Growing up under stress: Chemical pollution and heatwaves affect development and metamorphosis of abalone larvae

Successful development and dispersal of meroplanktonic larvae are critical for recruitment and population dynamics of benthic invertebrates. With increasing anthropogenic stressors on marine ecosystems, it is essential to understand how combined pressures impact these sensitive early life stages. We investigated the effects of different types of chemical pollution in combination with a simulated marine heatwave (+5 °C) on larval stages of the abalone Haliotis tuberculata coccinea, an endangered subspecies endemic to Macaronesia. Larvae were exposed for 48 h to crude oil, leachates of car tire particles, and leachates of beach-collected plastics. Two exposure experiments were conducted to examine (1) the effects on development and survival of early larvae and (2) the potential impacts on metamorphosis in late larvae. Early larvae were sensitive to all tested pollutants, shown by increased mortality. However, leachates of car tire particles induced the strongest effects with all surviving larvae being smaller than controls and showing signs of abnormal development. These responses were milder for the other pollutants. The heatwave treatment significantly reduced the survival of early and metamorphosis of late larvae. In contrast, metamorphosis was only slightly affected by the tested pollutants in the absence of an inducer, although we observed trends in different directions. Overall, our results demonstrate that abalone larval sensitivity is influenced both by developmental stage and the combination of stressors. The findings underscore that warming and chemical pollution pose a threat to the early life stages of H. tuberculata coccinea. This could present a considerable risk for these overexploited populations in Macaronesia.