As I blogged earlier, the reefs off Okinawa are undergoing a severe bleaching event. The latest news from researchers in the region suggest that it may be worse than previously thought:

Coral bleaching is observed in Ishigaki Is. since late July. High SST(>30C) has continued around the southwest Ryukyu archipelago this summer. SST is measured at 35 degree C at the most affected area of bleaching (shallow lagoon) in the daytime. – Takanori Sato

As a result of these high sea surface temperatures, the reefs are beginning to show signs of prolonged bleaching and subsequent mortality similar to that of the mass bleaching event in 1998:

As was quickly reported from Sato-san on 6 August at this ML, Ishigaki Is reef, the most flourished reef in Japan, is now heavily bleached. Shiraho reef known by its large distribution of Heliopora coerulea, is 60-70% bleached and some of the corals were already dead. Sea water temperature at Shirao reef increased over 33 degree centigrade during daytime, and never decreased below 30 degree centigrade even during nighttime since 21 July (measured by Tokyo Institute of Technology), and the bleaching started since 23 July.

50 to 90 % colonies of Porites lutea, Pavona frondifera, various species of Acropora, Pocillopora and Montipora aequituberculata were bleached and some of them were already dead. 70 % of Montipora digitata was bleached. Heliopora coerulea, on the other hand, was rarely bleached. Porites cylindrica was also bleached, but in an area near Heliopora distribution was not bleached.

The species difference was almost the same as that at 1998 bleaching event, except that Porites lutea, which was bleached but recovered its symbiotic algae after one month bleaching was already dead for the colonies along the shoreside. The situation seems to be more severe than that in 1998. Since 5 August, two typhoons passed near Ryukyu Islands, and I hope they reduced seawater temperature to stop the bleaching. -Hajime Kayanne

Mark Eakin from NOAA has been monitoring this for the past few months, and suggests that this bleaching event is likely to impact reefs across the region:

Warming has been seen in the region from the northern Philippines to southern Japan and Korea. NOAA Coral Reef Watch data reveal sea surface temperatures of 30-32 degrees and Coral Bleaching HotSpots reveal water temperatures of up to 2.9 degrees above the maximum monthly mean. The warmest thermal stress accumulation is currently found in the region south of Taipei and northwest of Luzon. Our Degree Heating Week product reveals that the waters off the Luzon coast now exceed 10 degree weeks of thermal stress. Reports, including two on the Coral List, indicate that bleaching is already underway at Kenting National Park, Taiwan, Ishigaki Island, Japan, and the Philippines.

Another large region of heat stress can be seen in the region east of the Mariana Islands and northwest of Wake Island. The SST anomalies and HotSpots are not as high in this region and are currently of less threat to coral reef systems.

More reports are coming in from around the region:

Starting from mid-late June, high SST (30C) is observed around the area of Southeast Taiwan, northern Philippine, and northern South China. Coral bleaching starts to develop in the mid July along the fringing reef at the Kenting National Park, Taiwan. Corals at shallow water (<5m) are bleaching intensively in the lat July. Over 45 hard coral species, mainly millepora and acroporids, are bleached at the first two surveys. Video transect surveys indicate over 70% of corals are affected. The most serious site is the fringing reef near the outlet of nuclear powerplant, where SST is measured at 35C degree at 3m in depth.

The coral bleaching can be ranked as the most serious bleaching event in the Kenting reef sincr the mass coral bleaching in 1998-1999. – Allen Chen

Keep an eye on Coral List or check back on Climate Shifts regularly for more updates.

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