Resumen

ESTRADAS-ROMERO, Alejandro; PROL-LEDESMA, Rosa María  y  ZAMUDIO-RESENDIZ, Ma. Eugenia. Relation between the geochemical characteristics of hydrothermal fluids and the abundance and richness of phytoplancton species in Bahía Concepción, Baja California Sur, Mexico. Bol. Soc. Geol. Mex [online]. 2009, vol.61, n.1, pp.87-96. ISSN 1405-3322.

The study of hydrothermal fluid discharge at Ensenada Mapachitos in Bahía Concepción (BCS) in October 2006 included the acquisition and review of geochemical data, and the determination of the phytoplankton abundance and richness. High nutrient concentration produced high phytoplankton abundance and the studied area was in a eutrophic state with respect to nutrient contents. In the vent area nitrate concentration (1.61 µM) was higher than in the control area (0.02 to 0.07 µM). The ammonium concentration in the vent area (88.09-648.95 µM) and control area (17.03-508 µM) were higher than those for seawater as well as sulphates (29.9 to 35.79 mM) and iron (0.18-0.72 µM). Phosphate concentration was within the range observed for ocean water. The dominant group in the three samples was diatoms, with a bloom of Chaetoceros curvisetus. The taxonomic analysis for hydrothermal fluid was characterized by an abundance of Cyanophyte; the most abundant species were Nostoc pruniforme and Trichodesmium erythraeum. Statistical analysis of the phytoplankton data indicates that there is a significant difference among the three samples, implying the presence of different communities. The observed differences in organism density, chlorophyll-a concentration and number of species observed can be related to the manifestations of hydrothermal discharge.

Palabras llave : Shallow hydrothermal vents; diatoms; Cyanophyte; nutrients.