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Seasonal distribution of epiphytic diatoms of “killer” seaweed Caulerpa taxifolia (Adriatic Sea, Croatia)

Seasonal distribution of the epiphytic diatom flora on the “killer” seaweed Caulerpa taxifolia was described within the Bay of Stari Grad (the Island of Hvar, Croatia) over a 2-year period (autumn 2008 – autumn 2010). The diatom assemblage was characterized by high abundances of genera Cocconeis, Hyalosinedra, Mastogloia, Nitzschia, Navicula, Amphora and Licmophora. The highest number of taxa was in summer (85 in July 2009, 102 in August 2009 and 74 in July 2010) and the lowest in the end of autumn/winter (eg. 32 in November 2008 and 25 in November 2009). The largest number of taxa was found within the genera Nitzschia (34), Mastogloia (32), Amphora (30), Navicula (18), Diploneis (17) and Cocconeis (15). Althought, the number of taxa within the genera Cocconeis is quite low, species of the genus Cocconeis, dominated the epiphytic diatom flora. The diatom assemblage was characterized by the abundance of a new species of Cocconeis, tiny Cocconeis caulerpacola Witkowski, Car et Dobosz, particularly during summer and autumn (eg. 63% in October 2009 and 40% in October 2010). Periods of higher abundance of C. caulerpacola appear to coincide with maximum toxicities observed for C. taxifolia in summer and autumn, while the minimum abundance is observed in winter and spring. The seasonal dynamics will be described on a fine time scale. Knowledge of the diatom community structure in the areas of Caulerpa spp. is important for studies of the toxic effects of the host.

epiphytic diatoms; Caulerpa taxifolia

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