RAH - I think you are very correct - ".... that every situation is different". Probably very different
In my experienced opinion
1. The deeper the pond the larger the DO amount of consumable oxygen that will be present in the pond due to lower surface to volume ratio. The shaller the water the quicker the water layer above the bottom loses its DO. When the DO is below what it requires for that particular specie at that temperature to survive then they usually die. Different species of pond inhabitants have different tolerances to low DO or lack of it.
2. Water clarity often has a significant influence on how fast the DO is consumed during lack of sufficient sunlight for photosynthesis going on under the ice during snow covered ice conditions. The clearer the water the deeper sunlight can penetrate into more volume of the pond to stimulate the various forms of oxygen production by photosynthesis usually by most often by winter dwelling phytoplankton. Winter dwelling phytoplankton in relatively clear water can often be as many as 150,000 cells per ounce of water.
3. Most all ponds have a high amount of dead decomposing suspended detritus that creates turbidity in the water column. Thus the clearer the water has less dead suspended detritus that is present to be consuming DO. Suspended detritus enveloped by bacteria is constantly consuming DO. Amount of DO consumption is dependent on water temperature. The lower the water temperature the slower and less DO that is consumed. Thus suspended detritus and dead dying phytoplankton together due to lack of sunlight can consume measurable amounts of DO in the water column above the bottom even during winter conditions.
3. The amount of dead organic biomass in the pond has a big influence on the rate of DO consumption due to bacterial decomposition. Bacterial decomposition in the pond is by far the greatest DO consumer in the pond. Without sunlight all the photosynthetic activity ceases and then all the plant life as it dies, it decomposes and adds to the DO consumption on the bottom. The accumulated dead organic biomass on the pond bottom is the biggest consumer of pond DO, thus the loss of DO starts mostly on the bottom and advances upward. When DO is exhausted on the bottom anaerobic bacteria begin producing hydrogen sulfide (H2S). H2S is toxic to fish and almost all invertebrates.
4. Ice Conditions. Various winter conditions affect the clarity of ice and how far sunlight will penetrate through the ice for producing DO via photosynthesis. Many times during the top surface freezing conditions snow accumulates and with any melting snow and refreezing this creates a top cloudy layer. The thickness of this layer varies from ¼” to several inches thickness of cloudy milky ice. Obviously this top cloudy ice layer inhibits sunlight penetration.
Here are some examples of light transmission through ice for sufficient photosynthesis of algae and plants (Mgmt of Lakes and Ponds G.W. Bennet 2nd edition).
Some photosynthesis can occur when 10-12% of the light on the ice reaches the water below.
7.5” of clear ice permits 85% of the light to pass through
1” of snow over 3” of clear ice stops all but 10-17% of the light
5” of snow over 3” thick of clear ice allows only 2.5% light penetration.
15” of clear ice with a cloudy toping permits 11.5% of the light to pass through
Water under ice needs penetration of 10-12% of the light for some dissolved oxygen to occur from the plants. In one reference I found, if one can diligently keep about 1.1% of the pond area as snow removed from an ice covered pond it ‘should’ allow enough sunlight penetration for plant life to increase the oxygen concentration enough under the ice for fish to survive. One acre of water is 43560 sqft. And 1.1% is at least 400 to 480 sqft such as 20 ft x 25ft.
Note - Some have suggested if one can create 10% of the pond as ice free with shallow water aeration, this will allow DO by diffusion and photosynthesis to be high enough for fish survival. In one acre, this is a shoreline open water area of about a 70ft circle as ~3800 sqft. IMO more research needs to be done on this entire topic. I think the big variable in all this is - how fast does the pond lose its DO?
Ponds are highly variable for this DO loss topic as noted in the first sentence of this post and by RAH. Literature showed in one ice/snow covered pond the DO decreased from 12.3 on Feb 12 to 2.4 on Feb 14 about 5ppm per day whereas on another pond with snow cleared ice the DO increased from 1.8 ppm of Feb 5 to 8.0ppm on Feb 8 as 2.7ppm increase per day.
Note - I try to make sure that some of that snow is removed from the shallow areas of the pond where algae & some plant-life are most likely to occur and create DO when those shallow are most likely to receive sufficient sunlight for photosynthesis.
Last edited by Bill Cody; 01/25/26 07:57 PM.
