Denise Akob - Animal/Plant Interaction Lab

St. Mary's College of Maryland, St. Mary's City, MD

The Role of Epibiont Sponges in the Nutrient

Limited Rhizophora mangle (Red Mangrove) Stands

            Rhizophora mangle, or red mangrove, is a tree species specially adapted to obtain the majority of its required nutrients from salt water.  Red mangrove forests are found in coastal regions with water temperatures greater than 23C, conditions existing primarily within 25 latitude of the equator.  The habit created by the trees is often important in maintaining coastlines by creating a check on erosion.  Along the intertidal region of the mangrove forests, growth of the trees is limited by the availability of nitrogen. We hypothesize that nutrient acquisition is positively affected by marine epibiont communities in the mangroves.  In this context, epibionts are organisms that live on the tree roots that extend into the water column surrounding the trees, including shellfish, algae, sponges and tunicates.  The focus of this study is an examination of the role of sponges as epibionts on the red mangroves.  Sponges are filter-feeding animals that have symbiotic microbes living within their tissues.  These microbial communities are diverse, with some members having the ability to process nitrogen.

            In our study, we hope to describe the structure of the symbiont community within the sponge and the role this plays in the mangrove ecosystem of Twin Cayes, Belize.  Our project included a field research trip to the Smithsonian research island Carrie Bow Cayes, Belize, which is adjacent to Twin Cayes.  The samples collected from Twin Cayes were frozen and shipped to the United States for further analysis under laboratory conditions.  Presently, molecular techniques are being used to examine the members of the bacterial symbiont community within the sponge in order to bring to light the relationship between sponges and the red mangrove trees.  This project is currently under construction and results are expected over the next few months. 

            The mangrove forests are a threatened environment.  In order to adequately protect this environment it is necessary that we understand the complex role of all organisms that make up the ecosystem.  This research has awakened our intellectual curiosity and we hope that it will have an impact on future understanding and enjoyment of the mangrove ecosystem. 

This project is a collaborative effort with Dr. Ilka C. Feller (SERC, mentor for D.M. Akob) and Dr. S. Craig Cary (University of Delaware College of Marine Studies, mentor for C. Ellison).  Support for field research is provided through the Caribbean Coral Reef Ecosystems Grant program.  A special thanks to Dr. M. Cristina Diaz for her assistance on the field research in Belize. 

Red mangrove roots at low tide

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