Will my micro-bros live?

1 Don't underestimate the amount of evaporation that takes place
2 The amount of possible aqueous colonizers just floating around is high, you might get algae overgrowth (perhaps not in 10 days, but idk, depends on sample)
3 If taken from habitat, the natural balance might shift and certain species might become outcompeted in a very short amount of time depending on what the conditions of your water are right now
4 It's really anyone's guess, because water can have a shit ton of organisms living in it..

How big are your containers?
Is there "just" water in it, or do you have some soil/rocks/plants in there too?
Was the place you took it from flowing or still water?
I'm no microbiologist either, but I have some basics, so other people with more knowledge will have to chime in on this..

just search for storage of microbial lake samples or something similar. this has some info around 5.6
http://www.who.int/water_sanitation_health/resourcesquality/wqmchap5.pdf?ua=1

The actual make up of your sample is going to be vastly different from what it was initially if anything is still living. I know in the teaching lab there is a small tank with mixed protists that they put a small tube in connected to the air outlet to oxygenate it. Research samples would normally be sealed and cooled to 2-6 C to slow down all biological reactions and transported within 12 hours for analysis. If you dont care about contamination you could make a hay infusion. You literally just put water sample in a jar and put some hay trimming and let it sit out of direct sunlight for a week. The hay provides nutrition for bacterial populations and protozoa eat the bacteria etc.

Even if you dont do a hay infusion this sheet mentions that protozoa require oxygen so each day use a plastic pipette to bubble some air in. You could do something like that to ensure sufficient oxygenation if you leave it at room temp.
https://www.carolina.com/teacher-resources/Document/carolina-labsheets-make-a-hay-infusion/tr41608.tr

Maybe you could try splitting your sample and trying a few different storage methods like room temp, and putting one in a small container filled with ice.

changing pH, chemical composition, dying microbes releasing junk and plenty of other things will occur over 3 days

>>2450893
Doesn't hay open up the risk for serious mold contamination though?

>>2450853
>The lids of the jars are removed to allow oxygenation of the water,
This doesn't actually oxygenate the water because in still water biofilms form across the surface blocking oxygen from reaching the water column. This is alleviated somewhat in nature by photosynthesizing organisms- mostly algae and cyanobacteria- adding oxygen below the biofilm. However you'll find that still, scummy water houses far fewer microorganisms and far less diversity.

So this may not be much of a problem if you sampled water from a scum-covered pond with no movement whatsoever. But if your samples came from clear water with no surface films you're going to have a bad time. An airstone would fix the problem perhaps. But even then it's just a matter of time before you get a bacterial bloom that consumes all the O2 and suffocates everything in your jar.