Environmental Engineering Reference
In-Depth Information
will be bene
cial when the initial temperature is
cooler than optimal and detrimental when it is
warmer than optimal, and the precise change in
performance can be predicted from the starting
and ending temperature values along the curve.
Unfortunately, the shapes of thermal perfor-
mance curves and the positions of their optima
are poorly described in most seaweed. Although
many physiological and ecological studies have
linked seaweed performance to temperature, a
substantial fraction of these studies do not inves-
tigate enough temperatures across a wide enough
range to characterize the underlying, nonlinear
relationship between the two. Furthermore, vari-
ous physiological parameters within an organism
differ in the shape and optimum temperature of
their thermal performance curves, which limits
our ability to use an easily measured parameter
(e.g. photosynthesis) as a proxy for parameters
that may be more ecologically relevant (e.g.
growth and reproduction). Indeed, growth rates do
tend to peak at lower temperatures than photo-
synthetic rates, presumably because metabolic
rates increase faster than photosynthetic rates at
higher temperatures. Much remains to be learned
regarding the thermal dependence of the key
physiological processes that control growth,
reproduction and survival across the full range of
temperatures experienced by an individual in its
lifetime.
A study conducted by Indian researchers
exhibits that the biochemical composition of a
red seaweed species in lower Gangetic delta
region is greatly in
E. Plate Tectonics
The movement of the Earth
s crust is the basis of
the theory of plate tectonics. In this theory, the
lithosphere is viewed as a series of rigid plates that
are separated by the earthquake belts of the world,
that is, the trenches, ridges and faults. There are
seven major lithospheric plates: the Paci
'
c, Eur-
asian, African, Australian, North American, South
American and Antarctic plates. Each plate is
composed of continental and/or oceanic crust.
At the mid-oceanic ridges, where plate bound-
aries move apart as new lithosphere is formed,
divergent plate boundaries occur. Convergent plate
boundaries occur at trenches, where plates move
towards each other and old lithosphere is destroyed.
The plates move past each other at regions known
as faults, which represent breaks in the Earth
'
scrust
where one plate can move past the other.
A transform fault is a special kind of fault that
is found in sections of the mid-ocean ridge. Each
side of a transform fault is formed by a different
plate, and these plates are moving away from
each other in opposite directions. The fault zone
produced by this movement is quite active and is
the site of frequent earthquakes. The motion of
the plates along these faults produces a nearly
continuous line of cliffs with sharp vertical drops,
known as escarpments. In these regions, there are
sudden changes in the ocean depth. Regions
where the lithosphere splits, separates and moves
apart as new crust is formed are called rift zones.
The mid-ocean ridge and rise systems represent
the major rift zones at this time. It is generally
thought that rifting occurs when rising magma
causes enough tension to stretch the overlying
crust, creating a sunken rift zone. As this process
continues, the rift spreads and the fault deepens
and cracks, allowing the magma to seep through
and eventually form a ridge. When this happens
to the lithosphere under the continents, a sunken
rift zone can occur. As the process continues, the
fault gets thinner and deeper and can eventually
uenced by temperature,
particularly the carbohydrate content exhibited
signi
fl
cant positive correlation with ambient
aquatic temperature (Table
7.1
). This table indi-
cates that salinity is a vital parameter regulating
the biochemical composition of coastal vegeta-
tion. High salinity is a major threat to the protein
level of the seaweed. The carbohydrate and as-
taxanthin levels are, however, positively corre-
lated with salinity proving that under salinity
stress the seaweeds survive by increasing the
astaxanthin content of the thallus. This is a major
biochemical adaptation in context to salinity
stress that is quite common in the coastal regions.
ll with sea water. The Red Sea is an example of
this type of formation.
As a plate moves away from the rift zone, it
cools and thickens. At the rift, thinning of the
crustal plate and increased
fl
ow of magma into
