Science

Dongsha Atoll in the South China Sea

Our 2014 field expedition to Dongsha Atoll in the South China Sea is a collaboration with George Wong, a biogeochemist based at Academia Sinica in Taipei. The purpose of the expedition is to investigate the interaction between the unique oceanographic environment of the atoll and the calcifying organisms - corals and coralline algae - that build the reef. The South China Sea is home to the world's largest "internal" waves. We are most familiar with the waves that we see on the surface of the ocean - the waves that we surf on, that crash against rocky shorelines, and that toss around boats in storms. But there are also waves within the ocean, between layers of water of different density. While these internal waves occur throughout the ocean, the unique underwater topography of the South China Sea produces massive internal waves. On the ocean surface, 2-meter waves draw a crowd of surfers, but the internal waves in the South China Sea can be a thousand times larger.

Dongsha Atoll, the only coral atoll in Taiwan, lies directly in the path of these waves. As the internal waves reach Dongsha, they shoal up the slope of the atoll, bringing cool, nutrient-rich, and low pH seawater to the shallow coral communities. Exposure to this water may enhance coral nutrition, and help buffer the corals from heat-induced bleaching - the loss of the symbiotic algae that corals need to survive. Internal waves potentially make Dongsha Atoll a unique coral reef, well suited to be resistant and resilient to the effects of climate change and ocean acidification.

We will test how corals on Dongsha Atoll are affected by internal waves. To do this, we will deploy a series of instruments on the reef to track how internal waves bring deeper water towards the surface and onto the reef. We can test how the corals respond to internal waves with a variety of tools - tracing chemical changes in the seawater, examining the structure and chemistry of coral skeletons, and studying coral population genetics.