Experiment: Trace Element Limitation in Reef Tank?

[taricha]

In my tank, it meant that I could dose to NSW levels and find none detectable by kit within a week, probably much less. That was the basis for my dosing: once a week to NSW seems a good dose even without measurement.

I'd guess that's likely the logic for Kent's recommended dosage (roughly to NSW once a week) because it'll deplete in well under that time, and they don't offer a test kit.

 

[taricha]

So I was going to dose some Iodide and watch it deplete, but turns out that was unnecessary.
I unintentionally fragged some fast growing gorgonians a couple of days ago, and they ended up laying in another coral.
Today, I noticed the gorg pieces had tissue eroding, so I pulled most of it out, and propped up one frag. As I pulled the pieces out, more tissue sloughed off.

(Pterogorgia probably)
Gorgs ought to have a TON of Iodine in their tissue, so I checked the water samples. (a couple of days ago water showed undetectable Iodine.)
Sure enough...
Sample from lights on = 0.0063ppm Iodide
Sample from 5 hours later, about an hour after I had pulled the gorg peices out (dislodging more tissue in the process.) = 0.0084ppm Iodide.

So, I have measurable trackable I in the water. I'll see how long it takes to deplete. Though this won't be a true Iodide uptake test, because there's still tissue in the tank decomposing and releasing Iodide as other things absorb it, but interesting anyway.

 

[Randy Holmes-Farley]

Though this won't be a true Iodide uptake test, because there's still tissue in the tank decomposing and releasing Iodide as other things absorb it, but interesting anyway.

Perhaps not even close, since the form in the gorgonia may be 3,5-diiodotyrosine (an organic form).

You may be tracking both its metabolism by bacteria to release iodide, and the uptake rate to reduce it.

https://www.advancedaquarist.com/2003/3/chemistry

Who Uses Iodine: Gorgonia And Antipatharian Corals (Black Coral)
Another set of creatures of the deep that use iodine are certain gorgonia, such as Plexaura flexuosa.42 They have 3,5-diiodotyrosine in their bodies, to the tune of 0.1 to 2.6% of the total dry weight as iodine. This iodoamino acid is presumably incorporated into proteins in the skeleton (stem), but the benefit is unclear. Again, it may be largely an antipredatory effect that is desired. The iodine incorporation in gorgonia seems to increase with age.43,44 The proteins of many different gorgonia species contain substantial iodine: Eunicella otenocalloides6.5-8.9% by weight%, Gorgonia verrucosa 4.2-9.0, G. lamarcki 3.3-6.8, G. scirpearia 0.4-0.6, Rhipidigorgia flabellum 0.6-1.1, Euplexora maghrebensis 0.19-0.23, and Plexaura kukenthali 1.9-2.2.44 It has also been demonstrated that at least one gorgonia (E. verrucosa) takes up iodine in the form of inorganic iodine from the water column.45

One study showed that the organoiodine compound thyroxine, and some related compounds, are localized to certain parts of the gorgonia L. virgulata.46 Most interestingly, one of the places it is localized to are scleroblasts (spicule-forming cells) and on the spicules themselves. Further, the addition of thyroxine to these cells impacted the uptake of calcium, and it is suggested that the thyroxine functions in spicule formation.

The antipatharian corals (the black corals) also seem to incorporate a lot of iodine. The basal regions of these corals are especially loaded with iodine, with more than 23% iodine by dry weight recorded in two species.43, 45 Again, the specific purpose is not known.

 

[taricha]

Cool, I looked up what form of I was stored in caulerpa, but forgot to check on the gorgs. Very cool that it registers Iodide, even though the test isn't detecting the organic form of I that the gorgs store.

I'll also note that a mini diatom dusting reappearance coincided with the decay of the gorg tissue. But that's almost certainly got zero to do with iodine.

It's a recurring pattern. Keeping N P Si available, I get tiny diatom dustings that reappear presumably when some scare resource becomes available, and fade a couple of days later.

It's generally assumed that available Si would trigger a big diatom bloom, but among systems (with dinoflagellate history) that have intentionally dosed N P, & Si, we're now like zero for a half dozen in creating a true diatom bloom. Something else is always missing. (Fe being the assumed likeliest choke point.)

 

[mcarroll]

It's a recurring pattern. Keeping N P Si available, I get tiny diatom dustings that reappear presumably when some scare resource becomes available, and fade a couple of days later.

