Abstract

The present work was realized in the framework of the project of the National Park of Guadeloupe of reintroduction of the manatee (Trichechus manatus). The aim was to study the dynamics of the leaf primary production, the associated litter and its micro-fauna in Thalassia testudinum seagrass beds in order to evaluate the potential grazing impact of manatees. According to sites, the leaf primary production fluctuated between 2.6 ± 0.4 g to 4.0 ± 0.7 g of dry weight/m2/day in the absence of grazing and between 0.9 ± 0.3 g and 1.4 ± 0.4 g of dry weight/m2/day when cutting the leaves to simulate manatees "grazing". Moreover, areas 50 cm x 50 cm were completely denuded from leaves and rhizomes to simulate the "rooting" by manatees. These areas have not recovered after three months. The average mass of leaf litter fluctuates between 36.12 ± 7.5 g dry weight/m2 and 6.2 ± 0.9 g dry weight/m2. According to sites, the decay of litter reached 82 % and 69.6 % in three months. The fauna associated with litter consisted mainly of polychaetes, crustaceans, plathelminths and nematodes, which constitute an important link in the seagrass food web. Results from this study show that manatees grazing might disturb the primary productivity of seagrass beds. It will be necessary to be careful in the choice of areas of acclimation in terms of surface and duration of use, and in the choice of the number of manatees that can be reintroduced in the seagrass habitats.

PDF Preview