WAMSI Node 3.2.2c - Spatial variation in algal-herbivore interactions on the Ningaloo Reef, Western Australia

This study was nested in sub-project 3.2.2 “Ecosystem impacts of human usage and the effectiveness of zoning for the biodiversity conservation” in Node 3.2. The focus of this study was on trophic effects in the NMP. Due to the importance of herbivores in coral-reef systems, this study focused on characterising and quantifying the process of herbivory in the NMP with a particular emphasis on the removal of adult macroalgae.

We used a range of approaches to gain an understanding of spatial and species-related patterns in herbivory in five distinct studies. Using underwater video cameras and Sargassum myriocystum assays, 23 different fish species were observed consuming macroalgae, but seven species (Naso unicornis, Kyphosus sp., K. vaigiensis, Siganus doliatus, Scarus ghobban, S. schlegeli and initial-phase Scarus sp.) together accounted for 95% of the observed bites across five regions. Of these species, three were identified as the most important in consuming macroalgae: N. unicornis, Kyphosus sp. and K. vaigiensis. These results were supported by stable isotope analyses that incorporate nutrients from food sources over far longer periods than those examined using the assay approach.

The attached final report provides details on the 5 studies conducted related to herbivory:

1. Spatial patterns in herbivory on a coral reef are influenced by structural complexity but not by algal traits.
2. Herbivore diversity on coral reefs: a transcontinental comparison.
3. Variation in macroalgal herbivory by fishes across a western-continental coral-reef system.
4. Variability in the food sources of herbivorous invertebrates and fishes in a coral-reef system: a stable isotope approach.
5. The role of herbivory on the spatial distribution of recruiting and established algal communities in coral versus algal dominated habitats.