1/2 July

R/V Pelagia Cruise HERMES

Saturday-Sunday, 1-2 July 2006	Boxcore with video camera
While the rough weather of last two days meant a long day of work for the CTD girls, others got some time to process the massive amount of samples, waiting to be sorted or administrated. For others the rough weather gave the opportunity to have a break, take some additional sleep or read a book. Some just enjoyed the moving ship, riding the waves.
The aftdeck was rocketing sky high and then diving deep down. As suddenly as the wind had picked up, as rapid the sea calmed down in the evening and night. So July made an excellent start. The world changed into a flat watery pancake as far as the eye could bring us, we saw nothing else then a slightly rippled sea. The fulmars and shearwaters did not even fly, but remained lazy swimming around the ship waiting until something edible would come along. This calm sea gave the opportunity to start hoppering. In this operation a video camera mounted on a boxcorer frame together with lamps is lowered on a cable to a height of about 2 meters above the seafloor. The slowly moving ship tows the camera over the study area. On basis of the obtained video images, insight is given in the zonation, compostion and structure of the coral reef. Marvelous video shots were taken and with the now working laserpointers it is evident that the sponges can be as large as 50 cm in diameter or even bigger. Earlier this cruise in the trial runs of the hopper camera there was a problem with one of the laser pointers, which made it impossible to estimate the sizes of the animals seen. It appeared that the pointer would not start due to a too low ambient temperature. However by preheating with a bucket of hot water before deployment, we were able to start it and keep it burning. So from now on all video's show two laser beams 30 cm apart, which gives the possibility to estimate sizes of animals and the coverage of live corals. It is however a strange idea that, with all the highly sophisticated instruments, we have to rely on a bucket of hot water. Because the hopper camera batteries need to be charged which takes a few hours, additional boxcore samples in between the hopper deployments were taken. These boxcore samples are sieved, used for respiration measurements and used to collect live animals for experimentation and sampling of the attached microbes. The live animals are used in the respiration experiments with the aim of getting an estimate for the energetic requirements of the reef. Apart from using optodes to follow the decrease in oxygen concentration we use winkler titration to determine the absolute concentration at the start and the end of these experiments. Water samples from the boxcore are taken to check the real bottom water concentration. Today, Sunday is even nicer than yesterday. The sea became an oily like surface so we again started with a hopper camera transect. After the batteries were finished we picked up the first mooring which was in this weather an easy job. All instruments, tied to the mooring, had worked excellent yielding a wealth of information on near bottom currents, particle concentration and sedimentation . After we had picked up the first mooring it was time for the morning break and lunch. On the television in the mess everyone came together looking at one of the taken videos of the coral reef. John the cook had prepared fagottini, filled with cheese and herbs and with glass of wine and port we toasted on the expedition. After the lunch we went to work again. The sun had got some strength and it was pleasant to work outside. Three boxcores were taken and the second made us remember that it is difficult ground to core. Back on deck, the complete edge of the corer was demolished by a medium sized boulder. Most of the sand was flushed away. A second try led to a better sample. After the coring operation we started one new hopper operation. It was meant to go "uphill" to determine where on the slope the first corals appear. Initially it all went well. A rough bottom with gravel and boulders. Scattered sponges, unidentified blue, yellow and red things were visible, probably also sponges. After approximately half an hour of towing the hopper camera along the bottom, we reached the coral zone. First scattered pieces were visible. Later somewhat bigger aggregations. But although the ship was sailing with a speed of half a knot, the preview picture on the online control system did not change anymore. Instead the camera tilted and was lifted to a position higher above the bottom. Ruud asked the winch driver to lower the camera another six meter and good was the view again. After 30 seconds the same happened again. Willem had to lower the camera again and the online picture was OK. This sequence repeated itself several times until we started wondering whether the hoppercamera was really moving or not. Checking with the bridge it appeared that the depth was only 500 meters and the winch driver had veered almost 900 metes of cable. There was evidently something wrong. We speculated that we were caught in a fishing line. The ship was stopped and started moving slowly backward while the kevlar cable with the suspended camera was hauled. Initially no extra tension was measured but once the cable had a length which corresponded to the water depth we had about 1 ton additional weight. This made it clear that indeed something was hanging on the hoppercamera. Slowly we continued hauling and once the frame came at the surface we saw a thick green nylon cable hanging over the frame. Clearly a fishing line. The green line was secured at the ship's side and simultaneously the hoppercamera was lowered, freeing itself from the line. Two of the connection cables of to the camera system were cut by the nylon line. We are lucky this time, it could have been worse. Rob Witbaar Royal NIOZ