Abstract
Blooms of the toxic dinoflagellate Karenia mikimotoi could threaten the survival of marine life, and modified clay (MC) is considered a promising method for the control of harmful algal blooms. Here, using marine medaka as the model organism, the toxicity of K. mikimotoi before and after MC disposal was investigated. The results showed that only a certain density of intact K. mikimotoi cells could cause obvious damage to fish gills and lead to rapid death. A systematic analysis of morphology, physiology, and molecular biology parameters revealed that the fish gills exhibited structural damage, oxidative damage, osmotic regulation impairment, immune response activation, and signal transduction enhancement. MC can flocculate K. mikimotoi rapidly in water and reduce its toxicity by reducing the density of intact algae cells and hemolytic toxicity. The results indicate that MC is an effective and safe method for controlling K. mikimotoi blooms.
Highlights
Karenia mikimotoi is a toxic species of harmful algal blooms (HABs), and the species form HABs in the offshore waters of many countries or regions, causing many marine organisms to die and the marine aquaculture and fisheries to incur huge economic losses [1]
As a method of treating HABs on site, modified clay (MC) is widely utilized for its ecological safety in China
The results of this study showed that 0.3 g/L MC did not have a significant impact on the survival of marine medaka
Summary
Karenia mikimotoi is a toxic species of harmful algal blooms (HABs), and the species form HABs in the offshore waters of many countries or regions, causing many marine organisms to die and the marine aquaculture and fisheries to incur huge economic losses [1]. Studies showed that the intact cell of K. mikimotoi, rather than the cellfree culture supernatant and the ruptured cell suspension, had the most toxic effects on marine organisms. After 10 h incubations, the survivorship of rotifers B. plicatilis exposed to K. mikimotoi (SUO-1) was 20%, and both the cell-free culture supernatant and the ruptured cell suspension were not toxic to rotifers [12] Both field and laboratory studies have shown that, compared to other organisms, fish were more sensitive to K. mikimotoi. The toxic effects and mechanisms of K. mikimotoi on marine medaka were studied at different levels of external gill morphology, physiology, biochemistry, and gene transcription expression. The effect of MC on the toxicity of K. mikimotoi was comprehensively discussed to provide a theoretical basis for controlling K. mikimotoi blooms on-site with MC
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