A test of an autonomous underwater vehicle as a monitoring tool in shallow water

Abstract

The utility of micro-autonomous underwater vehicles (AUVs) to detect hydrographic features that concentrate phytoplankton cells was evaluated during a study in a shallow tidal estuary. This study represented the first field test of Ranger^™, a micro-AUV adapted for environmental applications. Four micro-AUVs were launched from a small vessel anchored in the Newport River, North Carolina, USA, in March 2003. Each AUV was equipped with a CTD sensor to measure depth, conductivity and temperature. They were programmed to operate autonomously in a prescribed area, moving back and forth over a 0.4km path, while undulating from the surface to the bottom for a period of ∼2.5h. The study tested the ability of AUVs to detect a hydrographic feature (salinity frontal zone) associated with high phytoplankton abundance. In the course of the mission, the four AUVs collected approximately 145 000 discrete CTD measurements, which were used to map the progressive development of a salinity front in the estuary. The front was associated with more than a two-fold increase in phytoplankton fluorescence, illustrating the tight coupling between phytoplankton accumulation and hydrographic forcing in this system.

Keywords:

• AUV
• ENVIRONMENTAL MONITORING TECHNOLOGY
• ESTUARINE PHYTOPLANKTON
• SALINITY FRONT