Based on our recent surveys this year, here is a short summary on our findings of the status of the corals in the Maldives.
– First, all shallow snorkel depths from water surface to about 3 m was hardest hit by bleaching with a near total loss of table corals. We have found a few reefs on outside of atolls and in high water flow areas where table corals did survive. These areas are the most critical for recovery of the species. That said, it will likely take a min of five years before we start seeing a lot of table corals again and 10-15 years before they are a meter or more in size
– Throughout the country the massive Boulder corals ( Porites) mostly survived and these are now the dominant species on the reefs. These are very important in forming the framework of the reef and they also form the areas used by larger species as cleaning stations
– On many reefs where there were formally many branching corals what you see now are small Boulder corals mixed among dead coral skeletons. We are very fortunate that we didn’t lose these corals as they could take decades to centuries to recover
– Throughout lagoonal environments that once had large stands of staghorn coral, these are mostly dead. Again we have found patches of these corals on every atoll we have visited. These small patches will rapidly expand in size and within 5 years they should form thickets once again
– One of the most positive signs is the high numbers of juvenile corals that are approximately one year old. We find the highest number of these on reef slopes, especially in lagoonal areas. These are dominated by branching corals that were formally very abundant on all reefs. These look like they were babies of corals that spawned last year right before the bleaching event . This is a really positive sign as this means they were able to tolerate higher water temperature and are likely to survive during periods of future high water temperatures. Right now these are smaller than a baseball but will double in size within a year and within two to three years will be old enough to begin reproducing
– There are also a number of reefs where most corals survived the high temperatures last year and these are the ones that are most critical right now as they will produce new corals during annual spawning events that will start to recolonize other reefs
– It is important to note that coral grows very slowly and you can’t expect to see reefs that looked as they did over a year ago already. What is most positve is that these reefs are showing very positive signs of recovery unlike many other reefs in the Indian and Pacific oceans.
Are the Maldives under threat of another bleaching event?
Currently, it is unlikely that we will experience a bleaching event in the Maldives again. Although water temperatures have increased slightly during March, they are still well below that observed last year. Last year, due to the El nino, the thermocline disappeared, and warm water (30 C during the entire month of March and 31-35 C during April) extended to 30-40 m depth. The sea remained calm for over eight weeks, no rainfall, no wind, and blue skies (with only a short break due to a storm only lasting two days on April 22-23).
This year, we’ve had rainfall during March, periods of choppy seas, more cloud cover and only short periods of doldrum-like conditions. During calm periods, the surface water is warming to 30-32 C, but there is a pronounced drop in temperature at depths of 1-2 m and reef temperatures are 27-28 C ( a few places are 29 C). Due to tidal flow, the warm surface layer in lagoonal areas disappears during the evening and surface water is cool in the morning.
The traditional Maldivian calendar predicts that we are entering Reyva (26 Mar–Apr 7), which may be associated with storms at night and winds from the northwest. This is followed by Assidha (8-21 Apr), which will begin with a storm, then becoming hot and dry, with mild winds. At this time the water may heat up somewhat but this is followed by Burunu (22 Apr-5 May) which also begins with a storm and is characterized by rough seas which should moderate water temperatures.
Attached is one image from NOAA showing the current bleaching predictions for the eastern Hemisphere. For locations with abnormal temperatures, they are identified as a watch (1 degree C higher than normal for one week) , warning (1 degrees higher or more for 1-4 weeks = possible bleaching), alert level 1 (1 degrees higher or more for 4-8 weeks; bleaching is likely) and alert level 2 (abnormal temperature for more than 8 weeks; coral mortality is likely). This is updated two times per week. As of this past Monday, there was no temperature stress around the Maldives.
This is summarized using the best available knowledge and predictions we have access to. Corals may become pale in some locations, but the corals on these reefs now are those that survived much worse conditions last year, so it is unlikely that they will die.
Andrew Bruckner, PhD.
Coral Reef Conservation Protection and Restoration