Optical impact of an Emiliania huxleyi bloom in the frontal region of the Barents Sea

The impact on downwelling irradiance of phytoplankton, cromophoric dissolved organic matter (CDOM) and particulate inorganic carbon (PIC) in the form of coccoliths, is described using a radiative transfer model and field data from the Barents Sea (BS). While annual Emiliania huxleyi blooms in the BS have been detected with satellite remote sensing, this is the first bio-optical field study on E. huxleyi from this area. Bio-optical variables were measured in August 2007 along a transect through the Polar Front from Arctic Water (ArW) into an E. huxleyi bloom in Atlantic Water (AW). The depth of the euphoric zone was on average 52 m in ArW, 45 m in frontal mixed water (FMW) and 21 m in AW. At the 10% irradiance depth in AW, phytoplankton had attenuated 40%, CDOM 17% and PIC 18% of the irradiance from 400 to 700 nm. Numbers from ArW were 36%, 26% and <1%, respectively. The relative potential for Primary Production (PPpot) in AW was 1.8x higher than in ArW, and PIC had reduced PPpot in AW by 20-40% at stations with similar to 100-130 mg PIC m(-3). A novel approach for estimating PIC based on a theoretical relationship between diffuse attenuation and irradiance reflectance is also described. (C) 2012 Elsevier B.V. All rights reserved.