Anthropogenic stressors reduce marine biodiversity. Tolerant species may develop in altered areas where they occupy niches that native species are unable to use. Species of biosecurity concern, like invasive aliens or harmful microalgae, are especially successful in disturbed areas. Here, we employed multiple regression approach to investigate the relationship between the proportion of planktonic stages of invasives and anthropogenic stressors. Planktonic species were inventoried from environmental DNA on water samples from the Bay of Biscay. Key findings were that the proportion of invasives was associated with port and touristic activities that are vectors for biological invaders, and with industrial pollution, likely for their tolerance to disturbed environments. The proportion of toxic algae was correlated with port activity, reinforcing the role of maritime traffic as a vector of harmful microalgae. An increase of nuisance species is expected under the current growth of pollution in the ocean. Promoting awareness of biological invasions among maritime sectors and tourists, and controlling pollution, seem priorities for environmental conservation in this region and elsewhere.