Environmental factors influencing the pigment composition of in situ benthic microbial communities in east Antarctic lakes

Abstract

To compile reference data for palaeolimnological studies using fossil pigments, we examined the extent to which environmental variables, gross morphology and species composition influence the modern pigment content of in situ microbial communities in 62 east Antarctic lakes. Pigment contents, measured using HPLC, were compared with 32 environmental variables, gross microbial mat morphology and cyanobacterial species composition in each lake. Results showed low concentrations or an absence of pigments in the water columns of most lakes. For benthic microbial communities, multivariate statistical analyses identified lake depth as the most important factor explaining pigment composition. In deeper lakes the pigment composition was dominated by chlorophylls, in intermediate depth lakes by chlorophylls and carotenoids, and in shallow lakes by scytonemins, ultraviolet-screening pigments found in cyanobacteria. In addition to lake depth, conductivity, turbidity, dissolved oxygen, sulphate and geographical location were all significant (p ≤ 0.05) in explaining variance in the pigment content. Significant differences in microbial mat gross morphologies occurred at different lake depths (p ≤ 0.01), and were characterised by significant differences in their pigment content (p ≤ 0.004). Despite the high abundance of scytonemin in shallow lakes, there were only limited changes in the absolute concentrations of chlorophylls and carotenoids. We conclude that lake depth is the most significant factor influencing both gross mat morphology and pigment content, presumably as a result of its influence on the light climate. In general, the ability of the cyanobacteria to regulate their pigment content, morphology, community composition and motility to best exploit the light environment at different lake depths may explain their dominance in these systems.

Ace Lake: three decades of research on a meromictic, Antarctic lake

“…However, molecular analysis has revealed a greater diversity with a number of endemic species (Taton et al 2006a, b). These mats are poorly developed compared with algal mats in the lakes of the nearby Larsemann Hills and pinnacle mats seen in the lakes of the McMurdo Dry Valleys (Hawes and Schwarz 1999;Hodgson et al 2004). Nevertheless, the algal mats in Ace Lake provide a matrix for a diverse community of diatoms McMinn 1996, 1999) with Navicula spp., Fragilaria spp.…”

Nutrient limitation of periphyton growth in arctic lakes in south-west Greenland

“…A common feature of many of these studies is a focus on nutrient limitation of phytoplankton growing in the open water column (Levine and Whalen 2001;Jansson 2006, 2008;Elser et al 2009a, b). This is despite evidence which suggests that phytobenthos (periphyton) communities can achieve very high standing stocks (Bonilla et al 2005) and often dominate total lake biomass and/or production in high-latitude lakes (Vadeboncoeur et al 2003;Hodgson et al 2004;Bonilla et al 2005). The contribution of phytobenthos and phytoplankton communities towards total lake production is also highly variable and has been shown to shift in response to physico-chemical gradients, including nutrient availability (Vadeboncoeur et al 2003).…”

Diversity of RuBisCO gene responsible for CO2 fixation in an Antarctic moss pillar

“…Moreover, biologically harmful levels of solar radiation may penetrate through the ice cover and shallow water column (Vincent et al 1998) because of low concentrations of UV-absorbing material (Morris et al 1995). Benthic microbial communities in the lake produce carotenoids, xanthophyll, scytonemin, and mycosporine-like amino acids (Vincent et al 1993a;Quesada et al 1999;Hodgson et al 2004;Tanabe et al 2010), presumably to protect against intense light conditions (Kudoh et al 2009). Despite this extreme environment, large pillar communities of aquatic mosses have been found in on the lake-bed near the Syowa Station located in East Antarctica (Imura et al 1999).…”