Like "Cyano: Si Edition"

 

[taricha]

So I've been thinking about porewater, the stuff between the grains in the sand bed.
Some papers have suggested that bacterial processes in the substrate can free up all kinds of goodies that can encourage growth (fuel cyano mats for instance).
Some hobbyists have actually tried to test their porewater for nutrients, and some of those who have found interesting things- N, P, ammonia, even occasionally detected some iron.
In the past, my tank has been fed large consistent amounts of live phyto grown on f/2 media, and I've also dosed Fe well in excess (35+ ppb) of NSW concentration. I also rarely do anything to remove detritus. So it's at least plausible that my sand bed could be a storehouse of detectable available iron.
So I figured I'd give it a try.
Slooowly siphoned a total of 100ml of water over 3 hours from 1-2 cm down in 3 different low flow areas of tank where detritus accumulates.

No Fe detected. No surprise. Read "0ppb" on meter. Hanna LR Iron Meter has +-20ppb uncertainty, which is itself way higher than what you'd expect to find in NSW or a normal tank.
So, weak test - doesn't exclude presence of Fe, just says I don't have huge amounts of Fe in sandbed, which is nice. That would be harder to figure out what to do with if I did.

 

[Jose Mayo]

So I've been thinking about porewater, the stuff between the grains in the sand bed.
Some papers have suggested that bacterial processes in the substrate can free up all kinds of goodies that can encourage growth (fuel cyano mats for instance).
Some hobbyists have actually tried to test their porewater for nutrients, and some of those who have found interesting things- N, P, ammonia, even occasionally detected some iron.
In the past, my tank has been fed large consistent amounts of live phyto grown on f/2 media, and I've also dosed Fe well in excess (35+ ppb) of NSW concentration. I also rarely do anything to remove detritus. So it's at least plausible that my sand bed could be a storehouse of detectable available iron.
So I figured I'd give it a try.
Slooowly siphoned a total of 100ml of water over 3 hours from 1-2 cm down in 3 different low flow areas of tank where detritus accumulates.

No Fe detected. No surprise. Read "0ppb" on meter. Hanna LR Iron Meter has +-20ppb uncertainty, which is itself way higher than what you'd expect to find in NSW or a normal tank.
So, weak test - doesn't exclude presence of Fe, just says I don't have huge amounts of Fe in sandbed, which is nice. That would be harder to figure out what to do with if I did.

The very habit, widespread in marine aquarism, of controlling phosphates with hydroxylated iron media, is probably already a sufficient source and able to maintain iron levels well above the "natural" found in reef areas in the oceans. Add to the chemical speciation that this element suffers and the fact that its largest portion (up to 95%) is linked to siderophores that hide it from the "habitual" tests (hobby level), and we will have an idea of the degree of difficulty to maintain this parameter (which, yes, could be a spectacular "limiting" to the pest explosion), under control ... It will not be easy task "to tame it."

Regards

 

[taricha]

Quite true. GFO is one of the few typical things I'm not doing and haven't for some time.
Part of me thinks that iron is the biggest "invisible" factor in the variation of productivity of reef tanks and the composition of the unintended life that springs up around our chosen livestock.

The other part of me wonders if the very fact of its invisibility - untestable, and imports/ exports largely unnoticed - means that it's a too convenient explanation for anything since we can't ever prove otherwise.

Anyway, on with the testing: since I've got a nice baseline of data for rates of consumption under conditions that ought to be depleting trace elements - now i start adding commercial additives meant to address these depletions, and see if it changes consumption rates of things i can measure. First up: red sea trace colors A (iodine, Bromine, Fluorine) added yesterday at levels calculated to give 0.06ppm iodide. Test 1hr later confirmed Iodide maxed my test (which happens right at 0.06). I'll also watch the iodide depletion rate itself, for kicks and curiosity.

 

[taricha]

Oh, also if I sample one day but want to test it in a day or two or 3, what's best storage method for the sample to avoid change in parameters?
Room temp, fridge, freezer, microwave ?
I'm testing for NO3, P, Ca, Alk, Si, sometimes Mg, K, and I. Also test pH and temp, but those would be done at sample time.

 

[mcarroll]

Test 1hr later confirmed Iodide maxed my test (which happens right at 0.06).

Are you testing with the Salifert Iodine kit now?

 

[taricha]

Are you testing with the Salifert Iodine kit now?

The Seachem iodide kit you recommended (very good by itself) Frankenstein-ed with Hanna Silica meter.
Details here...
https://www.reef2reef.com/index.php?posts/4725012

 

[mcarroll]

Right!! I basically had to run parallel tests in all six pods, inlcuding one pod with using the iodine standard to have any shot at making a reading. HOW MUCH BETTER is using a colorimeter instead!? LOL Excellent hack.

 

[Randy Holmes-Farley]

Oh, also if I sample one day but want to test it in a day or two or 3, what's best storage method for the sample to avoid change in parameters?
Room temp, fridge, freezer, microwave ?
I'm testing for NO3, P, Ca, Alk, Si, sometimes Mg, K, and I. Also test pH and temp, but those would be done at sample time.

