The morning of 19 April started pleasantly with a mix of sun and clouds, an air temperature of 23.5 C, a sea-surface temperature slightly warmer at 24.2 C, and winds between 10 and 12 kts from the southwest.
We had arrived on station #3 about 0630 and work began with a 200 m vertical Reeve net tow to collect fragile near surface zooplankton. Shortly after, a pull test to around 5000 lbs was done to ensure that the new cable termination on the conducting trawl wire was secure. During this operation, a discussion ensued about the first tow deep tow. It was to have been a 10-m MOCNESS tow to 5000 m, but there was a desire to have a shorter tow in the upper 1000 m, so that the taxonomic specialists could start their work at this station sooner. So the order of the two tows was reversed without remembering that the way the trawl wire was laid on the drum would dictate a much deeper tow at the start of the station.
The setup of the MOC-1 for launch took about 45 minutes and the net system went into the water about 0900. As the net reached the intended maximum depth and retrieval started, a bad wrap on the winch was reported and wire had to be paid out to fix it. In fact, there were bad wraps on a number of the lays and it took paying out almost 5000 m of wire to get to the place where the wire was correctly laid down on the drum. A broken strand in the outer armor was also found at about the place where the wire started developing bad wraps and the loose strand had to be cut and the ends taped securely to prevent more unraveling of the strand. How the strand broke is not known, but it is suspected that it occurred because of wire, under tension, was snapping into gaps left by the level-wind failing to lay the cable evenly on the drum. Because this tow turned into a very deep one, it was decided to do 500 m intervals from 3500 m to the surface with the nets. After adjustments were made to the level-wind, the bosun reported that the level wind was now working very well and it has done so since. So rather than coming back on board around noon, the tow was now slated to arrive at the surface around sundown.
This was an ill-fated tow, however, for another reason. When the net system arrived at the surface, only a single net bar should have been left to drop. But in fact all were still locked in the release mechanism, except for bar #1, which dropped because of the cable/swaged fitting broke about 200 m below the surface (depth determined by a spurious net response at 200 m). So net zero fished down to 3300 m and back to 200 meters and then net 1 fished from 200 m to the surface. The failure of nets to release was because the cables were mounted into the toggle wrong and although the commands to step the release occurred only the release shaft rotated. No nets were released. What a learning experience. The problem was magnified by the fact that nearly 5000 m of cable had to be paid out to get the wire on the drum straight. If it had been a normal tow, the problem would have been discovered a lot earlier. Such is our luck so far this cruise. Well, we have been working in the Bermuda Triangle!
In the late afternoon while the MOC-1 was still coming up, the fire alarm went off and it was not a drill. Ultimately it proved to be a false alarm in a forward area over a tank, but the response was impressive, and all scientists arrived in the main lab muster area in a timely way. An "all clear" was sounded after it was determined that no fire was present.
The early evening was spent doing near surface ring net tows and 30-liter water collection for microzooplankton. Columban de Vagas was amazed to find very few planktonic formainifera in the net tow samples, a situation he has rarely encountered. Other larger species of interest were caught in these tows including a euphausiid, Sylocheiron suhmii, a lovely small transparent shrimp-like animal with elongated eyes with 3 facets and distinct photophores designed for counter-shading. Once identified, it along with others, was prepared for gene sequencing.
A night SCUBA dive took place later in the evening (see Figure 1) and although the divers reported relatively low abundances of animals, they none-the-less came on board with a good collection of live radiolarians, siphonophores (one with a leptocephalus [eel] larvae being consumed by the gastrozoids), a pyrosome, jelly fish and associated amphipods, and other fragile species that are destroyed in the nets.
The first official deep tow of the station started around mid-night on the 19th with the deployment of the 10-m MOCNESS under good sea conditions (winds in 10 to 12 kt range). The launch was a bit difficult at the start, but ultimately the frame rolled down into the water fairly smoothly and soon the net was headed down to depth. During the night there was a wind shift and light winds around 5 to 8 kts began from the north (0 deg). In the early morning it was cloudy with rain squalls in the area and cooler temperatures (20.73 C). It was raining lightly when the MOC10 came on board very nicely around 0930. This tow was also discovered to have problems. In pulling in the nets, it was found that the cod-end from net three had been lost in spite of the fact that the fasteners had been rubber-banded, which has been the standard way to prevent bucket loss. In addition, the tab on net bar #3 that had been fabricated by the engineers again broke, so that the net bar for net 3 dropped when net 2 was closed and it never fished. This opened net four prematurely. Later in the day, the broken tab fixture was repaired by the engineers, who made it more robust. The catch in the rest of the cod-ends, while sparse, proved to have another set of very interesting deeps sea invertebrates and vertebrates. One interesting species was a mysid in the Gnathophausia group. There are several well-known species, but this was none of them. In addition, there appeared to be no contamination by animals living shallower in the water column or very little. The modifications made to the system appeared to have worked.
The 1-m MOCNESS was next up. It went into the water about 1130, but at 70 m depth, the deck unit lost connection with the underwater unit and nothing would bring it back. So the system was brought back on board. After a series of tests that determined that the cable was OK, the underwater unit was switched with the one on the MOC-10. The tow was started again about an hour later. This time the underwater unit worked fine and a complete set of samples were obtained in the upper 1000 m. The net came on deck about 1600. Such are the gremlins out here, that when the unit that failed was bench-tested, it worked.
