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Aquatic Vegetation and Photosynthesis


garysj01
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Photosynthesis is the process by which land and aquatic plants use to produce food. Both types of plants require carbon dioxide, water and energy to produce glucose (their food). The only difference between photosynthesis in land and aquatic plants is where in their environments they get these nutrients. Land plants get food from the ground through their extensive root system, carbon dioxide from the air through their Stomata (tiny holes in a plants leaves) and energy from the sun. Aquatic plants get water and carbon dioxide form their aquatic environment and, like land plants, light energy from the sun. Oxygen is produced during photosynthesis and consumed during respiration and decomposition. Because it requires light, photosynthesis only occurs during day light hours. Respiration and decomposition, on the other hand, occur 24 hours a day. This difference alone can account for large daily variations in D,O concentrations.

D,O (dissolved oxygen) is oxygen that is dissolved in water, the oxygen dissolves by diffusion from the surrounding air, as a waste product of photosynthesis.

During the night, when photosynthesis cannot counterbalance the loss of oxygen through respiration and decomposition, D,O concentrations steadily decline. They are lowest just before dawn, when photosynthesis resumes. Where as at just before dusk, D,O concentrations are very high and many weedy waters can become super saturated, in other words the vegetation is producing more oxygen than is escaping.

Like all animals, fish need oxygen to live. As water moves past their gills, microscopic bubbles of oxygen (D,O) are transferred from the water to their blood.

Carp can tolerate a wide range of environmental conditions, including low D,O concentrations for several days, but its not without affect. Some species of carp can actually lower their own metabolic rate during periods of low D,O concentrations. They will become lethargic and stop feeding. As oxygen levels decrease, carp do not have enough energy to swim and feed. Carp can quite often be seen in the upper water layer column at the top of any vegetation where D,O levels are highest during the day. Most of the time you can just either see a dorsal fin or the back of a carp just protruding out of the surface of the water. Usually they remain very still unless they are spooked for some reason. It is believed that they are soaking up the rays from the sun but I also think that the carp are a lot more comfortable in this situation for a variety of reasons.

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Carp will often leave vegetated area's seeking open water that will have higher D,O concentration levels as weeded up area's are rapidly declining in D,O levels during the night.

To give an example Simon Scott took readings at the North Lake on the Yately Complex. The lowest readings were at dawn at 30% saturation which equates to 2.5 millilitres of oxygen per litre of water. Where as on the same water just before dusk the oxygen levels reached a height of 160% which is 14 to 15 millilitres of oxygen per litre of water.(super saturated), this happens when plants are producing more oxygen than can diffuse from the surface of the water. Now for a carp to have a healthy efficient digestion system it needs around the 5 millilitres of oxygen per litre of water.

We as terrestrial animals do not have to think about oxygen before we eat food, but fish do and will react accordingly. Their primary instinct is to survive and this instinct takes over the priority for feeding. These vegetated area's serve a multitude of advantages for carp during daylight hours. Firstly as talked about already the oxygen levels are quite high, they also give carp the much needed cover they need away from predator's eyes and these area's are usually rich in food, such as fresh water snails and invertebrates.

Aquatic plants are split up into three categories.

Marginal or Emergent Weeds

Rushes, reeds and sedges grow in shallow water in the margins.

Floating Plants

These form dense, unsightly mats across the whole water surface. Water Lilies, Duckweed, Water Fern, Floating Penny Wort and Broad Leaved Pond Weed.

Submerged Plants (oxygenating plants)

These plants mostly grow under water with usually only the flowering shoots appearing above the surface. Canadian Pondweed, Nuttall's Pondweed, Curly Water Weed and Water Milfoil.

And it is these plants I would like to concentrate on as they are the oxygenating plants.

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The most common aquatic plant we are most familiar with is, is the non native Canadian Pond Weed (Elodea Canadensis). Canadian Pond weed is classed as Submerged Oxygenating Plant. It grows indefinitely at the stem tips and single specimens may reach lengths of 3 metres or more. The leaves are bright green, translucent, oblong 6 – 17 mm long and 1 – 4mm broad, borne in whorls of three (rarely two and four) round the stem. It lives entirely underwater, the only exception being the small white or pale purple flowers which float at the surface and are attached to the plant by delicate stalks. This plant, along with others host a whole array of invertebrates and fresh water snails. This is why carp find vegetated area's so appealing during day light hours. You have higher levels of oxygen, cover and food. It only stands to reason why carp like these area's so much. But come dusk the carp will tend to move off, searching out more comfortable, oxygen richer water. Obviously there are exceptions to the rule, atmospheric pressure, angling pressure, wind direction and temperature. I have witnessed many times, carp sat absolutely still in weed for hours on end, only to see the fish fade with the darkness of night. Remember the switch over from the weed producing oxygen to producing carbon dioxide will be a gradual decline as the light fades, it doesn't just switch over. In my opinion fish will either hang around until the oxygen levels do drop to such a significant rate they feel uncomfortable and move off, or they will move when the light has faded as they will feel safer doing so, especially if there is a lot of angling pressure present. It is also worth a mention that, this is why you should never sack a fish up over night anywhere near any weed.

