Allelopathic activity of the bloom‐forming picocyanobacterium Synechococcus sp. on the coexisting microalgae: The role of eutrophication

Abstract

Allelopathic picocyanobacteria have been responsible for harmful incidents with severe ecological impacts in many parts of the world. The allelopathic interactions that have been shown to be implied in the dominance of various species of phytoplankton, forming massive blooms, are influenced by environmental factors such as nutrient concentration. This study aims to determine in what extent the allelopathic activity of the bloom‐forming picocyanobacterium Synechococcus sp. is impacted by water stoichiometry. We measured the allelopathic activity of Synechococcus sp. on growth, chlorophyll fluorescence, and photosynthetic performance of green algae Chlorella vulgaris and Oocystis submarina and diatoms Bacillaria paxillifer and Skeletonema marinoi by addition of cell‐free filtrate obtained from cultures growing in nutrient‐sufficient (NP), nitrogen‐deficient (−N), or phosphorus‐deficient (−P) culture medium. These studies indicated that sufficient amounts of nutrients affected the picocyanobacterium increasing its production of allelochemicals. Conversely, the weakest allelopathic activity was recorded after the addition of a filtrate obtained from Synechococcus sp. grown at −N medium. The highest decline in growth, the maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) and the photosynthetic capacity (Pm) were observed for diatom S. marinoi. On the other hand, Synechococcus sp. filtrate had no allelopathic effects on O. submarina. While confirming the allelopathic activity of Synechococcus sp. these findings show that production of allelopathic substances is influenced by the availability of nutrients.

The Importance of Allelopathic Picocyanobacterium Synechococcus sp. on the Abundance, Biomass Formation, and Structure of Phytoplankton Assemblages in Three Freshwater Lakes

“…Contrary to that, Synechococcus sp. filtrate had no allelopathic effects on Oocystis submarina Lagerheim [23,24]. In our work we have shown that Synechococcus sp.…”

“…That study pointed to the diatoms of the genera Navicula, Chaetoceros, Amphora, Coscinodiscus, Grammatophora, and Nitzschia as the most allelochemical-sensitive organisms. Moreover,Śliwińska-Wilczewska and Latała [23],Śliwińska-Wilczewska et al [24], and Konarzewska et al [26] demonstrated that the addition of Synechococcus sp. filtrate strongly inhibited the growth of Skeletonema marinoi Sarno and Zingone.…”

“…cell-free filtrate and co-culture inhibited the growth of Stichococcus bacillaris Nägeli. Moreover, Sliwińska-Wilczewska and Latała [23] andŚliwińska-Wilczewska et al [24] noted that Synechococcus sp. also inhibited the growth of Chlorella vulgaris Beyerinck [Beijerinck].…”

“…Controls consisted of the addition of 10 mL of f/2 medium to the 25 mL flasks containing 10 mL of the phytoplankton assemblages. The nutrient level was tested to make sure that it was the same as in the portions of fresh f/2 medium added in the control samples according to the methodology proposed by Śliwińska-Wilczewska and Latała [23]. The Synechococcus sp.…”

“…In this paper, Kovacs et al [17] for the first time described that the freshwater picocyanobacterium Cyanobium gracile Rippka and Cohen-Bazire has a strong negative effect on green alga Scenedesmus quadricauda (Turpin) Brébisson. Most of the work on the allelopathic activity of picoplanktonic cyanobacteria of the genus Synechococcus has been described for the strain CCBA BA-124, originating from the Baltic Sea [18][19][20][21][22][23][24][25]. Additionally, Konarzewska et al [26] showed allelopathic properties of Baltic Synechococcus sp.…”