Species Composition and Photoacclimation of Marine Antarctic Benthic Diatom Species

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Antarctic benthic diatom communities from coastal areas are exposed to drastic seasonal changes of light intensity and duration, and persist during the long polar winter at extreme low light intensities as food supply for the overwintering Antarctic fauna. However, due to the characteristics of these communities, there are few studies on the species composition and their low light photo-acclimation. In this study, the taxonomic species composition and their relative abundance of the benthic diatom community at different sites and depths at Bahía Covadonga (Bernardo O’Higgins Station) (63°19’15”S, 57°53’55”W) were assessed. The photosynthetic response of cultured species of the genus Navicula to different light intensities and their recovery capacity were determined by using a Modulated Pulse fluorometer (Water PAM) to register their Chlorophyll fluorescence after exposing the cells to different light intensities. The benthic diatoms community had a high species richness and diversity, with a characteristic and specific distribution among the different sites and depths analyzed. All species studied, from different depths showed low light photo acclimation and photoinhibition to light intensities >100 μMol Photons cm-2 sec-1. Nitzschia species showed a higher tolerance and recovery capacity to high light intensities than those from the genus Navicula. The results suggest that this characteristic photosynthetic response may be related to the different distribution of the abundance of species over different illumination status on the sites and depths where they were collected. Nitzschia species could cope in environments exposed to higher radiation, with higher recovery ability than those from the genus Navicula. The possible relationship of these observations with motility and other cellular properties of diatom species is discussed.

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