seasonality in the oceans
TRANSCRIPT
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SEASONALITY IN
THE OCEANSGarry & Brian
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SEASONS AND THE ANGLE OF THE EARTH
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PHOTOPERIOD
f It is the duration of daily exposure to sunlight for an organism.
f June 21st is the longest day of the year, ie. when plants and other
organisms receive the most daily sunlight, which is essential for
photosynthesis, and other biological processes.
f December 21st is the shortest day of the year.
f This exposure to amount of light(thusly the seasons) coincide often
with the growth, maturation and spawning seasons of most animals
f Areas in which receive the most light, along the equator often show less
extreme effects with change in photoperiod, while areas of higher
latitude shows a more sharp change along with the seasons
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EXPERIMENTATION WITH PHOTOPERIOD
f In a study done in New Brunswick on Atlantic Salmon, they changed
the photoperiod for two different groups. For the first they gave them a
longer photoperiod earlier on in November. The second group was
given a longer photoperiod in February.
f The first group grew faster, but lacked the ability to adapt to largechanges in salinity. They also showed poor flesh quality.
f There was a significant occurrence of deformities dealing with
insufficient O2 supply during critical stages of development.
f By causing early maturation and growth by exposing them to light in
november caused a large growth of salmon stock which differs about 1-2kg more than the normal growth of the salmon.
f It is estimated that this would save 100,000 in the fish market however
this is not include the effect of downgrading flesh quality
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TEMPERATURE
f It is colder in winter, causing freezing of water, pack-ice, and most
perennial plants to go dormant.
f Changes in temperature have to do with the angle of the sun in relation
to the earth. It is winter when that section of the earth is tilted away
from the sun, and thus receives less direct sunlight. The opposite is true
for summer. The more direct sunlight, the warmer that section of the
earth will be.
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SEA ICE AND PACK ICE
f There is a very large amount of sea ice and pack ice between October
and April in the northern hemisphere. Mostly coming from the polar ice
caps and the freezing of ocean-water.
f This pack ice, when melting in the spring, can deposit many boulders or
other sediments.f In the southern hemisphere sea ice rapidly decreases during the months
of mid-november and mid-june.
f Sea ice surrounding Antarctica undergoes large seasonal changes in (a
real extent). Satellite imaging shows a maximum ice coverage at 20x106
km2
to a minimum of 3x106
km2
.
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REFERENCES
f Seasonality of southern ocean science (1981), Arnold L. Gordon,
Journal of geophysical research vol.86 No.cs pgs. 4195-4197