MANGROVE ECOSYSTEMS AND SHRIMP FARMING INTERACTIONS ALONG TROPICAL COASTLINES; A PHYSICAL AND CHEMICAL ASSESSMENT

Frank David*, Pierre Taillardat, Cyril Marchand, Nathalie Molnar and Tarik Meziane

Unité Mixte de Recherche « Biologie des organismes et écosystèmes aquatiques » (BOREA, UMR 7208), Muséum national d'Histoire naturelle, Université Pierre et Marie Curie, Université de Caen Basse-Normandie, Centre National de la Recherche Scientifique, Institut de Recherche pour le Développement-207, Université des Antilles.
61 rue Buffon, CP53 ; 75005 Paris, France
frank.david@edu.mnhn.fr

Shrimp farming is one of the most serious threat to mangrove ecosystems. Expansion of shrimp ponds have diminished mangrove area and affected their natural biogeochemical dynamics. At global scale, carbon stocks from mangrove biomass and soil have been rapidly lost due to conversion to shrimp ponds. At local scale, effluent water, rich with particulate and dissolved organic and inorganic nutrients and with antibiotics and heavy metals, have modified assimilation, decomposition, mineralization and sequestration of natural elements. These modifications have a direct effect on species assemblages in sediments.

This presentation provides a brief assessment of biogeochemical interactions between shrimp farms, their associated effluents, and mangrove forests. In addition to the depletion of mangrove carbon stock, microbial processes, organic carbon concentration and degradation mechanisms differ from a pristine to a shrimp effluent mangrove. Similarly to the carbon element, ecosystem health is also impacted by adjacent shrimp farms. As an example, previous studies estimated that only about 30 and 15% of total nitrogen (N) and phosphorus (P) discharged in ponds are assimilated by shrimps, respectively. Therefore, most of these fertilizers are rapidly drained towards adjacent mangroves, leading to potential eutrophication, by stimulated primary production and bacterial activity. This presentation aims to know how shrimp farming is affecting the natural dynamic of mangrove ecosystems.

Describing the impact of shrimp aquaculture on mangroves is highly relevant in order to suggest sustainable practices along coastal areas. Studies that have evaluated the sustainability of shrimp farms led to two contrasting production methods: landscape integrated systems and closed systems. Since mangroves provide a large range of ecosystem services which protect and support coastal communities and activities, such as shrimp production, we argue that mangroves, and their natural processes, should be integrated in a comprehensive coastal management.