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Growth dynamics of a laminated microbial mat in response to variable irradiance in an Antarctic lake
Author(s) -
Hawes Ian,
Jungblut Anne D.,
Obryk Maciej K.,
Doran Peter T.
Publication year - 2016
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/fwb.12715
Subject(s) - irradiance , microbial mat , benthic zone , shading , phototroph , biomass (ecology) , photosynthesis , environmental science , ecology , ecosystem , biology , oceanography , botany , geology , cyanobacteria , art , physics , quantum mechanics , bacteria , visual arts , genetics
Summary Laminated microbial mats are important ecosystem components of perennially ice‐covered Antarctic dry valley lakes. In order to understand better their response to changing environment, we made observations and carried out a manipulation experiment to determine their response to variations in irradiance in Lake Hoare (77°38′ S, 162°53′ E). Ice transparency was the most variable parameter that affected benthic light dose, both spatially and between years. Patterns of lamina accrual corresponded to irradiance history, with laminae that were initiated in high transmission years thicker than those from low transmission years. A shading experiment confirmed that accrual of lamina thickness, calcite precipitation and ash‐free dry mass were determined by irradiance, but photosynthetic biomass and phototrophic species composition were less affected. Buried laminae decomposed only slowly over time, with potentially viable phototrophs many laminae down into the microbial mat. Decay rate increased only slightly with shading. We conclude that the microbial mats in Lake Hoare are characterised by remarkable stability, with slow accumulation rates and turnover of biomass over time. Photosynthetic biomass and species composition appeared to be stable across long time periods, with interannual variation in lamination pattern due to differential accumulation of extracellular polysaccharide and representing the visible expression of annual growth conditions.