Effects of combined exposure to temperature, salinity, and microplastic fibres on biological endpoints in the American lobster (Homarus americanus).

To assess the effects of climate change stressors and microplastic pollution on early life stages of the American lobster (Homarus americanus), we conducted two experiments on the (1) combined effects of temperature (10, 15 [control], and 25 °C) and salinity (25, 30 [control], and 35 PPT) on stage I and II larvae and (2) the combined effects of salinity (25, 30 [control], and 35 PPT) and microplastic fibres (0, 0.3, 5, and 10 MPF mL-1) at 15 °C on stage I larvae. To analyze their effects on H. americanus larvae in-vivo parameters including survival, heart rates, and tail flips were assessed. Elevated temperature significantly (P < 0.05) reduced survival compared to the control and was identified as the primary stressor in this experiment and was positively correlated with heart rate. Furthermore, both stages I and II had the highest mortality compared to all other treatment groups in response to the low salinity under high temperature group (25 PPT at 25 °C). These in-vivo effects were further validated by oxidative stress biomarkers including reactive oxygen species (ROS) and glutathione S-transferase (GST). There were no significant (P > 0.05) differences observed in survival in response to all microplastic fibre concentrations tested (0, 0.3, 5, and 10 MPF mL-1). No significant (P > 0.05) differences were observed in moulting, but 10 MPF mL-1 at control salinity group had the greatest number of moults compared to all other treatment groups. Microplastic fibres were observed within the carapace and the stomach of exposed larvae.