Mexico has a rich Pacific coastline, with migrating marine life coming from all areas of the world to bask in its waters and in the shelter of its outer islands. The Revillagigedos archipelago, which is located two day’s travel southwest Cabo San Lucas, is a small chain of 4 islands. These remote and barren spots of land in the Pacific Ocean host an amazing array of wildlife, from solitary coral colonies to vast schools of hammerhead sharks that have traveled thousands of miles to arrive there.
This year we entered the park during the final weeks of hurricane season. The park is still officially closed for public access during this time, which made it an ideal time for us to conduct scientific research and to make observations of the marine fauna undisturbed by other divers. With the permission of the Revillagigedos park authorities, and with partners from the Max Plank Institute for Chemistry and the Darwin Research Station, we completed our expedition, successfully mapping coral communities and collecting coral and seawater samples.
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 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, 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). We supplemented this approach by taking and analyzing water samples from the reefs across the Revillagigedos Archipelago, in order to better understand modern conditions and compare those to what we reconstruct from the coral cores.
The coral and water sampling onboard was done by Dr. Alan Foreman (Max Planck Institute for Chemistry).This sampling mission was extremely successful, collecting coral cores at locations across the Revillagigedos park that fill in a crucial gap in the historical reconstructions that currently exist for the area. This work also 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. The Revillagigedos cores are the northern most node in this effort, and preliminary research by the Max Planck team has shown that corals from this location are incredibly sensitive to changes in the size of the oxygen deficient zone. 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.
In addition to the coral sampling mission, we also focused on observing the distribution and behavior of charismatic megafauna at Revillagigedos. Led by Dr Pelayo Salinas, this effort aimedto further document and expandhis work protectingboth marine parks across the ETPand the migratory pathways that link these magnificent parks to one another. The latter is particularly important, as it hasbeenproven over and over that these corridors are the highwaysthat these animals take as they travel between refuges. The risk to these migratory animals is increasing rapidly as they are hunted and their habitat damaged through commercial fishing, and documenting their populations and behavior is a key first step.
by Dr. Alan Foreman & Dr Nic Durpey (Max Planck Institute for Chemistry) & SY Acadia Crew.
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