After Winston: Assessing Coral Reefs for Cyclone Damage and Coral Bleaching

By Sangeeta Mangubhai

[This is the first in a series of blogs by WCS-Fiji Director Sangeeta Mangubhai assessing the damage to coral reefs caused by Cyclone Winston, a Category 5 storm that hit Fiji on February 20]

On Saturday, 20 February 2016, Fiji – with a population of 900,000 – was hit by Category 5 Cyclone Winston. It was one of the largest cyclones we had experienced, with winds of up to 185mph. Over a 24-hour period the cyclone left a trail of destruction through the center of the country and through the Vatu-i-Ra Seascape, where WCS (Wildlife Conservation Society) works.

The Fijian Government immediately announced a 30-day state of emergency, calling for coordinated assistance from NGOs, the private sector, and humanitarian aid agencies. As images flood in from across the country, we are getting the full sense of the damage that has been done – especially within the communities we work – and the long road to recovery that is ahead of Fiji.

WCS Fiji office in the aftermath of Cyclone Winston. Photo by Sangeeta Mangubhai ©WCS.

Much of our effort so far, has been around providing food and water relief to our communities until authorities and humanitarian organizations can step in. However, over the next 10 days, through the generous support of Nai’a Cruises (a live-aboard ship that has been diving in Fiji since 1993), I have the opportunity to survey coral reefs throughout the Vatu-i-Ra Seascape to assess the damage caused by Cyclone Winston and collect data on coral bleaching.

Why is this important? Fijians are highly reliant on their coral reefs for both food and for livelihoods. Because fish are the main source of protein, healthy productive coral reefs and their associated fisheries are critical to Fiji’s food security.

I will be using two main techniques to assess the reefs. First, I will be taking a series of random underwater photos from about half a meter above the reef surface at 12-15m depth. They have to be random because I have to be careful not to bias my sampling and favour one type of substrate (e.g. coral) over another (e.g. sand).

So what I do is close my eyes for about five to ten kicks of my fins, open my eyes and wherever I land I point the camera down and take a photo. All the photos are later analysed in software specifically designed to help capture how much hard coral covers the reef, versus soft coral, algae, sand or rock.

Map produced by Phil Bright (, Statistics for Development Division, SPC, 23-02-16.
Map produced by Phil Bright (, Statistics for Development Division, SPC, 23-02-16.

Second, I will be assessing the scale and intensity of coral bleaching across different reefs throughout the Vatu-i-Ra Seascape. Just before the cyclone, there were increasing reports from dive operators and local scientists of coral bleaching throughout Fiji caused by the El Niño cycle.

Coral bleaching occurs when a coral is stressed – most often in response to increases in sea surface temperatures. Under stress, coral will sever the unique relationship they have with an algae living inside them called zooxanthellae. The algae gives coral their color and turns sunlight into food. Without zooxanethellae corals become pale to white (hence the term coral bleaching) and slowly start to starve.

On this trip, I will explore sites I surveyed in 2001 with Nai’a Cruises as well as several new areas. The data I will collect can also serve as a baseline for measuring both changes on coral reefs and the reefs’ recovery post-cyclone and post-bleaching. The ability of our reefs to resist stresses like cyclones and high sea surface temperatures will affect how healthy they are and therefore their ability to support local fisheries in Fiji.


Dr. Sangeeta Mangubhai is Director of the Fiji Program for WCS (Wildlife Conservation Society). Follow Sangeeta on Twitter at: @smangubhai.


Other blogs in Sangeeta Mangubhai’s series exploring the damage to Fiji’s coral reefs following Cyclone Winston:

* A First Post-Cyclone Look at Coral Reefs in the Vatu-I-Ra Seascape

* Diving Nigali Passage in Gau

* Coral Bleaching in the Vatu-I-Ra Seascape: How Bad Is It?

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