Anjali Narayanan
Abstract: The Arctic Ocean is experiencing unprecedented environmental change impacting all aspects of the marine ecosystem, including phytoplankton community composition and higher trophic levels of the marine food web. Studying the impact of long-term environmental change on phytoplankton and subsequent implications for food web, biogeochemical cycling and carbon export is enabled by unique capabilities offered by optical measurements that can be conducted over extended spatial and temporal scales, such as ocean color observations from space. Thus, development of optically-based algorithms for assessment of phytoplankton community composition in the ocean has been of particular interest in recent years, especially for applications using satellite ocean color observations. Although there have been efforts to develop such algorithms, they are limited to observations from lower latitudes and have not been evaluated in the Arctic. I will present the progress we have made towards the development of an operational ocean color algorithm to determine phytoplankton size classes (PSCs) from optical measurements in the Arctic using phytoplankton pigment composition and optical data compiled from four cruises in the Chukchi and Beaufort Seas. We use diagnostic phytoplankton pigment biomarkers to partition data into three distinct PSCs associated with picophytoplanton (dominant cell size <2 µm), nanophytoplankton (2-20 µm), and microphytoplankton (>20 µm), which can be linked to optical measurements. In this talk, I focus on the characterization of the spectral absorption coefficient of phytoplankton (aph), the inherent optical property most directly related to phytoplankton. I will discuss variations in the spectral shape of aph which exhibits significant differences with varying proportions of small (pico) and large (micro) sized phytoplankton cells in the total assemblage. This initial analysis indicates that some relatively simple spectral parameters derived from aph spectra alone provide an efficient means to discriminate between the microphytoplankton-dominated assemblages and other phytoplankton assemblages in the Arctic waters. Further work is ongoing to extend this analysis by including other optical measurements, such as the spectral backscattering coefficient and spectral remote-sensing reflectance of the ocean, to enhance the capability of optical approach to distinguish distinct PSCs and its ultimate application to satellite ocean color observations and possibly also in situ optical measurements from autonomous platforms. Contact: anarayan@ucsd.edu
Bio: Anjali Narayanan is a Ph.D. student in the Ocean Optics Research Laboratory working with Drs. Rick Reynolds and Dariusz Stramski studying phytoplankton community composition in the Arctic Ocean. She received her B.Sc. in mathematics from McMaster University. When not working, Anjali enjoys binging reality TV, doing yoga, or people watching with her two cats. Contact: anarayan@ucsd.edu