Effect of shell debris on macrobenthos community in a high productivity Peruvian bay

GAMERO, P.; GAMARRA A.; LOMOVASKY BETINA JUDITH; IRIBARNE O.; ROMERO L.; TARAZONA J.

Lima

Simposio; CENSOR Endterm Symposium; 2008

In this study we investigated if different proportion of shell debris could affect the structure of macrobenthos community in soft bottom shallow areas of Independencia Bay. This study was carry out in Independencia bay (14,15´S; 76o14´W) Pisco, Peru between May 2006 and May 2007. Four treatment, in wire cages, were carried out using shell debris of Argopecten purpuratus: 1) Full: cages with 100% shell cover, 3) Medium: cages with 50 % shell cover, 3) Empty: cages without shell and 4) Natural: control treatment. All cages were anchored at 12 m depth. Ten samples of macrobenthos were taken with a core, every two months in each treatment and  statistical analyses were performed. We found a total of 115 taxa. Polychaetes, crustaceans and mollusks were the most abundant groups (92%). Mollusk biomasa were higer in all treatment, but there were no differeces between treatments. Dominant species in abundance were the gastropod Nassarius gayi and polychaetes Aquilaspio peruana and Mediomastus branchiferus.In biomass, dominant species were Nasarius gayi, Tegula euryomphalus and Argopecten purpuratus. Biomass (wet weigh) and dry weigh shown significantly differences between treatments, but abundance didn’t. However, significantly differences between months were found in abundance, biomass and dry weigh. Treatment effects on richness species (S) and Shannon index (H) varied in each month. Similarity analisys (Bray-Curtis) showed that Natural, Empty and Full treatments were more associated that Medium treatment. Considering the biomassa two groups were formed Natural-Empty and Medium-Full. Multidimensional community analysis showed no effect of treatment. We discuss the variability of responses of the macrobenthos community to shell debris effect.