herbivores

How marine protected areas support healthy coral reefs

Publication specs

Title: Marine protected areas increase resilience among coral reef communities

Authors: Camille Mellin, M. Aaron MacNeil, Alistair J. Cheal, Michael J. Emslie, M. Julian Caley

Journal: Ecology Letters

Year: 2016

Many of our researchers are SCUBA divers, and we like to think that many of our followers also enjoy spending time under the sea or at the very least learning about it. It’s no wonder that we enjoy diving on vibrant reefs with a diversity of species. Of course, we also love getting the opportunity to see sharks and stingrays on our dives.

However, not all reefs are healthy. This has led scientists and advocates to push for more ocean protection. Marine protected areas (MPAs) are designed to support and protect the balance of life within them, making them valuable ocean conservation tools. Yet, their efficacy has been debated among scientists. 

Recently, a study was conducted using 20 years of data inside and outside marine protected areas of the Great Barrier Reef (GBR). A total of 46 locations were surveyed: 26 sites with fishing activity, and 20 sites without fishing activity. MPAs offered protection from natural disturbances like coral bleaching and disease, storms, and crown of thorn sea star outbreaks. On healthy reefs, crown of thorn sea stars feed on fast growing corals. However, outbreaks of these invertebrates can have devastating effects on the reef – crown of thorn sea stars accounted for 42% of coral loss from 1985 – 2012 on the GBR.

Researchers found that inside MPAs the effect of the disturbances was 30% lower and the recovery of the community was 20% faster than outside MPAs. On average, recovery time within MPAs took only six years compared to nine years outside these protected reefs. So why did reef sites in MPAs remain strong through disturbances and recover faster after disturbances? The study offered several potential explanations:        

  • Increased feeding on macroalgae, which allowed young coral to settle.

 

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  • Increased predation on coral-eating fish like butterflyfish.

 

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  • Lesser impact of crown of thorn sea stars resulting from more predation on them within MPAs.
  • Multiple species performing their ecological function together as a community.

Without these protected areas, researchers predicted that the recent loss of coral cover in the GBR might have been much worse. This study both recommended and demonstrated the value of MPAs that prohibit fishing.      

Dining in fear: the influence of predator and prey behavior on the health of coral reef ecosystems

Publication specs

Title: Reefscapes of fear: predation risk and reef heterogeneity interact to shape herbivore foraging behaviour
Authors: Laura B. Catano, Maria C. Rojas, Ryan J. Malossi, Joseph R. Peters, Michael R. Heithaus, James W. Fourqurean and Deron E. Burkepile
Journal: Journal of Animal Ecology
Year: 2015

Imagine: you’re quietly enjoying your breakfast when suddenly a lion barges through your front door. Do you continue eating? Run for cover? The answer for you, and other potential prey, is pretty clear. For small, plant-eating fish living on coral reefs, this is a constant threat. So much so that even just the fear of a potential predator, like sharks and grouper, can alter their behavior. While that may seem obvious, a recent study has revealed something not quite so intuitive – this fear is actually good for the entire coral reef ecosystem.

The findings of this study suggest something rather surprising – without predators, herbivorous fish cannot fulfill their normal function on the reef. Reefs come in a variety of structures and are comprised of a multitude of interdependent organisms. The feeding behavior of these fish, like surgeonfish and parrotfish, are influenced by both the structure of the reef and their predators. In the absence of predators, or in this case a grouper decoy, the fish ate almost two times more seagrass than when the decoy was present. In areas with and without complex reef structure, the fish did not eat as much when the grouper decoy was present.

Complex reef habitats don’t offer easy escape or shelter, which means that in areas with predators lurking, fish spend more time trying to find safe spaces rather than grazing. According to these findings, herbivorous fish concentrate their feeding to areas where they are less likely to encounter a roving predator, leaving more space for coral to settle, grow, and thrive. Reefs without predators encourage grazing across larger areas, leaving less open space for young coral to survive. This study suggests that this interplay – between predator, prey, and ecosystem – is crucial for healthy reefs.