The envior Mentalists blame the clear lake water on acid rain - or they did back in the 20th century. I haven’t heard much about acid rain since they latched onto global warming. Although they are now transitioning to global cooling.
That is because they put scrubbers on the coal burning plants in KY, OH, WV, PA, NY and others. OR those coal burning plants have shut down. Mostly because burning the Methane(natural gas)is cheaper, cleaner and readily available.
In addition, we all drive automobiles with catalytic converters. Our cars do not put out as much pollution. Neither do our Semi trucks, locomotives, tractors or diesel pickup trucks. All diesel engines over 25 HP either have a reburn valve or use DEF.
This has made the air cleaner. There is not the SMOG over the LA area like there used to be(except when the houses/forests are burning).
My previous house had an in ground pool. Whenever we would get a big thunderstorm in the summer and received an inch or two of rain in a short period it would screw up the PH in the pool. I asked the pool store guy why. He said that the rain washes all the sulfur and other particles out of the air and into your pool. A lot of those particles are Sulfur from auto exhausts. So, as they mix with water they make a very mild sulfuric acid. Which is why the PH in my pool got raised. So, I needed to pour a box of PH Decreaser into the pool(22M gallons) after a heavy rain.
Basically acid rain.
FYI, I am sure they still have acid rain in CHINA.
From all the coal fired electrical generation plants.
Also, keep in mind that we really did pollute the air and water back in the 1930s-1980s than we do today.
The river in Cleveland actually caught on fire because all the crap they were dumping in it. That all spilled into Lake Erie and Ontario.
I grew up in Buffalo. There used to warnings on the radio that pregnant women should not consume the fish out of Lake Ontario more than once a week. That is because the amount of MERCURY in the apex predator fish species like Lake Trout.
In Niagara Falls, NY they buried thousands of barrels of chemicals then built a school and neighborhood on top of it.
50% of the people living there got cancer.
It was called Love Canal.
The EPA really did clean up the environment in the USA.
I can think of three Super Fund sites within ten miles of where I live right now in NH. One company made hand tools. They dumped all sorts of chemicals out back. Another made paint. The ground around there is toxic from the stuff they poured into it.
Another is a plastics company that screwed up the water table so bad near their plant that they had to pay to put every house/condo on city water.