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The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 11:56 AM

Where does most of the oxygen in ocean water (used by fish) come from ? Is it just the surface contact between the atmosphere, and the surface of the water ? (If so how significant are the waves and churning of the water at the surface ?) Is the most important addition to the gases dissolved in the waters coming from the (fresh water) rains, that land in waters, or is it from the rivers that feed into the oceans and lakes ? A separate matter, is the question of whether the air that gets dissolved in ocean. is dissolved as "air", or whether the O2 comes in "independently", of the mixture of air (same questions relates to the bubblings of air into a fish tank.) Are there any chemical reactions (of significant scale) that are going on in the water ? Where does information like this come from, if you know it ? Of if you're guessing, just tell me "educated guess". Thanks.

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#1

Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 12:13 PM

Pho - to - syn - the - sis.

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#2
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 3:22 PM

That doesn't really ring correctly with me, but i surely could be wrong. After all think of all the fish tanks and fish bowls, that don't have any plants in them, or plastic plants or a minimal number of real plants. Fish tanks, do a big job on bubbling air through the water, there must be great gain in aeration/dissolved air from that or that method wouldn't be used. ---------------- Do you have any "authority" for your one word answer ? Are you talking about bacteria, or algae, or plankton ? Other than the algae, which isn't everywhere in the ocean I though the other organisms were "consumers" of oxygen. Is that correct. Can you point me to some "academic authority" that has statistics, percentages, etc.? Thanks.

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#3
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 5:08 PM

I was taught in grade school that plankton and other algae were the primary source of oxygen in sea water. They were the cause of water having a greenish color, which otherwise would be clear, or bluish due to reflection of the blue sky.

Certainly precipitation -- snow, rain, hail, the occasional airplane -- would mix air into the water. Wind/wave action would add a substantial amount. Other sources would include icebergs when they dissolve, and oxygen brought in from rivers.

You could always try one of those 'search engines' to see if there is any information from *certified* experts.

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#4
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 5:18 PM

Given new, recent decades information, how much faith should we put anymore in the "science" we were taught at an early age, for me 40+ years ago. Actually, I thought the plankton might be a source of the o2 in the atmosphere, not so much in the water/oceans, as its (the plankton) has been looked at as a sink for the excess co2. Would you still bet on plankton ? --------- I thought the big science understandings of the last decades were about surface effects. And where would you say that the aquarium analog fits in, if relevant. ? Should this question go into another category ? HN

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#6
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 7:43 PM

I was certified once, but thanks to lithium I'm a lot better now.

You are absolutely right about the photosynthesis. The whole cycle is a bit complicated because it has to include the carbon (or carbon dioxide) cycle as well, but NOAA has a lot of info on this.

Another GA to ya!

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#5

Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/29/2010 5:25 PM

Phytoplankton produce half the world's oxygen. It stands to reason that is the major source of oxygen in the water. GA usbport.

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#7

Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/30/2010 12:54 AM
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#8

Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/30/2010 7:45 AM

Most of this has been covered by others, but to answer "A separate matter, is the question of whether the air that gets dissolved in ocean. is dissolved as "air", or whether the O2 comes in "independently", of the mixture of air"

The different gases in air (nearly all oxygen and nitrogen) dissolve according to their solubility and partial pressure in the atmosphere. For a given partial pressure, the solubility of O2 is about 2x that of N2. So as the partial pressures in the atmosphere are O2 21%, N2 79%, the mass of N2 dissolved is about 2x O2, not 4x. If you boil the gas out of water and collect it, it contains ~ 1/3 O2, compared with 1/5 in atmosphere.

Cheers..........Codey

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#9
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/30/2010 11:07 AM

It seems like you are writing with the greatest authority of all who have answered. So I ask, is the O2 that ultimately become dissolved in the ocean waters coming mostly from photosynthesis, or from the ordinary contact between the water and the atmosphere, the wave actions, etc. ? (Perhaps same varies based on where among the "seas" one is focussing. Of course, the concern relates to whether the heavy growth of oil digesting microorganisms of the Gulf of Mexico are deoxygenating those waters, to the extreme detriment of other animal life, fish, shrimp, shellfish, etc.) Thanks.

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#10
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/30/2010 1:21 PM

Thanks for the compliment, but I can't add much to usbport et al. The figure of 1/2 the world's oxygen coming from the algae and plankton seems reasonable, and as we're told the oceans play a large part in absorbing atmospheric CO2, photosynthesis is returning oxygen. On that basis, the ocean is saturated with oxygen (about 10 mg/l, depending on temperature) and the excess goes out into the atmosphere. I'd expect the nitrogen concn. to be constant, in equilibrium with the atmosphere.

There's no chemical reaction between the atmosphere and seawater.

Cheers......Codey

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#11
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/30/2010 4:44 PM

Re the chemical reaction - I realize its not a chemical reaction at all. But here's a question I have no way to consider thru any sort of measurements. Suppose one had a 2 liter soda bottle half filled with tap water at 10degreees C (i.e. about 50 F). It was standing opened and exposed to the ordinary atmosphere. One put the cap back on and then shook it vigorously for a half minute. By what percent do you expect the concentration of O2 in the water would increase, after a minute of "settling". Is ball park most likely 5%, 10 % 20% or 50%. My uneducated guess would be the high end. Similarly, if someone has the ability to do the measurement: If one has carbonated water, in a 1 liter bottle, unopened, at refrigerator temperature, how much more is the concentration of CO2 at 20 seconds after its opened than a hour later, if its left standing. How much more than when its mostly flat 12 hours later ? Any venturing experimenters or guessers ?

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#12
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

07/31/2010 1:19 PM

Not sure what you mean by first question.

If the water has been in the bottle a long time it is already saturated with O2 (and N2) so there is no change when is capped and shaken.

If the water has no dissolved gases (eg because it has been boiled) and it is shaken long enough, it ends up close to saturation. At 10°C O2 (from normal atmosphere) needed to saturate 1 litre water is 11.25 mg. The 1 litre air contains about 300 mg O2 so is not significantly depleted. Similar for the N2. Whether half minute shaking is enough I'm not too sure, but I'd think it would be well on the way. It doesn't take very long time to dissolve. Incidentally, O2 saturation, mg/l, (from normal atmosphere) varies with temperature T°C as 468/(31.6 + T) near enough for most purposes over range 5 - 35°.

Second question - sorry, my guess would be no better than yours.

Cheers........Codey

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#13
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

08/01/2010 4:12 PM

Thanks, for your thoughts. I'm trying to understand mechanism by which water will take in gases. Let's say water had been boiled, and then poured into a glass (or beaker). No stirring, shaking or other agitation. Would atmospheric gases begin to dissolve in it, when it reached ambient temperature ? Given a long period of time standing with surface exposed, would there be a significant % difference between the amount of the gas dissolved in the top 10% of the container verses, the 10% closest to the bottom ? If the beaker was just standing still, do you think the water would reach its O2 and N2 near saturation levels for the given temperature within 2 days ? i.e. does the dissolved gas "migrate" evenly to all levels evenly ? or would you expect it migrates very little, from near the surface ? and if so why ? Thanks again.

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#14
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Re: The Oxygen in the Ocean Waters, Where Does it Come From?

08/03/2010 10:21 AM

If deaerated water is in contact with air it will begin to absorb gases, even without agitation. The question is - at what rate, and I have very little idea. Unless somebody comes up with a figure, if you really need to know, I suggest you get hold of a DO meter and do the experiment.

You could move the probe up and down gently to see how DO varies with depth, or to get an average you could stir gently, to mix but not enough to increase absorption.

Cheers...........Codey

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