Environmental Engineering Reference
In-Depth Information
incorporating PFTs into ecosystem models. The
spatial variability and concentration of various
PFTs are critical to improving primary produc-
tivity estimates and understanding the feedbacks
of climate change. The ability to observe PFTs on
a global scale that relate to key biogeochemical
processes such as nitrogen
accuracy and rapid processing. A relatively new
analysis tool called CHEMical TAXonomy
(CHEMTAX) has been developed that is
designed to yield information on the phyto-
plankton composition using HPLC data (Mackey
et al.
1996
), but it has to be recognized that HPLC
models have their limitations (Latasa
2007
).
Algorithm development for remote sensing is
focused on estimating the quantities of various
optically active constituents in the ocean. Var-
ious pigments present in phytoplankton play a
role in determining the total absorption coef
xation, silici
cation
and calci
cation is valuable to studies of marine
elemental cycles. Despite the paucity of data on
functional groups, our understanding of ecosys-
tem linkages is improving as we accrue larger
amounts of data. Major divisions of phytoplank-
ton taxonomic groups such as diatoms, cocco-
lithophores, dino
-
cient of phytoplankton, which is a key deter-
minant of
agellates, chlorophytes and
cyanobacteria are often separated into distinct
functional groups, as these taxonomic groups
have unique biogeochemical signatures. Aiken
et al. (
2009
) showed how different size classes of
phytoplankton are distributed globally, and size is
often related to function (Nair et al.
2008
).
Nonetheless, there are limitations to discriminat-
ing phytoplankton taxonomic composition or
even functional groups by remote sensing, due to
our inability to discriminate various phytoplank-
ton types optically. Remote sensing re
fl
the spectral variability in remote
sensing re
ectance. Many researchers utilize a
reconstruction model to demonstrate the spec-
tral variability of photoprotective and photo-
synthetic pigments (Sathyendranath et al.
1987
;
Bidigare et al.
1990
). There are differences in
the weight-speci
fl
c absorption spectra of various
in vitro (extracted) phytoplankton pigments
(Fig.
5.3
).
The comparison between maximal peaks of
mass-speci
c absorption spectra and centre
wavelengths on ocean colour satellite platforms
proves that coupling taxonomic and optical
properties is quite challenging (Table
5.1
).
Researches have been undertaken to upgrade
sensors with increased temporal and spectral res-
olution that will provide more spectral informa-
tion for the development of algorithms. Scientists
are also putting their efforts to develop hyper-
spectral sensors that would cover pigment-speci
fl
ectance
Rrs (
uenced by absorption and back-
scattering by sea water, phytoplankton, coloured
dissolved organic matter, detrital matter and other
suspended materials (Garver and Siegel
1997
).
Remote sensing of particular types of phyto-
plankton is only possible if optical characteristics
are identi
)isin
fl
λ
ed for those types that can be used to
distinguish them from all other types of materials
in the water.
New
c
peaks at relatively high spatial and temporal res-
olution, which would allow retrieval of photo-
synthetic and photoprotective pigments.
The multispectral radiance measurements from
the satellite sensor can be corrected for the in
technological
developments
and
improved scienti
c knowledge have allowed for
the development of several approaches for
detecting phytoplankton biomass and some
functional groups of phytoplankton including
coccolithophores (Balch et al.
1991
,
1996
) and
Trichodesmium
u-
ence of the atmosphere to yield remote sensing
re
fl
ectance.
The suspended solids in the aquatic phase
often in
fl
(Subramanian and Carpenter
1994
; Subramanian et al.
1999a
,
b
; Hu et al.
2010
). More recently, algorithms have been
developed to distinguish additional phytoplank-
ton groups and size classes (Sathyendranath et al.
2004
; Alvain et al.
2005
; Moisan et al.
2011a
,
b
).
HPLC is the in situ method of choice to serve as
ground truth for satellite products due to its
uence the spectral signatures of phyto-
pigment. Hence, development of site-speci
fl
c
algorithm has been suggested by researchers. On
this issue, a study was conducted in the Indian
Sundarbans estuaries during 2005 to assess the
in
uence of suspended solid on spectral signa-
tures of phytoplankton.
fl
