Abstract
Crown-of-thorns sea star (CoTS; Acanthaste r cf. solaris ) outbreaks are a significant cause of coral decline. Enhanced food supply for the larvae via eutrophication is implicated as a cause of outbreaks, yet larval feeding ecology is poorly understood. In this study, feeding experiments were carried out at two algal food concentrations of 1000 cells mL −1 (~ 1.52 µg chl a L −1 ) and 3000 cells mL −1 (~ 4.56 µg chl a L −1 ) across six successive larval stages to investigate the effect of food concentration on filtration rate and ingestion rate for these stages. Filtration rate increased with larval stage and more than tripled from 127 ± 32 µL larva −1 h −1 (mean ± SE) of the youngest (2–3 dpf) larvae to 497 ± 109 µL larva −1 h −1 at late brachiolaria stage (9–10 dpf). Ingestion rate increased with food concentration and larval age, with advanced brachiolaria larvae consuming 313.5 ± 39.1 cells larva −1 h −1 in the higher algal food treatment. Organic carbon (C) and nitrogen (N) measured in larvae and their food indicated that the youngest feeding larvae ingested 13% their body carbon content daily, with that number almost doubling to 24% by advanced bipinnaria stage. The C/N ratio decreased sharply for brachiolaria larvae, reflecting developmental changes and greater dependence on exogenous nutrition. These results add to our understanding of the role food concentration plays in the growth and survivorship of CoTS larvae in the field.