@Sea - Drifting Houses in the Gulf Stream

	MISSION DISPATCH 4 • 4/19/01 Today's Weather - images courtesy of NOAA & RSMAS 0945 - And We're Off! The crew of the R/V SEWARD JOHNSON casts off lines. We're heading back to the Gulf Stream; the first science dive of the mission is scheduled for this evening at 1930. The excitement levels of the Science Team are elevated, even as the ship and sub crews realize that shifting to night operations will make for a long double shift for most everyone on board. The Science Team gathers on the Bridge at 1100 for an orientation and safety meeting with Captain Ralph Van Hoek and Chief Submersible Pilot Don Liberatore. Go ahead and quiz me. Seven short horn blasts and one long one is a man overboard. One continuous horn or bell is a fire. As occupants of 2-man State Room No. 11, Jimmy and I can use either of the starboard life boats -- but not the port boats -- if we are forced to abandon ship. Jennifer Bossart is called upon to demonstrate how to put on a survival suit and we are briefed on the procedures to follow if someone does goes over. Don runs through sub safety procedures, and outlines the typical occupancy on a dive. The pilot and a chief scientist occupy the sphere, and a sub crewperson and a second scientist will occupy the dive chamber. "If a scientist doesn't want to sit in the aft chamber on a dive," says Don, "Then we'll ask if anyone in the ship crew wants the spot. We need the weight in the back, and finding human ballast is easier than moving lead." The sub guys are very practical. Don also reminds the novice submariners among us that there are no heads (restrooms) aboard the JOHNSON SEA-LINK submersibles. Passengers should either anticipate dthe need for bladder control during the dive, or else be prepared to to use "piddle packs" (dehydrated sponges) if Nature calls. 1330 - MOCNESS Tow Conducted We arrive on site some six hours before the slated first sub dive. It's the perfect opportunity to get an exploratory MOCNESS tow in. If we bring appendicularians up as part of the zooplankton from the initial MOCNESS haul, then we can feel fairly confident about hunting for them here using the sub this evening. The MOCNESS is a sophisticated net system that the Science Team hopes will minimize the degree to which the soft-bodied appendicularians are ravaged during the net tow. It consists of a series of nine separate plankton nets that can be electronically opened and closed from a shipboard computer. Only one net is open at a time, and they are triggered to open in succession - after a certain distance has been towed, after a certain time has elapsed, or once a specific volume of water has been filtered through a net. A suite of electronic whatzits attached to the MOCNESS array allow the shipboard computer to monitor the appropriate parameters and open/close the nets automatically when specified set points are reached. The team decides to set the MOCNESS to pull two nets each through 50, 100, 150, and finally 200 cubic meters of water, yielding a total of eight samples collected during the tow. Contents from the initial open net, called the drogue net, are not considered as part of the collection. Because the gelatinous appendicularians are fragile -- and their feeding houses even more so -- the team believes that the animals collected in the shorter (low volume) tows will come up more intact than those from loner tows. The catch is that, because the longer tows filter more water, they also tend to be the ones that capture the most animals. Hopefully, captured appendicularians will survive the rigors of a lengthy tow intact. The MOCNESS fishes for about 45 minutes before it is retrieved via an electric winch. It comes back with four missing cod ends -- the collectors at the tapered ends of the nets. The marine techs will have to reevaluate the method in which the cod ends are attached for future tows. The samples with the cod ends that do remain in place yield a high diversity of zooplankton, including, chaetognaths, pelagic gastropods, larval lobsters, various jellies, amphipods, and several species of copepods. The scientists hoped this preliminary tow would reveal that appendicularians were present in abundance, indicating that follow-up sub dives were indeed in order. Unfortunately, none of target appendicularians are recovered. The first sub dive is still on for 1930 this evening, however, so we will soon get an up-close look at what's really down there. 1440 - Ad Astra A memorable moment in the day came when Space Shuttle Endeavor took off from Kennedy Space Center to the Northwest of our current location. It was the first live shuttle launch for many of the Science Team, and it provided a brief break from the day's tasks. Less than five hours until dive time now. Hope you can make it. This expedition is made possible through a grant from the Biological Oceanography Program of the National Science Foundation with additional support from Harbor Branch Oceanographic Institution.