Sep 26, 2016
One of Hydromea’s VERTEX AUVs provided the first 3D map ever of water
quality parameters of Lago Cadagno in Ticino, Switzerland. The AUV was
fitted with a complete EXO2 sonde from YSI measuring a multitude of
parameters such as temperature, oxygen, turbidity and Chlorophyll-A in
parallel. In addition to the EXO2 sonde, the AUV also carried a custom
fast temperature sensor developed by Hydromea, capable of measuring
temperature with a sub milli-Kelvin resolution at a rate of 250 samples
per second.
The mapping effort is part of a 3 year collaborative project between
Hydromea, Ecole Polytechnique in Lausanne (EPFL) and the University of
Geneva. Lago Cadagno is of particular scientific interest as it is
clearly divided between an upper and a lower layer and remains
permanently stratified. Between those two layers a very dense layer of
anaerobic and phototrophic bacteria causes bio-convection, a very rare
phenomenon in nature. The fast temperature sensor was deployed to
examine the bio-convection phenomenon by measuring millimeter-sized
turbulence caused by the bacteria.
The VERTEX was particularly well suited to map the bacterial layer.
Its small size (70cm, 7kg) allowed for a deployment from a small
platform. Using its unique thruster configuration it was able to move
forward at a very slow speed (20cm/s) to account for the sensor response
time, while remaining level.
Upcoming experiments will see up to 5 VERTEX AUVs deployed
simultaneously to investigate complex physical-biological phenomena in
Swiss lakes.