Role of plastics (polymer and plasticizer) as vectors of harmful algae and their toxins: study case of the toxic dinoflagellates Vulcanodinium rugosum and Alexandrium pacificum

The combination of the two pollutants, plastics (physico-chemical and anthropogenic) and phycotoxins (natural biologic toxins from microalgae), that are present in most of the coastlines worldwide is a new risk for marine ecosystem that needs to be investigated with respect to marine ecosystem and human health. In this study, we investigated (i) the adhesion behavior of benthic (Vulcanodinium rugosum) and pelagic (Alexandrium pacificum) toxic microalgae present on the Mediterranean coast on two types of macroplastics, (ii) the risk of phycotoxins (lipophilic pinnatoxin G and portimine A produced by V. rugosum and hydrophilic saxitoxins by A. pacificum) adsorption on the same macroplastics. To evaluate the role of additives in this process, we used PVC after addition of either the petrochemical-derived phthalate or a biosourced additive as plasticizers. Results showed that laboratory cultures of V. rugosum and A. pacificum with strips of PVC with the biosourced additive rapidly declined in growth and photosynthetic activity. PVC with the biosourced additive enables senescent algal cells to adhere but the risk of dissemination seems limited due its deleterious effect. PVC-DEHP strips showed no or limited impact on algal growth and did not allow algal cell adhesion. Regarding phycotoxins, saxitoxins do not adsorb on PVC while portimine and pinnatoxin adsorb on PVC with higher affinity to PVC with the biosourced additive. These results highlight the risk of phycotoxin-contaminated plastics in coastal marine environment.