[1] Enhancement of primary and export production following dust deposition pulses is well established for High Nutrient Low Chlorophyll regions, but the effect of atmospheric dust on the biogeochemistry of oligotrophic gyre regions remains unclear.Here we report atmospheric dust concentrations measured on Gran Canaria, Canary Islands, concomitantly with upper water biogeochemistry at the oligotrophic time series station ESTOC (European Station for Time series in the Ocean, Canary Islands) during a 2-year period from winter 1997 to 1999. ESTOC is located in the eastern subtropical Atlantic gyre about 100 km north of Gran Canaria and 500 km west of the Sahara, and receives aeolian dust episodically mainly in winter and summer. We found a close correlation of the magnitude of atmospheric dust concentration in winter with the magnitude of downward particle flux at ESTOC, mainly due to a relative increase in lithogenic matter and carbonate sedimentation. Higher aerosol concentration was not accompanied by higher primary or export production, however, indicating that phytoplankton production remained unaffected by atmospheric nitrogen supply on a seasonal or yearly timescale. However, by estimating bioavailable iron input and the need of the phytoplankton population, we found that the highly episodic dust pulses might exert a feast and famine effect on the phytoplankton. Despite the high lithogenic matter input, carbonate, mainly stemming from coccolithophorids, exceeded in importance the role of lithogenic matter as ballasting agent of sinking organic matter.

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Little is known about cetacean communities around La Palma Island. Therefore, and in order to determine the presence and distribution of the cetacean species on its west coast, daily censuses were carried out from November 2003 to April 2005. The platform used was a whale watching vessel certified by the Canary Government. Data collected included time, position, species identity, group size and, in some cases, the presence of calves and/or any other outstanding parameter. During the study period, 570 sightings were made, with a mean sighting success of 1.7 sightings per day, showing a high cetacean presence in the area. Thirteen species and one genus (Globicephala spp.) were positively matched, three of them included in the Mysticeti suborder and the other ten in the Odontoceti one. The four most sighted species, in decreasing order, correspond to Tursiops truncatus, Steno bredanensis, Globicephala spp. and Stenella frontalis. Diversity of sighted species shows a moderate peak during spring time, which is in agreement with the presence of occasional species. Most sightings were located off the central west coast of the island, exceeding 1.5 nautical miles. This is particularly outstanding in relation to Franja Marina de Fuencaliente SCI, where 90% of all sightings were located outside its boundaries. High cetacean presence and diversity off the west coast of La Palma Island seem to be connected with oceanographic and ecological features. Results gained provide, for this region, baseline data on cetacean populations and a useful tool in conservation plans.

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