Mountaineering in the Indian Ocean

We are just into week three of the cruise. Coral seamount was reluctant to give up its’ secrets and we have contended with bad weather and various minor issues with equipment. In the end, however, we have documented incredibly an incredibly beautiful deep-sea ecosystem inhabitated by many remarkable animals. Particularly striking have been the corals and the sponges. The former range from white stony corals with bright orange polyps to tree-like octocorals, including a remarkable species which is bright purple. The sponges are often a creamy white colour but are remarkable for their amazing forms, from vase-like dimpled colonies to enormous undulating brain-like shapes, trumpets or plates. Almost everything comes with its’ resident other creatures. For example, the corals almost always come with a particular species of brittlestar, some large with snake-like arms. Squat lobsters inhabit almost every coral and sponge, their golden eyes reflecting the lights of the ROV. Miniature glass-like lobsters swim about by flapping their tails when the ROV lands near a coral. Hermit crabs, giant snails and carpets of anemones are also things we have observed. We have also seen evidence of human impacts, all the way out here more than a thousand miles from the nearest land. We are constantly accompanied by seabirds and I’ve counted more than 40 great wandering albatrosses from the vessel. There are also shy albatross, cape pidgeons, white chinned petrels and others. We have also seen sperm whales diving on Coral Seamount, a witness to the importance of this feature to ocean predators. More surprising perhaps was the fact that we also saw fur seals around the seamount summit. I had no idea that such relatively small creatures would be seen so far out to sea.

Everyone is working incredibly hard. For me, organising the various types of work we are doing around the weather is a complex and daily task. The other scientists are very busy recording information, collecting and preserving samples, analysing the chemistry of seawater and the flow of currents around the seamounts. Even mapping these features with acoustics has been hampered by difficult conditions. The crew remain positive and cheerful and everyone looks forward to mealtimes, the cooking has been great.

Yesterday (November 21^st) we arrived at a new seamount, Melville Bank, one we know has been heavily fished in the gold rush for orange roughy in the early 2000s. This fish, in case you are not aware, lives to as much as 150 years old and does not reproduce until it is 30 or 40 years of age. It is very vulnerable to overfishing and the “goldrush” fishery on the South West Indian Ocean ridge only lasted a few years before stocks collapsed. It is rumoured that a lot of fishing gear was lost on the seamounts and we look forward with some trepidation as to what we may find on this seamount. On the acoustic maps it is incredibly rugged, with cliffs and steep slopes. Tomorrow we will dive and find out for the first time what lives on Melville Bank, for no other human has seen what this seamount looks like underwater...

The Seamounts Cruise Gets Going

After a very pleasant day or two at Cape Town RRS James Cook sailed at 14.00 on Monday 7^th November. It was a beautiful sunny day and the ship moved smoothly out of the Waterfront harbour and out to sea. We all stood on the foredeck taking photographs of Table Mountain as the ship swung to the east to take up the first station. Cape fur seals were lying in rafts dotted here and there and would lazily swim off or suddenly dive as the vessel approached. Cape gulls drifted past and gannets flew low over the water passing by without heed to the ship. We made a stop and deployed the CTD (Conductivity, Temperature, Depth), a large metal frame with water sampling bottles and instruments for measuring temperature, oxygen concentration and fluorescence (chlorophyll) in the water column. After this it was time to calibrate the multifrequency echosounders we use to look at the behaviour of the animals living in the water column during the trip. This was a very fiddly operation requiring the suspension of a small metal sphere underneath the hull-mounted echosounders of the ship using a combination of three lines deployed from what resembled fishing rods over the side of the ship. We had heard horror stories about how long this operation could take but we were very lucky with calm weather and immediately managed to get echoes from the sphere. Outside fur seals swam around the ship. They were very sociable, often gathering in small groups, prodding each other with their noses or scratching or grooming themselves with teeth or flippers. Occassionally one would hang, tail up out of the water and head down on the surface. At one point out metal sphere and lines suddenly moved back towards the stern of the ship and we were quite suspicious that the seal’s curiosity had got the better of them and they had come to investigate our calibration sphere. We could see the seals diving on the echosounders as they were blowing trails of bubbles as they dived down to 70 or 80 meters below the ship, occasionally coming up chasing small fish (we had seen a large male trap some fish between the harbour wall and the ship while it was moored in Cape Town and then proceed to gorge itself for half an hour or more). The whole operation was completed by 02.00 on Tuesday morning, much quicker than we were expecting, at which point we recommenced our journey towards the first seamount, Coral. The moon appeared between clouds and the ships wake was bright blue green with bioluminescence, an amazing sight.