Trophic transfer between coastal habitats in a seagrass-dominated macrotidal embayment system as determined by stable isotope and fatty acid signatures

Abstract

Stable isotope and fatty acid analyses were used to examine trophic transfers within a seagrass bed and its adjacent shallow subtidal and intertidal habitats in a macrotidal embayment system in Korea. Suspended particulate organic matter (POM), sedimentary organic matter, benthic microalgae (BMA), green and decomposing leaves of Zostera marina, its epiphytes and a variety of consumers in different habitats were collected between May and June 2007. Z. marina, epiphytes and BMA were more 13C-enriched than offshore POM. The δ13C values of consumers from all habitats overlapped with those of BMA, Z. marina leaves and epiphytes, indicating the trophic importance of locally produced organic matter. Tissues of the dominant consumers in all habitats contained high quantities of fatty acid biomarkers for diatoms, but very low quantities of fatty acid biomarkers for seagrass. Principal component analysis based on fatty acids of consumers showed a very complex distribution, suggesting that they have diverse nutritive origins irrespective of feeding guilds and habitats. The isotopic mixing model showed that epiphytes and BMA served as major nutritional sources for consumer production in the seagrass and the adjacent intertidal habitats. Moreover, our results suggest that epiphytes and BMA outwell into the adjacent shallow subtidal habitats and provide considerable trophic subsidy for consumer production.