Study of the combined effect of microplastics and global warming factors on marine zooplankton

Microplastics (MP) and agrochemicals are frequently found as contaminants in the marine environment. Furthermore, the process of ocean acidification (OA) and ocean warming (OW) are projected to have indirect effects on organisms, as they can modify the availability and potentially increase the toxicity of various pollutants. The objective of this study is to evaluate if global change conditions (pH = 7.8 and temperature of 24ºC) could modify the toxicity of the combination of MP and chlorpyrifos (CPF) in Paracentrotus lividus larvae. Morphological, physiological, and biochemical responses were measured in P. lividus larvae resulting from embryos that had been exposed to these stressors at two different concentrations of CPF, 60 and 250 µg/L. The concentration of MP was fixed at 3000 particles (P)/mL. Growth and morphology of pluteus larvae were determined after 48 h of incubation. At low CPF doses, larval growth and morphology were affected as the number of stressors increased. Treatments that included thermal stress showed that larvae reared at 24ºC are not achieving their maximum growth potential when growth is expressed in Degree-Days (DD). At the morphological level, sea urchin larvae exhibit a trapezoidal shape instead of the typical triangular form, according to the different morphological measurements. Temperature was found to play a key role in the regulation of several enzymatic activities. Acetylcholinesterase (AChE) was found to have a temperature-dependent inhibition. Glutathione–S–transferase (GST) was induced in the presence of CPF, and inhibited as environmental stress factors increase. Glutathione reductase (GRx) activity increased when exposed to thermal stress, but it may also be inhibited by the interaction of various environmental stressors. At high CPF concentrations, the multi-factor treatments were strongly affected, both at growth and morphological level. The treatments that included global change conditions resulted in a significant reduction of 75% in larval size. Moreover, the parameters that were measured to detect larval deformities were also clearly affected. Biomarkers were mostly inhibited at high CPF concentrations, with almost no significant differences between treatments. Overall, in this study it was demonstrated that global climate change conditions influenced the impact of pollutants in marine biota, increasing the sensitivity of sea urchin embryos. This effect is detectable not only at the morphological level but also at the biochemical level, clearly affecting the fitness of organisms that are exposed to multiple stressors in their habitats.

Blanco Osorio A. V., 2023. Study of the combined effect of microplastics and global warming factors on marine zooplankton. MSc thesis, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, 53 p. Thesis.

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