Suarez-Castillo_Abstract

FAUNA ASOCIADA A MANTOS DE Sargassum (OCHROPHYTA: FUCALES) EN EL
SAUZOSO, BAJA CALIFORNIA SUR, MÉXICO
Associated fauna to the Sargassum beds (Ochrophyta: Fucales) in El Sauzoso, Baja California
Sur, México
Alvin Noe Suarez-Castillo, M.S.
Departamento de Biologia Marina
Universidad Autónoma de Baja California
La Paz, Baja California Sur, México
ABSTRACT
The Sargassum beds play an important ecological role in the intertidal and subtidal levels. They
provide direct food or habitat for a large diversity of organisms. In the Gulf of California, the
algae beds of this species are considered potentially harvestable resource, because their large
biomass generated could be used for food supplement for animals, including the humans, and for
polysaccharides extraction (i.e. alginates). However, there are not studies about the populations
associated to these beds. In this research it was studied the community of epiphyte fauna, and the
macrofauna (epibenthic invertebrates and fish) associated to Sargassum, and their changes as
function of the population dynamics of Sargassum in the site named El Sauzoso, La Paz Bay,
BCS. The composition and abundance of the epiphyte was estimated from September 2000 to
August 2001. The epibenthic invertebrates were quantified from February to March 2008 and the
fish from August 2007 to August 2008. The results obtained were: 17 taxa of epiphyte, 54 species
of epibenthic invertebrates, and 47 species of fish. The community structure for the epiphyte
associated to Sargassum showed a seasonal variation pattern coupled to the population dynamics
of Sargassum. The amphipods were the dominant taxa during the study period. Spatially, the
community structure did not show a significant seasonal variation pattern. The more abundant
groups were amphipods, copepods, and gastropods. The correlation of the morphometric
variables of the algae versus the abundance and richness of the epiphytes, and the abundance of
each taxon, allowed determining that Sargassum was being used as habitat for the epiphytes
community, and therefore the development of the algae population influenced the abundance of
the epiphytes. The higher abundance of the epibenthic invertebrate community in the control
group (with Sargassum, and other algae) versus the experimental group (without Sargassum, and
other algae), as well as the higher richness of the fish in the control group, allowed to determined
that in most of the months, the presence of the alga increased the complexity of the rocky habitat
and favor the increase of the number of species. Although the average yearly number and
richness of epibenthic invertebrate species was not significantly different in both treatments, the
dominance of species was different along the study period. The most abundant epibenthic
invertebrate were Tripneustes depressus, Balanus sp., Elysia diomedea, Eucidaris thouarsii,
Porites panamensis, Bispira rugosa monterea, one unidentified anemone (sp. 2). These results
showed the importance of Sargassum as critical habitat to maintain the diversity, as well as the
large temporal changes in some assemblages, and the exceptionally high diversity of this
subtropical community.
Key words: community, Sargassum, La Paz Bay, diversity