Vostok Benthic Tents
The second stop on our research cruise traversing the southern Line Islands brought us to Vostok Island. The morning after we departed Flint, we woke at 5am to find the tiny, triangular island to our starboard. We circumnavigated the island in an attempt to find the leeward side, out of the wind and with the calmest wave action. This proved tricky on such a small island, where there is little shelter from the elements. As a member of the benthic research team we study organisms on the benthos, or those attached to the sea floor. We came to this remote underwater paradise to better understand the structure and function of coral reefs that have been untouched by humans. This is a truly unique opportunity because there are very few intact coral reef systems left on the planet. Intact systems are those that are dominated by hard corals and a healthy population of top tier predators (sharks!).
One set of tools we are using to try and understand reef function are benthic tents- a pyramid of translucent plastic that we use to encapsulate approximately one square meter of the reef. Using this tent we can enclose benthic organisms in their natural habitat, and we monitor water chemistry, including oxygen and pH, using instruments we leave underwater with the tent over the course of several days. With these data we can better understand the “pulse” of the reef. How healthy, or productive, is the reef at Vostok, and how does that benthic productivity vary across the southern Line Islands? Constructing these tents underwater is no easy task, and requires a team of at least six divers over no less than three consecutive dives. At the end of this underwater feat, we leave the corals, algae and benthic neighbors to live and breathe alongside our sensors. We are finding that dissolved oxygen varies over the course of a 24 hour cycle based on photosynthesis and respiration of benthic organisms, with photosynthesis increasing and respiration decreasing oxygen concentrations respectively. We are also able to monitor the pH within the enclosure, and found the pH remained relatively constant over the course of a day on Vostok, while pH varied more within tents on Flint. With a few more weeks of benthic tenting ahead of us, we hope to better understand how these pristine reefs live and breathe. Data from these near-pristine reefs give us an understanding of how healthy coral reef ecosystems work and how we may be able to help degraded reefs in other parts of the world.
Photos: Photos courtesy of Emily Kelly. Top: Dr. Jennifer Smith surveys one the benthic tents. Left: Dr. Jennifer Smith dispenses an indicator dye (floroscien) to measure how long water stays within the benthic tent.