Coral reefs are affected by strong heat waves – albeit to different extents: Reefs with heavy coral colonization are particularly good at withstanding the high temperatures. This is reported by researchers working with Gregory Asner from Arizona State University in the journal Proceedings of the National Academy of Sciences.
The scientists investigated which coral reefs around the six main Hawaiian islands were resistant to marine heat waves. To do this, they evaluated the satellite and infrared images of the coral reefs before and after a hot period that lasted from July to October 2019. At the beginning of 2019, almost 23 percent of the 21,000-hectare area was still covered with living corals, but a year later it had shrunk by around 26 percent. However, individual reefs were affected to varying degrees: Up to 30 percent of the corals died in the reefs of the smallest Hawaiian island, Lana’i. In contrast, the researchers identified seven reefs where up to 40 percent more coral survived than in neighboring areas. They all had in common that a larger part of their area was colonized by corals.
How many corals died within a reef also depended in part on the extent to which the stretches of coastline had been developed and polluted by humans. And even within the reefs, some areas had withstood the heat better than others. The researchers explained that this is probably due to the different genetic make-up of the local corals.