Christopher J. Gobler, Sergio A. Sañudo-Wilhelmy
Marine Sciences Research Center, SUNY at Stony Brook, Stony Brook, New York 11794-5000, USA
Additions of nitrate [DON] or urea [DIC] either had no effect or significantly decreased the relative abundance of the brown tide among the algal community during experiments. In contrast, augmentation of A. anophagefferens growth and decreases in non-brown-tide phytoplankton (NBTP) growth during organic carbon (glucose) additions resulted in significant increases in the relative abundance of brown tide among phytoplankton.
This is a hardcore example of carbon dosing causing an undesirable imbalance in the microbial food web whereas nitrogen dosing had a suppressing effect on the imbalance.
The above quote continues…
Simultaneous enhancement of bacterial growth by glucose additions indicated a possible A. anophagefferens-NBTP-bacterial interaction by which monospecific brown tides may be initiated. Therefore, it is hypothesized that processes introducing copious amounts of labile DOC during A. anophagefferens blooms, such as leakage or remineralization of NBTP blooms, could promote monospecific brown tides.
Should we not, then, avoid introducing copious amounts of labile DOC to our tanks?!?
Lulijwa Ronald, Gilbert Van Stappen, Nguyen Van Hoa, Patrick Sorgeloos
Green water (GW) was supplied to all ponds, with the standard Vietnamese procedure of supplying GW and chicken manure (CM) as the control (C/N 1.8). Treatment ponds were supplemented with tapioca (TAP) as carbon source, combined with either CM, pig manure (PM) or rice bran (RB), with C/N ratios of 7.4, 10.5 or 20.1 respectively. After 6 weeks of culture, no single treatment supported both improved water quality and enhanced Artemia production. Overall, improved water quality was observed at C/N 20.1 and higher Artemia production at C/N 7.4.
This is interesting for more than just growing brine shrimp!
Malinsky-Rushansky NZ, Legrand C
Excretion of dissolved organic carbon by phytoplankton of different sizes and subsequent bacterial uptake MEPS 132:249-255 | Full text in pdf format
One of the more-hidden angles of our reef world.
EOC [excreted organic carbon -Ed) may be important as a source of primary growth substrates for free-living bacteria (Larsson & Hagstrom 1982). The importance of microbial food chains parallel to the conventional grazing ones in aquatic food webs is now recognised (Azam et al. 1983). The significance of phytoplankton excretion as contributor to the ‘microbial loop’ has been studied (Cole et a.1. 1982, Brock & Clyne 1984). EOC contributed to about half of the bacterial carbon requirement in some environments (Larsson & Hagstrom 1982). Some studies suggested that a considerable amount of the annual primary production passed through the bacterial component (Brock & Clyne 1984),and bacterial production averaged 20% of planktonic primary production (Cole et al. 1988).
This is a really nice review article that touches on many areas that are important to us as reefers. As a result, it has a GREAT collection of citations that are pretty directly applicable to us and our situation.
A few quotes to whet the appetite – then go read!
We have recently shown that increased nutrient levels might not negatively affect the physiological performance of zooxanthellae as long as all essential nutrients are available at sufficient concentrations to ensure their chemically balanced growth 28. These results could explain why some reefs and the nutritional status and metabolism of their inhabitants do not always show negative responses to eutrophication [29• ; 30•], at least in the absence of temperature and light stress.
Most recently, however, we could demonstrate that corals exposed to elevated nitrogen levels were more susceptible to bleaching when exposed to heat and light stress [28•]. Interestingly, the detrimental effects observed in these experiments could be attributed to the relative undersupply of phosphorus that resulted from the enhanced demand of the proliferating zooxanthellae population rather than to the elevated nitrogen levels themselves (Figure 1 ; Figure 2).
We’ve been promoting this information (at least here on the blog) for quite a while now.
Overall, bacterial biomass did not change during re-oligotrophication, whereas chlorophyll-specific biomass of bacteria increased, APP biomass and phosphorus concentration showed a unimodal pattern and HNF biomass strongly declined with decreasing trophy resulting in a unimodal relationship between chlorophyll-specific HNF biomass and phosphorus. This shows that the different components of the microbial food web responded in a complex and group-specific way to alterations in nutrient and chlorophyll concentration. In conclusion, HNF responded much stronger and bacteria less than chlorophyll concentrations to re-oligotrophication, whereas APP exhibited a more complex pattern.
So cleaning up the dissolved nutrients in our tanks probably has the same limited effect….bacteria are super-competitors for phosphorus and appear able to keep it locked up (cycling?) within their biomass, independently of dissolved levels in the water.
