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bgsu1332431260.pdf (9 MB)
ETD Abstract Container
Abstract Header
Psychrophilic diatoms in ice-covered Lake Erie
Author Info
D'souza, Nigel A.
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1332431260
Abstract Details
Year and Degree
2012, Doctor of Philosophy (Ph.D.), Bowling Green State University, Biological Sciences.
Abstract
Winter surveys across Lake Erie between 2007 to 2011 documented diatom assemblages associated with extensive ice cover. This study aims to characterize these winter assemblages in terms of their community structure, their interactions, adaptations to a psychrophylic lifestyle and their role in the biogeochemistry of the lake. The winter assemblage was dominated by diatoms, specifically by
Aulacoseira islandica
(O. Müller) Simonsen (≈80%) and
Stephanodiscus binderanus
(Kützing) Krieger (≈19%), with other taxa like
Fragilaria
spp.,
Cyclotella
spp.,
Asterionella
spp., and
Tabellaria
spp. making up less than 1% of the assemblage. The detailed morphology of the two dominant taxa observed are described in this study, and the presence of resting cells and auxospores in filaments of
A. islandica
, but not in the other taxa are documented. The study compares different sample processing techniques for scanning electron microscopy (SEM), and describes a rapid and effective technique, substituting critical point drying (CPD) with hexa-methyl-di-silazane (HMDS) treatment, that allows viewing of fine details including the epiphytic colonization of the diatoms by flagellated rod-shaped bacteria embedded in an extracellular matrix. The study also describes ice nucleating activity associated with assemblages of filamentous diatoms sampled during winter and early spring across the Laurentian Great Lakes. The ability to promote ice formation offers a previously undescribed mechanism by which non-motile phytoplankton can attach to overlying ice and, thereby, maintain a favorable position in the photic zone. The ice nucleating activity is attributed to bacteria. Bacteria isolated from the phytoplankton showed high temperatures of crystallization (T
c
) to -3°C. Ice-nucleating active (INA) isolates were identified as belonging to the genus
Pseudomonas
. Whereas INA bacteria have been isolated from lakes and streams, their presence in these environments is attributed primarily to runoff and atmospheric deposition as rain or snow consistent with their proposed role as biological ice nuclei in clouds. Far from a passive existence in the aquatic milieu, the INA microbes associated with winter diatoms in the Great Lakes may possess a role in promoting the formation of ice during winter and in so doing, promote the growth of their diatom hosts under ice. The novel mechanism presented may be relevant to temperate and polar ecosystems beyond the Great Lakes including coastal oceans. Finally, photosynthetic O
2
evolution rates measured in winter support characterization of the assemblage as a photosynthetically robust population, with rates of primary production in winter higher than those measured in spring and comparable to those reported in summer. Results further suggest that the winter diatom assemblage may play an important role in the export of carbon to the benthos, thereby potentially driving the hypolimnetic oxygen deficits observed months later in summer.
Committee
Robert Michael McKay, PhD (Advisor)
George Bullerjahn, PhD (Committee Member)
Scott Rogers, PhD (Committee Member)
Rex Lowe, PhD (Committee Member)
Jeffrey Snyder, PhD (Committee Member)
Pages
158 p.
Subject Headings
Aquatic Sciences
;
Biogeochemistry
;
Biology
;
Ecology
;
Freshwater Ecology
;
Limnology
;
Microbiology
;
Molecular Biology
Keywords
psychrophiles
;
diatoms
;
ice
;
lake
;
Erie
;
microscopy
;
ice nucleation
;
primary production
Recommended Citations
Refworks
EndNote
RIS
Mendeley
Citations
D'souza, N. A. (2012).
Psychrophilic diatoms in ice-covered Lake Erie
[Doctoral dissertation, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1332431260
APA Style (7th edition)
D'souza, Nigel.
Psychrophilic diatoms in ice-covered Lake Erie.
2012. Bowling Green State University, Doctoral dissertation.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1332431260.
MLA Style (8th edition)
D'souza, Nigel. "Psychrophilic diatoms in ice-covered Lake Erie." Doctoral dissertation, Bowling Green State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1332431260
Chicago Manual of Style (17th edition)
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Document number:
bgsu1332431260
Download Count:
1,183
Copyright Info
© 2012, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.