Environmental Engineering Reference
In-Depth Information
Fig. 5.1
Estimation of phytopigments through spectrophotometer
through analysis of phytopigments (Fig.
5.1
).
Chlorophyll is the key diagnostic marker of
phytoplankton. The spectrophotometric method
of chlorophyll estimation is widely used in
researches related to phytoplankton distribution.
For chlorophyll estimation of marine and
estuarine phytoplankton, 1 L of surface water,
collected from the sampling stations during high
tide condition, is
The values obtained from the equations were
then multiplied by the volume of the extract (in
ml) and divided by the volume of the water (in
litre)
ltered to express the chlorophyll content in
mg m
−
3
. All the analyses are usually conducted
in triplicate on the basis of collection of three
samples from the same site in order to ensure the
quality of the data.
In modern times, high-performance liquid
chromatography (HPLC) (Fig.
5.2
) is used to
evaluate the pigment discrimination and quanti-
ltered through a 0.45
µ
mMil-
lipore membrane
tted with a vacuum pump. The
residue along with the
lter paper is dissolved in
90 % acetone and kept in a refrigerator for about
24 h in order to facilitate the complete extraction
of the pigment. The solution is then centrifuged
for about 20 min under 5,000 rpm, and the
supernatant solution is considered for the deter-
mination of the chlorophyll pigment by recording
the optical density at 750, 664, 647 and 630 nm
with the help of spectrophotometer (Fig.
5.1
). All
the extinction values are corrected for a small
turbidity blank by subtracting the 750 nm signal
from all
cation directly from sea water samples. This
approach provides an idea about the distribution
of phytoplankton in different regions of the ocean
based on diagnostic carotenoids such as zea-
xanthin (speci
c for cyanobacteria) and para-
xanthine (speci
c for paraphycea).
5.1.3 Assessment Through Remote
Sensing
nally, the
phytoplankton chlorophyll is estimated as per the
expression of Jeffrey and Humphrey (
1975
).
the optical densities, and
Chlorophyll can also be identi
ed by remote
sensing. The critical Coastal Zone Colour Scan-
ner (CZCS) has made it possible to establish the
key
Chl a
¼
11
:
85 OD
664
1
:
54 OD
647
0
:
08 OD
630
features
of
phytoplankton
distribution
throughout the world ocean.
