On 20 February 2016, one of the largest cyclones on record in the Southern Hemisphere
passed through Fiji, with winds up to 185 mph, and gusts of 225 mph. Cyclone Winston
left a trail of destruction, with some of the most impacted landscape and communities
located in the Vatu-i-Ra Seascape. A rapid assessment of coral reefs in the Vatu-i-Ra
Seascape was conducted from 6-15 March 2016 focusing on tourist sites, using rapid
assessment techniques. The objectives of these surveys were to assess: (a) impact of
Cyclone Winston on coral reefs in the Vatu-i-Ra Seascape; (b) extent and intensity of
coral bleaching on corals; and (c) the health and diversity of areas being considered for
inclusion in deeper water marine managed areas. Over 10 days, 26 sites were surveyed
covering reef within and around the proposed Vatu-i-Ra Conservation Park in Nakorotubu
District, Gau, Batiki and Wakaya Islands, the Namena Marine Reserve in Kubulau
District, reefs in the Eastern Bligh Waters. Data were collected on benthic cover and
coral bleaching, and observations were recorded of the damage to coral reefs.
Tropical Cyclone Winston not only altered landscapes and communities along its main
pathway, but caused significant damage to coral reefs up to 20-30 m below the surface
in the Vatu-i-Ra Seascape. Damage to coral reefs was highest in the north where the eye
of the cyclone passed, and lowest in the south. However, the level of destruction was
highly variable and patchy between reefs. There was no clear pattern to the damage,
with both windward and leeward reefs equally impacted. There was extensive coral
breakage, coral abrasion, dislodgement of large coral colonies and structural damage to
the reef framework. While no data were collected on reef fish, there will likely be
changes to fish species composition and biomass, especially in areas that sustained high
coral and reef structural damage, like the Namena Marine Reserve. A reduction in corals
and the reef structure will reduce the available habitat, which may make some species
more vulnerable to predators.
Recovery from these types of disturbances, especially cyclones, can take decades,
depending on frequency of these events, the scale and intensity of structural damage
caused, and compounding anthropogenic stresses (e.g. pollution, overfishing) on coral
reefs, that might hinder or slow recovery. However, in additional to mechanical and
structural damage, Fiji’s reefs have the additional stress of coral bleaching. At the time
of the surveys, the bleaching was mild and the exception of Gau was <8% on most
reefs. While the SSTs have dropped 1-2°C since the cyclone, corals had not returned to
normal, a month after the cyclone.
The ability of Fiji’s coral reefs to persist and recover from cyclone Winston and bleaching
stress is dependent on a number of factors including the intensity, severity and
frequency of the disturbance, successful reproduction, availability of viable larvae,
oceanic current dynamics influencing larval dispersal, and settlement and recruitment
processes. Given the findings of the study, it is recommended that:
i) actions should be taken to minimize human-stresses to coral reefs (e.g. overfishing,
pollution), especially areas that are heavily impacted;
ii) protection should be provided to coral reefs that were undamaged by the cyclone, as
these will play a critical role in the recovery of adjacent more impacted reefs;
iii) more comprehensive assessments should be undertaken of coastal coral reefs to
document the intensity and scale of damage, to determine the potential impact to
local subsistence and commercial fisheries, and inform marine resource management
decisions;
iv) data from assessments should be reviewed in parallel with fisheries data Household
Income Expenditure Surveys (HIES) and other socioeconomic surveys, to determine
the impact of the cyclone on community food security and fisheries livelihoods; and
v) Lastly, monitoring programs be extended to measure the recovery of coral reefs over
the next 2-5 years, and ensure they are linked to management actions.