Abstract

CASAS VALDEZ, Margarita  and  AGUILA RAMIREZ, Ruth Noemí. Spatial variation of biomass of seaweed assemblages in the temperate-tropical transition zone of Baja California Peninsula, Mexico. Hidrobiológica [online]. 2008, vol.18, n.2, pp.137-146. ISSN 0188-8897.

Biomass changes of seaweed assemblages in four locations in a temperate-tropical transition zone were analyzed between October 1996 and August 1997. Locations with lower temperature, a high index of upwelling, and high quantities of hard substrate presented the largest values of biomass of seaweed (El Cardoncito (7.2 kg m^-2), and Las Boyitas (6.2 kg m^-2)) and the biggest quantity of species of temperate affinity. Conversely, El Datilito (0.366 kg m^-2), with a higher temperature, no evidence of upwelling, sandy substrate, and located in protected shallow waters, presented the lowest values of biomass and the lowest proportion of temperate affinity seaweed. The PCA and similarity analysis showed a close relationship between El Cardoncito and Las Boyitas. El Datilito was categorized as independent location, while Chester Rock (4.3 kg m^-2) displayed intermediate characteristics. The close relationship observed between the first two locations can be explained by the similarity of their high biomass and physiographic and environmental characteristics. El Datilito has very different physiographic and environmental characteristics and a very low biomass.

Keywords : Biomass; Transition zone; Gelidium; Macrocystis; physiographic.