Occurrence of structural aluminum (Al) in marine diatom biological silica: Visible evidence from microscopic analysis

The global marine biogeochemical cycle of aluminum (Al) is believed to be driven by marine diatoms, due to the uptake of dissolved Al (DAl) by living diatoms from surface seawater. The occurrence of Al in diatom biogenic silica (BSi) can inhibit the dissolution of BSi, thus benefiting the effects of the ballast role of diatoms in the biological pump and forming a coupled Si-Al biogeochemical cycle. However, the occurrence mechanism of Al in marine diatoms is still unclear. In particular, whether or not Al is incorporated into the structure of BSi of living diatoms is unrevealed, resulting in difficulties in understanding the biogeochemical behaviors of Al. In this study, Thalassiosira weissflogii, a widely distributed marine diatom in marginal seas, was selected as the model to evaluate the occurrence of structural Al in BSi based on culturing experiments with the addition of DAl. The structural Al in BSi was detected by combining focused ion beam (FIB) scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) mapping analysis. Direct evidence of structural Al in living BSi was obtained for the first time. The distribution and content of this Al were revealed by the EDS-mapping analysis. The structural Al in the BSi exhibited a homogeneous distribution, and the average Al / Si atomic ratio obtained through the FIB-EDS mapping analysis was 0.011. The effects of structural Al on BSi dissolution-inhibition are discussed based on the content of this Al. The fundamental results indicate the significant contribution of marine diatoms to the biogeochemical migration of marine Al.

Strong UV-Protection Property from Living Diatom Exoskeleton Modified by Eu3+-Complex

In this article, a natural biological porous material, from living diatoms, is used to prepare new UV-protection hybrid materials with Eu3+-complexes. By removing the organic protoplasm of living diatoms, the...

Differences in the optical properties of valve and girdle band in a centric diatom

Diatoms are phototrophic single-celled microalgae encased in a cell wall (frustule) made of amorphous silicate. The frustule comprises two valves connected by a variable number of girdle bands, all exhibiting periodic micro/nanoporous structures. We studied the optical properties in water of girdle bands from the centric diatom Coscinodiscus granii , a frustule part that so far has received little attention by the scientific community. We show that valves and girdle bands exhibit different optical properties, as valves attenuate shorter wavelengths and girdle bands attenuate longer wavelengths of the visible light spectrum. Girdle bands show iridescent coloration in dependence of the light direction. Although the biological meaning of periodic nanoscale structures of frustules is still a matter of debate, the differences of valve and girdle band optical properties indicate that living diatoms are complex optical systems, where valves, girdles and pigments modulate light inside the cell.

Arctic (Svalbard Islands) Active and Exported Diatom Stocks and Cell Health Status

Diatoms tend to dominate the Arctic spring bloom, a key event in the ecosystem. Large sinking of diatoms is expected at the end of the bloom driven by deteriorated cell status associated to nutrients (silicon) depletion. However, there are few reports on the status of diatoms' health during Arctic blooms and its possible role on sedimentary fluxes. Here we quantify, using the Bottle-Net, Arctic diatom stocks below and above the photic layer and assess their cell health status. The communities were sampled around the Svalbard Islands and encompassed a broad diversity of conditions and bloom stages. About 1/4 (mean±SE 24.2 ± 6.7 %) of the total water column (max. 415 m) diatom stock was found below the photic layer, indicating significant sinking of diatoms in the area. The fraction of living diatom cells in the photic layer averaged 59.4 ± 6.3 % but showed the highest percentages (72.0 %) in stations supporting active blooms. In contrast, populations below the photic layer were dominated by dead cells (20.8 ± 4.9 % living cells). The percentage of diatom’s stock found below the photic layer was negatively related to the percentage of living diatoms in the surface, indicating that healthy populations remained in the surface layer. An experiment on board in a tall (1.35 m) sedimentation column confirmed that dead diatom cells from the Arctic community sink faster that living ones. Also, diatoms cell mortality increased in darkness, showing an averaged half life of 1.025 ± 0.075 d−1. The results conform to a conceptual model where diatoms grow during the bloom until silicic acid stocks are depleted, and support a link between diatom cell health status and sedimentation fluxes in the Arctic. Healthy arctic phytoplankton communities remained at the photic layer, whereas dying communities exported a large fraction of the biomass to the aphotic zone, fuelling carbon sequestration and benthic ecosystems.

Diatom Epipelik sebagai Bioindikator Pencemaran di Estuari Suwung

Epiphelic diatoms are the living diatoms adhere to the bottom substrate of the waters. Epiphelic diatoms ware used as bioindicators because sensivity of enviromental change, widely distributed, and ware not affected by currents. Epiphelic diatom research as a bioindicator of pollution in the Suwung estuary was conducted in December 2016 and January 2017. The sampling of epiphelic diatom using the method of "Lens tissue trapping method". The results of research in December 2016 found 34 species of epiphelic diatoms, while in January 2017 found 24 species of epiphelic diatom. Species that are often found in this study are Pleurosigma clavei, Rhabdonema arcuatum, Synedra gailloni and Gomphonema angustatum. The highst of epipelic diatom abundance in estuari suwung in January 2017 was 8.82 Ind/and the lowest epiphelic diatom abundance of 0.41 Ind/. The assessment of contamination using epiphelic diatom using two methods such as diversity index and saprobik index. The pollution assessment based on the diversity index shows that in December 2016 it was varied, not contaminated, mildly polluted, moderately polluted while the saprobic index-based valuation was varied ie clean, moderately polluted and heavily polluted. Assessment of pollution with saprobik index is used to know the contamination of organic matter. Diversity index in January 2017 and the saprobic index had the same pattern that almost of station research in Suwung estuary research stations were moderately polluted and there was an increase in pollution

Light emitting silica nanostructures by surface functionalization of diatom algae shells with a triethoxysilane-functionalized π-conjugated fluorophore

ABSTRACTThe functionalization of biosilica shells (frustules) of diatoms microalgae with a tailored luminescent molecule is a convenient, scalable and biotechnological approach for obtaining new light emitting silica nanostructures with promising applications in photonics. In particular, here we report the synthesis of a red emitting organic fluorophore and its covalent linking to the surface of mesoporous biosilica extracted from Thalassiosira weissflogii diatoms cultured in our laboratories. The organic dye has a conjugated skeleton composed of thienyl, benzothiadiazolyl and phenyl units and a peripheral triethoxysilyl group which enables its stable binding onto the frustules surface. The protocol to extract the biosilica shells from living diatoms preserving their natural ornate nanostructured morphology is also discussed.