11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 19: Biogeochemical Cycles in Coral Reef Environments
19-25
Mangrove-Exported Nutrient Incorporation By Sessile Invertebrates On Adjacent
Coral Reefs
Elise GRANEK* 1
1 Environmental Sciences and Resources, Portland State University, Portland, OR
Understanding the consequences of the declining global cover of mangroves necessitates
consideration of how mangrove-derived nutrients contribute to threatened coral reef
systems. We sampled potential sources of organic matter and a suite of sessile reef
invertebrate consumers from six sites in Bocas del Toro, Panama in the Caribbean Sea to
conduct stable isotope analyses using δ 34 S or δ 13 C. Using IsoSource mixing models we
determined the range of potential contributions to consumers from the various organic
matter sources in the system. Mangrove organic matter contributed substantially to most
filter feeders ranging across sites from 11-53% for sponges, 18-44% for file clams, and
29-51% for feather duster worms. Mangroves contributed 7-31% of the organic matter to
coral species. To examine how mangrove contribution varied with distance from
mangrove source we conducted a transplant experiment. Results indicated that the
mangrove contribution to invertebrate species declined with increasing distance from
shore. These results provide the first evidence that mangrove inputs of organic matter to
sessile invertebrate species are substantial and offer an indication of the magnitude of
incorporation. Thus, removal of mangroves from tropical shores can potentially generate
a deficit in the organic inputs to reef organisms, with as yet unknown ecological
consequences for the integrity and persistence of reefs.
19-26
Habitat-Dependent Diet in Zooplanktivorous Fishes: Implications For Trophic
Connections With Coral Reef And Oceanic Food Webs
Kate HANSON* 1 , James LEICHTER 1
1 Scripps Institution of Oceanography, La Jolla, CA
The import and export of zooplankton from reef systems is an important pathway by
which coral reefs exchange organic matter, energy and nutrients with adjacent open
ocean ecosystems. Understanding the dynamics of this exchange requires knowledge of
the trophic pathways through which zooplankton enter the reef system. This study
examines the relative importance of oceanic versus reef-associated resources for siteattached
reef planktivores. We utilize gut-content and stable isotope analyses to examine
intra-specific spatial variability in the diet of zooplanktivorous reef fishes. Muscle tissue
was collected from individuals of the damselfish species Dascyllus flavicaudus inhabiting
three reef zones at 6 sites surrounding the island of Moorea, French Polynesia. Carbon
isotope values measured from fish inhabiting deep forereef sites are depleted relative to
values measured from shallow lagoon and fringing reef conspecifics by ~ 3 ‰, with
corresponding differences in nitrogen isotope values of up to 1.5 ‰. Similar results were
found for a second planktivorous species, Chromis viridis. Isotope values of forereef
Dascyllus flavicaudus are less variable through time than are values of fringing reef
individuals. Together with the results of gut-content analysis, comparison of isotope
values sampled from fish with those obtained from bulk zooplankton tows suggests that
forereef individuals rely on oceanic zooplankton while lagoon and fringing reef
individuals may be increasingly dependent on reef-associated zooplankton such as larval
decapods.
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