Pesticides and polychlorinated biphenyls (PCBs) contamination and ecotoxicity in estuarine biota

Tese de mestrado, Ciências do Mar, 2022, Universidade de Lisboa, Faculdade de CiênciasThis project reports the analysis of organochloride pesticides and polychlorinated biphenyls (PCBs) compoundsin a marsh environment, to observe its toxicological effects on a marine model organism. To achieve this goal, it was quantified the concentration of organocloride pesticides and PCBs in sediments and plants, with origin in Alcochete, Rosário in Seixal estuaries. In this case, we chose to study Spartina maritima. To extract the pollutants, it was used the ASE and QuEChERS techniquesin sediments and plants samples, respectively, and the GC-ECD technique to analyze its content. With this experiment, it was possible to conclude that pesticide compounds were more predominant in Rosário, while PCBs compounds were more predominant in Seixal, derived from the activities that occurred in the vicinity of those sites. Alcochete was the less polluted site that was analysed in this work. When comparing the results obtained in this work with other concentrations from the same compounds in other Portuguese estuaries, it was possible to observe that the Tagus estuary presented a higher level of these contaminants. This is due to the higher population and activity that occurs in this zone, in comparison to other Portuguese estuaries. When studying the compounds’ concentration on plants, it was possible to observe a higher concentration on the rhizosediments. To test the toxicity of these compounds we exposed PCB 153 at 1 µg/L, 3 µg/L and 6 µg/L to the diatom model Phaeodactylum tricornutum. Afterwards, we analysed the biomarkers growth rate, photochemistry, pigment, fatty acids, lipid peroxidation and antioxidant enzyme activity of the cell. It was possible to observe that, when exposed to the compound, the cells suffered from growth inhibition, oxidative stress, and photosynthesis inhibition, such as the closure of the reaction’s centres and damage in the photosystem. This occured even though they presented counter mechanisms to the toxic effects, such as the incrementation of photosynthetic effects, such as the grouping probability, increase of efficiency of the electron transport from PQH2 to PSI, and biochemical such as the incrementation of photoprotective pigments and pigments which increase the ability to trap photons for the reductions that happen in the photosynthesis and increases the activity of antioxidant enzymes