Pigment Analysis Research Articles

Changes in the Community Structure of Under-Ice and Open-Water Microbiomes in Urban Lakes Exposed to Road Salts.

Salinization of freshwater is increasingly observed in regions where chloride de-icing salts are applied to the roads in winter, but little is known about the effects on microbial communities. In this study, we analyzed the planktonic microbiomes of four lakes that differed in degree of urbanization, eutrophication and salinization, from an oligotrophic reference lake with no surrounding roads, to a eutrophic, salinized lake receiving runoff from a highway. We tested the hypothesis that an influence of road salts would be superimposed on the effects of season and trophic status. We evaluated the microbial community structure by 16S rRNA sequencing for Bacteria, and by four methods for eukaryotes: 16S rRNA chloroplast analysis, 18S rRNA sequencing, photosynthetic pigment analysis and microscopy. Consistent with our hypothesis, chloride and total nitrogen concentrations were among the most important statistical factors explaining the differences in taxonomic composition. These factors were positively correlated with the abundance of cryptophytes, haptophytes, and cyanobacteria. Ice-cover was also a major structuring factor, with clear differences between the winter communities and those of the open-water period. Nitrifying and methane oxidizing bacteria were more abundant in winter, suggesting the importance of anaerobic sediment processes and release of reduced compounds into the ice-covered water columns. The four methods for eukaryotic analysis provided complementary information. The 18S rRNA observations were strongly influenced by the presence of ribosome-rich ciliates, but revealed a much higher degree of taxonomic richness and greater separation of lakes, seasonal changes and potential salinity effects than the other methods.

Comparative characterization of two cyanobacteria strains of the order Spirulinales isolated from the Baltic Sea - polyphasic approach in practice

With the improved understanding of the cyanobacterial diversity, the polyphasic approach has become a widely accepted way to classify the organisms. The aim of the study was to describe and compare phenotypic and molecular traits of two strains of filamentous, helically coiled cyanobacteria CCNP1310 and 06S082, originating from different habitats of the Baltic Sea. Genotypic and phylogenetic analyses were focused on 16S rDNA, cpcBA-IGS and mcyE target sequences, while the phenotypic characterization included morphology, ultrastructures visualized with transmission electron microscopy, pigment and other metabolite profiles, determined with high-performance liquid chromatography and liquid chromatography-mass spectrometry, respectively. Results indicated that both tested strains belong to the Spirulinales order. 16S rDNA phylogeny confirmed that in the case of the analyzed microorganisms, cryptic diversity may occur. The final reclassification of this order requires analysis of a larger group of strains. Despite the high morphological similarity, the strains showed significant differences in the produced metabolites. The analysis of photosynthetic pigments indicated that in the cyanobacteria of the order Spirulinales the model of response to changing light regime might be preserved even after a long time of growth in culture. Cyanometabolite profiles determined spectrometrically showed that the characterized organisms differ in terms of the produced metabolites. The presented, comprehensive characterization of the strains can also be useful in further studies on the diversity, taxonomy, and metabolic potential of cyanobacteria of the order Spirulinales.

Contrasting phytoplankton and biogeochemical functioning in the eastern Arabian Sea shelf waters recorded by carbon isotopes (SW monsoon)

