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Coral Reefs in Northern Lau Show Amazing Recovery Potential from Disturbance

Aerial view of Kaibu and Yacata Islands in the northern Lau Group. Photo by Sangeeta Mangubhai/WCS.

By Yashika Nand

[Note: this is the sixth and final blog in a series documenting a new scientific survey of the waters and islands comprising Fiji’s Northern Lau Group]

The islands that make up the Lau Group have largely been unexplored. Local Fijian scientists from the Wildlife Conservation Society (WCS) and Vatuvara Foundation surveyed 35 sites on outer fringing reefs, reef flats, and lagoonal systems in the course of an 8-day expedition looking at five islands in the Northern Lau Group.

We knew before we started this trip that last year’s Category 5 Cyclone Winston had passed quickly through the Lau Group, but until now, no one had documented the impact caused to coral reefs. Sadly, we did survey cyclone damaged areas with large boulders and upturned corals, high sand and rubble cover, and an overgrowth of algae. However, we also documented extensive areas of reef that had very little to no damage, where there was a lot of intact structural complexity to reef systems surrounding the islands.

A grouper swimming over a healthy reef. Photo by Sangeeta Mangubhai/WCS.

In these places the marine life was clearly diverse, abundant, and thriving. We found many sites that were stunning “world class dive sites” according to coral reef expert, Helen Sykes, who has dived in many places around the world for more than 30 years. These areas are the hidden underwater jewels of Fiji, with lots of “spur and groove” structures, crevices, steep walls, small caves with sleeping sharks, and highly vulnerable species like groupers, humphead wrasse, and hammerhead sharks.

Despite the challenges of a Category 2 cyclone warning and unpredictable weather conditions bringing strong winds and ocean swell, we were able to complete our surveys. There were great encounters with bottlenose dolphins in between dives, curious sharks patrolling the reefs, green and hawksbill turtles swimming close to nesting beaches, courting triggerfish, and schools of parrotfish grazing on algae on the reefs.

Steven Lee recording benthic cover on reefs in northern Lau. Photo by Sangeeta Mangubhai/WCS.

We also documented diversity in habitats and species distribution of both corals and fish within and in between islands. For example, there was a distinct difference in reef structure and marine life between leeward (downwind or sheltered) and windward (mostly exposed) sides at each of the islands. Many of the windward reefs were in good condition, but were shaped by ocean swell and high energy waves.

The reefs had large areas of crustose coralline algae (pink algae) which is critical for cementing the reef and forming a smooth surface for new corals to settle on. There were a lot of small juvenile corals less than 5 cm forming a patchwork over boulders and upturned corals. This is a great sign, as it means that a year later, the reef already is starting to show signs of recovery. Many of these corals grow at rates of 5-10 cm per year, which means that in the next 2-3 years, we will see some significant regrowth.

Juvenile corals surrounded by crustose coralline algae. Photo ©Katy Miller.

And because there were extensive healthy and intact reefs and a high diversity and abundance of algal grazing parrotfish, there is a high probability of a rapid recovery of damaged reefs.

But the work is not over. Over the next 3-4 weeks the team will begin analyzing the data and producing a report on our findings. Results from the expedition will improve our understanding of the current state of the coral reef systems and fisheries resources in the Northern Lau Group.

The survey team at Kanacea Island. Photo ©Vatuvara Foundation.

The results will be used by the Vatuvara Foundation to work together with communities to make decisions on the use and protection of marine resources. This will include looking at opportunities to set up of a network of community tabu areas (traditional periodic closures) that can act as fish banks to help replenish reefs and sustain them well into the future.

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Yashika Nand is a marine scientist with the WCS Fiji Program.

 

Previous blogs in this series:

Exploring Coral Reefs in the Northern Lau Group

Signs of Adaptation to Climate Change

Impressive Lagoonal Coral Formations in a Community ‘Tabu’ Area

Why Weedy Species Matter on Coral Reefs

Vatuvara Island: A Haven for Threatened Species