Tropical Cyclone Narelle (currently Category 5) has developed in the Coral Sea and is forecast to decrease to a Category 4 before crossing the Far Northern region of the Marine Park and making landfall on Friday. The system is expected to bring strong wind and wave action and heavy rainfall, which are likely to damage some reefs and increase the likelihood of freshwater runoff into the Marine Park.

Sea surface temperatures have eased slightly over the past week, particularly in the Northern region (between Innisfail and just above Cooktown), while remaining relatively stable elsewhere.

Encouragingly, coral bleaching alert levels have eased in recent days. The USA’s National Oceanic and Atmospheric Administration (NOAA), which monitors ocean temperatures globally, has downgraded the Far Northern and Northern regions to bleaching watch status following a drop in sea surface temperatures. Most other areas of the Marine Park are expected to return to no heat stress conditions.

Temperature

Temperatures are still slightly above the long-term monthly average for March across the Marine Park. The Far Northern (between Cape York and north of Cooktown) region is around 0.6°C above average, the Northern region (between Innisfail and just above Cooktown) around 1.1°C above average, and the Central (between Mackay and Innisfail) and Southern (between Bundaberg and Mackay) regions are around 1°C above average.

Despite recent decreases in sea surface temperatures, some reefs in the Far Northern and Northern regions have accumulated exposure to heat stress that can cause some coral species to bleach.

The most likely outlook from NOAA’s four-month forecast suggests heat stress will remain low to moderate across the Marine Park into winter.

Rainfall

From 9–15 March, heavy rainfall occurred in parts of the Burnett–Mary, Wet Tropics and Fitzroy catchments.

Weekly totals ranged from 300–400mm in some areas, with several locations receiving more than 200mm in a single day. Rainfall in the Burnett–Mary catchment is among the highest on record for this time of year.

Flooding has been reported in the Burnett River, and flood warnings remain in place across affected catchments. These conditions may lead to freshwater runoff into the Marine Park, which will continue to be monitored.

Reef health

Over the past week, 139 Reef Health Impact Surveys were completed across 19 reefs in the Far Northern, Northern and Central regions. In the Far Northern region, most surveyed reefs showed no to low coral bleaching, with a small number recording low to medium levels (1–30%), and no fully bleached coral or mortality observed.

Coral bleaching in the Northern region varied, from moderate to very high (11–90%). Of the six reefs surveyed, four showed moderate to very high levels of coral bleaching. On these reefs, some corals were fully bleached, and two reefs also recorded small areas of coral mortality. These impacts are likely linked to a combination of exposure to recent heat stress and floodwaters.

In the Central region, one reef recorded low levels of bleaching, with no fully bleached coral or mortality. Additional observations from Eye on the Reef monitoring programs reported coral bleaching on 9 of the 22 reefs surveyed. Coral damage was recorded on 12 reefs and coral disease on seven reefs.

Crown-of-thorns starfish control

The Crown-of-thorns Starfish Control Program continues to manage ongoing outbreaks across the Marine Park, with updates shared in the first weekly Reef Health Update of each month.