A few days ago I posted about the alarming decline in Clary Lake’s water quality and promised an update. Here it is. Last Friday July 19th, David Hodsdon and Jack Holland hit the lake to conduct their regular water quality data collection exercise. The results have been posted on the Clary Lake Water Quality Data page. The bottom line is that the secchi disk reading (a measure of water clarity or transparency) was 8.04′ (2.45 meters), down from 10.01′ (3.05 meters) on June 30th. For comparison, the average secchi disk reading (based on the average of 88 secchi disk readings taken in the month of July from 1975 to 2011) is 12.28′ (3.74 meters) or 4.24′ (1.29 meters) more than the current reading. In statistical terms, that is a HUGE change- in the wrong direction.
The classic definition of an algae bloom is a secchi disk measurement of 2 meters or less and Volunteer Water Quality Monitors are expected to report when readings reach or fall below that value. Technically we’re not having a bloom yet but we’re getting close- we’re within 0.45 meters (1.45′) of that and it’s not even August yet. This does not bode well for lake water quality for the rest of the summer. I took the picture at left the other day off the end of my dock where the water is only 2′ deep. You can barely see the bottom. As I mentioned in the previous post about this, I did find a number of Anabena blue-green cyanobacteria, the kind that is responsible for the typical algal bloom such as we saw last summer. These suckers can multiply quickly under the right conditions. Clearly, reduced lake volume, higher water temperatures, and exposed sediments resulting from significantly lower water levels are all major contributing factors to algae bloom, and we all know who to blame for the low water.
The other form of algae “bloom” that people have mentioned to me lately are the clouds of green algae that range in size from a golf ball up to a small car. This algae is composed of filamentous green algae (think long threads or filaments) of various different types. I’ve seen this stuff in Clary Lake off and on for the past 8-10 years. I examined some under the microscope the other day and found 3 kinds of filamentous green algae prevalent in the sample I took: Spirogira, Zignema, and Gonium. I took pictures of them which didn’t turn out too well (the one at left is Spirogyra) so I downloaded some professionally produced photographs of them and have posted them in the Summer 2013 Album. There was also one variety I haven’t identified.
Collectively, these “cotton-candy” clouds of green slime are referred to as Metaphyton and it’s occurrence and growth in Maine lakes is now being tracked and studied by the The Maine Volunteer Lake Monitoring Program though it is too soon to say whether this is a real problem or not. Metaphyton form in shallow littoral zones of lakes and little is actually known about their growth and what their presence indicates. I’ll be putting up a page with more information about algae blooms in general and Metaphyton in particular.