Water Temp & Visibility

[shotthebreeze]

This may sound like an idiotic question, but do water temperatures have anything to do with visibility? I've noticed from my diving that the colder the water gets, the more visibility tends to decrease. I know a lot of it has to do with bottom composition and what kind of wind/surf your diving under, but is it in any way related to the temperature?

 

[BarryNL]

Temperature isn't particularly relevant. In the sea the main determinant of visibility is nutrient content in the water - when nutrients are available the phytoplankton can breed rapidly making visibility very poor. Generally, warm surface waters have low nutrient content and so little life and good visibility. When cold, nutrient rich water from greater depths comes to the surface this leads to an explosion of life and poor visibility.

 

[vladimir]

Oxygen solubility in water increases as temperatures decrease. Colder, more oxygenated water has more life floating around in it to obstruct your view:

Oxygen Solubility in Fresh and Sea Water

 

[spectrum]

Oxygen solubility in water increases as temperatures decrease. Colder, more oxygenated water has more life floating around in it to obstruct your view:

Oxygen Solubility in Fresh and Sea Water

Interacting with that the warmer water with the higher stronger sun of summer brings on more plant life.

The biggest influences I have seen are silting from fast flowing rivers after a rain and suspended debris churned by heavy seas. The mixing of brackish water near freshwater discharges also has it's own distorted effect.

Here in New England the most spectacular visibility can be found in the winter but you need a tranquil stretch.

Pete

 

[Sas]

Temperature isn't particularly relevant.

I would say temperature has a lot to do with visibility actually. As colder water has a much greater oxygen content I would imagine it would be host to more plankton, algae as well as other marine life and therefore have a lower visibility.

 

[parrothead600]

The best visibility that I have had was diving under the ice (can't get any colder than that). I'm not sure how much effect the temp has, but it does help when there is no boat traffic to stir up the bottom.

 

[Gary D.]

Some of the clearest water in the world is also the coldest. The Arctic and Antarctica.

Your theories may be true in some areas but not across the board.

GaryD.

 

[BarryNL]

I would say temperature has a lot to do with visibility actually. As colder water has a much greater oxygen content I would imagine it would be host to more plankton, algae as well as other marine life and therefore have a lower visibility.

As I said, it's the nutrient content, not the oxygen content that's important. In fact, phytoplankton is the base of the food chain and the most common cause of bad visibility and this photosynthesises and so requires CO₂ rather than O₂. Even so, warm tropical water can dissolve more than enough gas to support life - it just doesn't have the nutrients to support much.

 

[Sas]

What creates the increased amount of nutrient in the water then? I have always thought it is the increased oxygen levels.

Edit: probably sunlight has something to do with the increased nutrient so that would be why under ice and in winter you would have clear water? In winter the algae and plankton is less due to less sunlight, at least where I dive. I was also thinking, are the nutrients richer in some areas, not because of temperature, but because of currents and the like bringing the nutrients from other places? I am still confused about what the origin of the nutrients is and thus the lower visibility...

 

[BarryNL]

What creates the increased amount of nutrient in the water then? I have always thought it is the increased oxygen levels.

Phew, Dr. Bill might be along later to explain it properly but basically nutrients are used up by planktonic growth and, as the plankton dies it creates an organic "rain" or "snow" of material carrying the nutrients downwards in the water column leaving the upper ocean depleted of nutrients. In areas where this deeper, nutrient rich, water comes back to the surface huge amounts of growth are possible (global phytoplankton growth in the oceans is roughly equal in mass to plant growth on land). Also, rivers carrying large amounts of fertiliser run-off can cause high growth and poor visibility in the ocean. Also, rough weather conditions can cause mixing of shallow and deeper ocean water bringing nutrients back to the surface.