Last Thursday, the Reef Ecology and Restoration team carried out our monthly growth and health checks on the Acropora fragments at the nursery site. After taking measurements on length, number of branches, and number of apical polyps of each fragment, it was found that the majority had grown in length since September. This brings us closer to our long term goal of being able to replant the coral fragments on reefs to increase populations.
To keep the coral as healthy as possible, the team carried out a deep clean, which involves brushing off any smothering algae that can cause coral mortality. Unfortunately, bleaching was seen in several fragments; bleaching is characterised by the coral turning white. This occurs when the algae that lives within corals are expelled due to stress.
One of the main reasons for this increase in stress is a rise in water temperature. We could be seeing a large increase in bleaching because this is an El Niño year. NOAA has declared this year a major bleaching event, only the third major bleaching event on record. The first global bleaching event was in 1998, during a strong El Niño that was followed by an equally strong La Niña. A second one occurred in 2010. El Niño years are characterized by changes in upwelling. Upwelling of cold currents is replaced by warmer waters and increases sea surface temperatures. With this in mind, we will keep closely monitor the nursery, and we hope to see continual growth during the next check, despite the El Niño warm waters.
Here is a link to a time-lapse video of the team cleaning the coral nursery!