(72) Fish Behavior Prevents Major Food Subsidy Opportunity in Coral Reefs

     Food webs of ecosystems around the world are often augmented by external inputs of resources (subsidies) which can have a dramatic effect on the ecology of that system. An example of this from marine systems is the... [ view full abstract ]

     Food webs of ecosystems around the world are often augmented by external inputs of resources (subsidies) which can have a dramatic effect on the ecology of that system. An example of this from marine systems is the mass movement of large amounts of Sargassum seaweed (brown algae) from the open ocean (where it grows clonally in enormous floating island-like masses) into lagoon, coral reef, sandy beach and mangrove ecosystems of the Caribbean. We observed that herbivorous fishes associated with coral reefs would eat sargassum when it was closer to the benthos, but would not when it was floating on the surface.  It is possible the spatially restricted feeding behavior of reef fish prevent them from taking advantage of this abundant food resource floating over the reef.  Our study examined fish feeding behavior on Sargassum in relation to the distance from the benthos in the patch reefs just off of South Water Caye in Belize. We hypothesized that there would be a decrease in Sargassum herbivory as distance from the benthos increased. Sargassum was collected and arranged into equivalent sized bundles and tied onto lines at evenly spaced intervals. Lines were anchored immediately adjacent to patch reefs at South Water Caye in the Belizean Barrier Reef and subjected to herbivory for 2.5 hours. The data we collected displayed a decreasing amount of leaves eaten as the distance from the benthos increased, suggesting that fish will not take advantage of Sargassum at the surface, or even up to 2.5 meters from the benthos. Since coral reefs are a nutrient-limited system, the Sargassum could drastically alter the trophic dynamics of the community, however it was not inaccessible to the herbivorous fishes do to their unwillingness to approach the surface waters to feed.