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Photophysiologically active green, red, and brown macroalgae living in the Arctic Polar Night
Summary
Researchers compared the photophysiology and pigment composition of green, red, and brown macroalgae collected during the Arctic Polar Night and at the end of the light season. They found that macroalgae appeared healthier and showed new tissue growth during the dark period, with their photosynthetic apparatus remaining active but operating slowly. The study reveals that Arctic seaweeds have adapted to grow in complete darkness, challenging assumptions about their dependence on light.
Arctic macroalgae species have developed different growth strategies to survive extreme seasonal changes in irradiance in polar regions. We compared photophysiological parameters such as the light saturation parameter (Ek) and pigment composition of green, red, and brown macroalgae collected in January (Polar Night) and October 2020 (end of the light season). Macroalgae in January appeared healthier (morphologically) and had longer lamina (new growth) than those in October. EK values for red, and brown algae were higher with lower maximum quantum yield of PS II fluorescence (Fv/Fm) in January versus October. Furthermore, in January, new tissues in kelp species had higher EK than the older tissue. Higher EK and lower Fv/Fm during the Polar Night indicates that the photosynthetic apparatus is active but slow. Furthermore, we discuss Chlorophyll (Chl) a emission spectra under blue and green excitation light to determine the ratio of Chl a in photosystem II (PS II) vs photosystem I (PS I). Absorbance spectra of P. palmata was used to interpret the emission spectra. The observed spectral shifts in the absorbance and reflectance spectra of different macroalgae is discussed. Photophysiological methods provide health information complementary to future mapping and monitoring of macroalgae. These results reveal that macroalgae grow new tissue in darkness.
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