Environmental Engineering Reference
In-Depth Information
Fig. 2.36
Rhizosphere of
Avicennia marina
with soil
Fig. 2.38
Rhizosphere of
, a com-
mon salt marsh grass of lower Gangetic delta region
Portrersia coarctata
clinging on the roots
Moving away from the deep-sea vents, the
concentration of microbial population drops
dramatically (Atlas
1998
). There are heterotro-
phic bacteria in the sea
oor sediments which
feed on photoautotrophic cyanobacteria that drift
down attached to sediment particles.
fl
2.3.3 Role of Marine Micro-organisms
in the Carbon Cycle
In sea water, there are 34,500 billion tonnes of
carbon, the cycling of which occurs in a steady
state (Hobbie and Melillo
1984
). Carbon dioxide
xation to form organic molecules is performed
by producers such as algae, cyanobacteria and
various green and purple photosynthetic bacteria.
Global estimates of important
uxes or transfers
between reservoirs are shown in Fig.
2.39
. Net
primary production (NPP = gross photosynthesis-
respiration) is approximately equal in terrestrial
and marine environments. Approximately 20 % of
the ocean NPP occurs in the coastal ocean; 80 %
of this is deposited in surface sediments. Turnover
or residence times for the reservoirs range from
fl
Fig. 2.37
Rhizosphere of mangrove associates with soil
clinging on the roots
metabolic energy and to withstand the extreme
environmental conditions of high pressure and
temperature (over 100
°
C).