This study examines the relationship between the isotopic signature of phytoplankton-derived particulate organic matter (POM) (δ13CPOC) and estimates of growth rate and community composition along a north-south gradient in the western Indian shelf waters which possess contrasting biogeochemistry and mixed layers depths. The Eastern Arabian Sea/western Indian shelf turns highly productive due to the SW monsoon induced upwelling at its southern region and experiences drastic seasonal reversal. We have characterized the POM pool by quantifying Chla, particulate organic carbon (POC) and particulate nitrogen (PN), C:N ratios, along with δ13CPOC values during the SW Monsoon. The prevailing physicochemical features contrasted between the southern (8°N to 12°N) and northern (13°N to 21°N) stations. Close couplings between POC, PN, and Chla contents indicated the autochthonous nature of POM. Low temperature, shallow mixed layer depths (MLDs), high concentrations of nutrients, POM, and Chla, marked the upwelling signature in the south. Conversely, relatively higher temperatures, salinity, deeper mixed layers (MLs), lower concentrations of nutrients, POM, and Chla were evident at the northern stations. Five times higher POC concentrations were noticed in the south (65.5 ± 22.0 μmol L−1) than in the north (12.8± 5.4 μmol L−1) within the MLs. Phytoplankton community shift (based on marker pigment analysis) and the δ13CPOC values were closely coupled. The nutrient replete microphytoplankton (diatoms) dominated southern stations were associated with higher values of δ13CPOC (−23.0 ± 2.3‰) which was attributed to faster growth rate; conversely, the oligotrophic nitrogen-limited waters in the north dominated by pico and nanophytoplankton (haptophytes and cyanobacteria), were characterized by distinctly lower δ13CPOC values (−26.6 ± 0.9‰). Phytoplankton growth rates based on a model were consistent with this trend. Our results show that the autochthonous POC is the primary source of organic matter, and the contrasted biogeochemistry induced phytoplankton communities and their growth rates mostly governed the δ13CPOC variability in this region. However, the lower values in the subsurface waters at the south were likely to be influenced by light limitation and heterotrophy.

Decolorization property of living Lichen Evernia prunastri on textile Acid Red P-2BX dye

The removal of textile dye using the biosorption technique is important for improving water quality and avoiding the harmful effects of the traditional approach for removing wastewater on human health. Lichens are symbiotic organisms that have great potential for decolorization and degradation of textile dye. The present study evaluates Acid Red P-2BX dye decolorization by living lichen Evernia prunastri at the pH range of 2–10. Dye decolorization rates at pH 2 were 84.62%, 87.5% and 88.54% at 25, 50 and 100 mg/L of initial dye concentrations, respectively. The pigment analysis and mean intensity of chlorophyll autofluorescence results indicated that pH could be the main factor affecting lichen physiology and thalli decolorization capacity. Fourier transform infrared spectroscopy was used as a high-throughput method for understanding biomolecular changes in thalli. The lipid/amide I and carbohydrate/amide I ratio increased at pH 2. The present study also indicated, for the first time, that decolorization rate is related to altering lichen carbohydrate and especially lipid metabolism in the E. prunastri thalli. Thus, we demonstrated that the lichen E. prunastri could be a good candidate for use as a biosorbent.

Improving Production, Chlorophyll a and Carotenoids Contents of Gracilaria sp. with Liquid Organic Fertilizer from Alginate Waste

Chlorophyll is a photosynthetic pigment, used in the food sector as a natural dye in food. Carotenoids is used in the health sector to prevent several disease in humans. The production and pigment contents are influenced by nutrient availability. The aim of this study was to increase the production of chlorophyll a and carotenoids contents in Gracilaria sp. Seaweed obtained from Demak aquaculture ponds, then cultivated in aquarium for 28 days.Alginate from Sargassum sp. waste fertilizer was prepared by adding some compounds, fermented by commercial Saccharomyces cerevisiae. Five different treatments (FB (basal formulation: 75 g alginate waste + 22.5mL molase + 7.5 g S. cerevisiae + 250 mL aquadest)), FBL (basal formulation+100% Lamtoro leaves), FBLU (basal formulation+50%Lamtoro leaves+50% carapace shrimp waste), FBU (Basal formulation + 100% carapace shrimp waste) and control-without fertilizer) was applied. Analysis of pigments was determined using the spectrophotometric method. The research design was CRD with 4 treatments and a control. Data were analyzed using Kruskal-Wallis statistical analysis. The result showed that fertilization in culture media could increase the production (DW) and pigment contents. The highest levels of dry weight, chlorophyll a and carotenoids (P<0.05) were resulted from FBLU ie. 6.58 ± 0.07g dry weight; 5.47 mg.L-1 and 0.16 µmol.L-1.The application of organic fertilizer from alginate extract waste to Gracilaria sp. culture media had a significant effect towards growth, dry weight, chlorophyll a and carotenoids pigments content. This inexpensive fertilizer expected to be the solution of green and zero waste management which provide the enviromentally friendly fertilizer.

