Fouling communities associated to artificial substrates (pine-wood) under environmental stress conditions in Lake de Maracaibo, Venezuela

The use of artificial substrates to evaluate the faunistic composition of natural environments is a common technique employed to monitor fouling organisms in aquatic habitats. This technique allows one to see the chronological changes in diversity and abundance. With the objective to study the variation of this kind of fauna in an estuarine mangrove altered by alterations industrial and petrochemical wastes, a six-month monitoring program (May-October 1993) was performed at four stations with different degrees of perturbation and also different ecological conditions. New pine wood collectors of 20×8×1.5 cm were put and taken monthly at each station, one of them cleaned of fouling fauna and dissected looking for boring organisms. Another set of collectors (6) were put in each station along the whole period of study. The fauna composition, chronological changes and the effect of predation was studied. This fauna was analyzed qualitative and quantitatively searching for the lowest taxonomic identifications. A total of seven groups (Bivalvia, Gastropoda, Decapoda, Cirripedia, Annelida, Amphipoda, Isopoda and Platyhelmintha) were present at all stations and through time during the six month monitoring period. The most abundant species were Mytella maracaiboensis, Neritina reclivata, Psiloteredo healdi, Ritropanopeo harrisii, Balanus amphititre, Nereris sp. and Anopsilana crenata. The first colonizers were cirriped larvae, mollusks larvae, mainly teredinids and filamentous algae. This last group was in many occasions the only one present. Cirripedia and boring organisms were the most important component in all four stations because of their abundance, cover and sensibility to stressing factors. This was noted by changes in their behavior when facing industrial effluents. Perturbation was more evident in sessile organisms whose larval stages were adversely affected by daily pH and salinity oscillations. Daily changes were due to variation in the amount of waste discharge and tides. Other taxa responded more to other biotic factors such as predation by fishes