Microplastic consumption and physiological response in Acartia clausi and Centropages typicus: Possible roles of feeding mechanisms

Multi-day experiments were carried out with two Marmara Sea calanoid copepod species: Acartia clausi and Centropages typicus, to assess the possible role of the type of feeding on the consumption of microplastics and its influence on the rate of energy metabolism of these species. In a mixture of microplastic beads (6 mu m diameter) and algae Rhodomonas salina (5-10 mu m size range) with equal concentrations of about 5000 cells/beads mL(-1) the ambush feeder A. clausi consumed almost 5 times less microplastic 858.8 +/- 294.1 beads ind(-1) day(-1) than the cruising feeder C. typicus and halved its consumption of microplastics alone, while C. typicus, on the contrary, increased its consumption rate of pure microplastics to 20237.4 +/- 7020.41 beads ind(-1) day(-1). Both types of reaction to microplastics lead to a decrease in the respiratory rates of the copepods. During the 5 days of maintenance on a solely microplastic diet, the respiration rates of A. clausi and C. typicus decreased 2.2 and 3.4 times, respectively, due to a decrease in the energy spent on motor activity, whilst maintaining basal metabolic energy. It has been shown that in A. clausi, consuming microplastics, a decrease in respiration rate occurs in the same way as in individuals starving in filtered water. A more rapid respiration rate decrease in Centropages typicus consuming microplastics may be due to the greater energy expenditure on microplastic beads capture and egestion via fecal pellets. Acartia clausi seems to exhibit a better strategy in dealing with the adverse consequences of microplastics consumption in comparison to Centropages typicus. (C) 2021 Elsevier B.V. All rights reserved.