Biomarker Pigment Divinyl Chlorophyll a as a Tracer of Water Masses?

The ecological preferences of different Phytoplankton types drive their temporal and spatial distributions, reflecting their dependence on certain temperature ranges, light levels, nutrient availability and other environmental gradients. Hence, some phytoplankton taxa can be used as water mass tracers (biotracers)

Phytoplankton size structure and species composition as an indicator of trophic status in transitional ecosystems: the case study of a Mediterranean fjord-like karstic bay

The species composition and size-structure of the phytoplanktoncommunity in the Boka Kotorska Bay (SE Adriatic Sea) were analysed withrespect to abundance and carbon biomass, together with the physico-chemicalparameters, with the aim of evaluating the predefined oligo-mesotrophicstatus of this transitional water ecosystem. Three stations locatedin the inner part of the Bay were sampled with seasonal frequencyin 2008/2009. Picophytoplankton cells were counted using flowcytometry; nanophytoplankton and microphytoplankton were identifiedand counted by light microscopy. The relative importance of thepicoplankton in the Bay, in terms of both abundance and biomass,during all the investigated seasons emphasized their significancein the phytoplankton community. Picocyanobacteria (Synechococcus)constituted a significant part of the summer assemblages withregard to both abundance (up to 3.38 × 108 cellsL-1)and carbon biomass (up to 73% of total phytoplankton carbon).The contribution of the nanophytoplankton was found to be generallylow (Skeletonema marinoi, dominated the microphytoplanktonfraction. S. marinoi was the most abundant in spring/winter(up to 2.86 imes 106 cells L-1) above the halocline(making a 96% contribution to the microphytoplankton). The potentiallytoxin-producing diatom Pseudo-nitzschia pseudodelicatissimawas recorded at abundances greater than 105 cells L-1, togetherwith Thalassionema frauenfeldii, as well as the dinoflagellatesProrocentrummicans and the potentially harmful P. minimum. The higher valuesof phytoplankton biomass and the dominance of phytoplankton speciesor groups with preferences for nutrient-enriched conditions appear tobe consistent with the oligo-mesotrophic status of this specific ecosystem

Interoperable vocabulary for marine microbial flow cytometry

The recent development of biological sensors has extended marine plankton studies from conducting laboratory bench work to in vivo and real-time observations. Flow cytometry (FCM) has shed new light on marine microorganisms since the 1980s through its single-cell approach and robust detection of the smallest cells. FCM records valuable optical properties of light scattering and fluorescence from cells passing in a single file in front of a narrow-collimated light source, recording tens of thousands of cells within a few minutes. Depending on the instrument settings, the sampling strategy, and the automation level, it resolves the spatial and temporal distribution of microbial marine prokaryotes and eukaryotes. Cells are usually classified and grouped on cytograms by experts and are still lacking standards, reducing data sharing capacities. Therefore, the need to make FCM data sets FAIR (Findability, Accessibility, Interoperability, and Reusability of digital assets) is becoming critical. In this paper, we present a consensus vocabulary for the 13 most common marine microbial groups observed with FCM using blue and red-light excitation. The authors designed a common layout on two-dimensional log-transformed cytograms reinforced by a decision tree that facilitates the characterization of groups. The proposed vocabulary aims at standardising data analysis and definitions, to promote harmonisation and comparison of data between users and instruments. This represents a much-needed step towards FAIRification of flow cytometric data collected in various marine environments