NW Ohio pond report under winter ice and snow cover as of Jan 26 2026.
In mid-December 2025 pond had 3” of ice then it all melted and open water developed until Jan 01 26 when it refroze with subzero temps and 2-3 inches of snow cover. On Jan 25 the pond received 8” of snow.
Water sample was collected on January 26 from 14” deep over deep water ~14ft.
A standard phytoplankton analysis for the winter water condition of my pond revealed 147,946 algal cells per milliliter that equates to 4,379,201 cells per ounce of water!. All the algae were composed of very tiny cells composing 9 species and as a group that are called nanoplankton (2-20 um). No large planktonic algae forms larger than 20um were observed. Open water season algal densities almost always have some larger types of algae present in the samples.
Some other winter phytoplankton in a few select local municipal reservoirs are currently ranging in total densities of 2,000 to 80,000 cells per milliliter.
Suspended detritus density in the analyzed sample was 536,617 particles per milliliter as 15,883,863/ounce of water. Detritus is dead, decaying particulate organic material and ‘dirt’. Together the phytoplankton and detritus created a water clarity of around 3 ft. Water clarity was estimated by seeing a video camera lowered into the water and actual clarity not measured. Usually in my algal analyses, the suspended detritus is 5 to 20 times more abundant compared to the phytoplankton density, however as usual it always depends on the condition of the water body.
On one hand it is good there were lots of phytoplankton in my pond during winter. This is probably due to carryover from the Summer – Fall nutrient conditions where the water clarity ranged from 2.5 to 3ft due to the ample recycling of nutrients from the numerous introduced tilapia who were consuming available foods. On the other hand abundant phytoplankton can be bad during winter snow covered ice conditions because lack of sunlight into the pond means this could cause high numbers of dying & dead algae that would consume dissolved oxygen due to bacterial decomposition.
Advanced reading
The study of winter phytoplankton under ice cover has been a relatively unstudied science. Interest in the condition of that type of habitat is increasing. A few years ago I participated in the algal analyses and was co-author of a research study called the Winter Grab that reported on the phytoplankton under winter iced conditions of all five of the Laurentian Great Lakes that compose the largest freshwater ecosystem in the world.
https://doi.org/10.1002/lol2.10447
