Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8589
Author: C. E. Ikeda, W. P. Cochlan, Cayla M. Bronicheski, Vera L. Trainer, C. G. Trick
Publication Year: 2016
Journal: Journal of Phycology
Keywords: heterosigma,fish kill,salmon,heterosigma,Heterosigma akashiwo,fish kill,salmon

A laboratory study using the raphidophyte Heterosigma akashiwo, (Y. Hada) Y. Hada ex Y. Hara et M. Chihara, was conducted to examine its adaptive capability to grow at salinities below oceanic, and to test the perceived relationship between reduced salinities and increased ichthyotoxicity. A non-axenic strain of H. akashiwo isolated from the U.S. Pacific Northwest was exposed to a combination of three salinity (32, 20 and 10) and five temperature (14.7, 18.4, 21.4, 24.4 and 27.8 ºC) conditions. Our results demonstrate that cell permeability and cytotoxicity are strongly correlated in unialgal cultures of H. akashiwo, which both increased as salinity decreased from 32 to 10. Furthermore, over a broad median range of salinities (10 and 20), neither temperature nor specific growth rate were correlated with cytotoxicity. However in cultures grown at the salinity of 32, both temperature and specific growth rate were inversely proportional to toxicity; this relationship was likely due to the effect of contamination by an unidentified species of Skeletonema in those cultures. Competition with the Skeletonema sp. resulted in a cytotoxic response from H. akashiwo that was greater than the response caused by salinity alone. These laboratory results reveal the capability of H. akashiwo to become more toxic not only at reduced salinities, but also in competition with another algal species. Changes in cell permeability in response to salinity may be the adaptive mechanism by which H. akashiwo is able to rapidly respond to different salinities. Furthermore, due to its strong positive correlation with cytotoxicity, cellular permeability is potentially associated with the ichthyotoxic pathway of this raphytophyte.

Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Provide scientific support to ensure safe seafood for healthy populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants and biotoxins