Application of an underwater hyperspectral imager (UHI) for the study of sea ice algae

Abstract

Sea ice provides an important habitat for sea ice algae, the main primary producers in sea ice covered ocean areas. In order to reliably estimate sea ice algal distribution and production, it is important to develop remote sensing methods that can provide these estimates with minimal coring. Underwater hyperspectral imagers (UHI) can capture fine-scale variability in the transmitted spectral profile directly below the sea ice-water interface, which then can be related to core-derived chlorophyll a concentration, providing estimates of in situ chl a biomass across spatial scales. The aim of this research was to obtain optimal NDI wavelength combinations for in situ and in vivo surveys using two different approaches – standardized radiance and transmittance and using the resultant model for mapping fine scale (mm) chlorophyll a distribution. Results indicated successful application of laboratory-based NDI-combinations for estimating fine-scale chl a biomass variability in a natural fjord system. Combining the model with O2-based laboratory experiments, fine scale differences in net community production relative chlorophyll a was be estimated for UHI surveys from two contrasting Svalbard fjords, Tempelfjorden and Van Mijenfjorden. Additionally, the effect of accessory pigments, with a focus on fucoxanthin, on bio-optical models was investigated.