Larry Madin, Erich Horgan, and the two crew divers left the ship about 1630 for the next in a series of blue water dives, as the afternoon watch processed the MOC-1 samples. While the divers were away from the ship in the zodiac, some surface ring net tows were taken by hand. The divers returned with more wonderful animals around 1730. All went well with the dive.
The last events at station #3, were night 1-m and 10-m MOCNESS tows to 1000 m and 5000 m respectively, and a ring-net tow to 200 m. All of these tows were accomplished successfully. The 1–m system was towed early in the evening followed by the ring net tow. The 10-m system, which was set at midnight, came up at 1130 on the 21st This time all the nets fished their intended depths (5000 to 4000, 4000 to 3000, 3000 to 2000, and 2000 to 1000 meters) and the samples showed little or no contamination again. A perfect ending to a station that started off poorly.
The Ron Brown got underway for station #4 just after noon on the 21st of April with light winds, calm seas, warm air temperatures, and clear skies. The remainder of 21 April was spent steaming under very nice sea conditions.
The work on board in the laboratories continues unabated. The following snippets provide some insight into the variety of work taking place on the cruise.
Team DNA third report:
Prepared by Rob Jennings
At the end of station 3, Team DNA has extracted DNA from approximately 300 species comprising nine phyla. Our biggest collections are of copepod crustaceans (80 species), hydrozoan jellies (69 species), and ostracod crustaceans (45 species). Together, all of our arthropod specimens constitute just over half of the species we have been given to identify! The diverse array of life forms and the often beautiful shapes these organisms attain are truly staggering. The great team of taxonomic experts are often very interested to know how the diverse shapes and morphologies they see within single species might translate to genetic diversity. In some cases, a single species exhibits a range of sizes, or even a 'small' and 'large' form. We are all very excited to see if the gene sequences Team DNA obtains from these forms are different--implying that there might actually be two different species present--or whether a species really does exhibit disparate forms (leading to the question: why?). If one thinks of the diversity of body shapes that are known from the single human species, it becomes clear that it is not easy to extrapolate from easily seen morphological differences to features that separate one species from another. One of the goals of Team DNA is to use the gene sequences we collect to help answer the questions, "What kinds of morphological differences matter to species?" and "How well do the differences we see in morphology correlate to the differences we see in genetic content?"
To this end, Team DNA has been chugging away, amplifying portions of the COI gene and running them on our gene sequencer. So far, we have obtained great sequence data from about 70 species, with almost a hundred more ready to run. The process of checking, editing, and finalizing gene sequences for each species takes time and a careful eye, but analysis has already begun, so we are beginning to get answers--at least partial answers--to our questions.
Deep-pelagic fish results update
Prepared by Tracey Sutton
Seventy-seven fish species have been thus far been identified from the first three stations of the cruise, excluding fish larvae. Notable specimens include a possible new barracudina of the genus Macroparalepis, a larval gulper eel of the bathypelagic genus Saccopharynx, and a male anglerfish of the genus Rhynchactis, of which less than 10 specimens are known worldwide. Genetic analyses are currently being run on these specimens. To maximize the information gained from this valuable specimen cache, muscle, heart and liver samples from bathypelagic fishes were extracted and frozen to test for the presence of organic pollutants such as organochlorines and PCBs.
Dhugal Lindsay Report:
In the first 1-m2 MOCNESS net of the cruise we caught a tiny octopus that seemed to have greatly elongated, whiplike suckers on its arms (see Figure 2). This curious little animal is a male of the pelagic octopod Tremoctopus violaceus, the blanket octopus, and is carrying pieces of the tentacle of the Portuguese Man o' War jellyfish Physalia physalia on the suckers of its arms. The suckers are adapted to hold these fragments and the potent venom contained in the stinging cells of the Physalia tentacles acts as a deterrent to most predators. Females of this species grow to over 2m in length while the tiny males have a maximum size of less than 3cm. This is a classic case of biological diversity begetting more biological diversity - with jellyfish as key players. It was first described by E. C. Jones (Science, 1963, 139:764).
Francesc Pages Report:
The blue water diving team led by Larry Madin and Erich Horgan has collected several siphonophore specimens (Rosacea, Athorybia, Agalma, Rhizophysa) over 5 dives, but one of them is particularly remarkable. On the third dive, a physonect siphonophore of the genus Halistemma about 20 cm long was captured and it showed a conspicuous discontinuity in the siphosome. A close examination indicated that the irregularity actually was a gastrozooid with a large prey inside. The dissection of the gastrozooid revealed that it contained a leptocephalus larva (eel larva) 8 cm long folded 3-4 times (see Figure 3). Siphonophores are divided into the orders cystonects, physonects, and calycophorans. In general, cystonects (Physalia, Rhizophysa, and Bathyphysa) have a diet based on fish, while most of calycophorans (e.g. Rosacea, Lensia, Sphaeronectes) feed upon copepods. The few data available on physonects' (Nanomia) diet indicated large crustaceans (stage V of copepods, krill larvae, decapod larvae) as the main prey. To our knowledge fish have never been reported and certainly not of this size.
Figure 1. Larry Madin, Erich Horgan, Phil Pokorski, and Keegan Plaskon (left to right) ready to go out on a blue-water night dive to collect zooplankton in the Rigid Hull Inflatable Boat.
Figure 2. The pelagic octopod, Tremoctopus violaceus, collected at station #1, carrying pieces of the tentacle of the Portuguese Man o' War jellyfish on its arms.
Figure 3. The physonect siphonophore Halistemma sp. collected during a blue-water dive at station #3. Note the large gastrozoiid that contains the leptocephalus larva.