Structural and functional alterations under stress conditions by contamination: A multi-species study in a non-forced multi-compartmented mesocosm

Despite the existing connectivity and heterogeneity of aquatic habitats, the concept of interconnected landscapes has been frequently overlooked in ecotoxicological risk assessment studies. In this study, a novel mesocosm system, the HeMHAS (Heterogeneous Multi-Habitat Assay System), was constructed with the potential to assess structural and functional changes in a community resulting from exposure to contaminants, while also considering the complex ecological scenarios. Fish (Sparus aurata), shrimp (Palaemon varians) and three species of marine microalgae (Isochrysis galbana, Nannochloropsis gaditana and Tetraselmis chuii) were used as test organisms. Other species, such as Artemia sp. and macroalgae were also introduced into the system as environmental enrichment. All the species were distributed in five interconnected mesocosm compartments containing a copper gradient (0, 1, 10, 100 and 250 μg/L). The mobile fish avoided the copper contaminants from 1 μg/L (24 h-AC₅₀: 4.88 μg/L), while the shrimp avoided from 50 μg/L (24 h-AC50: 136.58 μg/L). This finding suggests interspecies interactions influence habitat selection in contaminated environments, potentially jeopardizing population persistence. Among the non-motile organisms, the growth and chlorophyll content of the microalgae were concentration dependent. The growth of I. galbana was more sensitive (growth inhibition of 50 % at the highest concentration) in contrast to N. gaditana (30 % inhibition at the highest concentration) and T. chuii (25 % inhibition at the last two highest concentrations). In summary, the mesocosm HeMHAS showed how contamination-driven responses can be studied at landscape scales, enhancing the ecological relevance of ecotoxicological research.