Does the presence of zooplankton influence growth and toxin production ofNodularia spumigena?

Abstract

The ecological role of toxin production in cyanobacteria is still unknown. Here, we studied the potential effect of different zooplankton taxa and density on growth and toxin production of the cyanobacterium Nodularia spumigena. In this experiment, N. spumigena was exposed to three different zooplankton taxa: Rotifera (Synchaeta baltica), Copepoda (Eurytemora affinis) and Cladocera (Daphnia magna) and as a comparison a zooplankton free control. We used false bottom chambers separating the cyanobacterium and zooplankton and were thereby able to prevent direct grazing. Overall, N. spumigena toxin levels (nodularin expressed as microcystin equivalents) were significantly lower when exposed to the different zooplankton compared to the zooplankton free control, whereas no effects could be detected on N. spumigena growth and biomass. Although we did not test the underlying mechanism, these findings suggest that the presence of zooplankton reduce toxin production in N. spumigena, independent of growth. Therefore, toxin production in N. spumigena should not be considered an induced defence mechanism against zooplankton, at least not on a short‐term basis.

A Less Saline Baltic Sea Promotes Cyanobacterial Growth, Hampers Intracellular Microcystin Production, and Leads to Strain-Specific Differences in Allelopathy

“…The role of microcystins has not yet been determined but several hypotheses for toxin production among cyanobacteria have been suggested including grazer avoidance, allelopathy, infochemicals and stress reduction (cf. [ 40 , 41 , 42 ]). For example, higher microcystin production of Microcystis during stress has been reported in elevated temperature and during low light [ 43 , 44 ].…”

Genomic and Metabolomic Analyses of Natural Products in Nodularia spumigena Isolated from a Shrimp Culture Pond

“…This gene cluster was later found in N. spumigena strain AV1 [70], followed by CCY9414 [46] and CENA596 [47]. The reason behind NOD production by cyanobacteria is unknown but probable functions have been proposed such as protection against oxidative and luminous stress, predation, and allelopathic competition [66,71]. We note that nda was absent in the Japanese benthic Nodularia sp.…”

Marine Microbial Secondary Metabolites

“…For example, blooms of cyanobacteria have been attributed to the grazing protection against mesozooplankton provided by the release of toxins (Gobler, Davis, Coyne, & Boyer, 2007). However, this is not supported by the zooplankton preference for non-toxic cyanobacteria (Davis & Gobler, 2011) or the induction of toxin production in response to grazing pressure (Brutemark & Engstr€ om-€ Ost, 2013). Bacterial secondary metabolism is likely to be activated by environmental stress (Crisafi, Denaro, Genovese, Yakimov, & Genovese, 2014;Penn, Wang, Fernando, & Thompson, 2014;Pettit, 2011;Schimel, Balser, & Wallenstein, 2007).…”