The Effects of Modified Clay on Abalone (Haliotis discus hannai) Based on Laboratory and Field Experiments

The abalone industry has suffered immense economic losses due to the occurrence of harmful algal blooms (HABs). Among the methods for mitigating HABs, modified clay is considered the most promising strategy and has been successfully used for field applications in many countries, and its environmental effects have become a subject of global concern. The effects of modified clay on the survival, growth, nutritional quality, and oxidative stress indicators of abalone were studied based on both laboratory and field experiments. The results showed that modified clay at 3-10 times the concentrations used for HAB treatment did not affect the survival of abalone. During the laboratory experiments, the increases in abalone shell length and weight nonsignificantly decreased with increasing concentrations of modified clay at 1-15 d, whereas the weight of abalone in the experimental groups increased rapidly during the recovery period at 16-30 d. The growth and nutrition qualities of abalone in field experiments showed negligible differences between the control and experimental groups. Catalase (CAT) activity in the hepatopancreas and superoxide dismutase (SOD) activity in the gills were significantly affected by certain concentrations of modified clay at individual time points, whereas the malondialdehyde (MDA) content decreased in all experimental groups within 96 h. The removal of bacteria and the mitigation of water quality decline were among the effects of modified clay that contributed to the decrease in MDA content. The present study showed that modified clay had no obvious adverse effects on the survival, growth, quality, or oxidative stress indicators of abalone at the experimental concentrations, thus providing a reference for the field application of modified clay in typical aquaculture areas. Environ Toxicol Chem 2020;39:2065-2075. © 2020 SETAC.