Competitive interactions between two allelopathic algal species: Heterosigma akashiwo and Phaeodactylum tricornutum

ABSTRACT

Both Heterosigma akashiwo and Phaeodactylum tricornutum have been reported to produce allelochemicals capable of inhibiting the growth of co-occurring microalgae. Here, potential allelopathy between H. akashiwo and P. tricornutum was evaluated using bi-algal culture, cell-free culture filtrate and a no-contact co-culturing system in nutrient-replete media. Experiments were also conducted in the no-contact co-culturing system under nutrient-limited conditions. In nutrient-replete bi-algal culture, the growth of P. tricornutum and H. akashiwo each tended to be strongly suppressed when the other species was inoculated at high cell densities. A mathematical model was used to simulate the growth interactions of the two species in bi-algal culture and showed that P. tricornutum outcompeted H. akashiwo over time with different initial cell densities under nutrient-sufficient conditions, indicating that P. tricornutum was more potent in allelopathy. Heterosigma akashiwo growth was inhibited both in the P. tricornutum culture filtrate and no-contact co-culturing system. This confirmed that the extracellular allelopathic compounds released by P. tricornutum were one of the sources of the H. akashiwo growth inhibition. Nutrient deficiency did not increase the extent of allelopathic activity of allelochemicals.

KEYWORDS:

• Allelopathy
• Heterosigma akashiwo
• Phaeodactylum tricornutum
• competition advantage
• allelochemicals

Acknowledgements

The authors wish to thank Prof. Donald M. Anderson from Woods Hole Oceanographic Institution for comments on an earlier version of this paper. The authors are also grateful for the technical help from Dr. P Zhang.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by National Natural Science Foundation of China under Grant [41876078]; Assessment of Nanomaterials on Biological and Ecological Effects in the Coastal Area under Grant [201505034]; National Program on Global Change and Air-Sea Interaction under Grant [GASI-03-01-02-01]; National Plan on Key Basic Research and Development under Grant [2016YFC1402101]; Shenzhen Science and Technology Innovation Commission under Grant [JCYJ20170818103413138] and China Postdoctoral Science Foundation under Grant [2018M633157].