@Sea - Drifting Houses in the Gulf Stream

	MISSION DISPATCH 6 • 4/20/01 - 4/21/01 Today's Weather - images courtesy of NOAA & RSMAS Second Night of JSL Science Dives Planned The second night of science dives is slated to get under way at 1930 this evening, east of Cape Canaveral, Florida. Two long (3.5 Hour) dives are planned, with target depths to be determined. Bathochordaeus individuals in houses will be collected in the six detritus samplers as before. More extensive in situ observations will also be conducted. Additionally, Dr. Marsh Youngbluth plans on trying out a technique for determining in situ sinking rates for discarded appendicularian houses. He'll use a delivery system on the JSL that will squirt a cloud of neutral-density fluorescein dye into the water, approximately 10-30 cm below an appendicularian house. The size of the house and the distance between the house and the dye will be determined with a paired-beam, small-scale laser. The time required for a house to sink downward to the dye will be measured through direct observation and recorded on videotape. 1300 - Return of the MOCNESS Monster Two MOCNESS tows are conducted in the afternoon, at around 1300 and 1600. The discovery from the previous night's sub dives that target animals were present in waters somewhat deeper than had been anticipated prompts the scientists to adjust the depth of these tows to between about 210 and 270 feet. For each of the eight discrete tow segments in a single MOCNESS set, the initial depth is targeted at the deep end of the 210 to 270-foot target range. Over the course of the tow segment, the net array is brought up to the upper portion of the target range, such that 20 meters or so of water column target depth is integrated over each tow segment. This up-and-down method of letting the nets fish the water has been dubbed the "tow-yo" technique. Despite the downward depth adjustments, both MOCNESS sets come up disappointingly appendicularian-free. The scientists know that towing for the fragile animals at a 3 knot speed can beat them up quite a bit. But even so, they would have expected to see at least parts of some damaged appendicularians in the tows. There are several scheduled research activities, such as organic carbon analysis, that don't require that the animals be in perfect condition. Hopefully, success with the MOCNESS improves so that the scientists can obtain animals in sufficient numbers to fulfil their objectives. 1930 - Diving Into the Unexpected 4/21/01 - JOHNSON SEA-LINK I - DIVE #4282 28°33.9404' N • 79°39.3290' W • Western Gulf Stream, off of Cape Canaveral, Florida Personnel - Sphere • Sub Pilot: Don Liberatore • Scientist Observer: Marsh Youngbluth Personnel - Aft Chamber • Tender: Alan Fuller • Diver: Alex Bochdansky Launch Time: 1940 • Time to Surface: 2032 • Dive Duration: 52 minutes The sub is launched for the first of two science dives tonight. Sub pilot Don Liberatore notes that the ship is having trouble tracking the location of the sub. He says that they will try to transmit their location on a different frequency after they reach the target depth. Unfortunately, adjusting to a different frequency does not fix the problem. Although the ship and sub are able to communicate on the radio, information on the sub's movement and position is not being received by the R/V SEWARD JOHNSON. It is not clear whether the problem is with the sub itself or with equipment on the ship. But, like I said in yesterday's communication, if a problem arises that might in any way endanger the sub occupants the dive is called off. The dive is scrubbed, and the vehicle returns to the surface less than hour after it was launched. 2130 - Isolating the Problem The Sub Crew checks a variety of possible causes for the communication glitch that resulted in the aborting of the sub dive. When the systems on the sub check out, they move on to the shipboard systems. After a couple of hours, the problem is isolated and found to lie with a faulty hydrophone on the ship. I am gathering images and beginning to write this dispatch as several of us are sitting around the dining area waiting for a status report from the Sub Crew. Dr. Flood climbs the stairs from his below quarters to join us. "So, I went to sleep, and that is how come everything went wrong, yes?" Shortly, the Sub Crew makes a determination that the hydrophone cannot be fixed while at sea. A decision is made to return to Fort Pierce to affect the necessary repairs that will allow the mission to proceed. The R/V SEWARD JOHNSON is now en route, and will be in Fort Pierce by morning. HAPPY EARTH DAY!! 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.