Effect of stranded algae in intertidal zone in Ancon bay, Peru

GAMARRA A.; HIDALGO F.J.; PERCY, G.; LOMOVASKY BETINA JUDITH; IRIBARNE O.; TARAZONA J.

Lima

Simposio; CENSOR Endterm Symposium; 2008

In many shallow waters marine habitats, a major natural disturbance is the stranding of mats of dead plant material, called wrack, in the intertidal zone beach. The stranded algae are generated by algal blooms and /or algal loosening. This fact is considered like important disturbance and determining factor in abundance of populations and the macroinfaunal zonation in sandy beaches. In highly productive systems, the El Niño periods appear like an interannual variation that depending on its intensity, can contribute in the increase of the extensions of the algal deposits. Thus, the main objective is to evaluate the effect of the algal deposits in the sandy intertidal in highly productive marine system. During 2006 and 2007, the coverage, composition and effect of stranded algae on infaunal organisms, shore birds and crabs were assessed in sandy beaches in Bahia Ancon, Peru. The algal coverage on beaches product of algae stranding did not show a pattern during the year sampled. The algae stranding composition was Ulva sp., and Gracilariopisis sp., as more frequent species, it did not show an occurrence pattern. The effect of algae stranded on the infaunal of intertidal sand was the alteration of species distribution and abundance, changing the zonation patterns of macroinfauna from sandy beaches previously established for the central coast of Peru. Seabirds remained on sandy beaches with algae stranded for a trophic reason. Certain bird species (Arenaria interpres, Actitis macularis, Calidris sp.) consumed the food supply (insects, marine invertebrates) which brings with the fresh algal stranding and algal in decomposition. In relation to the ghost crabs, coverage algal restricts their habitat, preferring places free of algal coverage; however, we observed activity of this specie on algae stranded.