31 Dec 2017 - With less than 5 percent of the world’s oceans currently explored, every year is an important one for ocean discovery, and 2017 was no exception. Scientists reported plenty of species new to science, including a glow-in-the-dark shark, a giant sunfish (the largest bony fish in the sea) and the ruby seadragon. Nearly 2,000 new described species were cataloged by the World Register of Marine Species as of mid-December.
Emerging technologies, from more affordable DNA sequencing and satellite data to autonomous underwater drones, are increasing the pace of discovery – a good thing as oceans are rapidly altered by climate change and overexploitation. For scientists, the mission of exploring the abundant diversity of the marine environment and learning lessons from its past has taken on an increasing sense of urgency.
Below, you’ll find just a few examples of the discoveries that fascinated us this year (a list that is by no means exhaustive).
Deepest Fish in the Sea
To this day, little is known about marine life in the Mariana Trench, the deepest region of the ocean, where depths in this stretch of the western Pacific reach 36,000ft (11,000m). That’s why it was compelling news in November when scientists reported the discovery of a new species of fish collected at a depth where no fish has been found before.
During expeditions to the Mariana Trench in 2014 and 2017, researchers deployed mackerel-baited traps to collect 37 specimens of the Mariana snailfish (Pseudoliparis swirei) at depths of up to 26,200ft (7,985m). With translucent white skin and no scales, its appearance is both strange and amazing. Not a lot is known about how the fish lives at such depth and pressure, but snailfish do get to live a predator-free life at the top of rich food chain – so, as report coauthor Thomas Linley of Newcastle University said, they seem to be doing pretty well.
Massive Craters Formed by Subsea Methane Explosions
Hundreds of massive craters – up to 0.6 miles (1km) wide – and mounds pock the Barents Sea near Norway, and scientists at Norway’s UiT Arctic University Centre for Arctic Gas Hydrate, Environment and Climate made progress mapping them and understanding the conditions under which they formed.
Scientists who went out to study the craters didn’t expect them to be so many and so large, based on the limited mapping done in the 1990s. In a paper, they described how these structures likely formed at the end of the last Ice Age as ice sheets retreated, and methane that had been previously trapped underground by the weight of ice eventually exploded. This process abruptly released large amounts of methane – a potent greenhouse gas – into the water, though it’s unclear to the researchers whether the gas reached the atmosphere. Methane still slowly seeps from these areas today through more than 600 gas flares, feeding an ecosystem of microbes in the ocean.
One of the researchers said in a statement that the study provides a “good past analogue” for abrupt methane releases that could occur as the Greenland and West Antarctic ice sheets melt.
A Tsunami of Sea Life Comes Ashore
Throughout Earth’s history, coastal lands have been naturally colonized by new species that travel the ocean by hitching a ride on marine debris. In 2017, scientists reported observing this “rafting” phenomenon at a scale never seen before.
“The 2011 East Japan earthquake generated a massive tsunami that launched an extraordinary transoceanic biological rafting event with no known historical precedent,” the researchers wrote in a study published in Science in September. They documented 289 living species, such as the Japanese barred knifejaw fish, that traveled from Japan to North American shores in the six years since the disaster. Many came on plastic or other non-biodegradable objects, including entire ships and docks, that were carried out to sea in the wake of the wave’s destruction. The authors call the phenomenon “mega-rafting” and worried that a global increase in marine debris combined with climate-change-fueled storms will speed the pace of coastal species invasions.
Sticky Remoras Provide Inspiration for Sticky Robots
Scientists studying how remoras – also known as suckerfish – attach and hitch rides on sharks and rays are developing new adhesive devices to do the same. A paper in the journal Science Robotics described how a team of researchers developed a prototype inspired by the remora’s adhesive disc. According to the paper, the device can stay stuck when pulled and twisted, similar to how the remora can withstand the shearing force of water while attached to a moving shark. Few scientists had studied in detail the adhesive function of remoras before.
The researchers envision that a remora-inspired adhesive device could aid ocean exploration, ship repair and biological research, among other potential uses. “This design has the potential to greatly extend the range and endurance of ocean exploration” underwater autonomous vehicles, Harvard University’s Yufeng Chen, coauthor of the study, told Oceans Deeply in October.
A ‘New’ Undersea Continent
A mostly submerged landmass in the southwest Pacific Ocean, dubbed Zealandia, gained recognition as a distinct continent this year – a term that is hard for scientists to agree upon and define. At the least, its exploration shows how little scientists know about what lies below large areas of the seas.
Once part of the supercontinent Gondwana, Zealandia is believed to have separated from Australia and Antarctica about 80 million years ago, and today is submerged nearly 1 mile (1.6km) below the surface. In March, researchers published the most extensive evidence yet that the 2 million square mile (5 million square km) region, which includes the lands of New Caledonia and New Zealand, is one contiguous swath of continental crust that is distinct from the Australian continent.
Then, in September, an international team of 32 scientists returned from a research cruise that drilled into Zealandia’s crust, discovering evidence of hundreds of fossil species, including shallow-water shelled organisms and plant pollen that supply additional evidence of its unique geographic history.