South Atlantic cruise on "RV Akademik Ioffe" 2009
Author: Dr. Angel Perez
October 31, 2009
After a long night of hydrological data collection, the Ak Ioffe resumed her route towards the SA MAR-ECO first superstation, approximately 48 hours’ travel away. Before arriving, while crossing the Sierra-Leone abyssal plain, we plan to conduct an opportunistic (non-MAR-ECO) benthic sample, to test our equipment and procedures. Since we had completed most of the preparations, there was not much to do today except for fine-tuning our lab and equipment arrangements. We did pass a large group of spinner dolphins, moving fast in the opposite direction – they looked as if they were fleeing from something ahead of us, and in fact, a short time later we met a tropical rainstorm. It lasted only a few minutes, but the rain was intense, so it seems these animals can perceive such weather events, and avoid them if they choose.
November 1, 2009
We reached our trawling location above the Sierra-Leone abyssal plain around 1000h on this rainy Sunday. The Sigsbee trawl descended to 4970m depth over 1.5 hours, monitored by acoustic "pingers." However, before it reached the bottom, there were two major interruptions – a section of the steel cable had frayed and needed splicing, and then the ship suffered a brief but major power failure. By 16:30 hours, the trawl was finally in action on the bottom, where it remained for another 1.5 hours. At 19:30 hours, the trawl returned to the surface... but the cable had tangled and the net was caught and twisted, essentially upside-down, probably due to dangling in the water column during the interruptions. Nevertheless, a small sample of abyssal organisms was collected. The Russian scientists are extremely skilful with the ship's machinery, but it is also good to be reminded how difficult it is to sample at these great depths, and what a rare opportunity we have. After dinner, the Ak Ioffe set her course for the Mid-Atlantic Ridge proper, 217 nautical miles from our present position.
November 2, 2009
We sailed continuously during the day, reaching our first official SA MAR-ECO superstation late at night. We were now 3233 metres above a geological feature known as the "Romanche Fracture Zone", in the boundary zone between the northern and southern sectors of the Mid-Atlantic Ridge. The benthos team decided not to sample in this area; the bottom was too irregular and the risks of losing the equipment too high. Instead, two pelagic trawls with the Isaac-Kidd Mid-water Trawl (IKMT) were conducted, the first from 1000 metres depth to the surface, and the second within the "scattering layer," a variable depth stratum at which high densities of nektonic and planktonic organisms aggregate. The first trawl suffered some equipment problems again, but the catch included hundreds of small pelagic fish and crustaceans, plus some exquisite small squid, and many gelatinous organisms (salps and jellyfish). Sorting, photographing, cataloguing, labelling and fixing these specimens was a time-consuming job, but we were glad that sampling had finally started.Between these two samples, the plankton net was also deployed for the first time, but with unsatisfactory results: This net, too, returned to the surface entangled in its cable, probably because it was too light for these depths. Modifications were necessary to make it work properly, although these would prevent us from closing it off at a particular depth. We worked until almost 08:00 hours on November 3, and then the Ak Ioffe set course to Superstation 2. After two hours’ transit (enough for a very short rest), we would start all over again.
November 3, 2009
Superstation 2 was at the crest of the Romanche Fracture Zone, approximately 1000 metres deep. We began again with two IKMT pelagic trawls, one sampling at 1000 metres (near the bottom) and another aimed at the scattering layer. Meanwhile, the geologists and benthologists worked together to sound out the bottom, using our acoustic equipment, to try to decide on a suitable location to deploy the Sigsbee trawl. By lunchtime the pelagic trawls were finished, and had brought large, diverse samples. While the fish and cephalopod teams busily sorted these pelagic samples, the Sigsbee trawl was deployed for the first time on the Southern Mid-Atlantic Ridge. Two trawl hauls were conducted consecutively on a 1000m-deep, moderately flat area, both of them lengthy and with rewarding catches. The last one in particular brought up a breathtaking collection of large, colourful animals, including urchins, holothurians (sea cucumbers), corals and sponges, amazing and delighting everyone on board. The superstation finished with one last plankton sample, using the already adapted net, set to collect continuously from 1000 metres to the surface. It worked quite well, and once this sample was fixed, we dropped into bed after our 24-hour marathon.
