Macro invertebrates associated to Zostera marina meadows at pacific Baja California sur coastal lagoons

Meiofaunal assemblages in seagrasses from Northwest Mexico were studied using NaGISA protocol. We evaluated spatiotemporal changes by sampling in the subtropical lagoon Laguna San Ignacio in December 2008 and April 2009. We took triplicate sediment core samples (10x15 cm dimensions) to quantify the abundance and taxa composition of invertebrates. We found 8 invertebrates taxa in the seagrass meadows of Zostera marina (ascidians, anomurans, amphipods, isopods, diplostraca, mollusks, ophiuroids, and polychaetes) with high spatiotemporal variability in their abundances. Mollusks, amphipods and polychaetes were the most frequent taxa observed. There were significant differences (p>0.05) between the abundances of amphipods found in the Mouth and Pitahaya zones. One of the ecological services provided by meiofaunal assemblages is that gray whales (Eschrichtius robustus) that visit this lagoon in the winter season, feed on the amphipods that live within the rhizomes of Zostera marina. Seagrass meadows in Northwest Mexico provide essential ecosystem functions; they form a community on which many species rely on whether as a habitat, food source or as a fishery ground for men. The ongoing monitoring of these meadows will serve as a baseline time series from which the effect of climate change on this community will be assessed. Natural Geography in Shore Areas (NaGISA) protocol represented a good method for our biological estimations in relation to other seagrass monitoring protocols reviewed during this study.