Assessing the Effects of Three Harmful Microalgal Species on Spermatozoa and Embryos of the King Scallop Pecten Maximus

Abstract

The reproductive process plays a crucial role in the renewal of populations of marine bivalves and represents an economic issue for exploited species like the king scallop Pecten maximus. However, environmental phenomena, such as harmful microalgal blooms (HAB), can affect key reproductive life stages, such as gametes and embryos. This study examines the effects of exposure to three harmful microalgal species (Alexandrium minutum, Lingulodinium polyedra, and Pseudo-nitzschia australis) on spermatozoa and embryos of king scallops P. maximus. The physiological responses of spermatozoa were evaluated after exposure to low (LC) and high concentrations (HC) of each microalgal species. While none of the tested microalgal strains showed direct toxicity, oxidative stress was associated to HC of A. minutum, and morphological changes were observed after exposure to L. polyedra and P. australis. Embryos of P. maximus were also exposed to HC of the same three microalgae species and examined under a microscope after 4h, 24h, and 48h of exposure. Exposure to A. minutum hindered cell division of embryos within the first four hours of development, leading to complete embryo lethality at 24 hours. No significant changes in early development were noted during the initial 48 hours of exposure to L. polyedra and P. australis. These findings underscore the diverse effects of harmful microalgal species, emphasizing the need for targeted fishery and shellfishery management, both spatially and temporally, especially when bivalves and harmful algal bloom species potentially coincide during bivalve reproduction and recruitment