Hot seawater imperils Saipan corals

Erwin Encinares Saipan Tribune 17 Nov 16;

Coral reefs on Saipan are in danger due to bleaching caused by the warming of the Pacific Ocean, according to Bureau of Environmental and Coastal Quality marine biologist and technical adviser Lyza Johnston. Coral bleaching occurs when seawater temperatures get too warm for the corals, causing them to expel the algae that give the corals their color.

Current reports by the National Oceanic and Atmospheric Administration have it that 2016 was the second warmest year to date. The situation is made worse by the Pacific Ocean phenomenon called El Niño, which also causes sea temperatures to rise.

Because of the warm temperature, the seawater has been warming up, causing corals to bleach. The bleaching of corals pose as a threat to the tourism industry of Saipan since the corals are one of the attractions for visitors who come to the islands.

The Saipan lagoon, one of the more popular dive sites on Saipan, is home to numerous coral reefs. According to Johnston, the corals in the lagoon are greatly stressed and 85 percent of the species known as the “staghorn coral” is already dead in BECQ monitoring sites.

“We have a lot of stress on the corals in the lagoon specifically,” she said.

“We have set up long-term monitoring sites in the lagoon and we’ve lost up to 85 percent of staghorn corals at our long-term monitoring sites. There are areas outside of our sites that are still alive, but we think our sites are pretty representative of what is going on in the lagoon,” added Johnston.

Johnston said that major coral bleaching happened during 2013 and 2014, and just a little for 2016. This, however, does not mean that the corals are doing well.

“Most of the bleaching we’ve seen is from thermal stress that the climate change is causing. The atmosphere is getting warmer and the sea surface is getting warmer as well. Corals have a very narrow temperature tolerance and corals actually have a symbiotic relationship with microscopic algae that lives in their tissue and when the water gets too warm, they expel the algae, which is the reason why they look white,” said Johnston.

Johnston clarified that corals that are bleaching are not dead.

“They are not dead at that point. The tissue of the coral is transparent, kind of like a jellyfish, so what you’re seeing is the exoskeleton underneath—but they are not necessarily dead. If the water doesn’t cool down quickly, and they don’t regain their symbiotes, they will die, though,” said Johnston.

Another enemy of the corals are the species known as the crown of thorns starfish, a multiple-armed starfish that feed off of coral polyps, preventing it from developing into a coral reef.

“We do monitor for the crown of thorns starfish. We’ve had breakouts in the past, but we haven’t seen any abnormally high numbers for 2016,” said Johnston.

Johnston said the monsoon systems during the summer helped the seawater cool down to some extent, but said that society must do its job in order to preserve the coral reefs of Saipan.

“Local scale threats will essentially reduce the coral’s resilience, such as land-based sources of pollution, habitat destruction, people stepping on the corals, and sedimentation from pollutants will actually make them bleach faster,” said Johnston.

“What we can do locally is reduce all of those stressors and keep them as healthy and strong as possible so they are able to better resist thermal stress and other global scale stressors,” she added.