Preliminary report on the epibenthic and benthic environment of San Ignacio Lagoon

Monitoring of invertebrate species composition, and spatial patterns in the epibenthic vegetation can be used to detect and mitigate impacts anthropogenic activities and large-scale environmental change. Here we present the preliminary results of an initial assessment of the epibenthic and benthic community in San Ignacio Lagoon, within the Viscaino Biosphere Reserve. In 2006 and 2007 we obtained benthic ponar grab samples from 44 and 67 sites and also recorded the epibenthic environment at 44 and 255 sites using an underwater camera throughout the lagoon. Seagrass (Zostera), algae and sea pens (Order: Pennatulacea) were detected in 34, 55 and 15 % of the 255 epibenthic videos in 2007. However in both years we observed few correlations between physical parameters, epibenthic vegetation and invertebrate densities. Non-parametric, univariate statistical analyses indicated that mollusc density was higher in areas with eel grass in 2006 and mollusks were more abundant in northern sections of the lagoon. In 2006 annelid density appeared to be higher in substrates with a high proportion of shells and in 2007 worms and echinoderms were more likely to be observed in muddy substrate. Three principal components extracted from our twelve variables characterizing the physical and biological conditions in the benthic environment accounted for 73 and 58 % of the overall variability in twelve variables in 2006 and 2007. In 2006 a total of 11 different phyla were found in invertebrate samples and the most numerous taxa were annelids and arthropods.