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01/01/2018, 07:51 AM | #1 |
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Reflects before you begin dosing carbohydrates
Nitrate assimilation
Nitrate assimilation is subjected to regulation that may differ depending on the organism. In general, nitrate assimilation is controlled at the transcriptional level by nitrate and nitrite induction and by ammonium repression. In the pre-genome sequence era, it was known that some, but not all, heterotrophic bacteria were capable of growth on nitrate as a sole nitrogen source. However, examination of currently available prokaryotic genome sequences suggests that assimilatory nitrate reductase (Nas) systems are widespread phylogenetically in bacterial and archaeal heterotrophs. In cyanobacteria, the transcription factor represses nitrate assimilation genes when ammonium is present whereas it activates transcription of these genes at a high carbon/nitrogen ratio. The nitrate-assimilation process begins with the transport of nitrate into the cell. Nitrate is further reduced to nitrite in a two-electron reaction by a cytoplasmic molybdenum containing nitrate reductase followed by a six-electron nitrite reduction to produce ammonia. The assimilatory reduction of nitrate to ammonium is an energetically expensive process since it requires eight electrons and complex prosthetic groups for the nitrate and nitrite reductase enzymes, in addition to the active nitrate transport. In order to avoid this energetic cost under unnecessary environmental conditions, bacteria have evolved a strict control of the expression of the Nas system. Thus expression of the Nas genes is subjected to dual control based on specific nitrate or nitrite induction, and ammonium repression, by a general nitrogen-regulatory system. http://www.baharini.eu/baharini/doku...traat_reductie When adding carbohydrates for the first time not a lot will change to the nitrate level. Ammonia, normally nitrified by autotrophs, is used first . Only when the supply of ammonia is insufficient nitrate will be used. When dosing is continued nitrification will be suppressed due to ammonia availability as the heterotrophs grow a lot faster. Heterotroph ammonium reduction ( assimilation) produces 40 x more bio mass compared to autotroph ammonia reduction. ( http://www.baharini.eu/baharini/doku...onium_reductie ) As a result less nitrate will be produced. The moment the C:N ratio increases due to dosing and increased ammonium take up ( and less or no nitrate production) nitrate may be used for celsynthesis. Nitrate is also taken up for respiration. Nitrate take up for respiration is not suppressed by ammonia. The nitrate level may be depleted fast at high C:N ratio. All this implements a very low nitrification and denitrification capacity. When biopellets are used in a reactor there is always a high C:N ratio available. An aquarium system that is kept in balance by carbohydrate dosing has a limited carrying capacity. Such systems are vulnerable for a system crash due to the well known new tank syndrome. Once started dosing it may be difficult to stop. Dosing should be build off during a period of at least 15 days. Please comment. |
01/01/2018, 09:23 AM | #2 |
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Well that made my head feel funny lol. Question though, you keep saying Carbohydrates, do you mean Carbon? Never heard of Carbohydrate dosing.
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01/01/2018, 10:07 AM | #3 |
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Thanks for sharing your knowledge. Some of the technical jargon in your post is beyond my level.
Assuming that you meant organic carbon by "carbohydrates", what you stated makes sense and is in fact well established in the literature. It is well known that reef organisms have preference for ammonia over nitrates for their nitrogen source. Daniel Knop and Michael Fatherree, for example, mention this phenomenon in their respective books on giant clams. I also agree with your statement that "Once started dosing it may be difficult to stop". I think if one decides to stop dosing organic carbon, he/she should do so in small steps instead of in a big bang approach. Last summer, I experimented with a commercial product that contains marine-based biopolymers in it. It is marketed as Reef Actif by Tropic Marin. Even though I knew that I should decommission the use of this product slowly when my experiment finally finished at the end of last October, I went against my own knowledge and stopped using it at once. My reef system did not crash, but it was seriously destabilised in terms of nutrients and their ratio. It took nearly two months to regain its balance and it is still not quite there yet. Moreover, in case you do not know, there is another commercial product marketed by Tropic Marin called NP-Bacto-Balance. It contains among other ingredients (e.g. organic carbon) organic and inorganic forms of phosphates and inorganic nitrates. The main idea is to prevent complete nitrogen and phosphorus depletion providing that the product is used according to its dosing instructions. I guess that there are ways of countering some of the disadvantages of organic carbon dosing, which you correctly pointed out in your post. It is possible to have a healthy reef that relies on organic carbon dosing. My system has been relying on it for the past three years. However, I will update this thread if it ever crashes one day. Happy new year. PS. The links you provided in your post are not accessible.
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01/01/2018, 02:19 PM | #4 | |
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01/01/2018, 03:07 PM | #5 | |
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In that case you must log in or register. Makazi Baharini is a closed dokuwiki. NP-BACTO-BALANCE: Can not find out how much usable organic carbon it contains. It claims creating an optimal nitrate-phosphate balance. It would be interesting to know how it is able to do so and what this optimal balance should be. For biosynthesis ( assimilation) this would be in weight +- 10 to 1. |
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01/01/2018, 03:12 PM | #6 | |
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I was informed by Hans-Werner Balling that Tropic Marin "have chosen a harmless simple organic N compound that releases ammonia after hydrolysis to avoid the potentially dangerous ammonia itself. The organic N compound is quite stable but can be hydrolyzed by enzymes of corals and bacteria quickly."
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01/01/2018, 04:03 PM | #7 |
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By providing additional carbohydrates a cycle is created from NH4 to NH4. Only +- 30% of the cultivated biomass will be removed by a skimmer. http://www.baharini.eu/baharini/doku...iwitafschuimer. The rest must be consumed. it becomes part of the food cycle.
