Remote takes on a whole new meaning when a destination requires more thantwice as long to navigate to (15 days)as it doesto complete the expedition’s scientific goals (7 days). Clipperton Atoll, which sits alone in the Eastern Pacific, is the onlyisland in this region of the Pacific Ocean.Located 800nm south of the tip of the Baja Peninsula(Mexico) and more than 1000nm east of Costa Rica, this atoll is a speck of whitesurround bya literal ocean of blue all around.
Beyond the joy of visiting this unique location, our trip was a refreshing reminder that a few nearly-pristine ecosystems remain that have as of yet only felt small direct anthropogenic impacts. While at Clipperton we observed the extensive presence and impact of the tuna fishery, but the large abundance of juvenile sharks gave us hope that Clipperton remains ahealthy ecosystem. With some of the largest and healthiest coral cover,Clipperton is also proof that with limited human involvement marine life and coral reefs can thrive even with the extreme effects of climate change on our planet and oceans.
We brought our partners from the Max Planck Institute for Chemistry, Dr. Alan Foreman and Dr. Nicolas Duprey, along on the trip to lead our scientific efforts at Clipperton. With our help they were able to conduct sampling efforts coring coral colonies, excising coral tissue samples, taking water samples, and making observations of the health of Clipperton’s reefs. This was a unique mission; in the history of Clipperton only a handful of expeditions have been able to collect coral cores at Clipperton’s reefs. The collection we acquired represents the most detailed and biggest set of coral cores collected at Clipperton for the 20th century.
One of the principal goals of this work is to understand the past evolution of the oxygen deficient zones of the Northern Tropical Eastern Pacific, and to use this information to extrapolate how these zones may change as the ocean continues to warm. For this work, we collected coral skeletal material in the form of cylindrical coral cores. As they grow, massive corals form their calcium carbonate skeleton in layers. The chemistry of these layers is set by changes in the physical and chemical properties of the ocean at the time that the coral skeletal material is laid down. By taking a core from these corals and analyzing the changes in the chemical composition of the different layers along the length of the core, we can understand how proxies for the size of the oxygen deficient zone may have changed, and how those changes are related to changes in ocean temperature or other variables (think of this approach as analogous to measuring chemical tree rings).
This work represents a key aspect of a larger project that we are participating in: reconstructing the history of the oxygen deficient zones of the entire Northern Tropical Eastern Pacific. Eventually this work will allow for the reconstruction of the history of the area going back across the 20th century, and will provide key data for modelling future changes in oxygen concentrations in the area.
A surprising finding from this expedition was that we observed massive bleaching (>50%) of the deep reefs at Clipperton across the entire southern edge of the island. This bleaching was likely a result of cold temperature stress on the reef as a result of wind-driven shallowing of the thermocline. In our travels we have been to other coastal reefs that experience upwelling of cold waters, but we have never observed such widespread bleaching. It was truly a unique event!
This cold bleaching event suggests that further study of the effects of upwelling on reefs across the Eastern Tropical Pacific is needed. We plan to continue this work with our other partners at the Smithsonian Tropical Research Institute in Panama, who spearhead the Rohr Reef Resilience Project. By understanding what makes the reefs of Panama resilient to bleaching and applying this knowledge, we hope to help ameloriate some of the worst effects of climate change on reefs worldwide.
by Dr. Alan Foreman & Dr Nic Durpey (Max Planck Institute for Chemistry) & SY Acadia Crew.
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