Effects of heavy rainfall on polychaetes: Differential spatial patterns generated by a large-scale disturbance

Heavy rainfall caused a severe disturbance on the Thalassia testudinum meadows at Morrocoy National Park in December 1999, affecting its associated infauna and inducing responses to stress in opportunistic polychaetes belonging to the Spionidae Family. The changes were evaluated at four seagrass beds, examining the structure and species composition of the Spionid macrofauna over eight samplings: four prior and four after the disturbance. Immediately after the heavy rainfall the Spionids showed transient changes, expressed as large increases of species density and richness, reaching values of 875 individuals m− 2 (against the usual 20 individuals m− 2) and 7 species (against the previous 1–3 species) during February 2000. These abundance pulses were represented by selected species at each location. Opportunistic species, having limited dispersion (Streblospio gynobranchiata and polydorids) were commonly found in continentally-influenced locations whereas species having dispersal mechanisms were commonly found in stations under oceanic influence (species of the Genus Prionospio). Likewise, the observed recovery patterns indicate different rhythms: while the oceanic communities showed a fast recovery, the continentally ones returned to their original states slowly. Hence, the patterns observed in the benthic polychaete communities associated with the T. testudinum beds from Morrocoy N.P. clearly indicate that the recolonization processes, succession dynamics and recovery time depend on the spatial scale of disturbance, the life history of species involved and the particular conditions of the habitat.