Although aquatic hypoxia can occur naturally, it is mostly attributed as a consequence of pollution and excessive loads of nitrogen from fertilizers, sewage and other sources that feed algal blooms in coastal water. Equipped with an Dissolved Oxygen (DO) sensor, an AUV can act as a mobile sensor node and be deployed around the coastal water to detect hypoxic layer at different water depth autonomously. With its capabilities in terms of mobility and mission adaptability, it not only able to provide a higher quality data collection, but also enable spatial-temporal sensing in the water column.
We equipped the Iver3-350 class AUV with a DO sensor (see picture above) and conducted field experiments at two separate sites around the Chesapeake Bay area, to detect and monitor hypoxia layer during the summer of 2015. The first site is the Swan Point, MD., which is close to the state line between Maryland and Delaware states. The second site is around the shorelines of the Pooles Island (see picture below). Besides validating the sensors’ operational performance, the results from the field experiments also helped to motivate the potential application of the AUV in environmental sensing and monitoring. The results clearly showed that there was a hypoxic layer at the bottom of the mission area, where the dissolved oxygen level dropped to around 0 mL/L.
Picture credit: M. Kobilarov