Parental effect of the marine heatwave and fish predator cues on F2 generation
One of our important findings was that parental exposure to MHW (F1-MHW) reduced reproductive success and grazing, but not survival of F2P. incisus when the F2 was returned to the control temperature. The reduced F2 reproductive success and cumulative faecals may result from reduced energy and resource investments for F1 reproduction, further limited by the lower F1 grazing. Poor maternal provisioning was likely the reason for the lower performance of F2 copepods whose parental generation was exposed to MHW. A similar result has been observed in a previous study on the same copepod species (Dinh et al., 2021).
Across treatments, the main parental effect of FPC accounted for only around ~2% positive effect of the cumulative nauplii and faecals. The positive effect of parental exposure to FPC on the reproductive outputs of offspring is common in zooplankton and this effect may last for several generations after removing the predation stress (see e.g. in Daphnia ambigua , Walsh, Cooley IV, Biles, & Munch, 2015). However, the positive parental FPC effect on P. incicus was at least an order of magnitude smaller than the negative parental MHW effects on these life history traits and was unlikely to shape the overall sensitivity of P. incicus to MHW. Both types of non-consumptive predation stress, including direct and parental exposure, had a generally small effect on P. incisus ,Pseudodiaptomus copepods account for the majority of the diet of fish predator Lates calcarifer (Davis, 1985). MHW-induced strong reduction in reproductive success of P. incisus may directly affect the food availability for fish larvae in the coastal environment (Chew et al., 2012).