Microbial Production of Melanin Pigments from Caffeic Acid and L-tyrosine Using Streptomyces glaucescens and FCS-ECH-Expressing Escherichia coli.

In this study, synthetic allomelanin was prepared from wild-type Streptomyces glaucescens and recombinant Escherichia coli BL21(DE3) strains. S. glaucescens could produce 125.25 ± 6.01 mg/L of melanin with a supply of 5 mM caffeic acid within 144 h. The ABTS radical scavenging capacity of S. glaucescens melanin was determined to be approximately 7.89 mg/mL of IC50 value, which was comparable to L-tyrosine-based eumelanin. The isolated melanin was used in cotton fabric dyeing, and the effect of copper ions, laccase enzyme treatment, and the dyeing cycle on dyeing performance was investigated. Interestingly, dyeing fastness was greatly improved upon treatment with the laccase enzyme during the cotton dyeing process. Besides, the supply of C5-diamine, which was reported to lead to more complex crosslinking between melanin units, to caffeic acid-based melanin synthesis was also investigated for higher production and novel functionalities. To facilitate the supply of caffeic acid and C5-diamine, E. coli strains expressing each or combinations of tyrosine ammonia lyase/p-coumarate 3-hydroxylase, feruloyl-CoA synthetase/enoyl-CoA hydratase/aldolase, and tyrosinase/lysine decarboxylase enzymes were prepared and investigated for their eumelanin, C5-diamine, and allomelanin production from L-tyrosine and L-lysine, respectively. Finally, H-NMR, FT-IR, and MALDI-TOF analysis of the synthetic melanin pigments were attempted to obtain the chemical information.

Morpho-physiological responses by Chlamydomonas reinhardtii to different concentrations of ibuprofen

ABSTRACT Pollution of aquatic bodies by pharmaceutical compounds is an emerging environmental problem because these drugs are extensively used in animal and human medicine. Ibuprofen, 2-[4-(2-methylpropyl)phenyl] propanoic acid, is the non-steroidal anti-inflammatory drug mainly present both in wastewater and in rivers and lakes in Europe. Despite this environmental emergency is giving rise a great interest in the scientific community, literature about the effects of ibuprofen on microalgae is scarce. A previous work on the freshwater microalga Scenedesmus rubescens had shown some morpho-physiological effects caused by treatment with 62.5, 250 and 1000 µg L−1 ibuprofen. In this paper, we presented the results of treatment with ibuprofen at the same concentrations, ranging from environmental levels up to higher values, on Chlamydomonas reinhardtii (P.J.L. Dangeard). Ibuprofen effects on the alga were assayed through analyses of growth curve. Moreover, analyses of cell morphology, ultrastructure, and photosynthetic pigments were performed. The first effect of drug was the stimulation of the microalga growth. In addition, following exposure to ibuprofen, cells exhibited morphological and ultrastructural alterations, the latter ones consisting of starch granules and both in vacuolar and cytoplasmatic inclusions. On the contrary, chlorophyll and carotenoids amounts, were not affected by drug treatment.

Microplastics and freshwater microalgae: what do we know so far?

The constant entry of microplastics in several environmental matrices has been of great concern to the scientific community and to society in general, mainly due to the mysteries that surround the implications of this pollutant in the environment. Freshwater ecosystems are resources especially susceptible to variations in environmental quality, and the lack of data on the impacts caused by plastic fragments exacerbates the vulnerability of this environment. Considering the results of other studies, which demonstrate the increasing entry of polymeric fragments in the aquatic environment can lead to algae growth inhibition, an investigation was carried out to determine the current state of research on the interaction between microplastics and freshwater microalgae. In total, 20 scientific articles were analyzed. Different species were subjected to toxicological tests under controlled conditions in the laboratory with small microplastics (size range between 0.1 and 1000 µm), primary and secondary microplastics of different types of polymer. Four toxicity class of indicators were chosen to assess the microalgae response to exposure to microplastic in the selected studies: growth inhibition; photosynthetic activity; pigment analysis; and enzymatic activity and oxidative stress. In this review, a critical analysis is made on the effects of the shape, size, concentration, and duration of exposure to microplastics and research gaps are identified to guide future research priorities in this area of study.

