Organics (DOC) measurement methods for aquarium water

[Dan_P]

But yeah, hot sulfuric acid solution in tiny glass tubes at high internal pressure - not even gonna be in the same room as that while it's running. And if it busts, you've got a mercury clean-up too.

So, worse than running with scissors then.

 

[Dan_P]

sure, I'll bite.
My thinking going into this was that methods that are sensitive, real-time, and track biological activity (like BOD or pH) are more useful than methods that require shipping time and don't track biological activity. Was curious if going back over these methods and measurements would change my perspective - not really.
In a reef tank what are the sources of labile organic carbon?
Food is a big one right? Well, we have measured the remineralization of ground fish food, amino aids etc and it takes days to a week of remineralization for the large majority of the organic content to be finished breaking down by saltwater community.
Are there other large sources of labile organics that are gone so fast we're missing them?
Probably the DOC released by algae (and to some extent all photosynthetic organisms). We believe that algae blasted with light releases DOC from the excess sugar beyond the growth needs of the algae. But you and I failed to find any sign of significant increased digestible organics in the water from lighted algae even with a bunch of different methods - some that were sensitive. The likeliest explanation is that the algae release DOC gradually, that feeds bacteria at or near the surface of the algae, which makes quick work of the gradual DOC release. And thus when you or I measure the water, maybe there's nothing for us to find there because the handoff from algae to bacteria is so local and instant that we don't catch it in the water.

Exactly, it’s complicated. Linking a DOC level to the health of an aquarium might only be advocated by vendors of DOC measurement at this time.

 

[Randy Holmes-Farley]

But yeah, hot sulfuric acid solution in tiny glass tubes at high internal pressure - not even gonna be in the same room as that while it's running. And if it busts, you've got a mercury clean-up too.

Oh man, so many memories...

I once had to walk back to my dorm from an advanced undergraduate lab with no pants on (just a borrowed lab coat) after a broken flask spilled a nasty purple inorganic chemical (a manganese carbonyl, I think) in tetrahydrofuran down my front.

I also had an experiment using the high pressure bomb reactor in that same class. You weren't allowed to be in the same room with it when pressurized, but use a mirror to look around a cinderblock corner to see if all was well. I had to check it at night and had my girlfriend with me as backup. We could not figure out how to turn the lights on in the bomb room and she was quite stressed by the situation as I had to hold a light around the corner. Still married to her.

 

[Dan_P]

Oh man, so many memories...

I once had to walk back to my dorm from an advanced undergraduate lab with no pants on (just a borrowed lab coat) after a broken flask spilled a nasty purple inorganic chemical (a manganese carbonyl, I think) in tetrahydrofuran down my front.

I also had an experiment using the high pressure bomb reactor in that same class. You weren't allowed to be in the same room with it when pressurized, but use a mirror to look around a cinderblock corner to see if all was well. I had to check it at night and had my girlfriend with me as backup. We could not figure out how to turn the lights on in the bomb room and she was quite stressed by the situation as I had to hold a light around the corner. Still married to her.

HaHa, I wonder if such things still happen anymore (the incidents, not marrying college sweethearts).

 

[Lasse]

Are there other large sources of labile organics that are gone so fast we're missing them?

Do you not see the elephant in the room? Or are you walking around the hot porridge like a cat? I´ll think that the rise in - at least fast - DOC in many aquarium is not anything else than a result of marketing a way to get rid of algae - or let us say pest control

Sincerely Lasse

 

[taricha]

Do you not see the elephant in the room? Or are you walking around the hot porridge like a cat? I´ll think that the rise in - at least fast - DOC in many aquarium is not anything else than a result of marketing a way to get rid of algae - or let us say pest control

Sincerely Lasse

If you mean carbon dosing, then yeah I guess I didn't include that as a fast organic source because I was thinking of mostly the less obvious sources, rather than those explicit intentional additions.

 

[Lasse]

I think that active dosing of fast DOC is one of the most common methods today - every brand have its own recipe and we other take the Vodka bottle. There is even salts that include organic carbon.

Sincerely Lasse

 

[Dan_P]

I think that active dosing of fast DOC is one of the most common methods today - every brand have its own recipe and we other take the Vodka bottle. There is even salts that include organic carbon.

Sincerely Lasse

Of the total DOC added per day (whatever that is) do we have a rough idea what fraction of the total is from carbon dosing?

 

[Randy Holmes-Farley]

Of the total DOC added per day (whatever that is) do we have a rough idea what fraction of the total is from carbon dosing?

I think that would require a very intensive investigation of how much DOC a fish, a macroalgae, or a coral for example, excretes.

