ROV and bio-optics

 

Klaus Meiners and Jessica Melbourne-Thomas

During the SIPEX-2 voyage, the Remotely Operated Vehicle (ROV) will be used to study physical and biological properties of sea ice. Sea ice, which is frozen sea water, consists of two phases: solid ice and brine. The brine fills an interconnected network of pockets that provide a habitat for so-called ice algae. These microscopic algae, especially those living at the bottom of ice floes, are considered as an important food source for Antarctic krill during late winter and spring. Krill are shrimp-like crustaceans that are in turn a key food source for penguins, seals and whales. Information on the biomass and distribution of ice algae is very scarce.

One of the methods of estimating ice algal biomass is using the instrumented Remotely Operated Vehicle (Figure 1). We will deploy the vehicle (which is about the size of two large suitcases) through a hole in the ice and pilot it via a 400m long fibre-optic tether. The ROV is instrumented with a positioning system, an up-ward looking sonar and hyperspectral radiometer (a very accurate light sensor), and a depth sensor. With these sensors we can locate the ROV, estimate the thickness of the ice, measure the amount of under-ice light that is available for algal growth, and importantly can also estimate the amount of algal living within the ice. The latter is achieved by measuring the effect that algal pigments have on the colour distribution of the under-ice light.

Additional cameras will be used to observe larger organisms living under the ice, e.g. Antarctic krill. The ROV mounted sensors will provide us with a wealth of information on the distribution of ice algae. In comparison with the classical method of ice-coring, the use of the ROV allows us to quantify ice algal biomass on the sea ice floe-scale.

We will analyse the ROV data in combination with both the AUV and surface measurements to better understand the coupling of physical and biological processes in the sea ice zone, e.g. relationships between sea ice thickness and ice algal biomass. Understanding these processes will help to assess climate change impacts on life in the frozen parts of the Southern Ocean. 

Klaus Meiners Klaus.Meiners@aad.gov.au

Jessica Melbourne Thomas Jessica.MelbourneThomas@utas.edu.au