By Dr. Jenn Caselle
It was with huge excitement that I learned that I would be traveling to Clipperton Island for a National Geographic Pristine Seas expedition, because this would be my second trip to this remote coral reef. My first visit here was almost two decades ago, in 1998. I was a graduate student on my first real remote expedition.
Now, as a more seasoned marine biologist, with many remote expeditions under my belt, I jumped at the chance to revisit this remote, isolated atoll and assess firsthand any changes that had occurred.
Back in 1998 we came with the goal of simply documenting and identifying the various fishes on reefs; now we visit both to assess the changes that have occurred over time and to use our modern tools to access locations impossible back then.
At that time, we used cameras with film, the diving was limited to relatively shallow depths for safety and we brought what was, at the time, a “state of the art” remotely operated vehicle (ROV) that captured the deeper reefs on grainy, dark and often wobbly video tapes. Now, armed with modern cameras, rebreathers, and even a submarine, we can access parts of the coral reef that just weren’t possible in 1998.
After a week of diving, I finally have some time to reflect on the changes I’ve observed.
First, the corals.
We are currently experiencing a large El Nino event in and coincidentally, my 1998 expedition also took place during El Nino conditions. El Nino is a climate event that brings warm water and increased wave action to much of the Pacific. Scientists have documented a worldwide coral bleaching event over the past year due to El Nino. Coral bleaching occurs when waters warm and stressed corals eject their symbiotic partners, the algae that provide nutrients and give corals their vibrant colors.
Prior to our current expedition I reviewed old footage and photos for evidence of coral bleaching back in 1998 and confirmed that the corals looked healthy then. Our Pristine Seas benthic science team has been searching for evidence of coral bleaching and similar to results from 1998, have documented minimal impact of this El Nino. Corals here are healthy and coral cover is high. Some hypothesize that healthy reefs can withstand the impacts of climate events or warming waters better than unhealthy reefs. Perhaps Clipperton is resilient in this way?
Second, the sharks.
Foremost in my memory of the 1998 expedition were the abundant and curious (dare I say aggressive?) sharks. However, even in 1998 we saw fishing line on the reefs and even saw large commercial fishing boats around the island. Could the abundance of sharks remain high at Clipperton over almost two decades when so many places in the world are losing these top predators?
We had heard reports prior to our current expedition that the sharks were gone–and our fish team was interested to see if these reports were accurate.
From our very first dive, we noticed that while sharks are numerous here, they are mainly small, some even newborns. After a week of extensive underwater surveys with divers and remote cameras, we are not disappointed. Clipperton sharks are not gone, although they are not as abundant as in 1998. The presence of large numbers of small sharks gives hope that recovery is possible. Large sharks are present, they tend to be shy, staying farther away from the shallow reefs and cruising in deeper water. As long as these large adults are present and reproducing, the populations can increase.
As we analyze the data we collected over the past week, and compare it to previous expeditions, more patterns will emerge. It’s a lucky scientist that gets to visit such a remote and difficult location twice in one career!