Creating marine protected areas (MPAs) has become a more popular management and conservation strategy to counteract various anthropogenic risks and hazards.
Nature’s treasure chests, coral reefs, encircled by bright majestic fish are succumbing to the disastrous effects of climate change. Increasingly warmer and more acidic oceans, reaching temperature and pH levels not seen in over 100,000 years, threaten these precious beds of jewels in the sea. In fact between 2016 and 2018 at least half of the Great Barrier Reef in Australia died.
Along with the effects of global warming, coral reefs also suffer due to overfishing, pollution, sediment runoff, and other disturbances. Following coral die-offs from hurricanes, disease outbreaks, and coral bleaching events, invasive species such as seaweed, a type of macroalgae, move in and build up on the reef. When there is too much seaweed on the reef, it is difficult for juvenile coral to survive. In order for the reef to recover, the coral relies on herbivorous fish such as parrotfish to browse on the excess algae.
Creating marine protected areas (MPAs) has become a more popular management and conservation strategy to counteract various anthropogenic risks and hazards. Many of these areas are hotspots of diversity including coral reef ecosystems such as the Great Barrier Reef or more locally in the Florida Keys.
Often MPAs are deemed successful if the numbers of target fish increase, particularly for fishery management. However, a new study published in 2019 shows that local management should also focus on retaining diverse fish populations and key species that feed on this seaweed in order to increase coral reef resilience to disturbances.
The study published in the journal Conservation Letters found that a more diverse range of herbivorous fish allows for the ecosystem to function better. Since macroalgae produce different defense toxins and chemicals, different fish will be able to consume various seaweed. With more niches to fill, there will be greater species richness, or number of different species. Each fish will consume a different type of seaweed, therefore creating an ecosystem more effective in reducing the threats from algal blooms that occur after disturbances.
Across the globe, this study showed that increased protection afforded by MPAs significantly enhanced the local herbivorous fish diversity and increased biomass (or number of fish). Further, it was investigated which fish were the most important to certain regions, including the Atlantic, the Pacific, and the Indian Oceans. In the Atlantic Ocean, the parrotfish was found to be the most important macroalgae browser. In the Pacific and Indian Oceans, there was more variation in importance and frequency of different contributors to grazing.
Stephanie Wear, a Nature Conservancy scientist, said in an interview, “Coral reefs are transforming into algae reefs in places where parrotfish populations are small. We know that if healthy populations of parrotfish are present – it can be a good indication that the reef is healthy.”
With the results and insight from this study, it is clear that action needs to be taken. First, coral reefs are and should continue to be sites included in marine protected areas. Due to their indispensable nature as homes, places of refuge, and feeding grounds for many marine organisms, coral reefs need to be protected. Further, using data from this study and others, MPAs can help protect certain key herbivorous species as well as retain certain levels of biodiversity in the ecosystem to improve its overall functioning.
Doug Rasher, a researcher at Bigelow Laboratory whose study came to a similar conclusion, wrote, “Scientists have long known that reefs are healthier when a large number, or a ‘high biomass,’ of plant-eating fish graze their surfaces. However… having a diverse portfolio of those fish species on the reef is equally important to keeping reefs well grazed and hospitable to baby corals.”
With rising ocean surface temperatures, ocean acidification, and other threats, it is imperative that local management strategies act so that coral reefs are as resilient as possible to external threats. The reefs can no longer afford to be damaged by overfishing, boating, and poor water quality. Creating well designed and managed MPAs that focus on increasing biodiversity will help restore healthy and resilient coral reef ecosystems. Without proper measures, these riches of the ocean will not be able to withstand the impending doom from climate change.
COURTNEY GANTT, MIDDLEBURY, VT.
Editor’s note: Gantt is a conservation biology major studying at Middlebury College.