Seaweeds in the southern Gulf of California

During 1993, quarterly systematic samplings were made at ten representative locations of the benthic environments of La Pat Bay. At each location we g athered algae in the subtidal and intertidal zones. We identified 126 speci es, of which 118 were previously reported. Eight are first records: Amphiro a beauvoisii, A. misakiensis, A. vanbosseae, A. valonioides, Dictyota cervi cornis, Endoplura aurea, Hydrolithon reinboldii, and Liagora celanoides f. leprosa. The greatest richness was at Calerita and the smallest at Isla Gav iota. The largest number of species was found in spring and the least in au tumn. In La Pat Bay the phycofloristic similarity between locations was det ermined by the degree of exposure to surge, depth, and type of substrate. T he association analysis allowed us to identify groups of species that inclu ded organisms with different morphological characteristics, from structural ly simple to complex, but that share a common preference for the same type of substrate and environment. The morphology of the algae that constituted the associations was different, however the organisms had strategies to ada pt, allowing coexistence in habitats with similar conditions. La Pat Bay ha s a great variety of environments, different types of substrates, and clima tic and oceanographic conditions which change during the year. In this sens e, seaweeds would be a quantitative and qualitative sign of certain environ mental characteristics. If the conditions change, there will be a variation in the species expression, which can be in number or in external morpholog y. This will depend on their ability to adapt.