Environmental Engineering Reference
In-Depth Information
A
B
5 μm
m
5 μm
15 μm
5 μm
(a)
(b)
Figure 4.70
(a)
Nitzschia
. Top: Live cells, each with two olive brown chloroplasts. Bottom: Acid digest, lake sediment
sample. The raphe (arrow) with punctae is displaced to the margin (keel). Reproduced with permission from M. Capstick.
(b) A:
Nitzschia linearis
. Straight-sided alga with small median constriction (m). B:
Nitzschia dubia.
structure itself is a canal supported by
bars which appear as carinal dots. There
is no clear central area in the striae which
may be fine or coarse in appearance. Two
large chloroplasts are present, one either
end of the central area. Cells (20-250 μm
long, 4.5-16 μm wide) are usually soli-
tary but can form stellate colonies or a
number can be present in a mucilagi-
nous tube. May be benthic or planktonic.
A very common and widespread genus
foundinavarietyofwatertypes.
Nitzschia
sp.
can grow in open water treatment fil-
ters in such numbers to cause blockage.
Bacillariophyta. Plate XXVI. Figs. 4.70a
and 4.70b.
(b) Chloroplasts not as above. No carinal
dotspresent.......................
193
193
(192) (a) One or two chloroplasts, plate-like or
H-shaped. Pyrenoid may be present or
obvious large droplets on the chloroplast
..................................
194
(b) Chloroplastsnotasabove......
195
194
(193) (a) Two plate-like, H-shaped chloro-
plasts, one above and one below the mid-
dle of the cell, often with two conspicu-
ous droplets. Striations on valve surface
interrupted by one or more marginal lines.
Polar terminals of the raphe forked, with
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