Diagnosis of the efficiency of the functioning of the plum (Prunus Domestica) promise cultivars and elite forms photosynthetic apparatus

The authors present the results of researching the functioning of the leaf apparatus of the plum promise cultivars and elite forms bred at the L.P. Symyrenko Research Station of Pomology that was carried out for the purpose of determining their potential adaptability and productivity. The plants functional state was studied by means of the portable fluorimetr ‘Floratest’ establishing the inductive changes of the leaves chlorophyll fluorescence. The analysis of the green pigments in them was conducted in spirit extracts applying the spectrophotometric method. The considerable negative correlation was revealed (r = -0,71) between the a/b chlorophylls correlation and pigments summary content (in mg/g of the humid substance), on the one hand, and the chlorophyll b and chlorophylls a/b correlation (r = -0,85), on the other hand. That proves the high regulatory capacity and adaptive ability (at the level of the chlorophylls certain forms synthesis) of the leaves chloroplasts pigment systems of all the investigated crop cultivars and elite forms to the changes of the light regime in the tree crown. Concerning the parameters which characterize the plants potential photosynthetic effectivity and productivity the variety Oda has been recognized the most productive one among early ripening, Cacakska Najbolja, Zamanchivaya and Yantarna Mliivs’ka among middle-ripening, Stanley, Bluefree and forms 8124 and 8143 among late-ripening. The form 9996 had the lowest photosynthetic processes efficiency as for all the parameters. The rather high adaptability has been detected of the leaf apparatus of the trees of all the cultivars and forms to the changes of the enlightenment conditions as regards the indicators of the chlorophylls Fpl 1 and Fpl 2 fluorescence induction and green pigments content in the leaves. According to the plateau Kpl coefficient the viral infection was not revealed.

Production, purification, and process optimization of intracellular pigment from novel psychrotolerant Paenibacillus sp. BPW19

A pink pigment-producing bacterial strain was isolated from wastewater and identified as Paenibacillus sp. BPW19. The motile bacterial strain was Gram-positive, acid fermenting, glucose, sucrose utilizing and rod-shaped with an average cell length of 1.55 μm as studied under the Environmental Scanning Electron Microscope. Even though being psychrotolerant, the cell growth condition of BPW19 was optimized as 25 ºC along with pH 8, and 2.25% inoculum concentration considering the operational ease of the production. Sonication assisted solvent extraction produced 5.41% crude pigment which showed zones of exclusion against gram-negative strains Escherichia coli DH5α, Enterobacter sp. EtK3, and Klebsiella sp. SHC1. Gas Chromatography-Mass Spectrometry analysis of the crude pigment exhibited the dominant presence of major compounds as dotriacontane; 3,7 dimethyl 7 octanal; 1-eicosene and erucic acid. While column chromatography (ethanol:chloroform in 1:4 (v/v) ratio) purified pigment was identified as erucic acid using Nuclear Magnetic Resonance with a net yield of 3.06%.

Microcystis species and their toxigenic strains in phytoplankton of ten Bulgarian waterbodies

The summer phytoplankton structure of ten Bulgarian waterbodies was studied by HPLC analysis of marker pigments, light microscopy (LM) and PCR amplification of mcyB and mcyE gene sequences. The aim was to detect biodiversity and spread of toxigenic strains of potential microcystin producers and the important bloom-forming genus Microcystis in particular. The screening was done in three waterbodies, where Microcystis had already been found (Lakes Ezerets and Durankulak and Reservoir Koprinka), three waterbodies from which it had not been reported (Reservoirs Shilkovtsi, Zhrebchevo, Suedinenie) and four reservoirs that were sampled for the first time (Malka Smolnitsa, Plachidol 2, Preselka, Duvanli). LM and HPLC data similarly showed that cyanoprokaryotes contributed significantly to the total phytoplankton composition (29%) and biomass (15–87%) in nine sampled waterbodies. Microcystis aeruginosa, M. natans, M. smithii, M. wesenbergii, Microcystis spp., M. cf. comperei and M. pseudofilamentosa, were identified using LM (the last two tropical species were found for the first time in the country). Despite the low contribution of Microcystis to the phytoplankton diversity (1–4 taxa per sample) and to the total phytoplankton biomass (< 0.01–0.5%), 57 toxigenic strains of this genus were revealed by PCR, most of which demonstrated high similarity with NCBI M. aeruginosa and M. wesenbergii strains.

