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Fine‐layer depth relationships of lakewater chemistry, planktonic algae and photosynthetic bacteria in meromictic Lake Fidler, Tasmania
Author(s) -
BAKER ALAN L.,
BAKER KATHLEEN KROMER,
TYLER PETER A.
Publication year - 1985
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/j.1365-2427.1985.tb00245.x
Subject(s) - chemocline , algae , water column , population , diel vertical migration , environmental chemistry , microbial mat , anoxygenic photosynthesis , ecology , botany , chemistry , photosynthesis , biology , phototroph , bacteria , paleontology , cyanobacteria , demography , sociology
SUMMARY.1 Use of a multi‐column thin‐layer pneumatic sampler and modified analytic procedures has enabled resolutions of chemical and biological strata at 2.5 or 5.0 cm depth intervals. Examination of meromictic Lake Fidler, Tasmania, indicates the presence of a thin, intense stratum of bacteriochlorohyll d in the upper monimolimnion, associated with a discrete stratum of Chlorobium cf. limicola at the microaerobic interface between the oxygenated and sulphide‐rich zones. 2 Algae included small populations of Chlorophyceae, Chrysophyceae, Bacillariophyceae and Cryptophyceae. Bacteria included microaerophils and obligate anaerobes, pigmented and colourless, in well‐defined strata in the upper monimolimnion. A population of the microcrustacean Calamoecia tasmanica tasmanica was present in the mixolimnion. Chaoborus larvae were concentrated within the Chlorobium layer. 3 The chemical profile of Lake Fidler was stable, with a chemocline constant in position relative to the lake bottom. The surface water levels rose and fell through a distance of 1m in conjunction with heavy rainfall in the rainforest, and with river level variation, but had no measurable effect on the absolute position of the chemocline. Marked heterogeneity of dissolved substances at depths in the vicinity of bacteria suggested endogenous influence on pH and gelbstoff (‘gilvin’ in Australia). 4 Downwelling light attenuation was influenced primarily by gelbstoff (‘gilvin’) in the mixolimnion, with only red light (peak at 700 nm) measurable below 2 m. Light was absorbed mainly by Chlorobium in the monimolimnion, and was unmeasurable deeper than 3 m. 5 The absorption spectrum of the bacteriochlorophyll d in vivo , with a maximum absorbance at 721 nm, corresponds with the available downwelling light penetrating the mixolimnion to the Chlorobium layer.