Orange Roughy seen through the lens of the ROV on top of the MAR at 1000m depth.
Wolf fish captured in the baited trap.
The enigmatic chimaera, a very large specimen caught in the trawl.
Author: Aino Hosia (Univ. Bergen, Norway), Monty Priede (Univ. Aberdeen, Scotland)
Today started with the Aglantha ROV descending to the crest of the western edge of the MAR. To the east was the deep median valley that marks the axis of the MAR and to the west undulating hills decreasing in height towards North America. Aglantha descended through clouds of plankton, spotting various kinds of jellyfish, and an unusual siphonophore colony.
The ROV dives we are conducting during the cruise can be divided into two main components: the pelagic, studying life in the water column, and the benthic, concentrating on the bottom fauna. The pelagic component is especially focusing on the gelatinous life forms, such as jellyfish, comb jellies and siphonophores. The latter are a strange group of organisms related to jellyfish, the most familiar (although not the most representative) member of which is probably the Portugese man-o-war.
A large portion of the pelagic dives looks more or less like the "starfield" -screensaver for Windows. Most of the particles passing by are so called marine snow: aggregates of organic matter slowly falling towards the sea floor. Boring, you might think. However, every once in a while we spot a exceptionally spectacular jelly, a fish swims into the picture flashing its photophores, or a squid jets by squirting ink as it goes.
The ROVs are also equipped with samplers capable of gently catching any interesting jellies encountered during the pelagic dive. We have so far used these to collect, among other things, specimens of a narcomedusa called Aeginura grimaldii which were brought to the surface alive and in prime condition unlik and the abused globs of jelly we get in old fashioned plankton nets.
Comparing the dives so far, the abundance of jellies in the water column seems to be much higher here in the middle box than it was in the southern box. Last night's dive was particularly rich, and hundreds of individuals belonging to numerous taxa were spotted. Many of the comb jellies and appendicularians (small pelagic tunicates that build drifting houses of mucus) were extremely interesting and of potentially rare or even unknown species. You can therefore imagine the frustration of the scientists, when a strong current made maneuvering the ROV difficult and prevented sampling.
As Aglantha reached the summit of the ridge crest a remarkable sight awaited, Orange roughy fish, floating in the water above the garden of corals, sponges, sea lilies, and anemones that were growing in profusion. These fish are looked so relaxed and unconcerned about life, when you have 100 years more to look forward to it seems wise not get excited.
When Aglantha had returned to the surface, it was time for the G.O. Sars to pick up an acoustic lander that had been deployed on Leg 1. For extra interest the technicians had put baited traps onto the legs of the lander and in these were caught two enormous wolf-fish. These are the ugliest of fish, with large crushing fang-like teeth that enable this species to eat sea-urchins whole, crunching up the spines, shells and everything inside. What these fish are doing out on the MAR we do not know. Later in the day we retrieved the ROBIO and found two of these wolf-fish approaching mackerel bait, there are obviously quite a number of this species living on this part of the MAR.
During the afternoon the trawl was deployed on a flat bit of ground reconnoitred by the Aglantha and a good catch of mainly roundnose grenadiers was retrieved. The star of the catch however was a big chimaera. These are very interesting fish, half way between sharks and bony fish. No one knows whether they are a truly "missing link" or whether they are they a relict of an ancient group of fish that existed before land vertebrates evolved. Chimaeras have a single pair of gill openings like bony fish (sharks have 5-7) and they tooth plates instead of teeth, otherwise their body form is that of a shark, hence the name chimaera, they are the "frankenstien fish" with bits borrowed from different types.
This was super station 60 of the cruise and we have settled into a leg 2 routine, on arrival at the location, deploy ROBIO, then profile the water using the CTD and ISIT, followed by an ROV survey. Then deploy UVP and a trawl to complete the sampling before the ROBIO is finally recovered.
As the day drew to a close we moved to station 62 but the weather was getting worse with a gale force wind and waves growing as we deployed ROBIO in the evening. It was looking too rough for ROVs.