Role of seagrasses and mangroves in estuarine food webs: temporal and spatial changes in stable isotope composition and amino acid content during decomposition

Abstract

Carbon, nitrogen, DC, DN, amino acid composition and OIL-amino acid ratios were measured during the early stages of decomposition of seagrass and mangrove leaves in two south florida estuaries. Isotopic compositions for plants and associated consumers were consistent within an estuary. Ouring decomposition seagrasses showed little change in D'3C, 15 IsN, but showed an increase in the OIL ratio of certain of the amino acids. Mangroves show little D'3C change but marked reduction in DN, and an increase in the OIL ratio ofthe amino acids. The percentage of total N accounted for by amino acids decreased in the seagrasses over the term of the experiment, but increased for the mangroves. These data suggest a different mode of decomposition for mangroves and seagrasses when decaying under similar conditions. The DC of consumers is closely coupled to the dominant carbon source in each