Wf. Vincent et al., ANTARCTIC CYANOBACTERIA - LIGHT, NUTRIENTS, AND PHOTOSYNTHESIS IN THEMICROBIAL MAT ENVIRONMENT, Journal of phycology, 29(6), 1993, pp. 745-755
The microenvironmental and photosynthetic characteristics of Antarctic
microbial mats were measured in a series of ponds near McMurdo Sound.
As elsewhere in Antarctica, these cold-water benthic communities were
dominated by oscillatoriacean cyanobacteria. Despite large variations
in mat thickness, surface morphology, and color, all of the communiti
es had a similar pigment organization, with a surface carotenoid-rich
layer that overlaid a deep chlorophyll maximum (DCM) enriched in phyco
cyanin as well as chlorophyll a. Spectroradiometric analyses showed th
at the DCM population inhabited an orange-red shade environment. In se
veral of the mats, the deep-living trichomes migrated up to the surfac
e of the mat within 2 h in response to a 10-fold decrease in surface i
rradiance. The euphotic layer of the mats was supersaturated in oxygen
and contained ammonium and dissolved reactive phosphorus concentratio
ns in excess of 100 mg N . m-3 or P . m-3. Integral photosynthesis by
core samples was saturated at low irradiances and varied two- to three
fold throughout the continuous 24-h radiation cycle. Oxygen microelect
rode analyses showed that the photosynthetic rates were slow to neglig
ible near the surface and maximal in the DCM. These compressed, nutrie
nt-rich euphotic zones have some properties analogous to planktonic sy
stems, but the integrated photosynthetic responses of the community re
flect the strong self-shading within the mat and physiological dominan
ce by the motile, DCM populations.