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The ecology and taxonomy of Synechococcus from saltwater lakes in the Vestfold Hills, Antarctica

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Rankin, LM (1998) The ecology and taxonomy of Synechococcus from saltwater lakes in the Vestfold Hills, Antarctica. PhD thesis, University of Tasmania.

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Abstract

In 1992, a marine Synechococcus was discovered in a meromictic lake in the
Vestfold Hills, Antarctica. This thesis describes the ecology and taxonomy of
this organism.
Ace Lake is a saltwater, meromictic that was isolated from the marine
environment approximately 6000 years ago. In 1992, The lake was 25 m deep,
the top 12 m was oxygenated and the lake had a salinity range of 16 to 40 g kg-1
salt. The recent discovery of Synechococcus in Ace Lake was aided by flow
cytometric methods. In Ace Lake, Synechococcus occured in the highest
densities below the pycnocline with maximum numbers occurring just above the
oxic/anoxic interface. Synechococcus bloomed in spring with numbers declining
again in early January. At the peak of the bloom in 1992, a density of 8 x 106
cells mr1 was recorded at 11 m in the lake. No diel periodicity in the growth of
Synechococcus was detected.
Synechococcus was also present in two of ten other meromictic lakes and basins.
The organism occured throughout the aerobic zone in Pendant Lake, in densities
of approximately 10-7 cells m1-1, and below the pycnocline in Lake Abraxas in
densities of 1.4 x 10 7 cells m1-1. It is possible that salinity restricts the
distribution of Synechococcus in the meromictic lakes of the Vestfold Hills.
Synechococcus strains were isolated from Ace Lake, Pendant Lake and Lake
Abraxas for further characterisation. The three strains were similar in size and
had the same lipid soluble pigment signature, with two unknown carotenoid pigments present in addition to the chlorophyll a, zeaxanthin and bb carotene.
The three strains had phycoerythrin as their principle accessory light harvesting
pigment. They were genetically similar (99. 7 % similarity in the 16S rRNA
sequence) and had a G + C content of between 57 and 58 mol %. They were also
genetically similar (95. 7 % similarity in the 16S rRNA sequence) to another
marine picocyano bacteria, Prochlorococcus marinus. Based on the square root
temperature dependence model, the minimum and maximum theoretical growth
temperatures of the Ace Lake Synechococcus strain was -8° C, and 29.8° C. The
optimal theoretical growth temperature was 19.7° C.
ln-situ growth rates of the Ace Lake Synechococcus strain at 6 m, 8 m and 10 m
in Ace Lake were determined. These rates were -0.118 d-1, 0.072 d-1 and
0.341 d-1 respectively. An increase in water temperature and a re~~on in light
intensity increased the in-situ growth rate of the Ace Lake Synechococcus
population. The grazing pressure on Synechococcus in Ace Lake was not
determined. It is probable, however, that the distribution and abundance of
Synechococcus in Ace Lake, Pendant Lake and Lake Abraxas is controlled by
grazing.
Chapter 1 summarises and reviews the current ecological and taxonomic research
that has been undertaken on Ace Lake. Chapter 2 describes the flow cytometric
techniques that were developed to study Synechococcus in Antarctic Lakes.
Chapter 3 discusses the ecology of Synechococcus in Ace Lake and chapter 4 the
distribution of Synechococcus in meromictic lakes in the Vestfold Hills. Chapter
5 describes the taxonomic characteristics of three Antarctic Synechococcus
strains and chapter 6 discusses controls of Synechococcus growth in Ace Lake.

Item Type: Thesis (PhD)
Keywords: Cyanobacteria, Cyanobacterial blooms, Microbial ecology
Copyright Holders: The Author
Copyright Information:

Copyright 1998 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1998. Includes bibliographical references

Date Deposited: 03 Feb 2015 03:14
Last Modified: 11 May 2016 03:10
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