For most scuba divers, few places underwater match the visual thrill of a kaleidoscopic coral reef teeming with fish. For Jeff Milisen, a marine biologist and photographer in Kona, Hawaii, there is no better place to dive than an open stretch of deep ocean. At night.
"There's no bottom, no walls, just this space that goes to infinity," he said. "There are a lot of sea monsters there, but they're tiny."
Those tiny creatures are part of a daily movement of larval fish and invertebrates, which rise from the depths each evening as part of one of the largest migrations of organisms on the planet. And the emerging hobby of taking pictures of them is known as blackwater photography.
Most of the larvae are no bigger than a fingernail; others are even smaller. Up close, when captured with a camera using a macro lens, the animals can appear to loom as large as wild animals on a safari — a safari on another planet.
The images and videos are revealing a secret world that scientists have struggled for decades to better understand. Now, scientists want to formalize the collaboration with blackwater photographers, most of whom have no scientific background, to participate in marine research.
"It really is a great advance in terms of what we can learn about the early life history of fishes," said David Johnson, a curator at the Smithsonian National Museum of Natural History.
If the photographers could collect specimens of the tiny animals they photograph, DNA could be extracted and analyzed, scientists wrote in a paper published in the journal Ichthyology & Herpetology. So far, the scientists leading the effort have recruited about a dozen divers, who have collected more than 60 specimens for analysis. More are in the pipeline.
"We're building a collection that for the first time has a live image," Johnson said. "We get the specimen and create a DNA record tied to it."
Marine researchers hope that examining images of animals photographed in their natural surroundings and pairing those images with data drawn from techniques such as dissection and DNA bar coding will expand the knowledge of how these animals change over time and why they behave as they do. Ideally, the work will also shed light on the mysterious daily migration of creatures, called the diurnal vertical migration, that takes place every night in every ocean around the globe.
The diurnal vertical migration includes trillions of tiny animals, many in the larval stage, that rise from depths of 1,000 feet or more to just beneath the surface to feed. The journey takes place at night, scientists believe, because it allows the animals to avoid predation by larger fish that locate their prey visually. The baby fish return to the lightless deep before sunrise.
Ai None aka, a Smithsonian researcher and lead author on the paper, said, "We believe this approach opens a new window for our understanding of these larvae and raises exciting questions for future research."
Almost all of the previous understanding of what these animals look like comes from expeditions that collected them in conical devices called plankton nets, which are dragged behind research vessels. Plankton nets draw the animals into a large open ring and funnel them into a jarlike device called a cod end. As water is forced into the jar, the animals are easily crushed and usually die before reaching the surface.
"What's really fascinating is when you send the scientists something and they have no idea what it is," said Steven Kovacs, a dentist in Palm Beach, Fla., and blackwater diver. "Or it's the first time being seen. That's one of the greatest thrills of all."