Environmental Engineering Reference
In-Depth Information
D. Variations in Solar Output
Several factors and parameters are responsible
for variations in solar output that cause temper-
ature difference in the planet Earth. The presence/
absence and number of sunspots is one of the
important reasons that regulate the magnitude of
solar radiation.
Sunspots have magnetic
biochemical and physiological adaptations,
including variation in the identity and concen-
tration of proteins and the properties of cell
membranes, that enable them to optimize their
performance with respect to the temperatures
they encounter (Eggert
2012
). Although sea-
weeds are generally well adapted to their thermal
environment, they nevertheless experience tem-
peratures in nature
elds of strength up to
3,000 times as great as the average magnetic
eld
of either the Sun or the Earth. Astronomers
believe the cause of sunspots is attributed to this
fact. According to a standard explanation, the
strong magnetic
particularly during periods
of environmental change
—
—
ciently
high or low to result in disruptive stress in the
form of cellular and subcellular damage
(reviewed in Davison and Pearson
1996
). Such
damage and any reallocation of resources for
protection and repair can slow growth, delay
development and lead to mortality (Davison and
Pearson
1996
). In response, seaweeds can pro-
duce heat shock proteins that repair or remove
damaged proteins (e.g. Vayda and Yuan
1994
;
Lewis et al.
2001
). However, protein thermal
physiology is not well understood in macroalgae
and the up regulation of heat shock protein pro-
duction is only one of many transcriptional
changes that occur in seaweeds during periods of
thermal stress (Collen et al.
2007
; Kim
et al.
2011
). Relevant genomic, transcriptomic
and proteomic studies are only just beginning to
scratch the surface and most links from gene
expression to organismal performance are far
from well established. As a result of non-stressful
conditions at intermediate temperatures and
stress at the extremes, the relationship between
temperature and most subcellular, tissue-level, or
whole-organism processes is described by a
hump-shaped thermal performance curve. From
colder to warmer, these curves generally rise
exponentially as rates of biochemical reactions
increase, peak at some optimum temperature, and
then fall rapidly as the biological components of
the system become less ef
that are suf
elds of the Sun have the shape
of tubes just below the solar surface at the
beginning of the sunspot cycle. These tubes lie
perpendicular to the Sun
s equator. The Sun
rotates faster at its equator than at its poles, and so
the tubes are stretched out
'
west
direction. Kinks then develop in the magnetic
tubes and push through the solar surface. A pair of
sunspots appears wherever a kink penetrates,
because the kink both leaves and re-enters the
surface. The number and size of sunspots show
cyclical patterns, reaching a maximum about
every 11, 90 and 180 years. The decrease in solar
energy observed in the early 1980s corresponds to
a period of maximum sunspot activity based on
the 11-year cycle. In addition, measurements
made with a solar telescope from 1976 to 1980
showed that during this period, as the number and
size of sunspots increased,
in the east
-
the Sun
'
s surface
°
cooled by about 6
C. Apparently, the sunspots
prevented some of the Sun
'
s energy from leaving
its surface. However, these
ndings tend to con-
tradict observations made on longer timescales.
During periods of maximum sunspot activity,
the Sun
eld is strong. When sunspot
activity is low, the Sun
'
s magnetic
'
s magnetic
eld weakens.
The magnetic
eld of the Sun also reverses every
22 years, during a sunspot minimum. Some
researchers believe that the periodic droughts on
the Great Plains of the USA are in someway
correlated with this 22-year cycle.
Temperature, a direct function of solar output,
determines the performance of coastal vegeta-
tion, and indeed all organisms, at the funda-
mental levels of enzymatic processes and
metabolic function. Seaweeds have evolved
cient or damaged
(Kordas et al.
2011
). When properly parameter-
ized across the full-temperature tolerance range
of a species, thermal performance curves have
the potential to predict the physiological effects
of any given warming or cooling scenario (bar-
ring any further acclimatization, adaptation or
context-dependent surprises; see below). The
effect of a small increase in thallus temperature
