Stress across life stages: Impacts, responses and consequences for marine organisms

Population dynamics of marine organisms are strongly driven by their survival in early life stages. As life stages are tightly linked, environmental stress experienced by organisms in the early life stage can worsen their performance in the subsequent life stage (i.e. carry-over effect). However, stressful events can be ephemeral and hence organisms may be able to counter the harmful effects of transient stress. Here, we analysed the published data to examine the relative strength of carry-over effects on the juvenile growth of marine organisms, caused by different stressors (hypoxia, salinity, starvation, ocean acidification and stress-induced delayed metamorphosis) confronted in their larval stage. Based on 31 relevant published studies, we revealed that food limitation had the greatest negative carry-over effect on juvenile growth. In the laboratory, we tested the effects of short-term early starvation and hypoxia on the larval growth and development of a model organism, polychaete Hydroides elegans, and assessed whether the larvae can accommodate the early stress to maintain their performance as juveniles (settlement and juvenile growth). Results showed that early starvation for 3 days (∼50% of normal larval period) retarded larval growth and development, leading to subsequent reduced settlement rate and juvenile growth. When the starvation period decreased to 1 day, however, the larvae could recover from early starvation through compensatory growth and performed normal as juveniles (c.f. control). Early exposure to hypoxia for 3 days did not affect larval growth (body length) and juvenile growth (tube length), but caused malformation of larvae and reduced settlement rate. We conclude that the adverse effects of transient stress can be carried across life stages (e.g. larval to juvenile stage), but depend on the duration of stressful events relative to larval period. As carry-over effects are primarily driven by energy acquisition, how food availability varies over time and space is fundamental to the population dynamics of marine organisms.