MICROALGAL LIGHT‐HARVESTING IN EXTREME LOW‐LIGHT ENVIRONMENTS IN MCMURDO SOUND, ANTARCTICA 1

• Published in: Journal of Phycology
• Main Authors: Robinson, Dale H., Arrigo, Kevin R., Iturriaga, Rodolfo, Sullivan, Cornelius W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1995
• Subjects: Austral; McMurdo Sound; Antarc*; Antarctica; ice algae
• Online Access: http://dx.doi.org/10.1111/j.1529-8817.1995.tb02544.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1529-8817.1995.tb02544.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1529-8817.1995.tb02544.x

ABSTRACT Microalgal pigment composition, photosynthetic characteristics, single‐cell absorption efficiency (Qa (λ) ) spectra, and fluorescence‐excitation (FE) spectra were determined for platelet ice and benthic communities underlying fast ice in M c Murdo Sound, Antarctica, during austral spring 1988. Measurements of spectral irradiance (E (λ) ) and photosynthetically active radiation (PAR) as well as samples for particulate absorption measurements were taken directly under the congelation ice, within the platelet layer, as profiles vertically through the water column, and at the benihic surface. Light attenuation by.sea ice, algal pigments, and particulates reduced PAR reaching the platelet ice layer to 3%(9–33 fimol photons m‐ 2 ‐ − s‐ 1 ) of surface values and narrowed its spectral distribution to a band between 400 and 580 nm. Attenuation by the water column further reduced PAR reaching the sea floor (28–m depth) to 0.05% of surface levels (< 1 μmol photons m‐ 2 s‐ 1 ), with a spectral distribution dominated by 470–580–nm wavelengths. The photoadaptive index (I) for platelet ice algae (5.9–12.6 μmol photons m‐ 2. s‐ 1 ) was similar to ambient PAR, indicating that algae had acclimated to their light environment (i.e. the algae were light‐replete). Maximum Qa (λ) at the blue absorption peak (440 nm) was 0.63, and enhanced absorption was observed from 460–500 nm and was consistent with observed high cellular chlorophyll (chi) c:chl a and fucoxanthin: chl a molar ratios (0.4 and 1.2, respectively). Benthic algae were light‐limited despite the maintenance of very low I k values (4–11 μmol photons.m‐ 2. s‐ 1 ). Extremely high fucoxanthin: chi a ratios (1.6) in benthic algae produced enhanced green light absorption, resulting in a high degree of complementation between algal absorption and ambient spectral irradiance. Qa (λ) values for benthic algae were maximal (0.9) between 400 and 510 nm but remained >0.35 even at absorption minima. Strong spectral flattening, a characteristic of intense pigment ...