Symposium Abstract: Controversy about Trawling and Santa Maria Key’s Causeway Effects on Seagrass
A. Quiros Espinosa, M. E. Perdomo López, and R. Arias Barreto
In the winter of 1989, building of a causeway to Santa Maria key was started, 48 kilometers from the coast, in the central region of Cuba. Before the initial actions, the hydrological influence zones of this road were determined, and some ecological aspects were included in the executive project. At the same time, a monitoring program was started, based on an initial assessment of the phytobenthos (biomass, diversity and functional groups). The monitoring took place in the springs of 1990, 1994 and 2002. Different sampling stations were located out of the causeway hydrological influences. In 1995, fishing activities began, using big trawls. The fishing zones are located in areas not influenced by the causeway, permitting comparison between the effects of fishing and the causeway on the phytobentos, mainly on seagrass. Between 1990 and 1994 no significant changes were observed in the control stations of the causeway monitoring. A different situation was observed in 2002: the seagrass density decreased significantly and the algae diversity increased considerably as consequence of a lower spatial competition by Thalassia testudinum. A graphic model of the phenomenon was presented, including the effect on fishes, other fauna, vegetation, transparency, photosynthesis and sediment retention, that shows a case of positive feedback.