Photophysiologically active green, red, and brown macroalgae living in the Arctic Polar Night

Abstract

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.

Quantifying pigment content in crustose coralline algae using hyperspectral imaging: A case study with Tethysphytum antarcticum (Ross Sea, Antarctica)

“…To improve regression algorithms, future studies could make use of additional sampling efforts to increase sample size and test multivariate analysis based on chemometrics or machine learning methods that can handle collinearity between predictors (i.e., different wavelengths from a spectrum), enabling the use of the whole spectral reflectance signature to measure different biochemical traits (Burnett et al., 2021; Che et al., 2023). Integration with multiple sensors, such as pulse amplitude modulation fluorometry (Burdett et al., 2012; Schwarz et al., 2005; Summers et al., 2023), along with measurements of different CCA response categories like calcification and primary production (Cornwall et al., 2019; Page et al., 2022), could further refine noninvasive assessments of their photo‐physiology response to different irradiance regimes. A critical aspect, beyond this study's scope, involves linking CCA phenotypic traits with environmental variables, such as irradiance regimes, sea‐ice cover duration, ice thickness, and underwater light composition (Clark et al., 2013; Huovinen & Gómez, 2020; Irving et al., 2005).…”