I would wait until the little creatures can survive in slightly warmer temps. March is still a pretty unpredictable month, so I'd wait. All that gunk at the bottom is protecting them.

It isn't protecting the fish much since is also hiding parasites. Net, dredge or filter out that debris. It is a potential cause of fish loss. If you have a good mechanical filter the smaller gunk won't be a problem. Use a good treatment for any parasites that escape once the temperature of the water is 55 or above. That is when they become active. Get it done now and the chances for problems gets smaller.

The water temperature changes much slower than air temps.

If your pond contains any hibernating frogs you will have to be very careful not to disturb them. Awakening at this time of year could definitely kill frogs.

I am much further south than you, which might make a difference, but I have been carefully cleaning mine.

Using a skimmer, I have been sweeping along the bottom slowly. I've been doing just a little at a time over the course of several days. Have had to clean the skimmer filter quite often with all the gunk coming up. Several weeks ago, I had quite alot of string algae. I took my toilet brush, and just scrubbed along the rocks and the sides a little, just enough to knock some of it down. My water is clear for now, and I'm hoping it stays that way. Not likely, I'm thinking. :(
One of the things that really helped was leaving the net on nearly all winter. I just took it off a few weeks ago. As this is my first winter with the pond, I'm trying to be careful. But, so far all the goldies and koi look great. Hopefully nothing bad happens during the warm-up.

Thanks everyone for the advice.

You know Hardin, I was thinking that same thing about the net. All the leaves that are in there are from the winter. The net doesn't look that great but it sure beats those rotten leaves. Ick.......all slimy Ugh! I guess I'll gradually and slowly net those leaves out. I hope I don't kill anything :(