You might know the Galápagos Islands for the giant tortoises that plod among the bushes and the finches that flit among the trees, but take a dip below the waves and things are a little less well known. Deep below the surface, the seabed is covered with seamounts formed out of the same volcanic processes that created the islands showing above the surface. But this deep-sea world is little known and little studied, which is why a three-week scientific expedition descended to the dark depths to map and study what lies beneath.
The tips of the islands that Charles Darwin made so famous during his visit in the 19th century only comprise around five percent of the volume of the archipelago, with the rest of the massive volcanic platform on which it sits submerged. The shallows of the surrounding water churn with sea lions and marine iguanas, but when you go deeper, the world becomes far weirder. Dominated by cold-water corals, the volcanic seamounts form the basis of a thriving community of species seldom studied by scientists and no doubt rich in new species.
A deep-water angler fish surrounded by lava talus about 600 meters (2,000 feet) down. Adam Soule/WHOI
Led by the Woods Hole Oceanographic Institute (WHOI), the expedition surveyed the seafloor using a few different methods, from a multi-beam sonar mounted to the bottom of a ship to high-resolution photo surveys using a camera sled system. These surveys then laid the groundwork for guide dives using two manned submersibles, which collected around 150 geological samples and over 300 biological samples.
In all, the researchers mapped over 70 seamounts – many of which were previously unknown – and think that these underwater mountains were probably once emergent in the past when the sea level was lower. “We've mapped only about 10 percent of the platform, and already we see tremendous value in how these types of studies can inform our understanding of the Galápagos archipelago,” explained Dan Fornari, a marine geologist at WHOI and co-principal investigator of the expedition. “We've just begun to scratch the surface as far as characterizing this environment.”
Submarine lava tubes host soft and hard corals around 700 meters (2,300 feet) down. Adam Soule/WHOI
One of the main aims of the project is to better understand the magmatic processes that formed the volcanic platform on which the islands sit, as up to now most data is only based on samples taken from above the shoreline. Whilst at the depths, the researchers revealed an ecosystem teeming with life. Dominated by deep-water hard and soft corals, they found throngs of fish and invertebrates, and might even have discovered a new species of catshark.
Now the team of scientists plan on analyzing all the samples they collected to help build a picture of the seamounts, and hopefully highlight their importance as biodiversity hotspots and stepping stones for migratory species. Eventually, the mounts might gain protection as part of the restructuring of the Galápagos Marine Reserve.