by Laura Lilly
For the first week of our cruise, we were carrying a stowaway science member onboard the Atlantis: Zippy the Zooglider! Zippy is four feet long, orange, and torpedo-shaped, but don’t mistake him for a giant carrot. On Monday, we released Zippy into the ocean to cruise underwater off central California for 20 days while we do our shipboard sampling.
Zippy comes from a class of Spray gliders, which are autonomous underwater vehicles (AUVs) developed by Russ Davis and Jeff Sherman at Scripps Institution of Oceanography. True to their name, AUVs are completely independent, remotely-operated vehicles that can navigate underwater without being tethered to a ship (if you are quick on your nautical literature references, you might recognize the name Spray from the ship that Joshua Slocum single-handedly sailed around the world, as told in his book A Solo Sailing Trip Around the World). The Spray gliders are controlled by engineers on land to ‘fly’ in any underwater pattern we designate. Underwater gliders are gaining popularity for precisely the reason that they can be left out in the ocean for months at a time to record data with no shipboard support. They just need to be launched and recovered! Most Spray gliders are deployed by small dinghys off Scripps, but since we want Zippy to profile the waters that we are sampling on our cruise, we brought him out to deploy at sea.
Similar to the SeaSoar, Spray gliders are equipped with oceanographic sensors to measure water temperature, salinity, oxygen, fluorescence, and biological particles in the ocean. Zippy has an additional characteristic beyond his standard Spray outfit: his “nose” has a shadowgraph plankton camera attached to it, which allows him to image live plankton in their real habitats. This addition was the product of a collaboration between the Instrument Development Group (which runs the Spray program) and Mark Ohman’s lab (also at Scripps), which studies mesozooplankton ecology and behavior. These in situ images give us important insights beyond what our standard shipboard plankton net tows tell us. As with all sampling metrics, plankton nets have advantages and disadvantages. Nets allow us to scoop up an actual sample of ocean plankton in order to visually and genomically identify animals and determine what they feed on, but nets can mangle fragile organisms (long tentacles and watery bodies don’t hold up well against nylon mesh) and they don’t capture animals in their natural habitats. The Zooglider’s camera gives us a literal picture of the natural shapes and orientations of animals, especially features like filamentous antennae and delicate shells. Best of all, it can cover an additional swath of the ocean that our ship won’t have time to sample. The Zooglider still requires land-based image processing, and we can’t always identify individual species, but Zippy does a powerful job of measuring who’s out there.
We hope that Zippy will encounter Hubert the Sea Llama while he is out and about. Hubert is a sharp-witted by elusive fellow who first befriended Steve the SeaSoar when Steve was out cruising last week. We’re looking forward to hearing about that and other adventures when Zippy comes back onboard at the end of our trip! In other news, we are just finishing our first four-day cycle, which sampled the heart of the newly-upwelled water filament we are tracking. The waters have literally been green with phytoplankton, so we are curious to see what our other measurements tell us about the new waters. Stay tuned for more updates.