Allelopathic interactions between the HAB dinoflagellate Ostreopsis cf. ovata and macroalgae

•All the investigated seaweed species exerted negative effects toward Ostreopsis.•Dictyota inhibited Ostreopsis growth in all tested experimental conditions.•Rhodymenia showed an inhibitory effect only with high concentrations of dry powder.•Ulva inhibited Ostreopsis in all conditions except that in...

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Bibliographic Details
Published in:Harmful algae 2015-11, Vol.49, p.147-155
Main Authors: Accoroni, Stefano, Percopo, Isabella, Cerino, Federica, Romagnoli, Tiziana, Pichierri, Salvatore, Perrone, Cesira, Totti, Cecilia
Format: Article
Language:English
Subjects:
Allelopathy
Cysts
Dictyota dichotoma
Growth inhibition
Harmful algae
Macroalgae
Ostreopsis
Rhodymenia pseudopalmata
Ulva
Ulva rigida
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Summary:•All the investigated seaweed species exerted negative effects toward Ostreopsis.•Dictyota inhibited Ostreopsis growth in all tested experimental conditions.•Rhodymenia showed an inhibitory effect only with high concentrations of dry powder.•Ulva inhibited Ostreopsis in all conditions except that in the filtrate experiment.•Ostreopsis produced a large amount of resting stages which permit its survival. Intense blooms of the toxic benthic dinoflagellate Ostreopsis cf. ovata have been a recurrent phenomenon along several Mediterranean coasts during summer in the last few years. These blooms are often associated with noxious effects on humans and deaths of benthic invertebrates. Previous studies carried out on the Conero Riviera (northern Adriatic Sea) highlighted that Ostreopsis abundances recorded on rocks were significantly higher than on the surface of seaweeds, suggesting that some allelopathic interactions might occur between Ostreopsis and macroalgal substrates. In this study we investigated under experimental conditions the interactions between O. cf. ovata and three of the most common macroalgae in this area: Dictyota dichotoma (brown alga), Rhodymenia pseudopalmata (red alga) and Ulva rigida (green alga). Three different experiments were set up: O. cf. ovata was grown (i) together with fresh macroalgal tissues, (ii) in media in which macroalgae were previously cultured, and (iii) in media with the addition of dry macroalgal powder at different concentrations. The results indicated that all the investigated seaweeds exerted negative effects toward the benthic dinoflagellate O. cf. ovata. D. dichotoma inhibited the growth of O. cf. ovata in all tested experimental conditions; U. rigida had inhibitory effect both in form of fresh thalli and dry powder but not as growth medium filtrate, suggesting that either Ulva does not release any allelopathic compound in the medium in absence of O. cf. ovata or the alleged released allelochemicals are rapidly degradable. Neither the fresh thalli of R. pseudopalmata or the filtrate of its culture medium showed any inhibitory effects, while a negative effect was only observed at high concentrations of dry thallus powder. With the exception of D. dichotoma co-culture experiment, a complete algicidal effect was never observed partly because O. cf. ovata produced a large amount of resting stages, which permitted its survival.
ISSN:1568-9883
1878-1470
DOI:10.1016/j.hal.2015.08.007