November 4, 2009
The Ak Ioffe reached a hydrographic station in the morning and remained at this site during the whole day. It was perfect for those who needed a good rest, and also helped us catch up with the identification and cataloguing of the previous day’s specimens. In between naps, many of us stayed in the labs with our identification keys, measuring tools, and vials, jars and buckets. Storage will be one of our challenges on board by the end of the trip, but for now, our precious specimens have plenty of room. In the afternoon, we resumed our route to the next superstation. The captain also announced that there would be an important event the next day to celebrate crossing the Equator, and those who had never crossed it at sea before would be duly initiated according to ancient maritime traditions. It was an uneasy night’s sleep...
November 5, 2009
Careful manipulation of the ship’s speed overnight ensured that we would cross the Equator around noon. By that time, Neptune and his royal court had assembled on the aft deck, ready to initiate the fresh sailors – including the whole South American/NZ team. The costumed crew and veteran scientists (now mermaids, sea demons, sirens, pirates and a host of other colourful characters) led us through the ritual. As we knelt before the royal entourage, we received smearing of black goo from the sea demons, plus ice down our backs, dustings of flour, strands of spaghetti hung from our ears and many other physical delights. Each person or group was given a task to complete, from playing soccer with the sea demons, to drawing portraits of Neptune, to carrying the sirens around the deck piggyback. The biology team (mercifully abused as a group) danced around the deck with the demons, ultimately forming a conga line. Finally, everyone were dumped into a pool specially constructed on deck for the occasion.After prolonged and vigorous showers, we were treated to a barbecue and dancing on the aft deck, and the Ak Ioffe steamed toward our next superstation at 10 knots.
November 6, 2009
Another sailing day. The whale-watching routine was reinstated, and extended to include any sea birds sighted. Although the latter are not particularly abundant, we have seen several, including petrels, gannets, and one or several egrets (a rather odd occurrence).
At night, an extra pelagic trawl was conducted using the IKMT in the scattering layers; these were densest at 200 and 45 metres. Although the net was only deployed for 10 and 20 minutes respectively, the resulting sample was large, mainly made up of fish (both small pelagic fishes and fish larvae).
November 7, 2009
We began work at 07: 00 hours at Superstation 3, on the main axis of the Mid-Atlantic Ridge at 3342 metres depth, still enjoying extremely favourable weather. We first sent down the CTD mounted on a rosette, with three bottles to collect water samples for microbiologists in Brazil, at 1000, 1500 and 2000 metres depth. Next came a plankton trawl, again sampling from 1000 metres to the surface, and two pelagic trawls with the IKMT finished the morning's work. The first, to 1250 metres, captured two beautiful specimens of the benthopelagic squid Mastigoteuthis, known for drifting slowly over the seafloor and catching prey by dragging its long, sticky tentacles (covered with tiny suckers). Once again, the benthologists used echo sounding during these trawls to identify their desired sampling transect. Their net was sent down to 3093 metres, starting at 14:00 hours and returning to the surface at 17:00 hours, bringing a small catch and evidence of a mostly rocky seafloor. With Superstation 3 finished, the Ak Ioffe moved off toward Superstation 4, arriving there two hours later: – a seamount, whose summit was at 1000–2000 metres depth. IKMT trawls were deployed during the night, again bringing in large fish and invertebrate catches. Around 02:00 hours (on November 8) the Sigsbee trawl was sent down again, this time to 19:05 metres, on the seamount flank. When the trawl was recovered three hours later, the iron frame was badly bent and twisted, indicating a crash into large rocks on the seafloor. Nevertheless, an interesting small catch was still retained, as well as large calcareous rocks – likely fossilized sponges. We have several reserve Sigsbee trawl nets in case of just such an event. The plankton net finished our fourth superstation, and we finally went to bed after breakfast. Next stop: Superstation 5, in approximately three days.