The Ups and Downs of Sea Life--

When you think of animal migrations, you probably think of the thousands of birds that fly south every winter. Perhaps you picture groups of gigantic whales travelling thousands of miles across the ocean, or maybe enormous herds of caribou stampeding across Alaska. But there is one migration pattern that absolutely dwarfs all of the others--billions of animals take part, and they do so every day in all the world's oceans, lakes, and even in ponds. Yet we know very little about this massive animal travel pattern, called vertical migration.

During vertical migration, billions of fish, shrimp, squid and jellyfish leave the deep, dark waters where they spend the day, and head for shallower waters around sunset to feed. Around sunrise, they head back down to deeper waters where the light is dim, helping to hide them from predators. Many ocean predators time their feeding around this massive movement of smaller animals. In one way or another, almost every animal in the sea is affected by vertical migration. These migrations are so huge that they form sonic scattering layers that can be picked up on shipboard sonar. In the early days of sonar, a few ship's captains saw the vertical migrations on their screens and thought that the ocean bottom was rising up underneath them.

Even though vertical migration is such a critical part of the ocean's ecosystems, very little is known about the light cues that trigger this nightly phenomenon. Obviously, it's cued by changes in the light field, but what aspect of the light field is the trigger? It has to be more than just the change in light intensity - otherwise, animals would start migrating up on dark stormy days, and this doesn't tend to happen. It might be that animals respond to the rate of change in light intensity. We just don't know why all of these countless animals migrate up and down exactly when they do...but it is important that we find out. If something like the growing ozone hole affects the downwelling light field, it could effect the migration pattern, and fundamentally alter the lives of a vast number of animals.

From July 10 - 24, @Sea will be posting dispatches from an NSF funded science cruise in the Gulf of Maine. Scientists Tammy Frank and Edie Widder will be making frequent submersible dives into the murky waters from the deck of the Research Vessel EDWIN LINK. The JOHNSON SEA-LINK sub, capable of diving 3000 feet beneath the surface, will be outfitted with highly-advanced light measuring equipment. As Drs. Frank and Widder follow multitudes of tiny creatures up and down, they'll be studying various aspects of the changing light field, trying to uncover important clues to one of the ocean's biggest mysteries.

While Dr. Frank works to fathom vertical migration, an international team of scientists will be using the R/V EDWIN LINK as a platform for research projects on bioluminescence, jellyfish, fish hearing, fish vision, and other interesting areas of inquiry. @Sea will follow all of these projects throughout the cruise, letting you look over the scientists' shoulders as important discoveries are made!