Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 20/09/2023 10:45:0020/09/2023 11:00:00Europe/ViennaAquaculture Europe 2023WILL MARINE BIOTOXINS BE A GREATER THREAT TO EXTENSIVE BIVALVE FARMING IN A CLIMATE CHANGE CONTEXT?  THE CASE STUDY OF Mytilus spp. EXPOSED TO Prorocentrum lima FOLLOWING THE OCCURRENCE OF AN EXTREME WEATHER EVENTSchubert 4The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


Marta Dias1,2,3*, João Ramos4, Busenur Özkan1, Rui Rosa4,5, António Marques1,6, Pedro R. Costa1,7, Ana L. Maulvault1,2,3


1 IPMA DivAV, Division of Aquaculture, Upgrading and Bioprospection, Portuguese Institute for the Sea and Atmosphere, Algés, Portugal

2 UCIBIO REQUIMTE, Applied Molecular Biosciences Unit, NOVA School of Science and Technology, NOVA University of Lisbon, Caparica, Portugal

3 Associate Laboratory i4HB Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University of Lisbon, Caparica, Portugal

4 Faculty of Sciences, University of Lisbon, Campo Grande, Portugal

5 MARE, Marine and Environmental Sciences Centre & ARNET, Aquatic Research Infrastructure Network Associate Laboratory, Faculty of Sciences, University of Lisbon (FCUL), Lisbon, Portugal

6 CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Porto, Portugal

7 Marine Plant Ecology Research Group, Centre of Marine Sciences, University of Algarve (CCMAR), Faro, Portugal




Every year, approximately 15 million tonnes of marine bivalves are produced for human consumption, out of which 89% come from extensive aquaculture production (Wijsman et al., 2019). The demand for these much appreciated seafood products has substantially increased over the last years, catapulting the expansion of this food production sector. Yet, the sector has been facing consistently higher mass animal mortality events worldwide (Soon and Zheng, 2020). Prorocentrum lima is a toxic benthic dinoflagellate that has a cosmopolitan distribution from temperate to tropical oceans. P. lima is capable of producing diarrhetic shellfish toxins (DSTs), such as okadaic acid (OA) and dinophysistoxin (DTX) to which bivalves are highly exposed upon active suspension feeding during harmful algal blooms (HABs) (Corriere et al., 2021). When the occurrence of an HAB leads to the detection of these toxins in bivalves’ flesh at levels above permissible levels, extensive bivalve farming areas are obliged to close, sometimes during long periods of time, as to avoid potential human hazards related with the exposure to these contaminants. Recently, HABs outbreaks have been increasing in frequency, duration and intensity in coastal areas throughout the world, as a result of climate change effects, such as warmer average seawater temperatures, alteration of typical seasonal patterns and, especially, increased occurrence of marine heatwaves which abruptly rise temperatures during a very short period of time. These extreme weather events can be particularly critical to the aquaculture sector in two ways: on one hand, farmed bivalves are acutely forced to live in conditions outside their physiological threshold without any previous thermal acclimation, potentially leading to substantial animal losses; on the other hand, acute temperature shifts often trigger the occurrence of HABs (Maulu et al., 2021), which further defy bivalves’ resilience and hamper their harvest for human consumption. Hence, it is utmost important to acquire deeper insights on toxins’ bioaccumulation mechanisms and the deleterious ecotoxicological responses they elicit, at both optimal and altered abiotic conditions, as such data will be crucial to develop early warning tools (e.g. modelling) to mitigate the devastating consequences that HABs can have in the aquaculture sector, at ecological, economic and public health levels.

Material and Methods

Mytilus spp. collected from Porto Brandão (Portugal) were transplanted to laboratory facilities at the Portuguese Institute for the Sea and Atmosphere (IPMA I.P.). Here, they were distributed into 12 tanks within recirculation aquaculture systems, comprising 4 treatments (NoToxin+20ºC, NoToxin+24ºC, Toxin+20ºC, Toxin+24ºC), each carried out in triplicate. Bivalves were kept at 20 ºC (the same temperature registered in their natural habitat), while being fed with a non-toxic commercial dried microalgae (Tetraselmis spp.) solution. After 20 days of acclimation, seawater temperature was raised to 24 ºC in treatments simulating a marine heatwave (i.e. NoToxin+24ºC and Toxin+24ºC). The occurrence of an HAB was then simulated in half of the tanks (i.e. Toxin+20ºC and Toxin+24ºC treatments) by replacing the non-toxic commercial dried microalgae (Tetraselmis spp.) solution for a toxic P. lima solution. Upon 5 days of exposure to these conditions, the simulated HAB was stopped, i.e. all animals were fed again with the non-toxic microalgae solution for another 5 days of trial. Mussels were collected at the beginning of the trial (i.e. T20 – before exposure), after 5 days of exposure (i.e. T25 – maximum time of exposure) and at the end of the trial (i.e. T30 - recovery), in order to assess DSTs (OA, DTX1, DTX2) bioaccumulation/detoxification in Mytilus spp., as well as the ecotoxicological responses [total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), lipid peroxidation (LPO), heat shock proteins (HSP70), lactate dehydrogenase (LDH) and citrate synthase (CS)] in different mussel tissues (digestive gland, muscle and gills).


Preliminary results indicate that DSTs uptake was higher at 20 ºC than at 24 ºC (T25), most likely, due to bivalves’ ability to remain inside their shells when subjected to stressful environmental conditions, which might have prevented them from being in direct contact with toxic microalgae. Yet, during the recovery period (T30) toxins’ concentrations were not significantly different in the two tested temperatures, therefore, suggesting that the exposure to a marine heatwave did not compromise mussels’ ability to detoxify these contaminants. Regarding ecotoxicological responses, even though results are still being analysed, the preliminary data already evidenced remarkable alterations of bivalves’ antioxidant (CAT, SOD and LPO) and metabolic (LDH and CS) enzymes activity upon exposure to P. lima, especially at warmer temperature. After 5 days of recovery period, most of the analysed biomarkers did not return to basal levels.


Corriere, M., Soliño, L., Costa, P. R., 2021. Effects of the marine biotoxins okadaic acid and dinophysistoxins on fish. Journal of Marine Science and Engineering, 9(3), 293.

Griffith, A. W., Gobler, C. J., 2020. Harmful algal blooms: A climate change co-stressor in marine and freshwater ecosystems. Harmful Algae, 91, 101590.

Maulu, S., Hasimuna, O. J., Haambiya, L. H., Monde, C., Musuka, C. G., Makorwa, T. H., et al., 2021. Climate change effects on aquaculture production: sustainability implications, mitigation, and adaptations. Frontiers in Sustainable Food Systems, 5, 609097.

Soon, T. K., Ransangan, J., 2019. Extrinsic factors and marine bivalve mass mortalities: an overview. Journal of Shellfish Research, 38:223-232.

Soon, T. K., Zheng, H., 2020. Climate change and bivalve mass mortality in temperate regions. Reviews of Environmental Contamination and Toxicology 251:109-129.

Wijsman, J. W. M., Troost, K., Fang, J., Roncarati, A., 2019. Global production of marine bivalves. Trends and Challenges. Goods and Services of Marine Bivalves, 7-26.