Seasonal variation in sedimentary amino acids and the association of organic matter with mineral surfaces in a sandy eelgrass meadow

Abstract

The eelgrass meadow in Padilla Bay, Washington, has a seasonal cycle of production that is dependent on nutrient remineralization from sedimentary organic matter. We observed seasonal differences in the loading of organic carbon (OC) on mineral surface area ranging from 0.90 ± 0.30 g C m-2, which is typical for coastal sediments, to 2.72 ± 0.49. There were also changes in organic matter quality as indicated by amino acid analyses. The fraction of OC composed of amino acids changed from 0.03 to 0.12 during the same time period. The molecular distribution of amino acids also varied seasonally as indicated by changes in the amino acid degradation index. Bacterial numbers were constant throughout the year, and we attribute changes in sedimentary organic matter primarily to changes in input from benthic algae.