Красочные изображения горы Тепсей

The article considers painted images of Tepsei, which is one of the petroglyphic complexes of the Minusa basin. The images are found on the riverside rocks of Mount Tepsei at the Tepsei I site. The images are hard to see due to their poor preservation. All the discovered panels with painted images have natural cornices that protect the panels from surface water flows and calcite incrustation. The latter make the images hard to see, on the one hand, and make a conservation layer to prevent the images from discoloration, shedding, and pigment washout. These observations, concentration of the images on a confined part of the slope and uninterpreted spots of pigment on some of the panels make us to think that, at some ancient times, there were many more painted figures on the Tepsei cliffs, and they were lost as time went by. During the investigation, we used non-contact methods of documenting based on photography and digital image post-processing. Due to the overlapping of some painted images with ancient carved ones, we are able to attribute some of the painted figures. Similar overlapping cases are rare in the Minusa basin and in South Siberia, which makes them particularly valuable for the replenishment of the source base of earliest rock art images on this territory. Attributing some images is hard for today. The stylistic analysis along with the analysis of pigment maps also gives some basis for the relative chronology of the paintings. Most of the documented images are self-sufficient ochre paintings. There are some animal-style figures: aurochs, a deer, some zoomorphic images that are hard to be taxonomically defined. There is possibly one anthropomorphic figure with a bow in his hands. There is a carved zoomorphic figure with traces of ochre in the carving. On three other panels with the earliest stratum, there are just some relics of pigment. On one of the panels, there is an ochre relic documented only along the contour of the carved image, which tells that the carving was made over the painted image. We consider the findings presented to be an evidence of a broad usage of the painting technique in antiquity that widen the source base of pre-written South Siberian peoples' history.

Carotenoid Biosynthesis in the Phylum Actinobacteria.

Actinobacteria is the phylum that has the biggest genome in the Bacteria domain and includes many colored species. Their pigment analysis revealed that structurally diverse carotenoids are responsible for their pigmentation. This chapter reviews the biosynthesis of the diverse carotenoids of Actinobacteria. Its carotenoids belong to three different types: 1) carotenoid of C50 chain length, 2) carotenoids with aromatic end groups, and 3) keto carotenoid like canthaxanthin (β,β-carotene-4,4'-dione) or monocyclic keto-γ-carotene derivatives. Species from the genus Rhodococcus are the only known Actinobacteria with a simultaneous pathway to aromatic and to keto carotenoids.

Monitoring of saxitoxin production in lakes in Denmark by molecular, chromatographic and microscopic approaches

Diversity of phytoplankton in three eutrophic and two mesotrophic lakes in Denmark was determined by microscopic and HPLC pigment analyses to identify and quantify potential saxitoxin (STX) producing cyanobacteria. Potential dominant STX-producers were identified to the filamentous genera Dolichospermum, Cuspidothrix, Phormidium and Planktolyngbya. Presence of STX production was documented by extraction of five intracellular STXs that included (in declining concentration in the cyanobacteria) dc-neo-STX, neo-STX, dc-STX, STX and GTX. Total concentrations of the five STXs varied from 9 to 142 fg per potential STX producer, corresponding to 87 to 985 ng L−1 in the lakes. For molecular detection of the STX-producers, a quantitative PCR method was developed by design of a new robust primer set with broad coverage to target the sxtA gene that is common to all STX-producing cyanobacteria. After validation, copy numbers of the sxtA gene were determined to vary from about 104 (mesotrophic lakes) to 108 per mL (the most eutrophic lake). A moderate but significant correlation was observed between abundance of the sxtA copies and concentrations of the five intracellular STXs. The qPCR assay was found to be a rapid and robust procedure for quantification of STX producers. Saxitoxin and its analogs appeared not to cause health concerns in the lakes, but commercial fishing for pike perch in the most eutrophic lake should be monitored to test for food web accumulation of STXs.

