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View Full Version : Water too pure for life or marketing BS?


Robrein
08-06-2014, 04:10 PM
The wiki entry for Lake McKenzie (http://en.wikipedia.org/wiki/Lake_McKenzie) on Frasier Island states:

The sands around the lake are composed of pure, white silica and the water in the lake is also so pure it is unsuitable for many species.[2]

the cite is from the states tourism office (http://www.queenslandholidays.com.au/destinations/fraser-coast/things-to-see-and-do/lake-mckenzie-9006259/index.cfm) and they say:

There are many different aspects to Fraser Island, but the awe-inspiring beauty of Lake McKenzie makes it probably the most visited natural site on the island. It is a 'perched' lake, which means it contains only rainwater, no groundwater, is not fed by streams and does not flow to the ocean. The sand and organic matter at the base of the lake form an impervious layer, preventing rainwater from draining away.

The sand here is pure, white silica and is not only beautiful to look at but feels beautifully soft to walk on. The sand acts as a filter, giving the water its clarity and helping to make the water so pure it can support very little life. The blues and greens of the lake are endlessly fascinating and it's well worth getting up early to look across it in the soft light of dawn.

So is this a real you know...thing? Does it happen elsewhere? Can bodies of water be naturally so pure to be unable to support much life?

Surely in such a lake the minerals and nutrients would be accumulating if the water is only being discharged by evaporation.

The aerial imagery (https://www.google.com.au/maps/place/Lake+Mckenzie,+Great+Sandy+National+Park,+Fraser+Island+QLD+4581/@-25.4477719,153.0568034,1441m/data=!3m1!1e3!4m2!3m1!1s0x6bec8fcbe4ce9cbd:0x2a00eef1b6b98c50) seems to show that the lake has two small beaches at the northern end but there is plant life totally surrounding the rest of the shoreline.

Mangetout
08-06-2014, 04:20 PM
If phosphates and nitrates are low (and they could be, if it's entirely rain fed), then algae may be scarce - and algae are the bottom level of many food chains, so it's not completely implausible.

picunurse
08-06-2014, 04:53 PM
It called an oligotrophic lake (means "little life). The water has a higher oxygen content than most fish and aquatic plants like.
It's actually a new lake (in geologic time). All lakes are working their way to becoming forests.

What most people mistake is that sewage and other polutants encourage life in lakes. Life like milfoil, bullheads and lampreys. The kinds of fish that live in oligotrophic lakes are game fish, trout and salmon. Because they use more energy, they require more oxygen.

Saintly Loser
08-06-2014, 05:00 PM
Western Brook Pond (http://en.wikipedia.org/wiki/Western_Brook_Pond), in Gros Morne National Park, Newfoundland, Canada is like that. It's beautiful -- I've hiked up there a couple of times.

Max Torque
08-07-2014, 08:43 AM
Pure water is thirsty (https://www.youtube.com/watch?v=hMh1lyeNsPc). It has a nasty tendency to strip things out of your body that your body would like to keep in order to, you know, survive, being that water is a solvent. So if that lake water is too pure, yes, it can be harmful to life. It's uncommon for such a thing to occur in nature, but apparently if the circumstances are just right, it can happen.

bob++
08-07-2014, 08:53 AM
Gotta love "Pissing Mare Falls"

Sigene
08-07-2014, 09:00 AM
Pure water is thirsty (https://www.youtube.com/watch?v=hMh1lyeNsPc). It has a nasty tendency to strip things out of your body that your body would like to keep in order to, you know, survive, being that water is a solvent. So if that lake water is too pure, yes, it can be harmful to life. It's uncommon for such a thing to occur in nature, but apparently if the circumstances are just right, it can happen.

I would dispute this. I know this is a common thought and I've had fellow Ph.D chemists spout this, but I am unconvinced. Tap water is generally 0.03% minerals; there really isn't that much difference between what you normally drink and this level of purity. Pure water will be rapidly contaminated with enough stuff just from touching your lips and spit.
The bigger danger is from bacterial contamination from the spigots of pure water dispensers, if those aren't kept clean than people may get sick from bacteria.
But 'stripping minerals' from your body and you die.....no....I don't believe it.

CannyDan
08-07-2014, 09:03 AM
Pure water is thirsty (https://www.youtube.com/watch?v=hMh1lyeNsPc). It has a nasty tendency to strip things out of your body that your body would like to keep in order to, you know, survive, being that water is a solvent. So if that lake water is too pure, yes, it can be harmful to life. It's uncommon for such a thing to occur in nature, but apparently if the circumstances are just right, it can happen.

I know this isn't GD but I'm having trouble with this concept. I watched the clip, and remain skeptical. After all, a drink of water doesn't remain as a "bolus of evil" capable of sucking up needed ions then dropping down a disposal pipe to elimination, as the video seems to show. Water is certainly a great solvent, a fact we often forget since our bodies are mostly made up of the stuff. But that is the reason we have differentially permeable membranes at the cellular level and things like kidneys at the organic level.

I thought the reason such lakes have so little life is because they contain so little dissolved nutrients to support primary producers (algae and higher plants) which could support secondary consumers.

If I am incorrect, I'll happily accept further instruction.

