Bioluminescence and Biodiversity Expedition 2007
July 27 - August 1, 2007
August 1, 2007
Alison Sweeney writes: We had near-perfect conditions for our blue water dive today, a big change from the rest of this trip. There was almost no wind, and a little bit of low-frequency swell, enough to make the boat ride fun. A blue-water dive on the Western Flyer begins with filling glass jars with seawater for animal collection and preparing our SCUBA gear. We then load all our gear onto a small zodiac boat. The boat tender then drives us a safe distance away from the big ship for our SCUBA dive. It’s fun to see what the ship looks like alone on the ocean, a view that not everyone on the ship gets! The water was slightly warmer than yesterday, about 60 degrees, with very good visibility. It was an interesting dive because while underwater, it wasn’t obvious there were many animals or different species in the water, but when comparing our collection notes, between the four divers, we collected several really rare and exciting specimens.
To execute a blue-water SCUBA dive, we use a special rig of lines, tethers and clips to stay together in the vast, featureless ocean. Without this equipment, it would be very easy to get lost or swim too deep. There is a large float on the surface of the water with a long rope tied to it that descends straight down for 100 ft. The divers clip a rope onto their vests that connects them to a “trapeze” linked to the downline. These ropes act like pulleys through the trapeze so that divers are free to move around and the lines don’t get tangled. There is a safety diver who doesn't collect animals, but stays near the downline watching the other divers, leading the dive, and making sure everyone stays safe. The divers, all connected together through the trapeze, descend into the water using the downline as a guide. We then swim around our area around the trapeze, collecting gelatinous animals in our glass jars.
Blue-water diving is an important complement to ROV dives and trawling for collecting gelatinous organisms. There are many smallish (about 1 inch or smaller) creatures that are so transparent and fragile that there is no other way to collect them but to hop in the ocean and get them yourself. As an example, intern Rebecca has been pining for a Cunina jellyfish to complete her sample set all six days we’ve been on the ship. While watching the ROV cameras, Rebecca was extremely persistent in examining the hundreds of small jellies that floated by to find her prize, but we pulled up the ROV for the last time today with no Cunina on board. On our SCUBA dive today, however, I nabbed a jellyfish that I’d never seen before and that seemed unusual. I mentioned this to Steve on the boat ride back to the ship, but since there are a lot of jellies I don’t recognize, we didn’t think much more of it. When sorting our samples a few hours later, however, in the last jar out of the sample cooler — the last possible opportunity for collecting an organism on this cruise — Steve found the elusive Cunina. We couldn’t wait to show it to our disappointed intern! The capabilities of the Western Flyer and the ROV Tiburon are completely amazing and have allowed us to see things that would otherwise remain undiscovered. But they still can’t fully replace the value of hands-on collection and physically experiencing the environment you’re studying.