Plankton and plankton-eating fish play an important part in the productivity of tropical reefs by igniting "sweet spots" of abundance, according to a new study by ARC Centre of Excellence for Coral Reef Studies (Coral CoE) and Research Hub for Coral Reef Ecosystem Functions at James Cook University (JCU).

According to lead author Dr Renato Morais, such areas are created when biological productivity converges from the ocean and spikes locally on the reefs. They are often driven by plankton-eating fish that consume the plankton from further offshore that are carried in by ocean currents.

When this happens, it means that energy and nutrients from offshore ecosystems are being transferred to the coral reef ecosystems. This influx boosts some reefs beyond their normal limits of biological production, enriching the reefs with life and diversity.

“By feeding on offshore plankton, these fish deliver extra resources to reef ecosystems, which drives the local concentration of extreme biological productivity—including for their own predators, which are large fish,” said coauthor Professor David Bellwood, also from Coral CoE at JCU.

The research added to knowledge about the extent to which oceanic plankton and plankton-eaters boosted the productivity of coral reef fishes.

Such information would prove useful for future of tropical reef fisheries. “Plankton-eating fish in some of these areas are responsible for more than half of the total fish production—up to 22 kg per hectare per day,” Prof. Bellwood added.