I know most plants get algified on the older growth parts from earlier in the year and some dont grow in water for long. I have low spots out back that L. palustris and P. palustris sprout up in when it rains, but the water usually vanishes before algae has a chance to hit.
But there is also a blue hole nearby that feeds a stream used for raising trout and it is bursting with algae free willow moss all year long.
I also think back to a thread on here about the guy's trips to a florida spring and the pics of aquatic plant life looked flawless.
Anyone with an 8th grade education knows the meaning of the word niche, I was looking for something a little more like... scientific findings perhaps? Maybe that cooler temps earlier in the year lead to larger amounts of dissolved gasses, including co2 AND o2. Little bit shorter day length, complete lighting spectrum? And then what allows some plants to successfuly combat algae year long and win? Oh yeah and most importantly, without someone blasting co2 into the stream.
Maybe the question could use a little refining, but answers like darwinism and everything has its niche leaves a little something to be desired.