fellas, Im new to the site and need some info on my 7 acre lake.
1. do cat tails add oxygen to the water?
2. does the algae that is green and stringy, elephant snot looking help or hinder the oxygen in the lake, water quality?
3.Water quality is very good, but we do not aerate or pump from the well.(unless water is low)
4. The bull frog population is extrordinary, but at least once their has been a fish kill 4 or 5 years ago.
should I leave it well enough alone?
Tempo, you may want to be a bit more specific on your short and long term goals for your lake. Do you want a world class fishery; do you want a reasonably clean/clear liquid surface to do some recreational boating; do you use it for livestock drinking/grazing, do you wish to attract waterfowl, etc. Your goal may well determine whether you leave well enough alone.
On your questions:
1. Any photosynthetic activity at or below the surface of the water will add oxygen to the water in the presence of sunlight While a good portion of the cattails are above water; cellular activity in those portions that are below or at the waterline will add O2 to the water in the presence of sunlight. At night (absence of sunlight) O2 will be consumed by the same cells that produce it.
2. The filamentous algae, when alive and in the presence of sunlight, will add oxygen to the water. All dead and decaying aquatic algae or vegetation will consume O2. These algal mats will reduce sunlight penetration and hence O2 production by other aquatic plants that might be found in the water column or rooted to the hydrosoil below. The presence of this algae is indicative of a nutrient rich and possibly oxygen starved lake where the biological oxygen demand far exceeds its availability.
3. You mention that water quality is good. More specifically, you may mean that it is reasonably clear with no objectional odors. Aeration will improve the quality of the water in many different ways. (Refer to the many excellent posts about the benefits of aeration). Addition of well water actually decreases oxygen in the water because well water if fed below the water level, and upon mixing, will reduce the overall average O2 level of the lake. Well water is low in O2.
4 You mention a fishkill about 4 to 5 years ago. There are many natural factors that could have caused this: i.e. a massive blue-green algae die-off followed by many consecutive cloudy or rainy days... A temperature inversion whereby anoxic water mixes with oxygen rich layers of water causing a homogeneous water column that is oxygen poor...
As your lake continues to naturally age, you will see the water quality deteriorate, more frequent fish kills, and a greater coverage of your lake with the 'elephant-snot' algae and other aquatic weeds. Eventually, over many years, even decades, it will fill up with sediment and cease to be a lake. If this is good enough for you, then leave well enough alone. However, there are many things that can be done to a lake to slow down or reverse aging and improve it as a fish habitat. All of which require time, effort and/or money. Your appetite to spend time, effort, or money will determine how you will impact the short-term and/or long-term health of your lake in direct relation to the goals that you wish to achieve.
Best of luck!