That said, my expectation is that the total DOC added by a heavy carbon dosing users (as in my tank) is much higher than other sources.

I also think that the effects of one type of organic may be entirely different than a second organic. Lumping them together has some merit (GAC depletion monitoring, etc.), but also has limitations.

 

[Lasse]

IMO - It does not matter how much the fast DOC it is of the total organic C input (feed, photosynthesis or what ever) - what´s matter is how digestible it is and if it is a limiting factor.

Organic carbon dosing (as it is done among aquarists) is the same as the use instant coffee and it is a very fast DOC fraction. I do not either like the term carbon dosing because it does not differ between inorganic Carbon and organic Carbon. When we dose the alkalinity part we do carbon dosing - but inorganic. when we need bacteria growth we dose carbon - but organic

Sincerely Lasse

 

[Dan_P]

I think that would require a very intensive investigation of how much DOC a fish, a macroalgae, or a coral for example, excretes.

We might find useful information about DOC production by coral and macro algae. Not seen a thing for fish but we might generate a useful estimate for a range for our discussion.

That said, my expectation is that the total DOC added by a heavy carbon dosing users (as in my tank) is much higher than other sources.

Just for laughs, 1 gram of fish food in 100 gallons is 2.6 ppm DOC if the food is 100% organic carbon ( GAC dinner). Maybe 1 ppm is more realistic if it is a high protein meal. 1 mL vinegar per gallon aquarium water is about 5 ppm DOC. Who knows what percent of that 1 ppm fish food becomes labile DOC, but this quick and dirty estimate supports your notion that carbon dosing is a large source of labile carbon.

I also think that the effects of one type of organic may be entirely different than a second organic. Lumping them together has some merit (GAC depletion monitoring, etc.), but also has limitations.

In the limited number of papers I have read, saccharides are the labile DOC villains which are produced by algae. Have not come across studies using amino acids or proteins to stress coral or investigate microbiome structure and function shifts.

 

[Randy Holmes-Farley]

We might find useful information about DOC production by coral and macro algae. Not seen a thing for fish but we might generate a useful estimate for a range for our discussion.

Just for laughs, 1 gram of fish food in 100 gallons is 2.6 ppm DOC if the food is 100% organic carbon ( GAC dinner). Maybe 1 ppm is more realistic if it is a high protein meal. 1 mL vinegar per gallon aquarium water is about 5 ppm DOC. Who knows what percent of that 1 ppm fish food becomes labile DOC, but this quick and dirty estimate supports your notion that carbon dosing is a large source of labile carbon.



In the limited number of papers I have read, saccharides are the labile DOC villains which are produced by algae. Have not come across studies using amino acids or proteins to stress coral or investigate microbiome structure and function shifts.

That food calculation would be a max, but metabolized organics and those released back as particles wouldn’t be doc.

 

[Dan_P]

That food calculation would be a max, but metabolized organics and those released back as particles wouldn’t be doc.

I imagine in an aquarium POC to DOC conversion happens on settled particles.

 

[Randy Holmes-Farley]

I imagine in an aquarium POC to DOC conversion happens on settled particles.

To some extent, yes, but lots of the POC coming from fish poop may be whole bacteria.

 

[Dan_P]

To some extent, yes, but lots of the POC coming from fish poop may be whole bacteria.

Yes, good point.

Would you expect all that poop bacteria added to the system to survive though? Food supply would certainly appear to be very depleted to the poor things once they leave the gut, and to add insult to injury, the surface biofilm potentially too over crowded to accept new tenants.

I am going to guess a higher trophic level organisms eat the liberated fish poop bacteria and poops out its own batch of refugees. And maybe the non-bacteria content of all this pooping is what is digested by cleanup heterotrophs to produce the DOC. Another guess is that the resulting DOC is not labile.

I seem to be losing the plot. Why do I care about the level of DOC?

 

[Lasse]

Note - by nature many poop bacteria are obligate anaerobs - not surviving in oxygenated tank water.

Sincerely Lasse

 

[Dan_P]

Note - by nature many poop bacteria are obligate anaerobs - not surviving in oxygenated tank water.

Sincerely Lasse

Excellent point! Poor things.