Microcystis aeruginosa and M. wesenbergii Were the Primary Planktonic Microcystin Producers in Several Bulgarian Waterbodies (August 2019)

The rising interest in harmful cyanoprokaryote blooms promotes an increase of phycological and ecological research on potentially toxic species and their hazardous substances. The present study aimed to identify the main microcystin (MC) producers and their contribution to the phytoplankton of shallow waterbodies in Bulgaria, applying different methods. The sampling was performed in August 2019 in nine lakes and reservoirs, two of which (reservoirs Kriva Reka and Izvornik 2) were studied for the first time. The high contribution of cyanoprokaryotes to the total species composition and phytoplankton abundance was proved by light microscopic (LM) observations and HPLC analysis of marker pigments. The LM identification of potential MC-producers was supported by PCR amplification of mcyE and mcyB genes. The MCs amounts, detected by HPLC-DAD, varied by sites with a range from undetectable concentrations to 0.46 µg L−1 with only one recorded variant, namely MC-LR. It was found only in the reservoirs Mandra and Durankulak, while toxigenic MC-strains were obtained by PCR from five more waterbodies. Both LM and PCR demonstrated that the MC-producers were Microcystis aeruginosa and M. wesenbergii, despite their occurrence in low amounts (<0.5–5% of the total biomass) when filamentous cyanoprokaryotes dominated.

Pigment analysis in four paintings by Vincent van Gogh by portable X-ray fluorescence (pXRF)

This work presents the characterization of the pigments present in four paintings by Vincent van Gogh, one of the most famous and influential figures in the history of western art. The studied paintings are “The Schoolboy”, “The Stone Bench in the Garden of Saint-Paul Hospital”, “Landscape with Couple Walking and Crescent Moon” and “The Arlesienne”, from the collection of the São Paulo Museum of Art (MASP). In situ XRF measurements were carried out by means of a portable system. XRF provided substantial information about the materials present in the paintings. The results shown in this work are in total agreement with those obtained by others works on paintings by Vincent van Gogh during his time in Arles and Saint-Remy.

Molecular Dynamics of Chloroplast Membranes Isolated from Wild-Type Barley and a Brassinosteroid-Deficient Mutant Acclimated to Low and High Temperatures.

Plants have developed various acclimation strategies in order to counteract the negative effects of abiotic stresses (including temperature stress), and biological membranes are important elements in these strategies. Brassinosteroids (BR) are plant steroid hormones that regulate plant growth and development and modulate their reaction against many environmental stresses including temperature stress, but their role in modifying the properties of the biological membrane is poorly known. In this paper, we characterise the molecular dynamics of chloroplast membranes that had been isolated from wild-type and a BR-deficient barley mutant that had been acclimated to low and high temperatures in order to enrich the knowledge about the role of BR as regulators of the dynamics of the photosynthetic membranes. The molecular dynamics of the membranes was investigated using electron paramagnetic resonance (EPR) spectroscopy in both a hydrophilic and hydrophobic area of the membranes. The content of BR was determined, and other important membrane components that affect their molecular dynamics such as chlorophylls, carotenoids and fatty acids in these membranes were also determined. The chloroplast membranes of the BR-mutant had a higher degree of rigidification than the membranes of the wild type. In the hydrophilic area, the most visible differences were observed in plants that had been grown at 20 °C, whereas in the hydrophobic core, they were visible at both 20 and 5 °C. There were no differences in the molecular dynamics of the studied membranes in the chloroplast membranes that had been isolated from plants that had been grown at 27 °C. The role of BR in regulating the molecular dynamics of the photosynthetic membranes will be discussed against the background of an analysis of the photosynthetic pigments and fatty acid composition in the chloroplasts.

