Plankton community changes in Bahia Concepción, México

Abstract

Changes in the plankton community structure were studied during the beginning (May 1991) and the end (October 1991) of the stratification parid in Bahía Concepción, Baja California Sur. Temperature, size-fractionated phytoplankton abundance, species composition, zooplankton biomass, chlorophyll a, and proteins and carbohydrates content in particulate organic matter were estimated. A Factor Analysis (FA) was applied to detect seasonal changes in the zooplankton community structure. The highest values of phytoplankton abundance, chlorophyll a, and zooplankton biomass were recorded in October. Diatoms, dinoflagellates, cladocerans, and copepods were the most abundant groups in both sampling dates. In May, nannoplankton was dominant and in October microplankton was most abundant. Differences in plankton species composition were observad in both months, however these differences are not reflectad in the diversity (H') of phytoplankton Variations in the zooplankton community structure in May were related to low diversity of the copepoda, which increased in October, according to the seasonal evolution of coastal lagoon zooplankton communities. For the biochemical composition of particulate organic matter, proteins were higher and carbohydrates were lower in October than in May. This increase in the size, quantity, and quality of the particles was associáted with high values of zooplankton biomass and the establishment of a complex community. The Factor Analysis emphasized the influence of the waters of the Gulf of California toward the entrance of the bay, and the succession stage of the community, as the main factors affecting the seasonal evolution of the zooplankton community