Plankton Survey System (PSS)

The plankton survey system (PSS) components have arrived at GLERL and are being tested out and assembled for our first pilot cruise on the R/V Lake Guardian on January 20. The PSS underwater assembly (443k jpeg) includes the Focal Technologies Mini-Optical Plankton Counter (OPC), the Ocean Sciences OS-200 CTD with X-Y tilt sensor, and a Chelsea Aquatracka III fluorometer (logarithmic amplifiers, chlorophyll range: 0.1-100 ug/L) mounted on an Endeco/YSI Type 493 V-fin (443k jpeg). A four conductor tow cable is used to provide power to and receive data from the OPC and to provide separate power to the CTD. The PSS will be towed in a vertically undulating (tow-yowed) mode as the ship travels at about 2.5 m/s to determine vertical structure of plankton and related physical variables along the ship's path.

On the deck, two personal computers are used to collect data and monitor the PSS. The data collection PC runs the OPC software provided by Focal. This software displays plankton counts and size, light attenuance, flow rate, depth and GPS information. The software also serves as the data acquisition system for all data including conductivity, temperature, pressure, fluorescence, pitch and roll. Since the PSS will be used in shallow water, very accurate depth and GPS location will be required. This information is provided by a differential GPS and depth sounder and monitored on a second PC. This monitoring system will display V-fin attitude as well as the bottom contour in front of the system. This will allow accurate control of PSS depth using a joystick winch control. For more detail, see the block diagram (339k gif).