Long-term quantitative observation of tubeworm colonies using an AUV

This paper proposes a comprehensive method to measure three dimensional distribution of tubeworms, a representative benthos of hydrothermal vent fields, for thousands of square meters by an autonomous underwater vehicle (AUV). Firstly, the AUV takes pictures and generates fine bathymetry of the seafloor through dense, low altitude scanning. The AUV can obtain accurate position in real-time with the aid of artificial landmarks. The three dimensional area of tubeworm colonies is then obtained using both the topological and visual features of seafloor. Finally, the quantitative value such as area, volume and average height of the colonies are obtained. The AUV Tri-Dog 1, a hovering type testbed, has been periodically deployed to the Tagiri vent field, Kagoshima Bay in Japan since 2006. The depth is around 100m and there exists the worlds shallowest tubeworm colonies. This paper reports the spatial and temporal distribution of the tubeworms revealed by series of deployments.