, Volume 12, Issue 3, pp 462-472
Date: 18 Feb 2009

Mangrove-Exported Nutrient Incorporation by Sessile Coral Reef Invertebrates

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Abstract

Coastal mangrove forests were historically considered as a source of organic matter (OM) for adjacent marine systems due to high net primary production; yet recent research suggesting little uptake through the food web because of low nutritional quality, challenges the concept of trophic linkage between mangrove forests and coral reefs. To examine the importance of mangrove forests to coral reef nutrient availability, we examined sessile reef-forming invertebrate consumers including hard corals, sponges, a bivalve mollusc, polychaete annelid and tunicate, and potential sources of OM (decaying mangrove leaves, microalgae, macroalgae, and seagrass) in Bocas del Toro, Panama. Using stable isotope analyses of δ34S and δ13C and a concentration-dependent version of the IsoSource mixing model, we were able to discriminate among and determine the range of potential contributions of our four OM sources to consumers. Contributions of microalgae and macroalgae were often indeterminate due to high variability, yet seagrass and mangrove contributions were often substantial. Mangrove OM ranged across sites and species of filter feeders from 0 to 57%, 7 to 41%, and 18 to 52% for sponges, file clams, and feather duster worms, respectively. Mangrove contribution to corals (Acropora cervicornis, Agaricia fragilis, Agaricia tenuifolia, Montastrea annularis, Diploria sp.) ranged from 0 to 44%. To examine whether OM contribution varied with distance from mangroves, we conducted a sponge transplant experiment that demonstrated declining mangrove contribution across three sponge species with increasing distance from the shore. These results supported the hypothesis of mangrove-coral reef nutrient linkages, providing the first evidence that mangrove inputs of OM to sessile invertebrates are substantial, accounting for 0–57% of the composition.

Author Contributions

EFG conceived of study, performed all field research, conducted data analysis and wrote the first draft of the manuscript. JEC assisted with study design, methods for sample processing, data analysis, and writing of the manuscript. DLP contributed new isotope models, assisted with data analysis, and contributed to writing of the manuscript.