Application of modern technology is considered one of the most critical factors for success in the challenging investigations MAR-ECO is aiming for. Substantial effort has therefore been invested in fitting RV G.O. Sars properly. In the end of April a test cruise was carried out onboard RV G.O. Sars.
Lander onboard RV G.O. Sars. Photo: Thomas de Lange Wennck
By: Olav Rune Godų, cruise leader
On the Mar-Eco cruise onboard RV G.O. Sars in June- July 200, technology is demanding. In fact, one of the driving forces behind the cruise is the new research vessel with its up-to-date technology.
Application of modern technology is considered one of the most critical factors for success in these challenging investigations. Substantial effort has therefore been invested in fitting RV G.O. Sars properly. A part of this has been done on two technology test cruises. One international cruise was carried out in November 2002, and in the end of April 2004 three days was spent on further tests of the functions of important equipment to be used during the cruise.
Going through the routines in the wet lab. Photo: Thomas de Lange Wennck
The April tests were focused on three issues; Operation of towed and anchored platform, simultaneous operation without disturbance of several acoustic instruments and operation of sampling instruments. On the agenda were also discussions on procedures and routines to secure the quality of the results.
Operation of towed and anchored platform
A towed body with two acoustic frequencies was tested on RV G.O. Sars for the first time. This vehicle will extend the range of the echosounders and improve resolution of acoustic layers at the deep water. The tests went well and only minor adjustments are needed before cruise start. We also trained the crew in launching and retrieving a stationary autonomous acoustic platform (see picture to the left). Three platforms of this type will be launched during leg 1 of the cruise and retrieved during leg 2. They will record vertical density distribution in their location including diurnal variation and more long-term trends. Finally, for the first time a new depressor vehicle (see picture below) was equipped with a EK 60 echosounder and operated with battery power during two runs. The results were promising and give us an opportunity for a replacement vehicle for the towed body (see above). Still some work remains and economic constraints may prevent this work to be completed.
Lander. Photo: Terje Torkelsen
Simultaneous operation without disturbance of several acoustic instruments
Depressor. Photo: Terje Torkelsen
Acoustic instruments disturb each other if not properly controlled. In our case we want to run five echosunder frequencies, one acoustic current profiler, a bottom mapping echo sounder and a sonar. As the information we collect is going to be used to quantify biomass, and physical and biological processes, it is important that the data are not contaminated with noise from other instruments. Further, the depth of operation at the Mid Atlantic Ridge, represent another challenge for efficient operation of multiple acoustic instruments. Communication among the involved instruments allowed us to establish a system for ping control that gives us the possibility to run all the mentioned instruments simultaneously.
Operation of sampling instruments
The multisampler instrumentation makes it possible to collect three samples during fish trawling and five samples during macro zooplankton trawling. A device opening and closing multiple codend facilitates this. Taking into consideration the time consumed for operating trawls at large depths, the device is extremely important for the efficiency of the survey. The challenge is twofold. In cooperation with the producer of the communication link to the multisampler we are developing automatic software based opening and closing system. This is necessary as the distance between trawl and vessel will be too long to communicate reliably. The producer will supply us with this update of the equipment. Further, the multisampler is not built for standing the depths of our operation and both flotation and containers for the electronics need to be renewed. We tested glass spheres as flotation during the test cruise with successful results. We have experience in fitting instruments into these glass spheres. Presently we are working on fitting the multisampler electronics into the flotation spheres.
Multisampler. Photo: Thomas de lange Wenneck
Also, we had a telecommunication company onboard to expand communication capacity and range of GO Sars to cope with the demands during the cruise. In addition to the technology work we also tested sampling routines for fish and plankton. Also, system for tracability of the collected biological material was discussed and routines developed. Finally, we had several discussions on problems and challenges associated with the data management. All in all, these few days were very useful and may be even crucial for elements of our mission at MAR. The realistic testing of sampling routines and discussions on data management with the involved expertise was also welcome.
Satelite. Photo: Anette W. Petersen