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MISSION DISPATCH 9 • 4/24/01 Today's Weather - images courtesy of NOAA & RSMAS 0900 - Final MOCNESS Series Completed The Science Team aboard the R/V SEWARD JOHNSON decided to complete one more set of MOCNESSS net tows on the last full sea day of the cruise. Earlier MOCNESS collections had yielded an impressive diversity of zooplankton. As with all net-based plankton collections, however, the MOCNESS samples are skewed so as to give the appearance of increased abundance of crustaceans, shelled molluscs, larval fish, and other animals with hard body parts --  i.e., those capable of holding up to the damage inflected by net collection. Less robust gelatinous animals
like ctenophores and jellyfish are significantly underrepresented by such sampling methods,
despite their presence in high numbers in the targeted pelagic community.
In spite of their known shortcomings, net sampling techniques are still used to make zooplankton collections because their use is simple and cost-effective. This is likewise why the MOCNESS gear has been employed on this cruise, though most of the scientists likely held preconceptions that success with this approach would be limited. Still, they feel it is important to conduct the more conventional net-based sampling protocols in tandem with the novel sub-based approach during this cruise. If the shipboard personnel needed one more object lesson in how not to catch the target appendicularians, we got it with the final MOCNESS haul. In total, the MOCNESS sets conducted during the cruise filtered nearly 30,000 cubic meters of the water column environment in which our sub dives have proven that the appendicularians do exist. In all of these samples, not a single intact or partial appenduicularian was found. The bottom line, according to Dr. Youngbluth : "It appears that appendicularians cannot be effectively sampled with nets, considering the fact that the MOCNESS was towed repeatedly at depths where the animals were easily observed and collected using the JSL I submersible." 1300 - Work Continues on the Previous Day's Dive Collections 
The single, deep sub dive yesterday returned with videotaped in situ observations of appendicularian appearance and behavior, and its detritus samplers filled with live animals for shipboard study. After having an evening to examine the specimens, Drs. Hopcroft and Flood have concluded that two distinct deepwater appendicularian species were collected. One species, Oikopleura inflata, is poorly known, having been earlier described from only a single specimen. The second species is actually an undescribed specimen of genus Mesoikopleura. Although taking measurements and recording novel structural features of these species is important, it is only one of several activities planned for the JSL-collected appendicularians. 
Each scientist in the team has his or her own interests in the live animals and feeding houses
that come up in the collectors.
Drs. Alex Bochdansky and Vicki Fabry
have been quickly collecting appendicularian fecal pellets from each of the samplers that come up containing
an animal. These are preserved for chemical analysis to determine the quantity and
possible origins of carbon and other elements comprising the feces.
Dr. Fabry also wants to get a better handle on the trophic importance of discarded appendicularian feeding houses, with regard to the manner in which they transport organic material to deepwater communities. A number of discarded houses taken from the samplers are prepared and frozen so that follow-on chemical analysis may be conducted. Dr. Russell Hopcroft is interested in the many small but important morphological differences between the specimens collected here and animals found elsewhere. For more than 20 years, Dr. Per Flood has been keenly interested in the functional and architectural details of the appendicularian feeding house. This mission is no exception. Discarded houses from the samplers that are in the best shape are carefully removed and mounted on fine mesh screens so that details may be later studied. 
Additionally, the team wants to see if collected animals will inflate new houses and initiate normal feeding behaviors under controlled laboratory settings. Latex microspheres of mixed size-classes are added to samplers containing animals that are then left alone to build new houses. If any animals do, in fact, build houses and initiate feeding, they can be preserved and later analyzed to see if certain species exhibit food selection based on particle size. 1600 - Green Light For Last Set of Sub Dives The last three sub dives of the mission are scheduled to commence at 1630. Dr. Fabry will be the scientist observer on the first dive. Because this dive is set to occur during the day, the Science Team decides to make it another deep dive, allowing animals to be collected from depths below that at which sunlight makes observing and collecting appendicularians difficult. 4/24/01 JOHNSON SEA-LINK I - DIVE #4284 27°30.86'N • 79°43.65' W • Western Gulf Stream, off of Fort Pierce Personnel - Sphere • Sub Pilot: Phil Santos • Scientist Observer: Vicki Fabry Personnel - Aft Chamber • Tender: Frank Lombardo • Diver: Jennifer Bossart Launch Time: 1646 • Time to Surface: 1857 • Dive Duration: 2 hours, 11 minutes 
Like the deep dive of the previous afternoon, this dive come up with live animals representing
O. inflata and the undescribed Mesoikopleura. Samplers are quickly removed from the
front of the sub and moved into the temperature and light-controlled environmental room. Discarded
houses are removed from the samplers for architectural study and chemical analysis. Individuals
of the larger of the two species, O. inflata, are set up for the microsphere
experiment, while Mesoikopleura animals are removed for taxonomic study by Dr. Hopcroft.
The various laboratory activities will continue up until launch time for the second dive. Scheduled for a 2130 launch, this night dive will return to shallow waters in pursuit of the large species Bathochordaeus. The microspere experiments utilizing the deepwater animals will have to be halted and the environmental room's temperature turned up for incoming animals. Dr. Youngbluth is the scientist in the sphere for the upcoming dive. Occupying the aft chamber along with sub crewman Frank Lombardo is Marine Technician Allison Heater. 4/24/01 • JOHNSON SEA-LINK I - DIVE #4285 27°30.98'N • 79°43.64' W • Western Gulf Stream, off of Fort Pierce Personnel - Sphere • Sub Pilot: Phil Santos • Scientist Observer: Marsh Youngbluth Personnel - Aft Chamber • Tender: Frank Lombardo • Diver: Allison Heater Launch Time: 2138 • Time to Surface: 2332 • Dive Duration: 1 hour, 54 minutes 
The sub returns with a full complement of animals and/or houses in its detritus samplers.
Material is divided up in the same manner as it had been previously, and shipboard lab activities
begin anew. These will persist until launch time for the third scheduled dive of the night. This
dive is slated for 0230, early Wednesday morning. It will be the final dive of the cruise.
Also, I finally get a chance to accompany the sub team as an aft chamber occupant. It's
exciting enough that I barely think about the sleep we are all doing without. Come back to see how
the dive and the mission wrap up.
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.  | |
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