Seasonal dynamics of the marine diatom genus Chaetoceros in two different environmental coastal areas of the NW Mediterranean Sea

Abstract

Chaetoceros is one of the most abundant and diverse diatom genus in the oceans. It is ecologically relevant due to its worldwide distribution and the fact that different species may reach bloom concentrations, mainly in coastal zones. Therefore, these organisms play an important role in the food webs and in the biogeochemical cycles of carbon and silica. However, little is known about the ecology of Chaetoceros, in part due to the difficulty of recognizing the different species in fixed samples. In the present work, concentrates of live phytoplankton (> 20 ¿m) were analysed in order to identify and count Chaetoceros species in monthly surface samples (from February 2017 to July 2018) of two different environmental coastal areas of the NW Mediterranean: Blanes and Barcelona. The objective was to relate the seasonal dynamics of the different Chaetoceros species with the environmental factors of these two coastal zones. We identified 40 species/morphotypes of Chaetoceros; the most abundant were C. vixvisibilis, C. curvisetus, C. contortus and those belonging to the C. lorenzianus complex. These taxa presented maximum abundances at different times of the year responding to different ecological conditions. Although the months of >blooming> for each Chaetoceros species were in general the same in both coastal areas, the intensity of the peaks were different. The diverse environmental parameters that control the different Chaetoceros succession patterns are discussed.