To reduce 1 g NH4-N, +- 8 g protein is produced, the equivalent of 20 grams food containing 30% protein. When the produced protein is consumed some is used to increase the total bioload but most of it will be released as ammonia and a bit ureum. To reduce 1gram nitrate by assimilation also 0,1gram phosphate is needed. http://www.baharini.eu/baharini/doku...onium_reductie This may become an issue in biopellet reactors. Once regular dosing carbohydrates, most of the dose is used to remove ammonia which is the result of previous doses. It must be clear that when additional carbohydrates are provided this must be taken in account for the total food supply. A refugium can be added to help consume the produced bacterial biomass by organisms which may be used as a food souce. It must also be clear that when the organic carbon supply is interrupted biomass will decay. Organisms which depend on it will die. On that moment nitrification capacity will be insufficient . Heterotrop ammonia reduction produces a lot of biomass, 40x more as nitrification. This is done every cycle from NH4 to NH4. It is a fact that +- 2% of the bacterial biomass will be lost as it is not recyclable and will be left as detritus. The growt may also become an issue when biofilters or DSB are used. They may clog. But at a high maintained C:N ratio these filters are not needed. Last edited by Belgian Anthias; 01/01/2018 at 04:19 PM. |
01/01/2018, 04:40 PM | #8 | |
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01/01/2018, 04:59 PM | #9 | ||||||
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01/01/2018, 08:23 PM | #10 | |
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01/02/2018, 02:59 AM | #11 | |
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In LNS a caveat may be the competition for available phosphate and other building materials certainly when the doses do not correspond the needs. In LNS the doses may be responsible for most of the biomass production, more as normal feedings. As the small amount ammonia is immediately taken up when it becomes available most LNS do have very little or no nitrification capacity. Not a problem as long as the ammonia take up rate will be maintained. The "carrying capacity" is the capacity of the system to reduce ammonia. Normally 2/3 is reduced by nitrification. The "carrying capacity" is decisive for the maximum bioload. When organic carbon dosing is used to reduce ammonia the carrying capacity is easily adjusted but the system may become completely dependable of these doses and the corresponding bacterial growth which growth is dependable of a lot of other factors and parameters. |
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01/02/2018, 04:37 AM | #12 | |
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In zero emission marine aquaculture systems ( ZMAS) using carbohydrates dosing to maintain a high C:N ratio no or little nitrate is produced. Which are the standard microbes? Nitrifiers and denitrifiers? How one can avoid the bacteria to overlap "physically"? For me It is logic that when ammonia is removed by assimilation this ammonia is not available for nitrification and denitrification. It is a fact that autotrophs are suppressed by heterotroph growth. |
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01/02/2018, 05:56 AM | #13 |
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more to think about.
It takes about 1 day for heterotrops to double there biomass. it takes about 15 days for autotrophs ( nitrifiers) to double there biomass. This means that at least 15 days are needed to double the nitrifying capacity when for some reason the heterotroph growth can not be maintained and longer to become normal.
All recipes for carbohydrate dosing are based on the nitrate level. But it is not nitrate that triggers the bacterial growth, it is ammonia by priority.. In nature and in aquaria usable organic carbon is limited available. This way making it possible most organic material can be recycled and the nitrogen cycle can be completed. Nitrogen is send back were it came from and is not stored in biomass. What happens when organic carbon is unlimited available? In LNS or VLNS dosing must be correct, corresponding to the needs. Otherwise not all of it may be used for growth due to not enough building material. The moment building material as phosphate is delivered the competition for the building material may end up in a real war. Guess who will win!? In general in LNS where the balance is maintained by carbon dosing a high C:N ratio is available. Are we going to assume that doses are ok or is there a way to be sure the dosing is correct.? What do we know about the hierarchy between organisms in using building materials? Commercial products which contain polymers and other building materials are available but how to dose these products if one thus not know how many organic carbon is actually released or used? Following the guidelines assuming it will be ok? Biopellets used in a reactor: the carbon source is unlimited available in the reactor but the other building materials are not. The question asked when biofilters are used for ammonia reduction is:"What to do with the nitrate produced" As nitrogen can easily be removed from the system to where it came from this problem can be solved. The question asked when carbohydrates are dosed for ammonia reduction may be:"What to do with the biomass produced?" In aquaculture systems the biomass is harvested and a new batch is started. When algae scrubbers are used for assimilative ammonia reduction the produced biomass is harvested. |
01/02/2018, 06:21 AM | #14 |
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You have not answered my previous question about the use of activated carbon to harvest the produced biomass.
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01/02/2018, 06:59 AM | #15 | |
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How do I register? What’s the Dutch word I am looking to click to register? Maybe you could cut and paste the references into this post so we can at least read the science behind conjectures. |
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01/02/2018, 02:12 PM | #17 | |
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01/02/2018, 02:33 PM | #18 | |
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01/02/2018, 02:34 PM | #19 | |
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01/02/2018, 06:22 PM | #20 | |
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As for heterotrophs consuming nitrate because we carbon dose, has this been proven in an aquarium this is what actually happens? Might another explanation be that nitrate production is minimized because of increased ammonia assimilation by hetertrophic bacteria and the nitrate already produced is simply converted to nitrogen by autotrophs? |
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01/02/2018, 06:37 PM | #21 | |
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01/02/2018, 06:41 PM | #22 | |
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01/02/2018, 06:48 PM | #23 | |
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A lot of things can be skimmed, and characterizing what comes out of the skimmer back into what was in the tank would be non-trivial, in my opinion. One guess is that carbon dosing removes nutrients by feeding bacteria that release skimmable organics. It's also likely that at least some of the carbon is consumed by bacteria that are themselves skimmed, but I don't know how much that would be.
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01/02/2018, 07:15 PM | #24 |
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