 

Temperature and Atmospheric Pressure

 

A carps metabolism and digestion are directly affected by temperature more so than atmospheric pressure. Day to day fluctuations won't bother carp to much, but prolonged spells of weather will, as it usually takes a few days for the water temperature to change. Colder weather does create higher D,O levels but anything below 7 degrees in temperature will slow a carps metabolism and therefore affect the digestive system. The enzymes in a carps gut break down the food through a process called chemical reaction. These enzymes do have an optimum temperature at which they work efficiently. The temperature is thought to be around 18 – 25 degrees, which is also the temperature that is the optimum growth rate for a carp. I could go on and on as there are many different enzymes for each breaking down process, but I won't baffle anyone with science. Basically if the enzymes are working at their peak, they are breaking down food quickly, lifting the metabolism rate, further lifting the hunger rate of a carp. The same can also be said for when the weather is to hot. The hotter the weather the lower the D,O concentrations, especially when it is very hot and there is no wind. Wind itself can increase D,O levels, as the waves create more surface area, more diffusion can occur. It is thought that atmospheric pressure affects carp by pushing them into different water columns. It is said the higher the pressure the lower you will find carp. I have read a few articles that suggest carp will feed best under 1000mb. Personally speaking I have found no scientific evidence to support this, other than prolonged spells of change may cause a change in behaviour. In fact many have documented that day to day fluctuations of atmospheric pressure has very little impact on fish at all.

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Guest Anonymous

Did you know plants drink water like fish something to do with osmosis, which is triggered by light for plants, not sure if it's the same for fish.

Which means at night plants go into reverse osmosis

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Guest Anonymous

To paraphrase Frank Zappa, (I’m doing a lot of that today) “That water is special, it makes its own sauce”. And that is why Mainline Cell works so well.... shhh I didn't say that :shock:

For those that aren’t familiar with big Frank, try this one, a classic.

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To paraphrase Frank Zappa, (I’m doing a lot of that today) “That water is special, it makes its own sauce”. And that is why Mainline Cell works so well.... shhh I didn't say that :shock:

For those that aren’t familiar with big Frank, try this one, a classic.

 

Well well. Ian, we share a Christian name and an enthusiasm for quality rock music it would seem.

 

I've got that album on vinyl somewhere. Wherever my wife has hidden it.

 

She doesn't like proper music.

 

Ian

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Guest Anonymous
To paraphrase Frank Zappa, (I’m doing a lot of that today) “That water is special, it makes its own sauce”. And that is why Mainline Cell works so well.... shhh I didn't say that :shock:

For those that aren’t familiar with big Frank, try this one, a classic.

 

Well well. Ian, we share a Christian name and an enthusiasm for quality rock music it would seem.

 

I've got that album on vinyl somewhere. Wherever my wife has hidden it.

 

She doesn't like proper music.

 

Ian

It was the wife that got me into Zappa, her old man was a bit of a biker back in the seventies, As for Ian being a Christian name I believe the Hebrew and the Gaels also claim the name as being part of their culture. I go with the Gaelic version, cus they are all mean and moody and look good in a skirt :)

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To paraphrase Frank Zappa, (I’m doing a lot of that today) “That water is special, it makes its own sauce”. And that is why Mainline Cell works so well.... shhh I didn't say that :shock:

For those that aren’t familiar with big Frank, try this one, a classic.

 

Well well. Ian, we share a Christian name and an enthusiasm for quality rock music it would seem.

 

I've got that album on vinyl somewhere. Wherever my wife has hidden it.

 

She doesn't like proper music.

 

Ian

It was the wife that got me into Zappa, her old man was a bit of a biker back in the seventies, As for Ian being a Christian name I believe the Hebrew and the Gaels also claim the name as being part of their culture. I go with the Gaelic version, cus they are all mean and moody and look good in a skirt :)

 

I'm a McLeod on my maternal side. Gaelic influence, I have a kilt which I wore at the wedding of one of my Aunts.

 

I was eleven-ish then. 63 now, but still got the legs for a skirt, honest!

 

Ian

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