ETA: and what Sigene said...

mmmiiikkkeee
08-07-2014, 12:02 PM
It called an oligotrophic lake (means "little life). The water has a higher oxygen content than most fish and aquatic plants like.
It's actually a new lake (in geologic time). All lakes are working their way to becoming forests.

What most people mistake is that sewage and other polutants encourage life in lakes. Life like milfoil, bullheads and lampreys. The kinds of fish that live in oligotrophic lakes are game fish, trout and salmon. Because they use more energy, they require more oxygen.

No, this isn't right. Oligotrophic lakes don't contain higher oxygen than most fish and plants like; water can only contain a certain amount of oxygen, and high concentrations are not avoided or detrimental to most fish and plants. Low oxygen concentration does have an impact however.

Trout and salmon don't require more oxygen because of their energy expenditures... They are usually in colder water, less productive systems( in fresh water at least) and grow slower than warm water fish. There are warm,cool, and cold water game fish; they are dependent on primary production as the eat either insects/benthic invertebrates or the smaller forage fish that feed on them.

Amateur Barbarian
08-07-2014, 12:37 PM
Pure water is thirsty (https://www.youtube.com/watch?v=hMh1lyeNsPc). It has a nasty tendency to strip things out of your body that your body would like to keep in order to, you know, survive, being that water is a solvent.

I would dispute this. I know this is a common thought and I've had fellow Ph.D chemists spout this, but I am unconvinced. Tap water is generally 0.03% minerals; there really isn't that much difference between what you normally drink and this level of purity.

I know this isn't GD but I'm having trouble with this concept. I watched the clip, and remain skeptical. After all, a drink of water doesn't remain as a "bolus of evil" capable of sucking up needed ions then dropping down a disposal pipe to elimination, as the video seems to show.
The purest bottled water is 50% pure BS... in its marketing.

Water is water, no matter where it comes from, and the mineral and other content is of nearly zero consequence in any nutrition or health way. That we have all been bamboozled into paying not just extraordinary amounts of money but collateral carbon footprint for moving essentially pure H2O all over the globe is a triumph of marketing over intelligence.

It's even less understandable when the sci-woo starts and doesn't even bother to thank homeopathy for the reach-around.

dracoi
08-07-2014, 02:47 PM
The whole thing about the lake being too pure for life is simply a lack of nutrients. If there was life, that life would be creating waste and the water would be less pure. Without nutrients, there's little life and there remains little nutrients. (In an oversimplified example).

Osmotic pressures could well be an issue for a fish - after all, they're looking at ounces of body weight to pounds of water. But for a human drinking that water, we're looking at pounds of body to ounces of water - by the time there was enough water to harm you, you'd be drowning in it regardless of purity.

Quercus
08-07-2014, 04:06 PM
No, this isn't right. Oligotrophic lakes don't contain higher oxygen than most fish and plants like; water can only contain a certain amount of oxygen, and high concentrations are not avoided or detrimental to most fish and plants. Low oxygen concentration does have an impact however.

Trout and salmon don't require more oxygen because of their energy expenditures... They are usually in colder water, less productive systems( in fresh water at least) and grow slower than warm water fish. There are warm,cool, and cold water game fish; they are dependent on primary production as the eat either insects/benthic invertebrates or the smaller forage fish that feed on them.
Yes, though there is an association between oxygen and nutrients.

In most unfrozen water bodies, there's plenty of sunlight and (of course) water, so the only thing limiting the growth of algae is nutrients -- almost always phosphorous in freshwater and nitrogen in salt water.

When there are a lot of nutrients (say from fertilizer runoff), then lots more algae grow. When they die and fall into the water column and to the bottom, the decay process uses up lots of oxygen. In the worst case, nearly all the oxygen is used up, and fish start dieing, with unwanted bottom-feeding species like carp and catfish generally able to stand low oxygen better than trout and the like.

Hari Seldon
08-07-2014, 04:58 PM
My WAG: if there is not enough calcium, shellfish won't be able to make shells and vertebrates won't be able to make bones. I know that seeding water with iron will encourage algal growth. Certainly soil can be so denuded of minerals that plants cannot grow; why not lakes.

jharvey963
08-07-2014, 05:06 PM
The Master Speaks (http://www.straightdope.com/columns/read/2339/can-water-be-too-pure-is-too-much-water-bad-for-you).

J.

johnpost
08-07-2014, 05:19 PM
throw in some cats. eventually life will start to exist in the water.

Amateur Barbarian
08-07-2014, 06:52 PM
There are two completely different things at play here:

1) Water in a natural pond or aquifer that is so free of dissolved minerals and chemicals that life forms that extract those substances from water can't live there. Possible if unlikely but irrelevant unless you're that species of tadpole, rotifer or clam.

2) Water so pure, so close to being 100% H2O molecules, that it somehow represents a hazard to humans who ingest it. (2a would be such water that is especially good for you because it's so perfectly pure.) Both are quite self-evident BS, an extension of the water mania marketing.

Princhester
08-07-2014, 08:10 PM
2) Water so pure, so close to being 100% H2O molecules, that it somehow represents a hazard to humans who ingest it. (2a would be such water that is especially good for you because it's so perfectly pure.) Both are quite self-evident BS, an extension of the water mania marketing.

Been there, swum in it, probably drank some - even if inadvertantly - and I'm still alive.

Maybe neither myself nor any of the other people who visit and swim and lived to tell the tale just didn't drink enough to die.