Emergency Response to Mass Coral Bleaching

Greetings from the very remote Christmas Island, Kiribati, midway between Fiji and Hawaii, and with only one flight per week. I am here for four weeks, as an unpaid volunteer to help the severely impacted coral populations of the island. This is the third trip made possible through GlobalGiving and with staff, boat, and materials assistance from the local Line Island Fisheries department.  Noone else has yet come in to do any sort of broad survey or assessment of the condition of the corals and to quantify the alarming situation. 

As you may remember, the corals on these reefs bleached severely in 2015-16, with hot waters over the bleaching threshold of 32C remaining for fourteen months, the longest recorded time that such water temperatures have remained on coral reefs anywhere on the planet.   As expected, on my trip last June I found the reefs mostly dead, with only six individuals of the important branching corals found alive after extensive searching.  Samples of these corals were taken and a coral nursery created in a sheltered area of the lagoon.

On the follow up trip in November we were very excited and encouraged to find the corals in the nursery thriving and several hundred, small, juvenile, branching Acropora corals settling in patches on some of the reefs, coming from an unknown source of adult corals. The source is thought to be Fanning Atoll, some 200km up current, as no adult individuals of these corals remain on Christmas Island.  Coral larvae can live for several weeks in the water as plankton, and so they can disperse over hundreds of kilometers. 

I was finally able to visit Fanning Atoll, which in 1975 was shown to have the highest coral diversity in the central Pacific, with over 70 species. This was the first time anyone had checked on the corals there since the bleaching disaster.  We were full of hope and expectation that staghorn and other corals might still survive in the Fanning lagoon, and we had our dreams come true.....  while 90 percent of the corals had died in the heat, unlike on Christmas Island, there were some remnant populations of branching staghorn corals which had surved.  

I was able to collect small samples and to bring over a hundred corals of numerous genotypes- from several reefs, back with me on the small plane to add to the coral nursery at Christmas Island.  In this way we have re-intoduced four species of lagon adapted corals which have become extinct locally on Christmas Island due to the bleaching. 

The plan is to grow the corals in the nursery and then to trim these ''mother'' corals when they grow big, to outplant these corals to restoration patches, to re-establish reproduction in the corals so that the extensive fields of dead and sanding staghorn corals dominating the inner lagoon can eventually be repopulated through the recruitent of coral larvae.  The corals on Fanning Atoll aparently fared better because they were pre-adapted to extreme warm temperatures due to the wide and deep lagoon there, while the extreme shallows of the Christmas Lagoon just too hot for long-term coral survival in the present warming climate.  We plan in the coming year to focus on restoring staghorn corals to the cooler outer lagoon.  

In summary, the corals planted last June have thrived in the nursery, and they have grown by at least five fold.  We greatly expanded the coral nursery at the Cook Islet site, adding a new culture table for corals, which then added space between the two tables for rope culture of corals. On monitoring the newly settled Acropora corals, we found that parrotfish are actively chewing on and damaging the new corals, biting off all emerging branches on some colonies.  We therefore have brought in 63 colonies to the coral nursery, from what is now roughly estimated at 1,000 recruits.  We noticed that these young corals appear to be dominated by two size classes, possibly indicating two years of recruitment from once-annual spawning. Data on recruit size was taken for later analysis. Unfortunately the normal surface currents are expected to soon revert to pre el-nino conditions, with Christmas Island becoming the up-current position, so that coral larvae from Fanning and other reefs will most likely go elsewhere. 

A full report on the trip and its findings and achievements will be written and posted when the trip is completed. Thanks for your support, and cheers for now….