Scientific question

[RUDD]

Plants give Cabon dioxide at night. At night, plants breath Oxygen in and discharge CO2.

 

At night alot of big wary fish get caught - I know they cannot see rigs as easily which helps but my mind has asked the question:

 

Do under water plants also give off CO2 at night?

 

If so does this mean fish get less oxygen?

 

If so does this effect fish like it does other animals by making them drowsey and therefore less aware leading to them making more mistakes?

 

Am I onto something or just thinking b0ll0cks?

Edited September 2, 2011 by RUDD

[Andy_1984]

Plants give Cabon dioxide at night. At night, plants breath Oxygen in and discharge CO2.

 

At night alot of big wary fish get caught - I know they cannot see rigs as easily which helps but my mind has asked the question:

 

Do under water plants also give off CO2 at night?

 

If so does this mean fish get less oxygen?

 

If so does this effect fish like it does other animals by making them drowsey and therefore less aware leading to them making more mistakes?

 

Am I onto something or just thinking b0ll0cks?

 

 

underwater plants do give off oxygen and CO2 as other plants do. what i dont know though is how much oxygen and CO2 they would produce that would actually have any effect on fish

[Vagabond]

Plants both photosynthesise (give out oxygen, use up CO2) and respire (use oxygen, give out CO2) during the day

 

At night, photosynthesis shuts down (no light) but respiration continues, although surely the lower temperatures at night mean there will be less respiration than in the daytime.

 

Also, don't forget that in natural waters, any oxygen used by fish, plants or invertebrates is easily replenished by oxygen dissolving in through the surface.

 

(I'm not talking about overstocked commercials where the high density of fish might be at risk from oxygen lack when the weather gets warm - there won't be any submerged weeds there anyway!)

[RUDD]

Plants both photosynthesise (give out oxygen, use up CO2) and respire (use oxygen, give out CO2) during the day

 

At night, photosynthesis shuts down (no light) but respiration continues, although surely the lower temperatures at night mean there will be less respiration than in the daytime.

 

Also, don't forget that in natural waters, any oxygen used by fish, plants or invertebrates is easily replenished by oxygen dissolving in through the surface.

 

(I'm not talking about overstocked commercials where the high density of fish might be at risk from oxygen lack when the weather gets warm - there won't be any submerged weeds there anyway!)

 

I was thinking B0ll0cks then And no alcohol in sight (gave blood this evening)!

[Phone]

Well your thinking is sort of right – and sort of not. Plants do take in oxygen and give off CO2 24 hrs a day. It’s called something unimportant to your thinking about angling.

 

The good stuff, Photosynthesis is the process plant use to make their own food. Plants leaves contain chlorophyll that let the blue and red light go through so leaves look green. Chlorophyll absorbs the sunlight (the green color) that makes photosynthesis possible. The sunlight is combined with water, carbon dioxide and nutrients from the soil. The chlorophyll processes those ingredients and makes sugar (plant food) and oxygen. Plants really just make oxygen. Mostly animals make co2. Plants only make tiny tiny amounts of co2 whilst “eating”. There is a word but I forget it.

 

50 acres of corn, every day make enough oxygen for like - 11 people(?). Really plants make all the oxygen in the air for all practical purposes.

 

Also, in the water where you fish there are algae. Algae are sort of like plants. When algae blooms they are making oxygen. Everything is cool up to this point. When the algae dies the oxygen is DEPLETED in the process of decomposition. Now things are not so cool. Decomposition often takes more oxygen out of the water than is being put in. Fish get their oxygen - - like 99% - - - (someone will look it up) from the air just like we do (some oxygen from underwater plants is dissolved on the way up from the soil on the bottom surface but not an important amount).

 

Oxygen can be dissolved in water like sugar for you coffee can be dissolved in water. The dissolved oxygen (DO) comes mostly from waves in the water. DO is what fish live on. DO is lowest at dawn.

 

Fresh water fishes need 6ish% DO and salts 3.5ish%. It’s usually not the salt that bothers freshwater fish in the ocean - it’s the lack of enough oxygen.

Well, this post will have to be “refined” and indeed I trust it will. I’m rambling from memory.

 

Phone

Edit: "respire" Vagabond used the word. Plants respire like 1:10,000,000,000+ the oxygen produced by photsys--- (I made up the number)

Edited September 2, 2011 by Phone

[Mark Wintle]

One effect of the fact that water plants give off CO2 at night is that fish tend to move away from weedbeds to open water. Water temperatures are likely to be lower at night meaning that the saturation of dissolved oxygen is increased.

 

I thought the problem with freshwater fish in saltwater is reverse osmosis, i.e. the fish loses water to the stronger solution of seawater and cannot cope with it. A few fish like salmon, eels, flounders, mullet, bass etc can cope with both fresh and salt.

[Ken L]

So many variables !

At night:

The temperature will drop.

The light levels will drop.

The level of dissolved Oxygen will decrease.

The level of dissolved Carbon Dioxide will increase.

The PH will drop - because of the increase in dissolved Carbon Dioxide.

 

There is an annual cycle (seasons) in addition to a diurnal cycle but most importantly, this is the environment is the one to which the fish are adapted in much the same way that we are adapted to a terrestrial environment.

The same thing is happening with land plants but if you're camping in a field or a forrest, it's unlikely that diurnal changes in Oxygen and Carbon Dioxide concentrations are going to effect your behaviour in the same way as the really big environmental changes in the temperature and light level.

[Renrag39]

I thought the problem with freshwater fish in saltwater is reverse osmosis, i.e. the fish loses water to the stronger solution of seawater and cannot cope with it. A few fish like salmon, eels, flounders, mullet, bass etc can cope with both fresh and salt.

You're definitely right there Mark. Its not due to O2 extraction I'm afraid Phone, its the Osmotic imbalance that prevents many species' survival. Freshwater fish in saltwater will die of dehydration/heart failure and Saltwater fish in freshwater die of overhydration/brain death, because the influx of water into their bodies creates an imbalance of electrolytes necessary for brain function.

 

For the other CO2 at night issue, regarding plants, it has very little impact on fish. The only place I HAVE known it to be an issue is in heavily planted aquaria where due to CO2 injection, dissolved O2 can drop to dangerous levels for fishes during the night.

 

Its not B0llocks Rudd, its a perfectly valid and well thought out question. Good one!

 

Renrag

Edited September 3, 2011 by Renrag39

[Phone]

All,

 

While it has nothing to do with the thread subject since I am the one who just had to "throw it in" I'll respond.

 

O2 extraction with osmotic imbalance I would agree it would commonly happen from "salt to fresh". However, from "fresh to salt" it may or may not preceed asphyxiation. Not sure, I'm off the cuff.

 

The important message is that living plants don't "make" co2 (worth talking about). The amount of dissolved co2 in water can be a huge range compaired to the amount of DO. Rarely does dissolved co2 influance the amount of DO. The extraction of DO to make co2 by decay is major. Salts and minerals are a far greater natural nemisis.

 

DO is a major player in angling in fresh water.

 

Pretty sure but also, off the cuff. You're not going to make me go down to the basement and go through old boxes are you?

 

Phone