 

[sixty_reefer]

sure, I'll bite.
My thinking going into this was that methods that are sensitive, real-time, and track biological activity (like BOD or pH) are more useful than methods that require shipping time and don't track biological activity. Was curious if going back over these methods and measurements would change my perspective - not really.
In a reef tank what are the sources of labile organic carbon?
Food is a big one right? Well, we have measured the remineralization of ground fish food, amino aids etc and it takes days to a week of remineralization for the large majority of the organic content to be finished breaking down by saltwater community.
Are there other large sources of labile organics that are gone so fast we're missing them?
Probably the DOC released by algae (and to some extent all photosynthetic organisms). We believe that algae blasted with light releases DOC from the excess sugar beyond the growth needs of the algae. But you and I failed to find any sign of significant increased digestible organics in the water from lighted algae even with a bunch of different methods - some that were sensitive. The likeliest explanation is that the algae release DOC gradually, that feeds bacteria at or near the surface of the algae, which makes quick work of the gradual DOC release. And thus when you or I measure the water, maybe there's nothing for us to find there because the handoff from algae to bacteria is so local and instant that we don't catch it in the water.

Would those not be classified as SLDOC (semi labile DOC) instead of LDOC (labile DOC). It’s my belief that those are assimilated directly by Protozoa and other unicellular and multicellular organisms (zooplankton), this would make them not available in the water column hence you wouldn’t being able to test for them in your tests. Some types of organic carbon in this group can stay locked in the water column’s and sand bed for weeks before organisms can break them down to labile forms.
Zooplankton would have to consume this type of doc first and only after passing through the digestive system enzymes could break it further in form to extract it and transform it into a labile form.
There is many different sources of SLDOC in reef aquaria including the excreted coral mucus that is carbohydrate rich.
Some of this SLDOC will be locked within the organism cell such as phytoplankton and other algaes.

Edit:
In addition this “locked” forms of organic carbon cannot be used by your typical denitrification process as it’s not labile but they will contribute for the reduction of N and P as some of these unicellular organisms are able to assimilate those two nutrients from the water column. This has very little effect on oxygen to be able to measure it under thank conditions.

Just for fun a video of a bristle worm larvae (multicellular) ingesting those SLDOC



And unicellular

 

[taricha]

Would those not be classified as SLDOC (semi labile DOC) instead of LDOC (labile DOC). It’s my belief that those are assimilated directly by Protozoa and other unicellular and multicellular organisms (zooplankton), this would make them not available in the water column hence you wouldn’t being able to test for them in your tests.

when talking about the DOC released by macroalgae Dan and I are using stuff like this as our baseline expectation....

"We therefore quantified total and dissolved organic carbon (TOC,
DOC) and total and dissolved organic nitrogen (TON, DON) of exudates released by 2 cosmopolitan coral reef-associated green algae species, Halimeda opuntia and Caulerpa serrulata. Glycosyl composition and content analyses, along with protein, lipid and chlorophyll a (chl a) quantifications of algae exudates were conducted. Findings revealed that organic matter released from both algae predominately consisted of carbohydrates (59 ± 5%) and proteins (32 ± 7%), which mainly (89 to 93%) dissolved in surrounding waters. Traces of fatty acids (C16:0; C18:0) and chl a were also found in
algae incubation waters, but in a quantitatively negligible amount. Carbohydrate analysis further showed that glucose was the dominant glycosyl released by algae, accounting for 77 ± 8% of the carbohydrate fraction and 42 ± 8% of TOC. Galactose (9 ± 4% of carbohydrate fraction), mannose (6 ± 3%), xylose (4 ± 1%), rhamnose (3 ± 1%) and fucose (2 ± 1%) were also detected in all incubation water samples. High glucose and protein contents of algae exudates found in the present study confirm assumptions on the fast microbial degradability of these exudates, with ensuing potential negative effects on O2 availability and on interactions between corals and algae in coral reef ecosystems.

source: Composition analysis of organic matter released by cosmopolitan coral reef-associated green algae

So if they are releasing stuff like glucose (and the other "-oses"), then that's mostly highly digestible. And there's a number of methods that Dan and I have used that would pick that up if it stuck around in the water. That we don't see it is what makes me wonder if it might be handed off to bacteria and digested very quickly, near or even on the surfaces of the algae.

The yummy stuff isn't all they release, and as you point out, the digestibility of some of the DOC varies significantly, with the well-known persistent yellow compounds being the most obvious examples of low digestibility DOC from algae.

Just for fun a video of a bristle worm larvae (multicellular) ingesting those SLDOC

For the sake of clarity, when people say DOC, in the "D" they refer to dissolved stuff. It's fine to talk about particulate organics too, some of the methods in this thread (chemical digestions for instance) can quantify particulates as well as dissolved - just don't call particulates DOC, unless you are really just trying to confuse us about what you are referring to

 

[taricha]

a functional simple experimental definition I've seen used in published studies - if they could pass it through an 0.2um filter, they call it "dissolved" otherwise - "particulate"