Herbivores play a key role in coral reef benthic communities by reducing the cover of macroalgae, which would otherwise out compete corals. Without herbivores to reduce macroalgal cover, dramatic phase shifts from coral to algal-dominated systems have been observed throughout the world, causing catastrophic degradation and system-wide collapse. Since coral reefs depend on particularly high levels of herbivory to persist in an animal-dominated state, understanding the quantitative nature of algal-herbivore interactions and the mechanisms that regulate herbivore feeding is essential for the successful management of these systems. This ongoing project aims to quantitatively characterise algal-herbivore interactions in Ningaloo Reef using a combination of descriptive and experimental approaches. Some of the specific topics tackled through this project are detailed below:
We are using stable isotopes and essential fatty acids to determine the ultimate source of primary productivity and to characterise the grazing pathway in a range of habitats (lagoon, reef flat, outer reef) and regions (Maud, Mandu and Bundegi).
We are using algal bioassays to quantify spatial variation in macroalgal herbivory in a cross-section of the Ningaloo Reef (lagoon, reef crest and outer reef habitats), and we are using fish, invertebrate and benthic surveys to compare community assemblages across habitats.
We are using settlement tiles and herbivore exclusion cages to determine the effects of herbivory on the recruitment and survival of algae in lagoon and reef flat habitats.
We aim to identify the key functional groups and fish species involved in herbivory and to quantify species-specific rates of herbivory across the length of the Ningaloo Reef.
We are comparing algal removal rates between Ningaloo Reef and the Keppel Islands, a reef system located at a similar latitude to Ningaloo in the Great Barrier Reef.
Dr Adriana Vergés
Associate Professor Glenn Hyndes
CSIRO, Dr Mat Vanderklift
CSIRO, Russ Babcock