The steam to Station #4 (20 N; 55W) took about 32 hours under mostly clear skies with only a few clouds. In the early morning, winds 10 to 15 kts were from the northeast, the sea surface temperature (SST) was 25.56 C, and the air temperature was slightly cooler (24.1 C). Work on board to analyze the samples taxonomically and genetically continued.
During the afternoon of the 23th, the second session in the seminar series was held with Larry Madin, Hege Hansen, and Tracey Sutton giving the talks. Larry talked about the Liquid Jungle Laboratory, which is a new tropical laboratory for marine and terrestrial research on the Pacific side of Panama. There is a shore-side wet lab in addition to lab space in the main building up on an island hillside, small boats for access to the coastal waters, and a newly installed cabled underwater observatory just offshore. Hege talked about the deep-sea shrimps that were collected on the Mar-Eco cruise to the mid-Atlantic ridge on the R/V GeoSars in summer 2004. She compared the species caught on that cruise with those collected so far on this one. She has found only one species that was not caught on the ridge cruise and there is a northern species that has not been collected on this cruise. Tracey gave an overview of the groups of deep-sea fish that exist and talked about those that he was finding in our samples. There are several rare species that he has found in our collections and one or more probable new species. The talks were split into two sessions because the ship’s personnel had a safety meeting at 1415 that went until about 1515.After dinner, the 10-m MOCNESS was made ready for the next watch to launch and tow. The cod-end buckets were attached to the nets and the nets arranged so that they could be deployed off the stern easily. In addition, some repairs to the newly fashioned trawl deflector flaps were made.
We arrived at Station #4 about 0035 on 23 April and started the work with a vertical Reeve net tow to 200 m. This was followed by a 10-m MOCNESS tow. The bottom of the tow was at 4500 m instead of 5000 m because of the very rough topography in the area. The SeaBeam bathymetry data showed that there were substantial ridges and valleys in the area and our tow line cut across them. The broken strand of 0.58" conducting cable at about 4700 m that was taped after the last tow, came loose after the tape was worn off going through the traction winch and had to be re-taped when it came past that spot going out and coming back in, but this did not interfere with the haul. The system came up and on board at 1245. As the nets were being hauled in (Figure 1), the catch in the buckets were initially examined. There was a spontaneous OOOOH!! as a large dragon fish was found in the bucket of net 4 (2000-1000 m). After later examination in the main lab, Tracey Sutton thinks that this fish might constitute a new genus as well as a new species. Also in that catch were some lovely large red deep-sea shrimps (Figure 2). This tow, like the last one, had all of the nets fish properly. It was a very nice haul.
A daylight blue water dive took place in the early afternoon under light winds (~8 kts) from the northeast and sunny skies. The divers returned with only a few animals. The dominant organisms were phytoplankton, the nitrogen fixer Trichodesmium and mats of Rhizoselina. The zooplankton were sparse.
While the divers were out, the 1-m MOCNESS was setup for a tow. The cable termination was changed from the MOC-10 to the MOC-1 and then the underwater unit moved to the MOC-1. About 1520, after a deck check to make sure the electronics and sensors were operational, the net entered the water and the tow began. This tow went fine, except that a collar came off of net 3 and the catch was lost along with the bucket.
Russ Hopcroft and Barbara Costas did a series of net tows and water collections casts, while the 1-m MOCNESS was prepared for a second evening tow. The net system went in smoothly from its position within the back of the MOC-10 frame. The tow, which came on board around 0130 on the 24th, was successfully concluded with more interesting animals in the catch including a small tropical squid in the surface sample that Dhugal Lindsey knew existed, but had not seen before.
In the wee hours of 24 April, the divers went out in the RHIB for a night dive in waters that were now around 26.5 C. Again the take was sparse, reflecting the oligotrophic nature of the station area, but they did collect two very interesting delicate ctenophores, Beroe mitrata, and Thalassocalyce inconstans. Larry Madin and Richard Harbison discovered and named the latter species some time ago and the genus means "cup of the sea" after its shape and inconstans because it is in constant motion. Both individuals were still alive in the evening of the 24th and were the subject of observation and photography, prior to being submitted for sequencing.
A quarter-meter MOCNESS tow was scheduled as the last item to be done at Station #4, but the underwater unit again proved to be unreliable on the deck and so the tow was scrubbed. The ship got underway for the last station (#5) about 0400.
Steaming during the day again gave the investigators an opportunity to catch up on the laboratory investigations of the samples collected at the station. There was also a concerted effort to update the CMarZ web site and to add additional photos of people and gear at work on the cruise. It was pleasant steaming weather with sunny skies sprinkled with puffy clouds, winds from the east (90 deg) at about 15 kts giving rise to some white caps and choppy seas on top of an underlying swell. Both the sea and air temperature was around 26 C.
At 1400 on the 24th, a subset of the scientific party (Martin Angel, Larry Madin, Rob Jennings, Russ Hopcroft, Tracey Sutton, and Peter Wiebe) met in the chief scientist cabin to take part in a press conference call organized by Fred Gorell of NOAA. In preparation for the call, two photos were put on the web of two of the first zooplankton (the copepod, Paraeucalanus attenuatus and the pteropod, Euclio pyramidata) collected on the cruise that were in the first group sequenced at sea. In addition, a photo of Paola Batta Lona "operating" the sequencer was also posted on the web. Reporters on the call included Christina Reed, a Free-Lance Reporter, Peter Spotts of the Christian Science Monitor, Warren Wise of the Charleston (SC) Post & Courier, and Noel Anenberg, who writes a children's / educational series for LA Times. In addition, there were several others including Ann Bucklin, the CMarZ lead investigator and a co-PI on this OE project responsible for the shipboard sequencing activities. The conference call lasted about 75 minutes and covered the overall rationale for CMarZ and the cruise objectives. Questions from the reporters then framed the remarks made by our group of scientists about what we had already learned and how the sequencing information would ultimately be used. The session was tape-recorded by NOAA.gov and would be used for production of a story to be podcast.
