RV Tangaroa voyage update
RV Tangaroa has just completed its last full day of sampling around the waters of Hunga Tonga-Hunga Ha’apai (HT-HH).
30 April 2022
At 8am, Tangaroa arrived at the active hydrothermal vent system where Bathymodiolus sp mussels occur on the seabed. They tend to grow in great numbers close to where hot sulphur-rich water wells up through the ocean floor. These hydrothermal ecosystems are vulnerable to external environmental factors and the impacts of the volcanic ashfall needed to be assessed.
Two deployments of the Deep Towed Imaging System (DTIS) showed images of bacterial mats, sulphurous sediment and beds of mussels, but no obvious signs of volcanic ash. A CTD (Conductivity, Temperature and Depth probe) with water sample rosette was deployed in the middle of a nearby hydrothermal vent field to measure and analyse the oceanographic properties of the water at this site. A DTIS and epibenthic sled were later deployed on a nearby slope, between the hydrothermal vents area and Tongatapu. We took images and sampled small fish, anemones and crabs.
More bathymetry data was collected using the multibeam echo sounder along the international cable, which was broken by the Jan 15th eruption, to gather more evidence as to what caused the cable to break. Surface water was also collected to analyse the presence of trace metals from the eruption and see if these amounts are toxic or nutritious for marine life.
