A Photomicrographic Survey of the Springtime
Phytoplankton Assemblage in Southampton Waters
Brian Wysor
Southampton College
Spring 1996
Desmids|Diatoms|Dinoflagellates
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Desmids
Micrasterias sp. (Phase Contrast)
Staurastrum sp. (Phase Contrast
& Bright Field)
- These freshwater chlorophytes show the characteristic
semicell morphology of the group of unicellular green algae referred to
as desmids. The unicell consists of two semi-cells connected by an isthmus
wherein the nucleus (not visible) is located. Also characteristic of this
group of algae are two plastids, one in each semicell which conforms to
the morphology of the cell. Desmids are important in understanding the
phylogeny of higher plants because they are part of a group of green algae
which, having a phragmoplast and a nuclear envelope that degrades with
the onset of mitosis, most resemble higher plants in terms of cellular
division.
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- more information on Desmids can be found at: http://www.rrz.uni-hamburg.de/biologie/b_online/ralfs/title.htm
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Diatoms
Eucampia sp. (Phase Contrast)
Asterionellopsis glacialis (Phase
contrast and Fluorescence Microscopy)
Stephanopyxis sp. (Phase Contrast)
- Diatoms constitute an enormous group of organisms, approximating
100,000 different species by some estimates (Round and Crawford, 1990).
They occur in abundance in all types of habitats, including marine and
freshwater systems as well as on damp rocks or in soil. All of the examples
shown here are estuarine species collected in the waters surrounding Long
Island, NY. These unicellular organisms are unique in that they have a
siliceous cell wall called a frustule. This "glass shell"
sinks following the death of the diatom and can accumulate in large densities.
Fossil deposits consisting largely of diatom frustules are presently mined
as diatomaceous earth (also known as diatomite ) and used
as a filtration medium, as abrasives (sometimes used in toothpaste), deodorants
and decoloring agents (Hoek, et al., 1993). Diatoms are important ecologically
as well, contributing an estimated 20-25% of global primary production
(Werner, 1977) and forming the basis of food webs in both marine and freshwater
systems.
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- Hoek, C. van den, D. G. Mann and H. M. Jahns. 1993. Algae,
An Introduction to Phycology. Cambridge University Press, Cambridge,
627 p.
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- Round, F. E. and R. M. Crawford. 1990. Phylum Bacillariophyta.
In Margulis, L., J. O. Corliss, M. Melkonian & D. J. Chapman
(Eds.), Handbook of Protoctista, pp. 574-596. Jones & Bartlett,
Boston.
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- Werner, D. 1977. Introduction with a note on taxonomy.
In Werner, D. (Ed), The Biology of Diatoms, , pp. 1-17. Blackwell,
Oxford.
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Dinoflagellate
Ceratium sp. (Phase Contrast)
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