Let’s Find Nemo Some Friends: The Importance of Biodiversity in Coral Reef Ecosystems

Article:

Jonathan S. Lefcheck, Anne A. Innes-Gold, Simon J. Brandl, Robert S. Steneck, Ruben E. Torres, Douglas B. Rasher (2019). Tropical fish diversity enhances coral reef functioning across multiple scales. Science Advances 5:3, eaav6420. DOI: https://doi.org/10.1126/sciadv.aav6420

 

Key Terms to Know

Biodiversity: the variety of life in a specified area, usually a habitat or ecosystem

Species richness: the number of different species in an area (separate from the abundance of any species)

Ecosystem function: the biological, geochemical and physical processes that take place within an ecosystem

Herbivory: the act of eating plants

 

Background

Countless studies have shown that an environmental ecosystem suffers when it loses native species. This is particularly the case for smaller, local and laboratory scales, but there are few studies of how (or if) this theory holds up in nature on the larger scales at which we generally manage natural resources.  Because there is a lack of evidence to support the role biodiversity plays in ecosystem health, a theory is that high numbers of just a few key species might be enough to maintain a functioning ecosystem. However, recent studies have shown that different coral algae and fish species interact in different ways, indicating that the composition of species present on a coral reef might impact its ecosystem function.  Herbivory is an important process on coral reefs, as algae-eating fish prevent algae from suppressing the growth, survival, and reproduction of coral. See Figure 1 for a description of coral bleaching and some basic coral processes.

Figure 1. Infographic by NOAA describing coral bleaching and illustrating the symbiotic relationship between coral and algae. https://oceanservice.noaa.gov/facts/coral_bleach.html

 

Study: Herbivory Rates on Coral Reefs

To track this phenomenon, Lefcheck et al. deployed remote video cameras on 10 reefs spanning more than 1000 km of coastline in the Dominican Republic. After recording grazing rates for all species on these reefs, the researchers found that biomass (a measure of fish using total weight) as well as two different measures of biodiversity were positively associated with rates of herbivory. In other words, when the total number of fish and the diversity of fish increased, the health of the ecosystem increased.

 

Why is this important?

Throughout the world, coral reefs have lost fish inhabitants through disease, temperature-induced bleaching events, and overfishing. This study shows that maintaining biodiversity in stressed ecosystems might be one tool we can use to help combat the negative effects of these stressors. Maintaining high levels of biodiversity is a clear, quantifiable target, which is very helpful in natural resource management. It will be important to continue this type of monitoring in this and other habitats around the world to ensure we are managing ecosystems to the best of our ability.

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Maddie Halloran

Maddie Halloran

I am a second year master's student at Humboldt State University in the Fisheries Biology Department. I'm interested in human impacts on the environment and conservation. When I'm not counting fish you can probably find me outside on an adventure or eating ice cream on my porch.

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