Assessment of the risk posed by three antifouling biocides to Pacific oyster embryos and larvae in Hiroshima Bay, Japan

• Published in: Environmental science and pollution research international Vol. 29; no. 6; pp. 9011 - 9022
• Main Authors: Onduka, Toshimitsu, Mizuno, Ken-ichiro, Shikata, Tomoyuki, Mastubara, Tadashi, Onitsuka, Goh, Hamaguchi, Masami
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-02-2022; Springer Nature B.V
• Subjects: Animals; Antifouling; Antifouling substances; Aquaculture; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bays; Biocides; Biofouling - prevention & control; Chemical analysis; Crassostrea gigas; Developmental stages; Disinfectants - toxicity; Diuron; Earth and Environmental Science; Ecotoxicology; Embryos; Environment; Environmental Chemistry; Environmental Health; Environmental science; Farming; Japan; Larva; Larvae; Oysters; Physical growth; Research Article; Risk assessment; Seawater; Shellfish farming; Toxicity; Waste Water Technology; Water analysis; Water Management; Water Pollution Control; Japan; Hiroshima Bay; Larva settlement test; Diuron; Embryotoxicity test; Oyster farming; DCOIT; Irgarol 1051
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-021-16346-4

The Pacific oyster (
Crassostrea gigas
) is an important species in oyster farming worldwide, including in Japan. Hiroshima Bay is one of the most important oyster farming areas in Japan. We investigated the occurrence of antifouling biocides used worldwide including diuron, Irgarol 1051 (Irgarol), and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), which have been detected at sub-ppb levels in seawater in Japan, and estimated their no observed effect concentrations (NOECs). In recent years, the spat settlement of Pacific oysters has become poor, which presents a challenge for oyster aquaculture in Hiroshima Bay; hence, we conducted embryotoxicity and larva settlement tests using Pacific oysters. Compared to diuron and Irgarol, DCOIT exhibited a higher toxicity toward oyster embryos, and the minimum 24-h NOEC toxicity value for the oyster embryos was <3 ng/L. The highest concentrations of diuron, Irgarol, and DCOIT in the environmental seawater in the Seto Inland Sea were 27.6, 3.2, and 24 ng/L, respectively. Considering the NOECs, the environmental concentrations of these biocides suggest that the ecological risks posed by diuron and Irgarol are low, whereas those posed by DCOIT are high. However, the rate of detection of DCOIT was low because it degraded rapidly in the seawater before treatment for chemical analysis, except in the case of the treatment on the research vessel.