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Abstract: The feasibility of using time domain of wavelet transform as characteristics to establish a fluorometric discrimination method of phytoplankton was discussed. Twelve phytoplankton species belonging to nine genera of five divisions were studied. Five steps were introduced: firstly, the feasibility of utilizing 3D fluorescence spectra (3D-FS) to discriminate phytoplankton was discussed; the relative standard deviation (RSD) and included angle cosine (IAC) were used as the test criterion. 3D-FS had such potentials, for most RSD were <5% and most IAC were >0.990. Secondly, the 3D-FS were decomposed by db7 wavelet and time-series vectors (TSVs) were generated. Thirdly, the optimal characteristic spectra (OCS) were selected from the TSV by Bayesian linear discriminant analysis (BLDA). The ability of OCS to classify phytoplankton was tested, and the correct classification ratios (CCRs) at different levels were obtained. Most CCRs were 90–100% at the species level. They were >98% at the genus level, and >99% at the division level. Fourthly, the growth and light stability of the OCS were tested. Both stabilities were high with lower RSD (<3%) and higher IAC (>0.999) compared with 3D-FS. Fifthly, a “database of reference spectra” consisting of 46 reference spectra was established by hierarchical cluster analysis (HCA). Based on this, the discrimination method of phytoplankton species was established by nonnegative least squares (NNLSs). Most reference spectra were representative to phytoplankton species; and had moderate anti-noise ability: With noise ≤10%, the correct discrimination ratios (CDRs) were >98% at the genus level and >99% at the division level. 20% noise was a larger interference which made CDRs down to 85% at the genus level and to 99% at the division level. A fluorometric discrimination method of phytoplankton could be established based on TSV of wavelet transform. [Copyright &y& Elsevier]

Abstract: Phytoplankton carbon and nitrogen production in newly opened waters of the Western Arctic Ocean were measured using a 13C–15N dual isotope tracer technique in summer 2008, when Arctic sea ice was at its second lowest extent since 1979. Daily integrated carbon-uptake rates were highest (675.8±931.3mgCm–2 d–1) in ice-free shelf regions of the Chukchi Sea. In deeper regions, the daily integrated carbon-uptake rates (73.5±45.0mgCm–2 d–1) in newly opened deep waters with adjacent sea ice cover (10–90%) were significantly higher than those (32.0±22.8mgCm–2 d–1) in ice-free deep waters. The average contributions of small cell-size phytoplankton (0.7–5μm) to total carbon-uptake rates were 19.8%, 62.8%, and 55.5% in shelf regions, ice-free deep waters, and newly opened waters, respectively, although the average biomass contributions of the small phytoplankton was 54.9–96.5% of total algal biomass in the three study areas. Daily total nitrogen-uptake rates were similar between newly opened deep waters and ice-free deep waters, although nitrate assimilation rates were higher in newly opened waters compared to ammonium uptake rates in ice-free waters. Lower carbon- and nitrate-assimilation rates in ice-free waters were due to strong stratification in the euphotic layer caused by melted sea ice, which limited nutrient availability to phytoplankton, although phytoplankton had greater light availability in ice-free waters than in newly opened waters. [Copyright &y& Elsevier]

Abstract: Flow cytometry (FCM) is efficient in detecting both abundance and optical physiological parameters including cell size and cellular carbon content—side scatter (SSC), carotenoids—green and orange fluorescence (FL1 and FL2), and red fluorescence—chlorophylls (FL3) can be obtained by FCM. The utilization of these physiological parameters in indicating water masses in Prydz Bay was investigated for the first time. Picophytoplankton were very sensitive to hydrophysical changes and present distinct characteristics of water masses: Picophytoplankton in water closer to the Amery Ice Shelf were more affected by salinity than by temperature, while temperature became more important than salinity the nearer the picophytoplankton were to the deep sea. The picophytoplankton dealt with declines in light by increasing the size of cells, which increase the fixation of carbon. This can also be increased by high temperature and salinity. Pure water masses can increase the content of chlorophylls and cellular carbon. Generally, the distributions of all the five parameters at upper water depths were less affected by temperature and salinity than by water masses; and these parameters can be as indicators to Summer Surface Water (SSW), Winter Water (WW) and Continental Shelf Water (CSW). [Copyright &y& Elsevier]

Abstract: An in vivo 3D fluorescence discrimination technique for ten harmful algal bloom (HAB) species that belong to eight genera of four divisions was developed by wavelet analysis. Daubechies-7 (db7) was employed as the mother wavelet. The fifth scale domains were selected as the discriminant characteristic spectra (DCS). Based on the DCS, The phytoplankton species at different growth stages were classified correctly at both the division and the genus level by Bayesian discriminant analysis (BDA). Based on the reference spectra of the DCS, the discrimination method of the phytoplankton species was established by the nonnegative least squares (NNLS) method. The correct discrimination ratios (CDRs) for samples of the single species were 96.1% with 0% blank noise and 93.3% with 10% noise at the genus level, while the CDRs were both 100% with 0% or 10% blank noise at the division level. When blank noise was up to 20%, the CDRs were down to 85.2% at the genus level and 98.0% at the division level. For the mixture samples, the CDRs of the dominant species were 98.3% and 96.3%, respectively, at the division level and at the genus level. As dominant species, Prorocentrum minimum (Pm), Gymnodinium simplex (Gs), Scrippsiella trochoidea (Sc), Skeletonema costatuma (Sk), Chaetoceros (Cu and De), Phaeocystis globosa (Cg) and Chlorella pynnoidosa (Ch) can be correctly discriminated at both the division level and the genus level. [Copyright &y& Elsevier]