It has become a phenomenon of increasing frequency in the reefing hobby today to have “too clean” of a tank. Zero nitrates, and sometimes even zero phosphates are found behind more and more tank issues. Either can be quite problematic for the tank.
With the ever popular “ULNS” systems and all methods of carbon dosing exponentially increasing in usage, nutrient starvation in our glass boxes is almost as common as the opposite. Pale colors in corals are one of the more common side effects. But there can be many side effects to a tank’s microbial food web ,aka microbial loop. (Also see other entries in the Nutrients section of the blog. –Ed)
Thankfully, there are many ways to increase and maintain nutrients.
Limiting nutrient export (e.g. water changes, reduced skimmer usage, shorter refugium lighting hours, etc) and increasing the rate of nutrients introduced into the system with extra feedings might be the two easiest ways.
However, in some cases, “nutrient dosing” is definitely something of interest – particularly nitrate dosing.
There has been a lot of discussion about the different reagents that could be used – a great one being potassium nitrate (KNO3). Also known as salt peter.
I was intrigued by the idea of being able to add exactly what the system needs.
The instructions on the thread are fairly easy and straightforward:
Add 2 tablespoons of the Sump Remover (granules) in a plastic cup of RODI water.
Use that to dose approximately one milliliter per ten gallons of aquarium water.
Then test and adjust accordingly.
Although this is a very simple approach, I had an uneasy feeling which kept me from slapping a quick dilution together and dumping it in. I wanted to have some additional confidence that it would succeed and perform as expected. Knowing that I can easily calculate the exact dilution to raise nitrate exactly, I started digging a little further.
My first data was the SDS (Safety Data Sheet) of the Spectracide product. It states unequivocally that the composition is 100% potassium nitrate. This is a bold statement to make as many SDS like to leave room for impurities – anything up to 99% potassium nitrate would have left the door open for some impurity. 100% purity gives a good comfort in using the product and expecting it to be and perform as predicted.
Ideally, for my purposes, a calculator is created to assist with the dosing.
The calculator I created (depicted to the left) consists of three main parts.
The first part helps with the creation of a stock solution that has a known nitrate content.
The second part helps with determining how much of that stock should be added in a known volume (your tank’s volume) to increase nitrate by how much.
The third section is where specific doses are calculated to address specific deficiencies.
The calculator is assembled as a Google docs sheet here.
Look closer at the KNO3 molecule in the Molecular Properties section of the calculator.
In order to know how much nitrate we will be adding, we need to know what is the ratio of nitrate is to other atoms in the KNO3 molecule by mass.
That section concludes that the ratio is about .61. Or in other words, about 61% of the weight of the KNO3 molecule is nitrate.
Solution Properties, the second section of the table, shows that if we create a stock solution of 10 grams of KNO3 in 500 milliliters of RODI water we are going to have a solution that has approximately 12,265 ppm of nitrate.
The third block, Dosing Calculations, shows that if we take 1 milliliter of the stock solution and we dose it into a 30 gallon system, we are going to increase nitrate by 0.1 ppm.
Indeed, following this, I created the depicted solution and dosed 5 milliliters in my 30 gallon tank and after an hour, when I tested, I had 0.5 ppm of nitrate.
It’s worth noting that to help keep the integrity of the calculations, the sheet is shared as “view only”.
You can still make a copy of it on your drive or if you don’t have a Google account you can also download the file to your computer.
In that calculator, there are a couple more things worth mentioning.
First, the other different forms of nitrate available also have calculators built into the Full tab of the spreadsheet – namely sodium nitrate and calcium nitrate each have their own calculator table.
It is fairly straight forward to make a similar table for any salt like those just by looking at the molecule and determining the nitrate ratio. For instance, the calcium nitrate molecule has two nitrates for one calcium. That has to be taken into account when calculating as this relationship makes it “nitrate heavy”. This methodology can be used for other compounds as well. Another good example checmical is potassium chloride for dosing potassium in the tank, but without affecting nitrates. The idea is the same within the calculator.
Secondly, there is also a tab called Simple which allows for a quick and dirty calculation resembling the ones everyone is used to from the venerable Reef Chemisty Calculator, and others.
The Simple View tab answers the question “how many grams of potassium nitrate to add to the tank to increase by how many ppm”. This foregoes the middle step of creating a stock solution and dosing that one which might be useful when dosing with a pump.
All things considered, any method of adding it can work. If you want something simple, then just putting the recipe together from the post on Reef2Reef might be all you need. If you want to achieve more control, the calculator might be more your style.