Autumn Die off

[jwo1124]

Ok, I know that during fall most of the leaves fall off the trees around bodies of water, the aquatic vegetation starts to die, and phytoplankton die. The two latter occurances: the plankton and aquatic veg. kill can lower the amount of O2 that is being produced in the water. Along with the diminishing amount of O2 being produced, the decompostion of the aquatic plants is a big consumer of O2.

SO here we have less O2 being produced and more O2 being consumed. This can cause and oxygen defecit in ponds.

Today I noticed A LOT of the leaves from the trees surrounding a local pond are falling into the shallows of the pond where they sit on the bottom or float on the surface.

Is it logical to say that these dead leaves falling into the pond are also being decomposed and thus usingh even more O2 in the process?

I haven;t been catching or seeing much fish while fishing the shallows(less than 10' deep) in the past couple weeks. And I am starting to think that all the decomposition off aquatic plant life and the fallen leaves is sucking up all the O2 in these areas.

I have learned though that the colder the water the more O2 it can hold. So will there be a blancing act here? Even though more O2 is being used by decomp. more O2 is actually in the water so the effects of the decomp. may not be that bad.

Plus I have learned that wind stirs up surface water making it more suseptable to oxygen diffusing into the surface water. And it has been very windy here.

Any thoughts on this?

[Gatorbassman]

As the water cools the fish's metabolism slows down. Due to their decreased movement and energy they don't need nearly as much oxygen as they did during the warmer months. Therefor the lower oxygen levels aren't a problem.

[Low_Budget_Hooker]

And once your lake turns, all that good dissolved Oxygen is going to be in the deepest parts of the lake anyway.  (the avg lake)

[Crestliner2008]

And don't forget all those underground springs that EVERY pond/lake has. They keep the exchange happening. Nature is a wonderful thing  

[jwo1124]

That's a relief then. I was just putting to use what I had learned in Environmental Science. SO much for that though  

[BaitMS]

Quote

And don't forget all those underground springs that EVERY pond/lake has. They keep the exchange happening. Nature is a wonderful thing

Sorry. Every lake/pond does not have a spring(s).

All of the phytoplankton do not die. If that was the case many ecosystems would not do very well (bottom-up theory). These are the primary producers of the system and thus provide energy to all levels above them. You are correct that the decomposition of plant material does contribute to decreasing oxygen levels and that colder water can "hold" more oxygen. But depending on where you live there may be some plants or other factors producing/providing the oxygen for the waterbody.

Fish are cold-blooded and slow there metabolism accordingly. That's why in the winter we tell you to fish VERY SLOOOOOW. Fish are not going to expend any more energy than what is necessary.

Low budget, if the lake turns over it creates habitat from the top of the lake to the bottom of the lake. Oxygen will be consistent (relatively speaking) throughout. Not just at the bottom or the top. Lake turnover is just the mixing of the system to the point where the thermocline is not as noticeable.

Hope this helps.

[tyrius.]

And don't forget all those underground springs that EVERY pond/lake has.

Not the ponds I fish the most!  Those were created by bulldozers and rainwater.

[Bassnajr]

Hey jwo...

Sounds like were fishing the same ponds!! I have had sucess this past week with jerk baits in the shallow areas (rocky mostly) where the wind is blowing into these areas. I have also had sucess with large spinner baits in a little deeper water, slow retrieve. I live in New England and thought the bass hibernated in the cold weather (LOL) Despite the weather and water turnover, their still hitting well.

bassinajr

[Low_Budget_Hooker]

Quote

Quote

And don't forget all those underground springs that EVERY pond/lake has. They keep the exchange happening. Nature is a wonderful thing  

Sorry. Every lake/pond does not have a spring(s).

All of the phytoplankton do not die. If that was the case many ecosystems would not do very well (bottom-up theory). These are the primary producers of the system and thus provide energy to all levels above them. You are correct that the decomposition of plant material does contribute to decreasing oxygen levels and that colder water can "hold" more oxygen. But depending on where you live there may be some plants or other factors producing/providing the oxygen for the waterbody.

Fish are cold-blooded and slow there metabolism accordingly. That's why in the winter we tell you to fish VERY SLOOOOOW. Fish are not going to expend any more energy than what is necessary.

Low budget, if the lake turns over it creates habitat from the top of the lake to the bottom of the lake. Oxygen will be consistent (relatively speaking) throughout. Not just at the bottom or the top. Lake turnover is just the mixing of the system to the point where the thermocline is not as noticeable.

Hope this helps.

Not here.  The lake goes to a mixed state where you can't get a consistent reading w/ the D.O. meter at any depth, for roughly a week to 10 days, depending on wind.  

Once it turns, it is a drastic as night and day.  when it turns back in the spring, it is not as drastic.  I always wrote it off to Oxygen being produced in higher amounts again due to the grasses coming back to life in the spring.  Im the spring, the higher readings are in the 2-6 ft range, never on top which always surprised me seeing as how the highest readings at ice out are always in the deepest part of the lake (31 ft)

Again, every lake is different.  I would imagine that lakes with a consistent feed from springs would be more of a mix.

[WRB]

The key element to adding DO to water during the fall transition to winter is wind. Without windy conditions the small ponds may stagnate do to loss of DO from the decaying organic matter and fish kills can occur as a rssult, if no wind combined with unseasonal warm weather during drought conditions. The spring water is dependant on normal water table levels and we don't have that in several regions at this time.

WRB

[jwo1124]

One of the three ponds I mainly fish is spring fed...so I've heard by an older guy that I spoke to one day. That's why I think there can be a lot of hold over stockies here. Plus, it has been very very windy here for the past week. We had a couple nice mild autumn days in the high 50's, but then once you get to the water the wind is blowing 15-20 and the air temp drops easy by at least 10 degrees.

I just wasn't sure about the technicalities of Dissolved Oxygen, decomposition, and plankton kill. I hve a broad understanding of it all, but don;t really know exactly is going on, biologically speaking. I know that the warm water fish will slow down, so they probably don;t need as much O2 as the did during the warmer months which makes sense.

I was just worried because I haven;t been seeing any signs of, or catching, the cold water trout and salmon they stock. That's why I was questioning the O2 levels because this seems liek the weather these fish thrive in.

My only other theory is that since it has been so windy, the water is probably getting churned up, and it is probably harder for the fish to see their prey as they search for food, since the water movement breaks up visibility. Maybe the majority of the fish feed earlier in the AM before the wind picks up.

Maybe this isn;t the case either, just a thought,