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composition of sea water (average)

 
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Joined: 24 Oct 2004
Posts: 47
Location: Nearwater

PostPosted: Wed Nov 10, 2004 11:48 pm    Post subject: composition of sea water (average) Reply with quote

Open ocean salinity ranges from around 33ppt around the poles and 38ppt around equatorial regions. The

average is around 35ppt and the chemical compostion for this average is shown below.

Factors effecting this salinity are such things as ice melt, inflow of river

water, rain, snowfall, wind, wave motion and evaporation. The coastal waters are more often of less salinity then the open ocean, especially around river

mouths.


Chemical Composition ................. Content ppt (parts per thousand)

Chloride (Cl).................................. 19.350
Sodium

(Na).................................. 10.710
Sulphate (SO4)............................... 2.690
Magnesium (Mg)............................. 1.304
Calcium

(Ca)................................... 0.419
Potassium (K)................................. 0.390
Bicarbonate (HCO3)........................ 0.146
Bromide

(Br).................................... 0.070

Total dissolved solids (salinity)...... 35.079
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Sally



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PostPosted: Sat Nov 27, 2004 1:37 pm    Post subject: Reply with quote

Does this vary much in individual rock pools (of a reasonable size) by any chance.
I'm thinking, on a hot day for example, that evapouration

would only remove fresh water, so that the salt content would be left (in an ever decreasing volume of water in the pool), and so is getting more saline?

Sally
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natalie
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PostPosted: Sat Nov 27, 2004 1:42 pm    Post subject: Reply with quote

Sounds about right, Sally. No salt gets evapourated and so gets left in full, in the decreasing volume, this would indeed certainly increase the

salinity.
Natalie
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PostPosted: Sat Nov 27, 2004 1:50 pm    Post subject: Reply with quote

Variations of salinity within a rockpool occur within the time of the tide rise and fall of course, so once isolated from the main sea it is a little

ecosystem in itself that undergoes this salinity variation...... all in it must have methods to survive this often sizable variation.

The surface area compared to the

depth of the pool would be a factor effecting the amount of evapouration possible (as well as the time exposed as mentioned before).

Osmosis is a powerful

influence on tissue cells, so a lot of adaptation/ability is in place in order to survive within some pools.

Stephen


Last edited by administration on Sun Jan 23, 2005 9:31 pm; edited 2 times in total
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Sally



Joined: 24 Oct 2004
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Location: Surrey

PostPosted: Sat Nov 27, 2004 1:55 pm    Post subject: Reply with quote

no salt removed in evapouration = increased salinity

increased duration exposed = increased evapouration (unless raining!)

surface

area and depth = differ the range of evapouration rate and overall salinity.

osmosis effects cell tissues = adaptation/ability to survive if caught in a pool.....

through choice (or by accident!)


OK, I'm off to the library to tackle these headers!!
Thanks very much
Sally x
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PostPosted: Sat Nov 27, 2004 2:00 pm    Post subject: Reply with quote

Quote:
increased duration exposed = increased evapouration (unless raining!)
(Sally 27thNov 1.55pm)

...

unless raining.... good point. If precipitation is more influential than exposure to evaporation, then a dilution will occur and so obviously cause a decrease of

salinity.

Good luck with further research
Stephen
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