Studies on picophytoplankton in the southern Gulf of Mexico: pigment analysis and potential importance of the picoeukaryote Prasinophyte Micromonas pusilla

Abstract

Two coastal zones (influenced by the Coatzacoalcos and Grijalva-Usumacinta rivers) and an oceanic one (Campeche Canyon), from the southern Gulf of Mexico, were sampled during the ‘nortes’ or windy (February, 2004) season, to study the concentration and distribution of the phytoplanktonic pigments and the picoeukaryote fraction. Vertical profiles of accessory pigments indicated the presence and potential importance of autotrophic picoplankton in the waters of the Southern Gulf of Mexico. These pigments showed different distributions, associated with different hydrographic conditions between the oceanic zone and the coastal regions (e.g. presence and depth of a thermocline), indicating contrasting phytoplankton communities. The highest concentrations of accessory pigments (fucoxanthin, zeaxanthin, divinyl-chlorophyll a) were associated with shallow coastal zones (above 1% PAR_I), except for prasinoxanthin that also showed high concentrations in the Campeche Canyon. Pigments associated with prokaryotic picoplankton (zeaxanthin, divinyl-chlorophyll a) were more distinguishable in the Campeche Canyon than in the coastal zones. Chlorophyll a was not directly related to accessory pigments in most of the stations studied. Relatively high cell abundances of Prasinophyte Micromonas pusilla occurred at one coastal zone station, using molecular probes (FISH-TSA), and revealed the potential importance of this Prasinophyte in the picoeukaryote fraction from the study area, providing a new insight into their ecological role, relative to diatoms and coccolithophorids.

Keywords:

• Accessory pigments
• autotrophic picoplankton
• Micromonas pusilla
• southern Gulf of Mexico

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We thank the captain and crew of the R/V Justo Sierra. The research was supported by the Consejo Nacional de Ciencia y Tecnología of México (CONACyT) under grant G27777-B. DUH-B especially thanks to Drs D. Vaulot, L. Guillou and F. Not (Station Biologique de Roscoff-SBR-, France) for their hospitality and help during a short stay at the SBR for learning and practicing the protocol for FISH-TSA. Special thanks are due to the subject editor, Dr David Montagnes, for his considerable help in producing a final draft.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark