Superoxide Production by the Red Tide-Producing Chattonella marina Complex (Raphidophyceae) Correlates with Toxicity to Aquacultured Fishes

Abstract

The marine raphidophyte Chattonella marina complex forms red tides, causing heavy mortalities of aquacultured fishes in temperate coastal waters worldwide. The mechanism for Chattonella fish mortality remains unresolved. Although several toxic chemicals have been proposed as responsible for fish mortality, the cause is still unclear. In this study, we performed toxicity bioassays with red sea bream and yellowtail. We also measured biological parameters potentially related to ichthyotoxicity, such as cell size, superoxide (O2•−) production, and compositions of fatty acids and sugars, in up to eight Chattonella strains to investigate possible correlations with toxicity. There were significant differences in moribundity rates of fish and in all biological parameters among strains. One strain displayed no ichthyotoxicity even at high cell densities. Strains were categorized into three groups based on cell length, but this classification did not significantly correlate with ichthyotoxicity. O2•− production differed by a factor of more than 13 between strains at the late exponential growth phase. O2•− production was significantly correlated with ichthyotoxicity. Differences in fatty acid and sugar contents were not related to ichthyotoxicity. Our study supports the hypothesis that superoxide can directly or indirectly play an important role in the Chattonella-related mortality of aquacultured fishes.

Changes in Toxin Production, Morphology and Viability of Gymnodinium catenatum Associated with Allelopathy of Chattonella marina var. marina and Gymnodinium impudicum

“…However, production of PST in response to the allelopathic effect is unknown. Chattonella marina produces and releases polyunsaturated fatty acids and reactive oxygen species into the marine environment [21][22][23][24], whereas G. impudicum produces mucilage formed by exopolysaccharides [25,26]. During the early exponential phase, G. impudicum can produce superoxide radicals in similar concentrations to those of C. marina var.…”

Generation of Reactive Oxygen Species (ROS) by Harmful Algal Bloom (HAB)-Forming Phytoplankton and Their Potential Impact on Surrounding Living Organisms

“…Despite extensive studies [ 86 , 88 , 93 , 100 , 159 , 160 , 166 , 171 , 208 , 209 , 210 , 211 , 212 ], the exact mechanism through which Chattonella cause fish death is still poorly understood. Recently, Shikata et al [ 213 ] examined the ichthyotoxicity of eight strains of Chattonella with different backgrounds against different fish species (red sea bream and yellowtail) and found that the generation level of superoxide was most well-correlated with fish-killing activity among several factors examined, which supports the notion that ROS are mainly involved in the Chattonella -related fish mortality.…”

Strain, cell density, and nutrient condition affect patterns of diurnal vertical migration and superoxide production in a red-tide alga

“…All strains were isolated from Japanese coastal areas. In cell shape, the length:width ratio of Chattonella antiqua-like cells are larger than Chattonella marina-like cells (Shikata et al, 2021).…”

“…Compared to 4KGY (early log phase), 3KGY has higher surface accumulation ratios during the dark periods and accumulates at the bottom during the light periods in the same experimental setup, indicating that DVM in 3KGY has more entrainability. Although Chattonella shows variations in cell shape and toxicity among strains ( Demura et al, 2009 ; Shikata et al, 2021 ), the relationship between their phenotypes ( Table 1 ) and DVM pattern remains obscure. Our findings indicate that the strain composition of a Chattonella population may influence the vertical cell distribution at each time point in the field, although it is unclear what produced the interstrain differences in the DVM pattern.…”

“…Chattonella can produce a large amount of superoxide (•O 2 − ) in the cell membrane and excrete it from the cell. This •O 2 − and hydrogen peroxide has antimicrobial activity and is a candidate toxin related to fish mortality ( Oda et al, 1992 ), as the level of •O 2 − is highly correlated with toxicity to aquacultured fishes in seawater that contains Chattonella cells ( Shikata et al, 2021 ). Ichthyotoxicity can disappear within a short period and only live Chattonella cells can kill fishes; ruptured cells and culture supernatant have no toxicity to fish ( Matsusato and Kobayashi, 1974 ; Ishimatsu et al, 1996 ; Shen et al, 2010 ).…”