Water organisms in cold water

[lilewis]

This may sound like a silly question (and something I may have learned in elementary school) but do amoebae and other larger pond organisms such as water fleas, etc. become less active in water approaching freezing temperatures, do they move to deeper parts of the pond, or are they impervious to temperatures changes?

The reason I'm asking is because I'd like to know what to expect if in fact they aren't going to be as available and easy to find as they are in the warmer months.

[Oliver]

Hello,
Organisms frequently become less active in colder temperature, because chemical reactions generally slow down the colder the temperature. Life, after all, is based on complex chemical reactions. At colder temperature, therefore, cell division is also generally slows down. I say generally, because different organisms have different optimum temperatures. Some bacteria thrive best around freezing temperature, I am certain that similar cases also apply to protozoa and higher organisms such as water fleas.

Now you asked if they move to deeper parts of the pond when the top surface freezes. Nature is complex and I can imagine that many indeed do this. However, I think that for most the migration to different parts of the pond does not even apply. It is possible that water fleas "survive" in the form of eggs. And many other microscopic organisms simply hang around and wait until temperature increases. Many single celled organisms can not even be found in the free water body, but accumulate in the biofilm found on rocks and plants. They might not even actively move around in the free water body, because due to their microscopic size the water currents are much stronger. Movement might only be restricted to within the biofilm.

There are plenty of things to observe even during the winter months, provided that you have a look at the biofilm (slimy stuff on rocks, plants etc). I recommend that you take a jar of pond water, plus a bit of slimy stuff from rocks, and then add a drop of liquid artificial fertilizer (not too much!) user for flowers. This will stimulate the growth of algae and you then have your own mini aquarium to take samples from throughout the winter months. Watch the wall of the jar turn green and take samples from there. As a rule of thumb, if the water is clear, then you will not be able to observe much under the microscope as well, so you must observe the layer formed on the glass.

To enrich protozoa, take a second jar and add a drop of milk. Again not too much as overfeeding stimulates bacterial growth. Liquid should turn slightly turbid. This turbidity will disappear as the protozoa eat the mild/fat droplets. Aerate well (bubbler from aquarium works, or frequent stirring). Alternatively you can take a rice grain and drop it into the pond water and watch protozoa (etc) accumulate around it after a few days. Experimentation is needed.

And forget about the hay infusion (which is often recommended). This is high in nutrients and really promotes bacterial growth. In my view almost a biohazard.

Oliver.

[lilewis]

Thanks Oliver, for a such an informative and thorough reply.
I may just do what you suggest here! It's going to be a long winter in New England.

[charlie g]

Hello all...yup..it's cold in finger-lakes NY too. Butm majority of protists and meiofauna..yes and snails, fish,insects are active under the ice. Of course we all have heard of folks who enjoy 'ice-fishing'..well these multitudes of fish share their waters with the smaller protists and meiofauna communities.

Plenty of natural freshwater life to enjoy with a microscope..all winter long...the trick is getting sample wide mouth jars of freshwater life...and getting it safely...know where you are collecting. I have a few articles in Olivers magazine regarding freshwater microscopy..all winter long..take a look when you have time. warmly, charlie guevara

[Joab]

Charlie Guevara, I'm interested in reading your articles about this topic, could you possibly post a link to the magazine(s) where they can be found?

Regards

[charlie g]

Hello...go to Olivers: 'author index'...look for charles guevara...keep warm...and keep microscopy looking in winter!

[Oliver]

The index needs to be updated, I will do this.
Oliver