Tropical coral reef ecosystems are threatened by ocean warming, pollution, and other human impacts. To understand how reef ecosystems are changing, scientists survey the abundance and diversity of corals, fish, and other animals present. However, it can be very difficult to accurately count these creatures underwater! The photo above shows Cecile Vimond, graduate student at the University of Hawaiʻi at Mānoa, conducting a visual coral reef diversity survey in Kāneʻohe Bay. To do so, she uses a transect (the measuring tape) and quadrat (the white PVC frame), which she will place on the bottom, then count and identify every organism inside.
Below: Invertebrates like this bright red urchin (Heterocentrotus mamillatus) make up a substantial part of coral reef communities, yet they can be well-hidden and are often under-counted in traditional visual surveys. Using environmental DNA (eDNA) surveys of coral reefs—which involves collecting and sequencing genetic material shed by organisms into the water—allows the entire community to be detected from small samples of seawater from within the reef. Researchers at UC Mānoa combine eDNA with visual surveys to study community structuring, the effects of climate change, and the spread of invasive species on coral reefs.
Photos by Patrick K. Nichols; captions by Jessica Schaefer & Patrick K. Nichols.
Edited by Jessica Schaefer