Marine biodiversity increases in protected areas

A study of Fiji's coral reefs shows that the area of coral cover in marine protected areas is three times that in unprotected areas.

By Peter Moon  |  Agência FAPESP – Viti Levu is the largest and most populated island in the Republic of Fiji, which is located in the South Pacific. Its southwestern coast is flanked by an extensive system of coral reefs that follows the shape of the shoreline. The corals stretch from just beyond the white sandy beaches to approximately 1 km out to sea.

Several areas of the Coral Coast have been damaged in recent decades by subsistence and predatory fishing, Fiji’s thriving tourism industry, and local population growth (currently 600,000). Live corals and rock are regularly removed and, consequently, parts of the reefs have been directly destroyed.

There are exceptions, however. At some locations along the Coral Coast, there are marine protected areas (MPAs) where all forms of fishing and harvesting are banned. As a result, the coral cover in these MPAs is three times that in the unprotected areas. Thus, even these relatively small, protected areas are vital to the maintenance of biodiversity throughout the entire coral reef system.

This conservation strategy has only succeeded thanks to participation by the local communities. This is one of the main conclusions of a research project conducted by biologist Roberta Martini Bonaldo on the Coral Coast of Viti Levu.

Bonaldo is currently a researcher affiliated with the Vertebrate Natural History Group at the University of Campinas (UNICAMP).

She chose Fiji’s coral reefs for her fieldwork during the course of two postdoctoral programs, the first of which was in the Biology Department of the Georgia Institute of Technology in the United States, and the second of which was at the University of São Paulo’s Bioscience Institute (IB-USP) in Brazil. The latter was supported by a scholarship from FAPESP.

During her first postdoctoral project (2010-12), she was responsible for managing a research station at Votua, a traditional village on Viti Levu’s Coral Coast. The goal of the project was to study the composition of marine life inside the MPAs and to compare it with the situation in the unprotected areas. Her findings were published in an article in PLOS ONE.

In addition to managing the research station, Bonaldo conducted studies of the structure of benthic and fish communities, and also investigated ecological interactions (coral-algal competition, herbivory, and shoal formation), where she compared the MPAs and the unprotected areas in Fiji in terms of the effects of fishing and marine degradation.

“Fiji was chosen because most of the protected areas, if not all, are managed by communities who live in nearby villages,” Bonaldo told Agência FAPESP.

Viti Levu’s MPAs were established in 2002 and 2003. At the time, the extent of coral cover had shrunk to only 7% of the protected areas, and macroalgae coverage had expanded to between 35% and 45%.

Fishing and harvesting are completely banned in the MPAs. The local communities comply with these restrictions and keep an eye open to make sure other people, including tourists, do not enter the protected areas.

“The local population’s commitment to protecting the coral reefs is fundamental to the conservation strategy implemented on Viti Levu,” Bonaldo said.

Bonaldo studied three MPAs that are located adjacent to three small communities – the villages of Votua, Vatu-o-lalai and Namada. She remembers very clearly her first impressions upon coming into contact with the coral reefs there.

“Only small parts of the reefs are inside the MPAs. When I went diving in the unprotected area, I was shocked by their degraded condition. There was a lot of dead coral, and the reefs were overwhelmed with seaweed,” said Bonaldo, who has experience as a diver, underwater photographer and filmmaker.

In addition to the coral shrinkage, there were fewer fish in the unprotected areas. In the absence of herbivorous fish, the algal population had exploded out of control. 

The coral reefs that Bonaldo studied are quite rarified, and some parts are almost exposed at low tide. “People wade into the pools left behind when the tide goes out to catch fish and octopus, and they can break the coral colonies as they step on them, especially the most delicate ones. At high tide, the reefs are about 2 m underwater and you can swim over them,” Bonaldo said.

During her dive, Bonaldo crossed a line of buoys that delimits the protected areas of the reefs. “Crossing the ring of buoys, I felt as if I had left chaos behind and entered paradise,” she recalled. “As we entered the protected area, we saw larger and larger fish. I was surprised by the extraordinary diversity of marine life below the surface and the density of the corals in such a small area, less than a square kilometer.”

Bonaldo produced a census of the fish that live in the coral reefs. She divided them into two major groups – herbivores and non-herbivores. She then classified the herbivores into four categories: browsers, grazers, scraping parrotfish, and excavating parrotfish. 

According to Bonaldo, browsers remove mature, fleshy macroalgae, while grazers crop algal turfs (algae less than 1 cm high that carpet the reef) and leave the basal portions intact. Scraping parrotfish feed predominantly on algal turfs by scraping the reef with their “beaks,” as do excavating parrotfish, which also remove pieces of the underlying substratum when feeding.

From the data collected, Bonaldo concluded that the removal of algae by parrotfish was three to six times greater in MPAs than in unprotected areas. She was assisted in her analysis by Mathias M. Pires, a Brazilian scientist whose postdoctoral research was also supported by FAPESP.

On average, the MPAs had almost three times as much coral cover as the unprotected areas (260%-280%). The amount of seaweed in the unprotected areas was between 4 and 20 times as much as in the MPAs. 

Coral reefs in Brazil

Despite the very small sizes of Fiji’s MPAs, the success of their conservation strategy was obvious to Bonaldo in the sense that the overall coral reef biodiversity had clearly been conserved.

“A key question for biodiversity conservation, and not only in marine environments, is how big a protected area should be to create real benefits,” said Paulo Roberto Guimarães Junior, a professor in IB-USP’s Ecology Department and supervisor of Bonaldo’s postdoctoral research.

“It’s an important question, because social, economic and logistical factors impose limits on the size of protected areas. What Roberta has shown is that there is evidence for positive effects in marine reserves even when they’re very small, as in the case of Fiji’s MPAs.”

“Brazil has some coral reefs, especially in the region of Abrolhos, but even these are quite different from the coral reefs I studied in Fiji,” Bonaldo said. “The main coral species in Fiji belong to the genus Acropora. Their colonies are multi-branched and grow very fast, in some cases more than 10 cm per year.”

There are no species of Acropora in Brazil. The main species found in Brazilian coral reefs belong to the genus Mussismilia, which form massive rounded colonies that resemble boulders. They grow less quickly than species of Acropora but are more resistant to high sedimentation rates and water turbidity. 

According to Bonaldo, the Brazilian coast has much less biodiversity in terms of coral reef species than the region of Fiji, but they share fish families such as Acanthuridae (which includes surgeonfish and unicornfish), Labridae (wrasses) and Serranidae (groupers), among others.

According to Guimarães, who is also a co-author of the article in PLOS ONE, a strategy similar to that used in Fiji would work well in Brazil. “I believe there’s plenty of potential for similar experiences, not just in marine ecosystems but in any type of ecosystem,” he said. “For example, paired microreserve systems could be used to study whether these microreserves maintain ecosystem processes in the Atlantic Rainforest or Caatinga biomes.”

“I’d like to add that our study shows the importance of effective management of protected areas, whether they’re on land or at sea,” Bonaldo said. “In the case of Fiji, participation by local communities in taking care of the areas was crucial to the positive results obtained in the MPAs, despite their small size.”

The article “Small marine protected areas in Fiji provide refuge for reef fish assemblages, feeding groups, and corals” (doi:10.1371/journal.pone.0170638), by Roberta M. Bonaldo, Mathias M. Pires, Paulo Roberto Guimarães Junior, Andrew S. Hoey and Mark E. Hay, can be read at: journals.plos.org/plosone/article?id=10.1371/journal.pone.0170638.