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AME prepress abstract   -  DOI: https://doi.org/10.3354/ame01991

Microalgal characterization during a mucilaginous event on deep gorgonian forests of Tavolara Punta Coda Cavallo MPA

Francesca Panizzuti, Sandra Citterio, Rodolfo Gentili, Augusto Navone, Pieraugusto Panzalis, Isabella Provera, Sarah Caronni*

*Corresponding author:

ABSTRACT: Harmful algal blooms (HABs) have increased in frequency, but despite an extreme rise in research on this topic, general knowledge on HABs is still scarce. Mucilaginous algal blooms, in particular, are ever more present and can heavily affect marine ecosystems. Gorgonians, in particular, appear significantly affected, as their branches are easily entangled (pelagic aggregates) and overgrown (benthic aggregates) by mucilage. Moreover, the proximity to the bottom makes them susceptible to benthic anoxia. In the present study, we investigated the mucilaginous bloom (summer 2020) that affected the gorgonian forests of Tavolara Punta Coda Cavallo Marine Protected Area (NE coast of Sardinia). We focused mainly on the characterization of dominant benthic microalgae, identifying those responsible for the bloom. Sampling was performed considering the colonies of Paramuricea clavata present on hard substrata along 2 transects near the Secca del Papa, in the B Zone of the Marine Protected Area. The characterization of the microalgal community and the count of the most abundant species (>10 cells ml-1) were carried out following Utermöhl’s sedimentation method. The community was mainly composed of diatoms (Bacillariophyta), belonging to Pseudo-nitzschia, Nitzschia and Cylindrotheca genera. Cylindrotheca closterium appeared to be the most abundant species. These results confirm the importance of diatoms during Tyrrhenian mucilaginous blooms, which could be particularly harmful to gorgonians.