Environmental Engineering Reference
In-Depth Information
The phytoplankton community encompasses both
prokaryotic and eukaryotic species. Till the end of
1980s, living plankton
or other activities. Within these, species groups
that largely control the community energetics and
that have profound in
fl
ora of the world ocean
uence on the survival
strategy of other species are known as ecological
dominants. The degree to which the dominance is
concentrated in one, several or many species can
be expressed through index of dominance that
re
fl
amounted to 474
504 genera and 3,444
4,375
-
-
species including the insuf
ciently known or
doubtful species (Sournia et al. 1991 ). To allow
for undescribed species and to avoid a spurious
impression of accuracy, Tett and Barton ( 1995 )
round up to a total (
ects the importance of a species or a group of
species in the community as a whole. However, if
the environmental parameters of the ecosystem or
the habitat are highly favourable for the survival of
all types of species, the value of index of domi-
nance is eclipsed by the values of richness index,
evenness
fl
) of 5,000 extant species of
marine phytoplankton distinguishable by classi-
cal, mainly morphological, criteria. In the estuar-
ies of Indian Sundarbans, about 102 species of
phytoplankton were documented since 2004
(Mitra et al. 2004 ). In this chapter, we have
identi
N
Weiner index,
which express the uniform importance of almost
all the species present in the community. A few
useful indices for analysing the community
structure of marine and estuarine phytoplankton
are discussed here.
index and Shannon
-
ed and listed 137 species of diatoms, 26
species of dino
agellates and 15 species of other
algae (green and blue green algae) from the
inshore waters of Bay of Bengal. Many of the
species were recorded from the brackishwater
ponds of Indian Sundarbans during 2010
fl
2013
(Annexure) . This documentation is the spin-off
product of a pilot project entitled
-
Index of Dominance
A single species or a group of species that modify
the environment in
Study on
carbon stock and response of estuarine phyto-
plankton to iron fertilization
'…
uences biologically controlled
phytoplankton communities. These organisms are
called dominants. It is not a very easy task to
determine the criteria of dominance. The domi-
nants in a community may be the most numerous,
possess the highest biomass, occupy the most
space, make the largest contribution to energy
fl
…'
funded by DST,
Govt. of India, during 2010
2014.
Assessment of phytoplankton standing stock
and species composition is extremely important to
understand the productivity of the aquatic system
in the framework of climate change. Standing
stock of phytoplankton can serve as the
2011 to 2013
-
-
ow
or mineral cycling or by some other means control
or in
fl
nger-
prints of carbon-sequestering zone. For over a
century, light microscopy was the basic tool to
observe phytoplankton and the method is still in
use with certain developments to determine the
species composition of phytoplankton. The spe-
cies composition and community structure of
phytoplankton are important to understand the
stress or favourable condition of the environment
in which these
uence the rest of the community. Many
ecologists have designated those phytoplankton
species as dominant, which are numerically supe-
rior. The index of dominance (Simpson 1949 )is
calculated according to the following expression:
fl
2
X n i
N
Index of dominance ð C Þ¼
oating organisms are
dwelling. A brief description of the different
species diversity indices are highlighted here with
their respective mathematical expressions.
The nature and function of phytoplankton
community are not determined by all the organ-
isms or the species present in the community,
but a relatively few species or species group
generally exert the major controlling in
free-
fl
where
= importance value for each species
(number of
n
individuals, biomass, production,
etc.) and
= total of importance values.
The index of dominance is always lower
where the dominancy is shared by a large number
of species (Whittacker and Niering 1965 ), or the
total populations of the community are uniformly
distributed among different species that are usu-
ally witnessed in clean, pollution-free waters
N
uence by
virtue of their size, number, production ef
fl
ciency
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