A schedule of MOCNESS tows, blue-water dives, and other net tow and water collection was prepared in the late afternoon for the first day and a half of the time at Station #5. The early evening was spent setting up the 1-m MOCNESS for a tow tomorrow morning after the ship arrives on station now estimated to be 0830 on the 25th of April.
Then late in the evening around 2300, the third in the seminar series took place. This late hour was chosen because this is when most of the scientists are up. With the last station quickly approaching and the end of the cruise in sight, there is an increased impetus to make the most of the time remaining. Barabar Costas provided an introduction to the ciliates and in particular the groups that include tintinids, oligotrhichs, and choreotrichs. She described her work on tintinnids (small ciliate microzooplankton) and the difficulties involved in using the classical methods to preserve and identify them . She has been developing molecular methods to determine species identification and finding that a number of forms that have previously described as distinct species appear to have very similar genetics and may not be separate species. A library of ciliate genetics is being built and is to the point in some areas where bulk DNA analysis can be used to track the presence and perhaps the abundance of the different species. Rob Jennings described the steps carried out by Team DNA in the processing of the animals in the sequencing lab. This involves extracting the DNA, amplifying it, running the sequencing reactions, and then run the product on the sequencer. He described how to resolve the data from noise in the reaction by sequencing a forward strand and a reverse strand. Once the sequence has been finalized, the next step is to compare it to known sequences in the bank of sequences to see if the sequence matches one for a known species. Since the cruise began about 500 species have been submitted to the lab for sequencing and there has been 775 extractions. This number will go up since station #5 is not included. Russ Hopcroft gave a tutorial on larvacean diversity and ecology. Like the tintinnids, the larvaceans are extremely fragile animals and are difficult to collect intact. They make an elaborate external feeding structure that they use and then discard when it gets clogged up. This may happen as often as 14 times per day. Russ described the house structure, which is unique to each species, so the house can be used to identify the species. There area 3 families, 15 genera, and 69 known species. On this cruise, he has collected fewer larvaceans than expected as he describes below.
A visit to the CMarZ website reveals a section devoted to photos of some of the zooplankton collected on this cruise. The following report is by Russ Hopcroft, who has been patiently and painstakingly getting the animals to pose for their pictures. In addition, microzooplankton work also continues as described below by Barbara Costas.
I have two principle purposes during the cruise: general photography of zooplankton, and identification of larvacean species for the bar-coding (sequencing) effort.
Photography has been an almost full-time task. To date, more then 800 useful images of have been taken on ~60 different living species of zooplankton at 4 MPix resolution. Depending on the species, from one to 20 pictures have been taken per specimen. Hundreds of additional images have been made on the 2 MPix system by other investigators. These images will constitute one of the more visible "public" legacies of the cruise.
In regard to the larvaceans, progress thus far has been disappointing. Only 8 of the ~70 species described in this group have been encountered during this cruise. With the possible exception of the smallest MOCNESS, the collecting systems have extruded the larvaceans, and rendered those remaining unidentifiable in the collections. The Reeve net has been generally successful, but densities of animals have been unusually low, and even for this net there appears to be a relatively limited time-window over which material in the collection remains in useful condition. Only the most common smaller tropical species have been encountered. The larger tropical genera have not been encountered with the notable exception of the giant "mesopelagic" species, Bathochordaeus stygius. In the table below C = common, P = present and Stn0 was where a net tow was taken before reaching station #1. There appears to have been a distinct faunal change after station 1.
Not to be idle and because pelagic mollusks were present in many of the collections, taxonomic attention has expanded to this also neglected group. Of the pteropods with calcareous shells (Euthecosomes), 16 of the ~45 known species have been encountered, along with 3 species of the naked pteropods (Gymnosomes). Several Pseudothecosomes have been observed in the samples, but none in suitable condition for definitive identification. For the heteropods, 5 of the shelled species have been collected, and 1 of the "naked" species has been identified. The nudibranch Phylloroe has also been collected.
Through Station 4, we have identified up to 18 species of tintinnids greater than 50µm and have collected DNA from all of these for sequencing of the ITS (internal transcribed spacer) region, as well as the COI gene for most of the species. Smaller sized tintinnids will be identified later through high powered microscope examination from preserved samples, which will provide an overall picture of the tintinnid diversity at the different stations. We continue to note that tintinnid abundance, while still low, is highest near the first structure of the water column, usually around 100m. In terms of diversity, there are several of the species that are common to all stations as well as species that we have only identified at one or two stations. In addition, we have started the process of attempting to identify the effective population size of two of the species we have found at multiple stations.
Figure 1. Hauling in the 10m MOCNESS nets after a deep tow to 4500 m at station #4 - Barbara Costa, Martin Angel, Tracey Sutton, Leo Bercial, Ebru Unal LtoR in front (23 April 2006 - Photo by PHW).
Figure 2. Nancy Copley holding a deep-sea shrimp and Tracy Sutton (not shown) holding a Dragon Fish collected between 1000 and 2000 m at Station #4.