The underwater microscope

The ocean floor as we’ve not seen it before.

UNTIL VERY RECENTLY, scientists who wanted to study sea creatures in microscopic detail usually had to remove those creatures from their habitats to place them on glass slides in a laboratory. This is one reason (along with vast size, crushing pressure, and darkness) why the sea is the Earth’s final frontier: the bulk of the important stuff functions best in a place we don’t. Take coral reefs – they span kilometres of ocean, but are made up of millions of millimetre-wide individual coral polyps. We know that each polyp has a symbiotic relationship with single-celled algae called zooxanthellae, which provides energy for the coral. We know that warm water makes the algae leave, turning the reefs white. But we currently have no idea how to fix a bleaching episode, nor do we have enough information to even imagine how that would work.

The world’s first microscope capable of imaging the seafloor might change this. The Benthic Underwater Microscope (BUM) was invented at the University of California, San Diego, and named for the ocean’s deepest layer, the benthic zone. It is the first camera that can take micro--

So far, the microscope has been to the Red Sea in Israel and the coast of Maui, and already it’s caught never-before-seen shots of coral polyps in real life.

scopic photos, videos and time-lapse shots of organisms such as coral polyps in their natural habitats – watching without harming to give us more information than we’ve ever had before.

So far, the BUM has been on just two trips, to the Red Sea and to the coast of Maui in Hawaii, and already it’s caught never-before-seen footage of coral polyp behaviour that could help scientists better manage reefs in the future. In Maui the team discovered that, after a bleaching, dangerous algae invade the coral in a very specific way that might be a target for a solution. Outside Israel, they discovered that healthy coral polyps from the same colony periodically connect their “mouths” throughout the night. “We’re not exactly sure of its purpose,” says Andrew Mullen, a lead author on the microscope’s debut study. “But we think that the neighbouring polyps are exchanging or sharing organic materials.” For now, they’re calling it “kissing”.

As for how the scope works, it has two pieces: an imaging unit that houses the lenses and camera, and a control unit with a computer, hard drive and live display. A diver sets the imaging unit up on a tripod with the optical port about six centimetres away from its subject. Six LEDS light up the sample.

Because the hardest part of underwater microscopy is focusing, the scientists built an electrically tunable lens that works much like the lens in your eye. Soft and flexible, it slightly changes shape to focus on objects at different depths. The diver can adjust the lens to focus on a target using the computer control unit. Once the diver selects a setting, an actuator presses on optical fluid. The fluid puts pressure on the lens.

Although easy to adjust, the tunable lens can focus on only one plane of an image at a time. When the diver wants to take a picture, he does some manual focusing to get the image within the rough range he wants and then the lens rapidly and automatically adjusts through different planes of focus, like the Burst feature on an iphone. The scope captures about 100 of these individual shots per image. Back in the lab, the researchers use a computer program to reconstruct a photo out of about 20 of the individual shots. Using an alternative technique that uses single shots, the microscope can also create realtime or time-lapse videos – a photo per minute for eight hours, for example – to show how a slow-moving coral changes throughout a day.

Apart from pictures that would make a nature documentary director drool, the results of BUM studies could help us save the oceans. “The interactions between corals and algae are very important,” says Mullen. “If we want to understand what’s affecting the health of a whole reef, we need to understand what affects the health of these teeny organisms.” Which is a lot easier now that we can see what the heck they’re doing.