The cold weather arrives and the green algae goes

You may remember that, at the beginning of October, when it was still incredibly mild over here, I posted a pic of a canal and a bridge, where it was debatable as to what ran under the bridge - grass or water.  At that time, many of the waterways around here were covered with a thick layer of tiny green pond life (I've called it algae but I'm not sure what it was exactly) and they had lost the appearance of being waterways.  

The weather has now cooled down and it would seem that this green pond life isn't at all fond of the cold.  Slowly but surely, it is disappearing from the surface of the canals and ponds.  The picture here is of the same bridge and canal and, I'm glad to say, it now looks like what it is - a stretch of water.