#19. Deep Discoveries
In which the E@L proposes worldwide protection of cold-water coral habitats
An expedition to map the seafloor around the Galapagos islands has discovered deepwater coral reefs growing on vertical rock walls. The Schmidt Ocean Institute has been exploring the reefs with its remotely operated vehicle (ROV) Subastian, and discovered an oasis of biodiversity. An article in the Washington Post suggests that this was an unexpected discovery, but in fact, the presence of corals at that location was either already known or highly suspected. And it should have come as no surprise to the scientists involved, since they were revealed by prior research on the Galapagos seamounts, and deepwater corals are common throughout the ocean at those depths (300-500 m).
Corals growing in the deep ocean are considered cold-water corals because they typically grow at temperatures of 3 to 10 C (39 to 50 F for the Celsius-challenged). Most seamounts and volcanic islands harbor cold-water corals on their flanks at those depths.
Darwin's Theory
We commonly associate Charles Darwin with the Theory of Evolution, formed during his 5-year expedition aboard the HMS Beagle in 1831-1836. But Darwin was also responsible for our understanding of seamount formation. He visited many islands during the voyage, including the Azores, Cape Verde, the Galapagos, Tahiti and the Society Islands, and formed a theory about how the islands, atolls, fringing, and barrier reefs formed over time.
Seamounts are extinct underwater volcanoes that typically exist in chains, like the Hawaiian Islands. In Darwin's model of seamount formation (it doesn't quite rise to the level of "Theory"), lava plumes rise from the earth's mantle through fissures, creating volcanoes. The location where they form is considered a "hotspot" in the earth's crust. The pressure of magma beneath the hotspot causes the earth's crust to swell up like a pimple, raising the base of the islands about 500 m above the surrounding seafloor. After the volcanoes become extinct, waves erode them down to sea level. As tectonic plates shift over millennia, the island moves with the crust, away from the hotspot, and off the dome of the "pimple". As they migrate they sink back down to the surrounding seafloor level. For this reason, the tops of most seamounts lie about 500 m below the ocean surface. New volcanoes eventually erupt and create new islands. Over millions of years, this process produces a chain of seamounts and islands of different heights.
Corals growing in shallow tropical waters are called reef-building, or hermatypic, because they grow on top of older dead corals. They must remain near the surface, in the photic zone, because their tissues include photosynthetic microalgae that take up carbon dioxide and provide oxygen and nutrients to the corals. As volcanic islands sink over time, fringing coral reefs growing around the island keep building themselves upward, to stay in the photic zone. As long as the rate of coral growth exceeds that of the island sinking, the reef will continue to grow. When the island finally sinks below sea level, it leaves only a ring of coral, called an atoll. We know now, though, that climate change also plays a role. A newer model of seamount formation suggests that alternating changes in sea level roughly every 100,000 years contributed greatly to the formation of Hawaii and other non-tropic seamounts.
Underwater Forests
But cold-water corals do not build reefs. Most are gorgonians, members of the family Gorgoniidae, that grow in tree-like formations up to 2 m in height and are common on the slopes or vertical sides of seamounts. They typically live at depths of 300 to 1000 m in extremely cold temperatures. As a result, they grow slowly and may live hundreds of years. And like trees, they form growth rings that can be aged and used to document climate change. Also like trees, they form "forests" that create shelter and habitat for many other organisms including crabs, worms, and basket stars. If damaged, such as by mobile fishing gear, it may take years or centuries for them to recover (See E@L #2 "The Trouble with Traps"). For this reason, many seamounts are now protected from commercial fishing, such as the New England Seamount chain, parts of which are now included in the Northeast Canyons and Seamounts Marine National Monument.
I was a bit surprised when I read the comments left by other readers of the Washington Post story. The most common comment was that announcing the discovery would automatically lead to destruction by humans, who would now come and disrupt the habitat, either via tourism or exploitation. While we should be concerned about that, I don’t think the Galapagos deep-water corals are in immediate danger, because deep-sea tourism is not highly developed, there are few species of commercial value in those habitats, and fishing for them would not be cost-effective. Others assumed that the expedition was conducted to enable exploitation, which is also incorrect.
