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Spectral fluorescence measurements of phytoplankton chlorophyll a (Chl a ), phytoplankton phycobilipigments and variable fluorescence (Fv/Fm), are utilized with High Performance Liquid Chromatography (HPLC) estimates of phytoplankton pigments and microscopic cells counts to construct a comprehensive picture of summer-time phytoplankton communities and their photosynthetic competency in the eastern Bering Sea shelf. Although the Bering Sea was ice-free during our study, the exceptionally cold winter that preceded the summer of 2008 when our cruise took place, facilitated the formation of a “Cold Pool” (<2 °C) and its entrapment at depth in the northern middle shelf. The presence of a strong pycnocline over the entire middle and outer shelves restricted inorganic nutrient fluxes into the surface waters resulting in phytoplankton populations that were photo-physiologically stressed due to nutrient limitation. Elevated Chl a concentr a tions recorded in the Green Belt along the shelf edge of the Bering Sea, were due to Phaeocystis pouchetii and nano-sized cryptophytes. Although inorganic nutrients were not limiting in the Green Belt, Fv/Fm values were low in all probability due to iron limitation. Phytoplankton communities in the low biomass surface waters of the middle shelf were comprised of prasinophytes, haptophytes, cryptophytes and diatoms. In the northern part of the middle shelf, a sinking bloom made up of the centric diatoms Chaeotoceros socialis , Thalassiosira nordenskioeldii and Porosira glacialis was located above the Cold Pool. The high biomass associated with this senescent bloom and its accretion above the pycnocline, suggests that the Cold Pool acts as a barrier, preventing sinking phytoplankton from reaching the bottom where they can become available to benthic organisms. We further posit that if summer-time storms are not energetic enough and the Cold Pool is not eroded, its presence facilitates the transfer of the large spring phytoplankton bloom to the pelagic ecosystem. [ABSTRACT FROM AUTHOR]

Abstract: Phytoplankton cell density, chlorophyll a (chl a) concentration and pigment data collected during a series of five cruises in the northern Arabian Sea in the Northeast Monsoon (NEM, Nov–Jan) and the Spring Intermonsoon (SIM, Mar–May) since 2003 contradicted the established notion that winter blooms mainly consist of diatom communities. Recent data show that following the NEM and well into the SIM, phytoplankton populations are dominated by the dinoflagellate Noctiluca miliaris Suriray (synonym Noctiluca scintillans Macartney). In the SIM they were often in association with the well-known blooms of the diazotroph Trichodesmium sp. Large blooms of N. miliaris have also begun making their appearance annually in the Gulf of Oman and off the coast of Oman. This study uses NASA''s recently developed product of merged SeaWiFS and Aqua-MODIS chl a data to investigate the temporal evolution and spatial extent of these taxonomically validated blooms. Satellite chl a in relation to Aqua-MODIS SST and altimetry data suggest that mesoscale eddies that populate the western Arabian Sea during the NEM contribute to the genesis and dispersal of these blooms from the Gulf of Oman into the central Arabian Sea. [Copyright &y& Elsevier]

Presents information on a study which described a method used for estimating sea surface nitrate from space using satellite measurements of sea surface temperature and chlorophyll. Materials and method; Results and discussion; Conclusions.

The accurate retrieval of chlorophyll-a concentration (Chl-a) from ocean color satellite data is extremely challenging in turbid, optically complex coastal waters. Ariake Bay in Japan is a turbid semi-enclosed bay of great socio-economic significance, but it suffers from serious water quality problems, particularly due to red tide events. Chl-a derived from the MODerate resolution Imaging Spectroradiometer (MODIS) sensor on satellite Aqua in Ariake Bay was investigated, and it was determined that the causes of the errors were from inaccurate atmospheric correction and inappropriate in-water algorithms. To improve the accuracy of MODIS remote sensing reflectance (Rrs) in the blue and green bands, a simple method was adopted using in situ Rrs data. This method assumes that the error in MODIS Rrs(547) is small, and MODIS Rrs(412) can be estimated from MODIS Rrs(547) using a linear relation between in situ Rrs(412) and Rrs(547). We also showed that the standard MODIS Chl-a algorithm, OC3M, underestimated Chl-a, which was mostly due to water column turbidity. A new empirical switching algorithm was generated based on the relationship between in situ Chl-a and the blue-to-green band ratio, max(Rrs(443), Rrs(448)/Rrs(547), which was the same as the OC3M algorithm. The criterion of Rrs(667) of 0.005 sr−1 was used to evaluate the extent of turbidity for the switching algorithm. The results showed that the switching algorithm performed better than OC3M, and the root mean square error (RMSE) of estimated Chl-a decreased from 0.414 to 0.326. The RMSE for MODIS Chl-a using the recalculated Rrs and the switching algorithm was 0.287, which was a significant improvement from the RMSE of 0.610, which was obtained using standard MODIS Chl-a. Finally, the accuracy of our method was tested with an independent dataset collected by the local Fisheries Research Institute, and the results revealed that the switching algorithm with the recalculated Rrs reduced the RMSE of MODIS Chl-a from 0.412 of the standard to 0.335. [ABSTRACT FROM AUTHOR]

The Labrador Sea is known for strong surface heat losses and deep ocean ventilation in the wintertime as well as high biological productivity and carbon export associated with extensive spring blooms. Using satellite-derived estimates of chlorophyll-a and net primary productivity, this study documents that the Labrador Sea has recently become more productive, evident in the form of more intense and spatially extensive phytoplankton blooms. The spatial and temporal variability in chlorophyll-a was compared against trends in nutrient concentrations across the Labrador Sea. Nutrient concentrations were obtained on a repeat hydrography line running from the Labrador to Greenland shelves. The 25-year long time series of nitrate, phosphate and silicate concentrations along the AR7 W line reveal decadal trends in the upper Labrador Sea. A comparison of these nutrients with basin-averaged annual mean surface chlorophyll-a concentrations reveals positive correlations in the upper 1000 m of the Labrador Sea. Furthermore, nutrient concentrations in the upper 1000 m were strongly correlated with wintertime convection depth. During years of strong winter convection, more nutrients are entrained from the deeper Labrador Sea, which then can be distributed through the Western Greenland and Irminger Currents and eddy activity, allowing sustained phytoplankton growth further north in the Labrador Sea. • Multidecadal increases in chlorophyll-a and NPP are observed in the Labrador Sea. • Upper layers are richer in nutrients during years of high biological productivity. • Wintertime convection is influencing long term variability in nutrient concentrations. [ABSTRACT FROM AUTHOR]