Resumen del producto

Calcareous nannoplannkton comprise a group of organisms that play an important role in the global carbon cycle. Although several studies concerning the vertical flux of coccolithophores to the sediment have been carried out in recent years, little in known about their distribution and response to short-term events. As part of a multidisciplinary program, a time-series sediment trap has been deployed in Cuenca Alfonso, located in Bahía de La Paz, Gulf of California, since january 2002. This area is often influenced by hurricanes during late summer- early autumn. This has provided a unique opportunity to study the seasonal variation of calcareous nannoplankton and their response to short-term environmental events. During 2003, two hurricanes occurred whitin one month of each other. Hurricanes Ignacio and Hurricane Marty, followed similar tracks from south to north across the bay, and brought high winds, intense precipitation, heavy runoff and, for the two weeks including and following the day of each hurricane, high bulk sedimentation rates were observed (Silverberg et al., 2007). Very high coccolith fluxes were also registered in all 6 samples recovered during the entire 6-week period. During Hurricane Ignacio, values of 15x10 8 coccoliths/m2/d were encountered. In the 2 weeks following the passage of Ignacio, fluxes remained higher than non-hurricane years. Fluxes then peaked again, to even higher values (129x10 8 coccoliths/m2/d), for the 2-weeks following the passage of Marty. Furthermore, the species compositionof the nannoplankton changed from a dominance of G. Oceanica and E. huxleyi under normal conditions, to a dominance of F. profunda during the hurricane-influenced period. Some species encountered rarely or in low abundance during non-hurricane seasons were more common or abundant during non-hurricane period, while some minor species were apparently unaffected.

Palabras clave: hurricanes; Ciclo biogeoquímico del carbono; nanoplancton calcareo; cocolitofóridos; flujos biogenicos

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