites. These results were compared with results from six other sites where we and others have measured amino acid fluxes. This comparison shows that the flux of amino acids on sinking particles is related to primary productivity. This relationship exists in spite of differences in the oceanic regimes sampled and in the sediment traps, bactericides, and amino acid analysis techniques used. The amount of particulate amino acids leaving the euphotic zone in areas of higher productivity is a higher proportion of the primary production than in less productive areas. And, a larger amount of particulate amino acids reaches deeper waters in more productive areas. However, the particulate amino acids leaving the euphotic zone decompose faster with depth in more productive areas. Faster decomposition below the surface waters in areas of high productivity suggests that (1) decomposition of particulate organic matter may be mediated more by zooplankton and less by microbial processes than in areas of lower productivity, or (2) phytoplankton growing in more productive areas are more easily remineralized than those growing in less productive areas.