Do abiotic environmental drivers disrupt the biotic response of marine larvae?
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Phenotypic plasticity, the ability of a given genotype to express different phenotypes in response to altered environmental conditions has been identified as a means by which organisms may be able to cope with environmental change. While significant progress has been made in the study of phenotypic plasticity in response to both individual and combined abiotic environmental drivers, very few studies have investigated the effects of abiotic and biotic drivers in combination. In this thesis, I investigate the combined effects of increased temperature (15 °C versus 20 °C) and the presence of predation threat in the form of predatory kairomones (skin mucus of predatory fish) on the embryonic development and subsequent locomotion of hatchling veliger larvae of the marine gastropod L. littorea. There were significant interactive effects of developmental exposure to predator kairomones and increased temperature. At 15 °C, exposure to predator kairomone led to accelerated development, whereas at 20 °C they retarded development. Predator kairomones also influenced the morphology and swimming of hatched veliger larvae. Larvae that were exposed developmentally to predator kairomones had significantly larger shells (20 %) and velums (22 %), and swimming was significantly faster, regardless of temperature. Veliger swimming speed was also positively correlated with velum size for those developed under predator presence, but no such relationship was present in control treatment larvae. This study demonstrates that abiotic and biotic environmental drivers may lead to complex responses in marine larvae, including carry-over effects between life history stages. Such effects may have ecological implications due to the alteration in the relationships between predators and prey in projected climate change conditions. This study also explores how climate drivers and predation threat interact on the development rates and morphology of L. littorea, and trade-offs between accelerated development and increased morphological size at hatch. The trade-off may have implications on further developed L. littorea, and would need further investigation to explore this interaction up to and exceeding the settlement stages.