TY - JOUR
T1 - Phototrophic microbes form endolithic biofilms in ikaite tufa columns (SW Greenland)
AU - Trampe, Erik Christian Løvbjerg
AU - Castenholz, Richard W.
AU - Larsen, Jens Erik Nybo
AU - Kühl, Michael
PY - 2017/11
Y1 - 2017/11
N2 - Marine tufa-columns, formed by the hydrated carbonate mineral ikaite, present a unique alkaline microbial habitat only found in Ikka Fjord (SW-Greenland). The outermost parts of the ikaite columns exhibit a multitude of physico-chemical gradients, and the porous ikaite is colonized by endolithic phototrophic biofilms serving as a substrate for grazing epifauna, where scraping by sea urchins affects overall column-topography. We present a detailed study of the optical microenvironment, spatial organization, and photosynthetic activity of endolithic phototrophs within the porous ikaite crystal matrix. Cyanobacteria and diatoms formed distinctly coloured zones and were closely associated with ikaite-crystals via excretion of exopolymers. Scalar-irradiance measurements showed strong attenuation of visible light (400–700 nm), where only ∼1% of incident irradiance remained at 20 mm depth. Transmission spectra showed in vivo absorption signatures of diatom and cyanobacterial photopigments, which were confirmed by HPLC-analysis. Variable-chlorophyll-fluorescence-imaging showed active photosynthesis with high-light acclimation in the outer diatom layer, and low-light acclimation in the underlying cyanobacterial part. Phototrophs in ikaite thus thrive in polymer-bound endolithic biofilms in a complex gradient microhabitat experiencing constant slow percolation of highly alkaline phosphate-enriched spring water mixing with cold seawater at the tufa-column-apex. We discuss the potential role of these biofilms in ikaite column formation.
AB - Marine tufa-columns, formed by the hydrated carbonate mineral ikaite, present a unique alkaline microbial habitat only found in Ikka Fjord (SW-Greenland). The outermost parts of the ikaite columns exhibit a multitude of physico-chemical gradients, and the porous ikaite is colonized by endolithic phototrophic biofilms serving as a substrate for grazing epifauna, where scraping by sea urchins affects overall column-topography. We present a detailed study of the optical microenvironment, spatial organization, and photosynthetic activity of endolithic phototrophs within the porous ikaite crystal matrix. Cyanobacteria and diatoms formed distinctly coloured zones and were closely associated with ikaite-crystals via excretion of exopolymers. Scalar-irradiance measurements showed strong attenuation of visible light (400–700 nm), where only ∼1% of incident irradiance remained at 20 mm depth. Transmission spectra showed in vivo absorption signatures of diatom and cyanobacterial photopigments, which were confirmed by HPLC-analysis. Variable-chlorophyll-fluorescence-imaging showed active photosynthesis with high-light acclimation in the outer diatom layer, and low-light acclimation in the underlying cyanobacterial part. Phototrophs in ikaite thus thrive in polymer-bound endolithic biofilms in a complex gradient microhabitat experiencing constant slow percolation of highly alkaline phosphate-enriched spring water mixing with cold seawater at the tufa-column-apex. We discuss the potential role of these biofilms in ikaite column formation.
U2 - 10.1111/1462-2920.13940
DO - 10.1111/1462-2920.13940
M3 - Journal article
C2 - 28949068
SN - 1462-2912
VL - 19
SP - 4754
EP - 4770
JO - Environmental Microbiology
JF - Environmental Microbiology
IS - 11
ER -
