On the use of the HUGIN 1000 HUS Autonomous Underwater Vehicle for high resolution zooplankton measurements

This paper evaluates and tests the HUGIN 1000 HUS AUV as a carrier platform for the Laser Optical Plankton Counter (LOPC). The LOPC was mounted outside on top of the carrier platform, and the tests confirm that this concept did not create turbulence and zooplankton avoidance. A negligible velocity difference between the flow passing through the sampling tube and the AUV speed was detected. The abundance recorded by the LOPC onboard HUGIN 1000 HUS was within the same order of magnitude compared to the zooplankton abundance from traditional net-based measurements. The results showed zooplankton abundance in the range of 70 to 180 individuals m(-3), while other, traditional net-based measurements have indicated 27-332 individuals m(-3) from the same area and same depth layer. Note that these numbers are minimum and maximum values observed from a vast number of samples. The mean is approximately 200 individuals m(-3). The results provide new and unique high-resolution biological data of deep-water copepod communities. The application of AUVs in marine ecological research introduces advanced methodology with potential to address new scientific questions in deep water habitats.