Plankton community response to Saharan dust fertilization in subtropical waters off the Canary Islands

Abstract

Abstract. The plankton community response to natural fertilization caused by the Saharan dust was studied in the Canary Islands waters during winter–spring 2010. For this, a weekly sampling was carried out to characterize the pico-, nano- and microplankton communities. During this period several dust events were identified from atmospheric suspended matter and metal composition. Temperatures above 19 °C in the mixed layer, high stratification and a very low concentration of chlorophyll a, indicated the absence of the characteristic late winter bloom during this year. However, relatively high primary production rates were measured, probably fuelled by nutrient release from the deposited atmospheric dust. In fact, this winter–spring was one of the most intense dust periods during the last years and Saharan dust events were identified in every month. The effect of the Saharan dust over the plankton community mainly consisted in the enhancement of primary producers, mostly diatoms, and the increase of the mesozooplankton stock, whereas cyanobacteria and autotrophic picoeukaryotes were negatively affected. These results suggest that the Saharan dust deposition would be partly fuelling the primary production in these oligotrophic waters of the northeast Atlantic, and could be especially significant during stratified periods, when the atmospheric dust would be the most important nutrient source.