Study of the toxic benthic dinoflagellate Vulcanodinium rugosum in Mediterranean lagoons subject to global change: toxinic characterization and in situ dynamics, toxin transfer in upper trophic levels and associated risks

Abstract

Harmful phytoplankton blooms have growing impacts on ecosystems and human populations. In the context of warming waters and oceans, they are one of the main issues linking environmental, animal and human health. This research focuses on the toxic microalga Vulcanodinium rugosum, which produces pinnatoxins (PnTX) and portimines (Prtn). These toxins accumulate in marine organisms and are frequently detected worldwide, particularly in French Mediterranean lagoons. The objectives were to study the microalga distribution in relationship with environmental conditions in four French Mediterranean lagoons, the contamination by PnTX G and Prtn A of various marine organisms, the ecological impacts and the health risks.At first, we developed a sensitive and specific methodology for detecting Vulcanodinium rugosum cells in marine environments, based on artificial substrates coupled with qPCR (AS-qPCR). The results of our field campaign showed that microalgae and toxins were present in all studied lagoons, and that they could contaminate a wide variety of marine species including bivalve molluscs, fish, gastropods and echinoderms. The spatiotemporal dynamics of microalgae and toxins in mussels were linked to seasonal variations in temperature and other hydrochemical factors. A modeling approach based on environmental parameters enabled us to assess the risks to human populations at different times of the year. We estimated that over 25 % of seafood consumers exceeded the provisional acute benchmark value in summer at Ingril and Vic. We did not observe any impact of mullet juvenile exposure to Vulcanodinium rugosum, but this species could be involved in the expansion of the microalga within the lagoons via transport through the intestinal tract. Finally, the kinetics of contamination and elimination in oysters showed that high concentrations could be linked to long-term exposure, and that PnTX G persisted for a long time in bivalve molluscs’ tissues.This work provided therefore important knowledge on the impacts of Vulcanodinium rugosum on ecosystems and humans. The information and tools developed should be of great interest to environmental and health monitoring managers. This study also led to questions concerning the general expansion of Vulcanodinium rugosum area, other species that could possibly be contaminated, sub-lethal impacts on marine organisms, and the chronic risks to humans inherent in persistent contamination in seafood products. They therefore show the importance of studies focusing on this dinoflagellate and its toxins, particularly in the context of warming waters favoring blooms on a global scale.

Part of CIRS Nexus · Curated by Lauren Lowenstein, The Biotoxin Lady