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Keeping coral reefs healthy

Herbivores and nutrients affect the amount and type of seaweed growing on coral reefs. In an NSF-funded study, researchers at the University of Hawaii found that grazing urchins and fish have the greatest effect on seaweed growth. Seaweed blooms when grazing decreases and nutrient levels rise.

During the study, the researchers examined seaweed growth on settling tiles and experimentally reduced grazing using herbivore exclusion cages to mimic the effects of overfishing. The experiment was placed in areas of high- and low-nutrient concentrations on coral reefs to examine how herbivory and nutrients effect what types and how much algae grows in these areas.

This research provides coral reef managers with information on the relative roles of water quality and herbivory in keeping coral reef ecosystems healthy and free of algae blooms. It also provides insights on the current conditions of seaweed growth and provides information on reef outcomes if herbivores are overfished or nutrient additions reduce water quality.

Images (1 of )

  • fish graze on a coral reef in hawaii
  • seaweed blooms on seaweed settling tiles when plant-eaters are excluded
Fish graze on seaweed on a coral reef in Hawaii.
Rebecca Most, University of Hawaii at Hilo
Seaweed blooms on seaweed settling tiles (left) when plant-eaters are excluded.
Rebecca Most, University of Hawaii at Hilo

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