| Summary: | The Barents Sea is a highly seasonal and productive shelf ecosystem, representing a gateway between the Atlantic and Arctic Oceans. Anthropogenic climate change is causing rapid changes in temperature, ocean chemistry, water column structure and sea-ice persistence. Sea-ice extents are declining twice as fast in the Barents Sea as other Arctic regions, establishing a mandate to investigate the impact of these environmental changes on productivity in the Seasonal Ice Zone. This is the remit of Arctic PRIZE (PRoductivity in the Seasonal Ice ZonE), and this thesis was conducted under the auspices of work package 3, studying phytoplankton compositional and phenological variability. Remote-sensing is a key means by which ocean ecosystems are monitored and there have been recent efforts in the literature to employ ocean-colour to recognise different assemblages of phytoplankton. It is routine practice in the remote-sensing literature to distinguish functional assemblages from cell-counts and then seek bio-optical signatures to be targeted in remotely-sensed imagery. The analysis herein suggests that switching between different data types in this way introduces a translation error that undermines remote-detection efforts. We therefore recommend that functional assemblages are defined and identified directly from their bio-optical properties. Thereafter, a scheme of bio-optical functional types is defined, based on Barents Sea phytoplankton communities, and a bio-optical algorithm is developed with the aim of retrieving this structure in remotely-sensed ocean-colour. This algorithm is applied to study community compositional change, facilitating the integration of previous in-situ studies towards a more complete understanding of incipient ecosystem change. In addition, the ascendancy of temperate-mode autumnal phytoplankton blooms is investigated and relationships to evolving environmental conditions are explored, producing strong evidence that Atlantic inflow currents regulate the intensity of autumnal blooms in the ...
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