Variability of phytoplankton light absorption in stratified waters of the NW Mediterranean Sea: The interplay between pigment composition and the packaging effect

The Variability of chlorophyll-specific phytoplankton light absorption [a*ph (λ)] was examined over depth and time in stratified offshore waters of the North-Western Mediterranean Sea. Coherent water patches were tracked with Lagrangian drifters during two oceanographic cruises in September (late summer) and May (post-spring bloom phase). By simultaneously analysing the phytoplankton absorption and pigment measurements, we explicitly separated the impact of pigment composition from that of pigment packaging on a*ph (λ). We further partitioned the packaging effect by comparing the variation of the packaging index [Qa*(440)], the phytoplankton community size structure (derived from diagnostic pigment analysis), and the chlorophyll-specific beam attenuation by particles [cp* (660)] as an optical index of phytoplankton photophysiology. In the ensemble of cruises, around 50% of the a*ph (440) vertical variation was explained by changes in the pigment composition (ruled by the decrease of photoprotective pigments with depth). The remaining vertical and inter-cruise variation of a*ph (440) was attributed to the packaging effect. We found that differences in the cp*(660) index (most likely indicating changes in the intracellular pigment concentration due to photoacclimation) mainly explained the observed variation in the packaging effect. Differences in cp* (660) were coincident with either the vertical gradient of light availability or the lower mean daily PAR irradiance in the euphotic layer of the September cruise. These explained the stronger packaging and lower a*ph (440) values observed with increasing depth in both cruises, and in September relative to May. On the other hand, differences in the phytoplankton community size structure did not explain the observed patterns in the packing effect. Our results highlight the importance of phytoplankton short-term acclimation to the prevailing light conditions, determining the vertical and temporal variability of a*ph (λ). A better understanding of the a*ph (λ) variability and its main drivers are key to improve different bio-optical applications.

Biogeochemical and ecological variability during the late summer–early autumn transition at an ice‐floe drift station in the Central Arctic Ocean

AbstractAs the annual expanse of Arctic summer ice‐cover steadily decreases, concomitant biogeochemical and ecological changes in this region are likely to occur. Because the Central Arctic Ocean is often nutrient and light limited, it is essential to understand how environmental changes will affect productivity, phytoplankton species composition, and ensuing changes in biogeochemistry in the region. During the transition from late summer to early autumn, water column sampling of various biogeochemical parameters was conducted along an ice‐floe drift station near the North Pole. Our results show that as the upper water column stratification weakened during the late summer–early autumn transition, nutrient concentrations, particulate dimethylsulfoniopropionate (DMSPp) levels, photosynthetic efficiency, and biological productivity, as estimated by ΔO2/Ar ratios, all decreased. Chemotaxonomic (CHEMTAX) analysis of phytoplankton pigments revealed a taxonomically diverse picoautotrophic community, with chlorophyll (Chl) c3‐containing flagellates and the prasinophyte, Pyramimonas spp., as the most abundant groups, comprising ~ 30% and 20% of the total Chl a (TChl a) biomass, respectively. In contrast to previous studies, the picoprasinophyte, Micromonas spp., represented only 5% to 10% of the TChl a biomass. Of the nine taxonomic groups identified, DMSPp was most closely associated with Pyramimonas spp., a Chl b‐containing species not usually considered a high DMSP producer. As the extent and duration of open, ice‐free waters in the Central Arctic Ocean progressively increases, we suggest that enhanced light transmission could potentially expand the ecological niche of Pyramimonas spp. in the region.

Conservation and virtual reconstruction of the Lucanian Paintings from the National Archaeological Museum of Paestum (ITALY)

This contribution presents the restoration and virtual reconstruction of a painted tomb from the Lucan period (4th century BC), now dismounted and kept in the deposits of the National Archaeological Museum of Paestum. The virtual reconstruction that was carried out is based on several elements: identification of traces of the original color on the surfaces; pigment analysis; study of the execution technique; iconographic comparison with other painted pieces of the same corpus and reconstruction by levels (colored backgrounds, decorative elements; figurative elements). The video, which illustrates both the restoration intervention of the tomb and the virtual reconstruction, was presented at the RECH5 conference and it can be seen at: https://www.facebook.com/officinabeniculturali.info/videos/200967307895086. It shows the different phases of the restoration work, such as cleaning and consolidation, and the subsequent reintegration of the virtual models, presenting how the intervention was carried out in a way that respects the authenticity of the work.