Last month, a new kind of aquatic robot took a test cruise through the waters of Monterey Bay off California. The Tethys autonomous underwater vehicle (AUV), developed by the Monterey Bay Aquarium Research Institute (MBARI), could be just the thing to circumvent some of the problems that have been holding back marine research bots:
The two types of AUVs that researchers have relied on in the past both had their drawbacks. Propeller-driven vehicles could travel at a relatively quick pace and carry big payloads but could only be out at sea for a few days. Another type, called gliders, could endure weeks-long expeditions but were seriously lacking in the speed category. Traditional gliders top out at about 0.5 mph, according to the team’s statement. [CNET]
Tethys, however, enjoys the best of both worlds—endurance and scientific prowess. It employs variable buoyancy, rather than the less efficient “slightly buoyant” feature most AUVs use so they’ll float up to the surface in an emergency. Its power-saving software turns off systems not in use. All this, plus its efficient propeller and hull design, allows Tethys to save enough energy to carry sophisticated scientific equipment and still stay out to sea for more than a few days.
Of all the planet hacking possibilities floated as last-minute ways to stave off a climate catastrophe (building a solar shade for the Earth, injecting the atmosphere with sunlight-reflecting aerosols, etc.), iron seeding seems one of the more practical and feasible ideas. The scheme calls for the fertilization of patches of ocean with iron to spur blooms of plankton, which eventually die, sink, and sequester carbon at the seafloor.
However, worries over the consequences of tinkering with the ocean ecosystem have held up plans to attempt this. And now, in a study in the Proceedings of the National Academy of Sciences, researchers claim that such a plan could risk putting a neurotoxin into the food chain.
Iron seeders have targeted the large swaths of ocean surface with high levels of nitrate and low chlorophyll, where an injection of iron could potentially turn a dearth of plankton into a bloom. But too many phytoplankton can be a bad thing, especially when it comes to members of the genus Pseudonitzschia. This alga produces domoic acid, which it spews into the surrounding seawater to help it ingest iron [ScienceNOW]. Sea lions off California have gotten sick from the toxin. In Canada, three people died in the 1980s from eating shellfish that themselves had eaten Pseudonitzschia.
A single-celled phytoplankton that forms enormous blooms in the ocean and plays a vital role in regulating the carbon cycle has an unusual defense against a virus: When the virus appears, the microbe switches into a different life phase, thereby avoiding an attack from the virus. Researchers call the clever defense a “Cheshire Cat escape strategy” after the cat in Alice in Wonderland that occasionally vanished.
“In this paper, we show how a species can escape from [environmental] pressure by switching to a life-cycle phase or form that’s not recognizable by a predator,” said Miguel Frada, a marine microbiologist [The Scientist]. The microbe, named Emiliania huxleyi, is so abundant in the ocean that its massive blooms can form turquoise patches visible from space, yet these blooms are often cut off abruptly in a boom-and-bust cycle. The new study suggests that the busts are caused when a virus causes the microbes to switch forms.