Environmental Engineering Reference
In-Depth Information
2.3.1 Taxonomy of Micro-organisms
in the Blue Soup
possess the pinnate diatom,
.
On seaweeds diatoms, yeast and bacteria thrive
luxuriantly.
Microbes are also available in plenty in the
rhizosphere of mangroves. The rhizosphere is the
narrow region of soil that is directly in
Cocconeis scutellum
The marine environment is the dwelling place of
a diverse group of micro-organisms such as
bacteria,
uenced
by root secretions and associated soil microor-
ganisms. Soil which is not part of the rhizosphere
is known as bulk soil. The rhizosphere contains
several strains of bacteria that feed on sloughed-
off plant cells, termed rhizodeposition, and the
proteins and sugars released by roots. Protozoa
and nematodes that graze on bacteria are also
more abundant in the rhizosphere. Thus, much of
the nutrient cycling and disease suppression
needed by plants occurs immediately adjacent to
roots. We enumerated microorganisms in the
rhizosphere and non-rhizosphere soil samples of
mangroves and mangrove associate species and
observed that the rhizosphere soil sample con-
tained higher microbial populations compared to
non-rhizosphere soil (Figs. 2.36 , 2.37 and 2.38 ).
Most of the bacteria in mangrove rhizosphere
belong to Gram-negative type. Gram-positive
bacteria constituted less than 15 % of the total
bacterial population in the rhizosphere zone of
Indian Sundarban mangroves.
fl
lamentous fungi, yeasts, microalgae
and protozoa. All these groups of marine micro-
organisms have different divisions and subdivi-
sions as stated here in tabular forms (Tables 2.23 ,
2.24 and 2.25 ).
2.3.2 Habitats of Marine Micro-
organisms
Marine micro-organisms inhabit various types of
habitats. They are distributed at the surface of the
sea as neuston (also known as pleuston ) or at the
photic zone of the pelagic region as plankton or at
the epibiotic habitats (attached communities).
They are also present inside the tissues of other
marine organisms (endobiotic habitats). Many
marinemicrobes are also distributed on the seabed.
Approximately 5,000 species of nekton swim
freely through the neritic and pelagic zones of the
ocean. The important members of nekton are
Arthrobacter
and
shes, reptiles and mammals. These animals also
produce organic debris referred to as seston
which contribute signi
endospore-producing forms
Bacillus
and
Clos-
tridium
(Family: Bacillaceae) have also been
isolated. Majority of bacteria belong to the fam-
ilies Pseudomonadaceae and Vibrionaceae. Most
rhizosphere zone occupied by bacteria is aerobic
or facultatively anaerobic. Nitrogen-
cantly to nutrition of the
micro-organisms.
Epibiotic habitats may be inanimate (such as
biofouling communities) or animate surfaces on
which attached communities occur. The endobi-
otic usually denotes the environment within the
tissues of other
xing bac-
teria such as members of the genera
Azospiril-
lum
,
Azotobacter
,
Rhizobium
,
Clostridium
and
larger organisms. Here,
the
Klebsiella
were isolated from the sediments,
rhizosphere and root surfaces of various man-
grove species, where the soil pH is slightly acidic
in nature.
The deep-sea environment is also an impor-
tant site of marine micro-organisms. Turner
( 1979 ) observed bacteria on the surface of faecal
pellets and concluded that many of the deep-sea
micro-organisms have their origin at the surface
layer of the ocean. This view has been supported
to some extent by the results of experiments
which
relationship with the host may be bene
cial
(mutualism), detrimental to the host (parasitism)
or may cause diseases (pathogenesis).
The intertidal zone of the marine environment
is rich in seagrass, salt marsh grass, seaweeds,
etc., which offer unique site for dwelling of
marine microbes. Evidences suggest that grasses
pose a narrower range of micro-organisms than
seaweeds. Sieburth et al. ( 1974 ) observed that
cord grass
Spartina alterniflora
is colonized
initially by fungi notably
Sphaerulina pedicel-
demonstrated
an
enhanced
rate
of
lata
, whereas eel grass (
Zostrea marina
) mostly
Search WWH ::




Custom Search