Predicting the Electron Requirement for Carbon Fixation in Seas and Oceans

Marine phytoplankton account for about 50% of all global net primary productivity (NPP). Active fluorometry, mainly Fast Repetition Rate fluorometry (FRRf), has been advocated as means of providing high resolution estimates of NPP. However, not measuring CO2-fixation directly, FRRf instead provides photosynthetic quantum efficiency estimates from which electron transfer rates (ETR) and ultimately CO2-fixation rates can be derived. Consequently, conversions of ETRs to CO2-fixation requires knowledge of the electron requirement for carbon fixation (Φe,C, ETR/CO2 uptake rate) and its dependence on environmental gradients. Such knowledge is critical for large scale implementation of active fluorescence to better characterise CO2-uptake. Here we examine the variability of experimentally determined Φe,C values in relation to key environmental variables with the aim of developing new working algorithms for the calculation of Φe,C from environmental variables. Coincident FRRf and 14C-uptake and environmental data from 14 studies covering 12 marine regions were analysed via a meta-analytical, non-parametric, multivariate approach. Combining all studies, Φe,C varied between 1.15 and 54.2 mol e- (mol C)-1 with a mean of 10.9±6.91 mol e- mol C)-1. Although variability of Φe,C was related to environmental gradients at global scales, region-specific analyses provided far improved predictive capability. However, use of regional Φe,C algorithms requires objective means of defining regions of interest, which remains challenging. Considering individual studies and specific small-scale regions, temperature, nutrient and light availability were correlated with Φe,C albeit to varying degrees and depending on the study/region and the composition of the extant phytoplankton community. At the level of large biogeographic regions and distinct water masses, Φe,C was related to nutrient availability, chlorophyll, as well as temperature and/or salinity in most regions, while light availability was also important in Baltic Sea and shelf waters. The novel Φe,C algorithms provide a major step forward for widespread fluorometry-based NPP estimates and highlight the need for further studying the natural variability of Φe,C to verify and develop algorithms with improved accuracy. © 2013 Lawrenz et al

The clonal nature of circulating Sezary cells [published erratum appears in Blood 1996 Jun 1;87(11):4923]

To determine if circulating Sezary cells can be classified as reactive or neoplastic based on the ability to detect the presence or absence of clonal T-cell receptor beta chain (TCR-beta) gene rearrangements by Southern blot analysis, we evaluated the peripheral blood of 25 patients: 11 patients with Sezary syndrome (SS), 11 with benign inflammatory dermatoses (BID), and three normal controls. Three of 11 patients with SS, with Sezary counts ranging from 14% to 52%, did not demonstrate any clonal TCR-beta gene rearrangements in the peripheral blood, despite a TCR-beta rearrangement by Southern blot analysis in the skin. Ten of 11 BID patients and all normal controls showed no evidence of a TCR-beta gene rearrangement in the peripheral blood. However, one patient with psoriasis demonstrated a TCR-beta gene rearrangement in the peripheral blood. The TCR-beta gene rearrangement detected in this patient, confirmed with polymerase chain reaction (PCR) amplification of the TCR-gamma gene rearrangement, did not correlate with the presence of circulating Sezary cells or the increased risk of neoplasia. Our results indicate that circulating Sezary cells may be monoclonal (neoplastic) or polyclonal (reactive), as defined by TCR gene rearrangement studies. Circulating Sezary cells in SS may be reactive in nature and not accurately reflect the actual tumor burden in the peripheral blood. The presence of circulating Sezary cells or the presence of a clone of cells defined by TCR-beta gene rearrangement in the peripheral blood is not limited to neoplastic disease processes.</jats:p