Direct and delayed synergistic effects of marine heatwaves, metals and food limitation on tropical reef-associated fish larvae

Abstract

Tropical fish are fast-growing and high energetic-demand organisms, which can be highly vulnerable to long-lasting effects of heat stress and pollution, particularly under food shortages. We tested this by assessing highly complex direct and delayed interactive effects of an extreme temperature (32°C) from a simulated marine heatwave (MHW), copper (Cu, 0, 100, 150 and 175 micro g L-1) and food availability (limited and saturated food) on larvae of a tropical, reef-associated seaperch (Psammoperca waigiensis). Cu, MHW, and food limitation independently reduced survival and growth, partly explained by reduced feeding. The negative effect of Cu on fish survival was more substantial under MHW, particularly under limited food. Delayed interactive effects of Cu, MHW, and food limitation were still lethal to fish larvae during the post-exposure period. These results indicate that reef-associated fish larvae are highly vulnerable to these dominant stressors, impairing their ecological function as predators in the coral reefs.