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Assessment of the efficacy of clay flocculation in Korean fish farm waters: Cochlodinium cell removal and mitigation of ichthyotoxicity


Seger, A and Park, T-G and Hallegraeff, G, Assessment of the efficacy of clay flocculation in Korean fish farm waters: Cochlodinium cell removal and mitigation of ichthyotoxicity, Harmful Algae, 61 pp. 46-55. ISSN 1568-9883 (2017) [Refereed Article]

Copyright Statement

Copyright 2016 Elsevier B.V.

DOI: doi:10.1016/j.hal.2016.11.014


The ichthyotoxic dinoflagellate Cochlodinium polykrikoides poses a significant threat to the Korean finfish aquaculture industry, thus calling for effective mitigation strategies. We here report for the first time on investigations to assess the efficacy of routine application of clay to a naturally occurring Cochlodinium polykrikoides bloom off Namhae Island in South Korea during August-September 2015. Applications of conventional Korean loess reduced Cochlodinium cell concentrations from a maximum of 4600mL−1 to levels considered safe for aquaculture operations (<1000 cells mL−1). However, at the same time, two clay application episodes increased ichthyotoxicity in water samples (measured by the gill cell line RTgill-W1 assay) by up to 32% compared to non-treated areas. Simulated laboratory culture experiments identified clay mediated Cochlodinium cell lysis as the probable cause. Lysed cells maintained cytotoxicity for up to 48h (gill cell viability reduced to 397% after 2.5h exposure), but application of a finely-milled Korean loess completely eliminated ichthyotoxicity. Our results suggest that the fish-killing mechanism of Cochlodinium is comprised of both a stable (up to 48h) and a transient fraction (decay within minutes). The latter indicates potential involvement of reactive oxygen species (ROS). We offer recommendations to fine-tune existing clay application regimes in Korean waters by focusing not on Cochlodinium cell removal, but on the adsorptive properties of clays to eliminate ichthyotoxicity.

Item Details

Item Type:Refereed Article
Keywords:Clochlodinium, clay, icthyotoxin, absorption, flocculation, ROS, algal blooms
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Phycology (incl. marine grasses)
Objective Division:Animal Production and Animal Primary Products
Objective Group:Fisheries - aquaculture
Objective Field:Fisheries - aquaculture not elsewhere classified
UTAS Author:Seger, A (Dr Andreas Seger)
UTAS Author:Hallegraeff, G (Professor Gustaaf Hallegraeff)
ID Code:112845
Year Published:2017
Web of Science® Times Cited:12
Deposited By:Ecology and Biodiversity
Deposited On:2016-11-30
Last Modified:2018-04-05

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