Abstract
Understanding the environmental drivers of Crown-of-thorns seastar outbreaks is important for predicting and managing coral reef decline. Larval survival and development are strongly influenced by phytoplankton food availability, which is highly variable in space and time and often occurs as short-lived nutrient-driven pulses. Light may also indirectly support larval nutrition via phototrophic bacteria. Here, we investigated in a series of experiments how light conditions and the timing and duration of high food availability effect larval development and settlement. Light had no effect on larvae and did not compensate for low food availability. High food availability accelerated development and settlement success. Larvae exposed to low food in early development showed delayed progression but partially recovered when subsequently provided with high food, indicating developmental plasticity. Early access to high food resulted in the fastest development and a threshold response whereby exposure ≥ 4 d of high food directly after onset of feeding substantially increased progression to advanced larval stages and enhanced settlement success. These results demonstrate that short term variability in food resources can influence larval performance. Episodic phytoplankton blooms driven by runoff and/or upwelling may provide transient windows that enhance larval development and recruitment, contributing to outbreak initiation.