What will this freeze do to hydrilla/milfoil?

Just curious, was here in the 80's when we had this but none of our stock tanks had grass, will this kill it back or all? We actually have one we put triploid grass carp in to control it, will this freeze kill those carp?

Fish can live when it freezes if the water is greater than 2 feet deep. As to the grass, I have grass in my pond in ABQ in dies back and I have to buy more every year. In ABQ it is below freezing Dec, Jan, Feb usually. Dying grass and plants with ice covered ponds takes all the oxygen away so a pump with an aerator is good, I use one. My water lilies die back and grow again in the spring.

It'll definitely take a hit. The deeper grass should survive

The vegetation will return unless the ground it was rooted in was exposed and froze hard. Even then, the seed bank may survive and regrow this spring. Seconding Jerrett, vegetation 10+ ft deep may not be effected much. The carp should be fine. The cold may have knocked the plants back farther than normal, so it'll help the carp get a jump on controlling regrowth this year.

Interesting, with the years of siltation I would guess the tank with the carp is only 8 feet deep, its a little more protected and barley froze over completely compared to some of our other tanks which you could walk across. I wouldn't mind it killing the grass completely if it does that, we put the carp in there because it had basically become choked out with grass and unfishable other than throwing a frog.

Explain the northern fisheries that are full of shallow grass and freeze over every year for months at a time then lol

There is grass deeper than 8 feet, this was the final ice thickness, it got thicker until friday morning

Not sure which comment this was referring to. It looked like everyone that commented said the plants would return.

Of the five species of water milfoil I've found data on, most were negatively effected or showed no change by being exposed to drying and freezing during winter drawdowns. If they're not exposed to air and the soil does not freeze hard during a drawdown, there probably won't be much effect to their biomass the following year. I should have made that more clear in my original post. Frozen water over hydrated soil isn't the same thing as bare soil exposed to freezing in terms of vegetation control. Hydrilla is more resistant than milfoil and its seedbank can survive for years waiting for favorable conditions so I'd suspect little change in the hydrilla abundance, except for the grazing done by the newly stocked grass carp (it may take 1-2 years for them to get things under control depending on stocking rate and plant density).

The colder water may have more thoroughly killed the stems in the shallow areas so there may be less visible plant material in the pond early in the year. But, the roots and seeds are still there and it will return. May just be a little later in the year to see the same thickness as previous years, as fewer stems will make it through the winter. Also, cold sensitivity doesn't get culled out of the population in the south like it does in the north so I would suspect a larger impact on plants here than the same species would experience in the north where they have acclimated to the cooler climate.

Some light reading on the subject.
Cooke, G. D. 1980. Lake Level Drawdown as a Macrophyte Control Technique. American Water Resources Association 16(2): 317-322.
Ch13 of Cooke, G. D., E. B. Welch, S. A. Peterson, and S. A. Nichols. 2005. Restoration and Management of Lakes and Reservoirs, 3rd Edition. Taylor and Francis, Boca Raton, FL.