PMC

Conceptual model synthesizing two possible dynamics describing variations in linear oxygenated fatty acid (LOFA) synthesis potential along diatom density gradient. Circles indicate diatom cells and fill gradient indicates the oxylipin synthesis potential (red is the highest, white is the lowest). Dotted blue lines show the positive relation between ng-LOFAs/L and diatom cells/L; dashed red lines show the inverse relation between fg-LOFAs/diatom cell and diatom cells/L. a “Cheater” dynamic: some diatom cells can reduce oxylipin synthesis depending on the abundance of diatom cells with constantly high oxylipin synthesis potentials. At low diatom densities, diatom community is dominated by cells with high oxylipin synthesis potentials. In this condition, low ng-LOFAs/L are detected because of the low abundance of diatoms showing high oxylipin synthesis potentials. However, high fg-LOFAs/diatom cell are measured because community is dominated by cells with high synthesis potentials. At high diatom densities, both cheaters and oxylipin producers increase, thus more ng-LOFAs/L are detected, but lower fg-LOFAs/diatom cell are measured. After grazing on diatom cells at low and high abundances, copepod grazer recruitment can be hypothesized to vary depending on selective (orange lines) or unselective (green lines) feeding strategies. b “Common physiology” dynamic: all diatom cells share the same physiological adaptation and synthesize the same amount of molecules. At low diatom concentrations, higher oxylipin synthesis potentials are shown by each diatom cell. At high diatom densities, lower oxylipin synthesis potentials are shown by each diatom cell. Amount of ng-LOFAs/L and fg-LOFAs/diatom cell does not vary in comparison to the “cheater scenario”. Copepod grazer recruitment after feeding on diatom cells at low and high abundances is different because of different ingestion of harmful molecules, but it does not vary depending on selective or unselective feeding strategies

Diatom Dissolution Index (DDI) and diatom concentrations (10⁴ valves/g DW) are shown alongside diatom abundances (species with > 2% abundance). SCD dissimilarity scores are shown for the diatom dataset. The timings of significant breakpoints in the SCD scores are highlighted in grey for BAIK13-7A_SB and BAIK13-11C_BS diatom assemblages. No significant breakpoints were found in the BAIK13-18A_NB diatom assemblage data. [SB: South basin; BS: Buguldieka Saddle; NB: North basin].

Fabrication and characterization of the MnO₂ nanosheets-doped diatom. (a) SEM image of diatom. (b) Schematic illustration of fabrication steps for MnO₂ nanosheets-doped diatom. (c) Elemental mapping images showing homogenous distribution of MnO₂ nanosheets on diatom. (d) High-resolution TEM image of MnO₂ nanosheets on diatom. (e, f) Nitrogen adsorption–desorption isotherms (e) and powder X-ray diffraction patterns (f) of diatom and MnO₂ nanosheets-doped diatom.

a) Biological Condition Gradient (BCG) scores (number of diatom species = 73, 1 = specialist species, 2 = highly sensitive species, 3 = sensitive species, 4 = indiscriminate species and 5 = tolerant species); b) Habitat types (number of diatom species = 84); c) Eastern Canadian Diatom Index classes (number of diatom species = 14, A = reference condition, B = slightly altered, C = altered, D = severely altered conditions).