Tuesday, December 15, 2009

Cabled observatory in Loch Etive (Scotland) successfully deployed

On 28.11.2009, Henrik Stahl and coworkers from the HYPOX team at the Scottish Association of Marine Science (SAMS) successfully deployed a cabled observatory in the upper basin of Loch Etive. The deployment took place at best weather conditions with almost no wind after a several week long bad weather period - not unusual at Scotlands west coast at this time of the year. The calm weather allowed to lay the 1200m long cable from the center of Loch Etive to the base station at the shore. Deployment works started out early in the morning with three boats involved: One for deploying the mooring, one for laying the underwater cable and another smaller boat for taking the last bit of the cable into shore. Thanks to the eminent crew of the boats and the marine Technology/Physics department at SAMS everything went according to plan. After plugging in the cable and switching on the power the instruments came alive right away sending data through the cable. The next step is now to connect the base station to the internet for making the data available online in real-time.

Fig. 1: RV Calanus (SAMS) and a supplementary vessel involved in deployment works

Fig. 2: Laying out the underwater cable

Fig. 3: The recording current meter and data processing and communication unit during deployment

First HYPOX observatory deployed in the Koljö Fjord area, Sweden

Per Hall, Anders Tengberg, and coworkers from the HYPOX team at Gothenburg University (UGOT) deployed the first HYPOX observatory in the Havstens Fjord. Havstens Fjord is located in the Koljö Fjord area and supplies the Koljö Fjord with water. After successful testing in October 2009 a string type observatory was deployed on 3.11.2009. The deployment is planned to continue until at least March 2010.
The string observatory hosts three oxygen optodes and four sensors for conductivity (salinity) distributed at water depths between 6 and 18m. At the lower end of the string (at ca 25 m water depth) there is a recording current meter (“Seaguard”, AADI, Norway), measuring currents and pressure (depth and sea level change), and logging all sensor data. Temperature is measured at all depths. For future deployments, a total of fourteen sensors can be connected to the string at seven different depths at a vertical distance of 3m. To prevent damage from ice cover in winter the string is deployed without surface buoy.

The string-type observatory on deck of the UGOT R/V Skagerak just before deployment (photo: Per Hall, UGOT).

Autumn-expedition to the Tarkhankut gas seep region by HYPOX partner IBSS

In November 2009, the Institute of Biology of the Southern Seas (IBSS) performs a land-based expedition to the Tarkhankut gas seeps region – a shallow area near the Crimea Peninsula. In continuation of the last field trip in September the intention is to follow up on the former investigations and to monitor seasonal changes that may occur. The observations conducted include physico-chemical as well as biological parameters:

Water column above the gas seeps: Dissolved oxygen, oxygen demand, temperature, pH

Seep-associated microbial mats: Sulfide and oxygen, redox-potential, pH, organic matter content (unstable and stable); micro- and macrozoobenthos under hypoxic conditions.

Preliminary conclusions:

Hypoxic conditions in the seep associated microbial mats as well as in the nearby water column prevail also in late autumn. However, compared to the situation in September, oxygen was found to penetrate deeper into the mat while sulfide concentrations decreased. Higher organisms adapted to microbial mats were observed to tolerate high sulphide concentrations and oxygen depletion for at least two months.

Fig. 1: Natasha Orekhova and Yury Vnukov in front of a profiling device that advances microsensors for oxygen and sulfide at 1mm steps into microbial mats (photo - M.Gulin).

Video: Vitaly Timofeev (diving) and Maksim Gulin (operating the rubberboat) take samples of mats, zoobenthos, and the water column (video - N.Orekhova).

Sunday, December 13, 2009

Oxygen optode calibration workshop at the Max Planck Institut in Bremen (9.-11.12.09)

The Max Planck Institute for Marine Microbiology in Bremen (MPI, www.mpi-bremen.de) hosts a three-day workshop on the calibration of macro oxygen optodes. These sensors, that are manufactured by the Aanderaa Data Instruments in Norway (AADI; www.aadi.no), determine dissolved oxygen concentrations based on the changes in optical properties of an oxygen sensitive fluorophor. Due to their outstanding long-term stability and their insensitivity to pressure, macro oxygen optodes have become a standard tool for long term monitoring of dissolved oxygen in the water column and will be the main sensor type used for oxygen monitoring in HYPOX. The main goal of the workshop is to test a simplified procedure for the calibration of these sensors. This is done by exposing optodes of unknown or outdated calibration (“test optodes”) and known calibration (“reference optodes”) to a large variety of temperatures and oxygen partial pressures in a big airtight calibration vessel. Different partial pressures are established when water temperature (and, hence, oxygen solubility) is changed in the vessel. By running a temperature gradient at several oxygen concentrations the entire range of environmentally relevant temperatures and oxygen partial pressures can be covered with a reasonable effort. The workshop was attended by eight people from the Gothenburg University, the MPI, and AADI.

The workshop participants (Photograph: M. Schloesser, MPI)

Close up of the optodes in the calibration vessel (Photograph: M. Schloesser, MPI)

M. Holtappels and F. Janssen filling the calibration vessel (Photograph: M. Schloesser, MPI)