Watching the videos, I did identify a species of king crab (family Lithodidae), but they are probably too scarce to be commercially valuable. On the other hand, corals and sponges produce lots of interesting chemical compounds that may be of use to science or medicine. While it would be useful to sample a few specimens for the presence of such compounds, larger scale harvesting is not practical because they are too scarce and slow growing. Besides, if any medically useful compounds were discovered it would probably be more economical to synthesize them.
A Visit to Paradise
I've had the good fortune to visit and study deep-water coral ecosystems during two expeditions to explore seamounts in the Gulf of Alaska (the GOASex Expedition) using the three-person submersible Alvin, with funding from NOAA’s Ocean Exploration Program. Diving on Patton Seamount to depths from 250 to 3700 m, we found expansive habitats of corals, sponges, sea stars and crabs, that collectively formed a mid-slope faunal assemblage. Tree-like gorgonian corals sprouted from rocky outcrops. Perched among their branches, spindly squat lobsters (actually anomuran crabs) extended their elongate chelae, covered with setae to filter out drifting food particles. Basket stars with their elaborately branched arms wrapped themselves around and through the coral branches. Many-armed crinoids launched themselves off the rocks and swam with undulating pulses, like something dreamed up by H.P. Lovecraft. Scarlet king crabs clung to the sides of vase sponges, where they found security while mating. It was a veritable underwater Garden of Eden; unlike anything I have ever seen.
While our first thoughts may be that such habitats and organisms seem completely alien to us, in fact the opposite is true. In their habitats, we are the aliens. They survive and prosper in extreme conditions of low temperature (3 C), high pressure (1500 psi), and low oxygen (3% saturation) that would kill a human instantly. Coming back to the surface after a dive to those depths was such a dramatic transition that I felt as if I had returned from an alien planet through a galactic wormhole. If we ever do find life on other planets, I highly suspect they will resemble crinoids.
Better Left Alone
Partly because of those experiences, I strongly support protection of cold-water coral habitats around the world. They are sparsely distributed and populated by organisms that have been growing for centuries. Damage to these ecosystems would be non-recoverable in our lifetimes. The diversity of life in those habitats is still poorly known, and many organisms have yet to be identified. Yes, they harbor interesting organisms and chemicals, but these can be studied and sampled carefully and non-destructively. Beyond that, we have no business trying to exploit, remove, or harvest anything growing there.
The best reasons to explore these depths are not to seek possibilities for future exploitation, but to understand our planet. Discoveries like the Galapagos deep reefs are amazing, but not completely surprising. They serve as a reminder that we know more about the surface of the moon than about the bottom of the ocean, comprising 70% of earth's surface. To date, we have explored less than 5% of the ocean. While the 2023 budget for NASA exceeded $33 billion, the budget for NOAA was only about $7 billion, and NOAA's Ocean Exploration Program received only $44 million. Thus, the budget for exploring our oceans is about 0.13% of the budget for exploring space. This disparity is almost criminal.
A Deep Proposal
I hereby propose that the United Nations should institute protection for all cold-water coral habitats anywhere in the world. These protections should prohibit all commercial exploitation or activities including fishing and extraction of minerals or hydrocarbons. They should allow for scientific exploration and limited sampling. Deep-water tourism should only be allowed if it meets stringent guidelines for safety and sustainability, especially in light of the Titan disaster. Furthermore, deep sea tours should be required to include scientific observers and provide some minimum level of data to the scientific community.
Every time we explore the deep sea, we make fascinating new discoveries. What would we learn if we explored it with a budget more like that of NASA? I can only imagine. But then again, I probably cannot.
In case you haven’t read it: Reef Madness by David Dobbs. (The curtain pulled back on Agassiz alone is amazing.)