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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