Fridge.

 

[taricha]

Right!! I basically had to run parallel tests in all six pods, inlcuding one pod with using the iodine standard to have any shot at making a reading. HOW MUCH BETTER is using a colorimeter instead!? LOL Excellent hack.

Yep. I figure I can't be the only one who gets tired of the game "rate this blue/pink".

Plus, (unnecessary) precision warms my nerdy heart.

 

[Hans-Werner]

Slooowly siphoned a total of 100ml of water over 3 hours from 1-2 cm down in 3 different low flow areas of tank where detritus accumulates.

No Fe detected. No surprise. Read "0ppb" on meter.

There may be another cause why you can´t detect Fe in this way. At least a highly sensitive Merck test only shows free iron, I guess in the Hanna test it may be the same. In seawater you will hardly find any free iron and the same in reef aquaria. Iron will always be bound to bacterial chelators (except for a short time after dosing free iron ions) that mask the iron for the test.

There are at least two ways to detect the real iron concentration: Destroy all organics with oxidizing agents like sulfuric acid and do the test then or send a water sample to a laboratory that does ICP-OES.

 

[taricha]

There may be another cause why you can´t detect Fe in this way. At least a highly sensitive Merck test only shows free iron, I guess in the Hanna test it may be the same. In seawater you will hardly find any free iron and the same in reef aquaria. Iron will always be bound to bacterial chelators (except for a short time after dosing free iron ions) that mask the iron for the test.

There are at least two ways to detect the real iron concentration: Destroy all organics with oxidizing agents like sulfuric acid and do the test then or send a water sample to a laboratory that does ICP-OES.

"We choose to search for iron in this reef tank and do the other things, not because they are easy, but because they are hard; because that goal will serve to organize and measure the best of our skills and test kits..."
- said President Kennedy probably never.

 

[taricha]

Ok, so for stuff we can test.... check out the Iodide progression.

The first data point is well within the error range of zero. The non-zero measured iodide from days 2-7 correspond to the decomposition of some gorgonian frag tissue discussed in posts #102-103.
The action on the right side is after I dosed Red Sea Trace Colors A. You can see the rapid consumption of Iodide from the dosing target 0.06ppm down quickly below the approximate NSW level of 0.02ppm. One of the last two samples had some problems. One suggests the consumption is linear (green line) and will fully deplete in 1-2 days. The other implies a more gradual uptake (exponential decay function in red) as Iodide becomes scarcer and maybe closer to a week before the I is undetectable.
Which one is right? I have a hunch it's the red, but we'll see.

 

[Randy Holmes-Farley]

The Red line would be more expected of just about anything being taken up. It gets harder and harder so slower and slower as the concentration declines.

 

[taricha]

The Red line would be more expected of just about anything being taken up. It gets harder and harder so slower and slower as the concentration declines.

True. Of things I can think of only NO3 just zooms straight to "zero" without much hesitation.

Hmm... looks like you'd use waaaay more iodide supplement trying to maintain close to 0.06 than you would aiming for 0.02ppm.

 

[mcarroll]

Iron will always be bound to bacterial chelators (except for a short time after dosing free iron ions) that mask the iron for the test.

Thanks for another excellent post.

I finally had to look up Siderophore. ;Brb;Bookworm;Happy

Maybe it's just me, but that word sounds like an animal or a kind of seed or something, so I had no idea:

Siderophores = Bacterial chelators!

I can't be the only one who didn't know, so here's the relevant summary from the W:

Marine Water
In contrast to most fresh-water sources, iron levels in surface sea-water are extremely low (1 nM to 1 μM in the upper 200 m) and much lower than those of V, Cr, Co, Ni, Cu and Zn. Virtually all this iron is in the iron(III) state and complexed to organic ligands.[31]These low levels of iron limit the primary production of phytoplankton and have led to the Iron Hypothesis[32] where it was proposed that an influx of iron would promote phytoplankton growth and thereby reduce atmospheric CO2. This hypothesis has been tested on more than 10 different occasions and in all cases, massive blooms resulted. However, the blooms persisted for variable periods of time. An interesting observation made in some of these studies was that the concentration of the organic ligands increased over a short time span in order to match the concentration of added iron, thus implying biological origin and in view of their affinity for iron possibly being of a siderophore or siderophore-like nature.[33] Significantly, heterotrophic bacteria were also found to markedly increase in number in the iron-induced blooms. Thus there is the element of synergism between phytoplankton and heterotrophic bacteria. Phytoplankton require iron (provided by bacterial siderophores), and heterotrophic bacteria require non-CO2 carbon sources (provided by phytoplankton).

The dilute nature of the pelagic marine environment promotes large diffusive losses and renders the efficiency of the normal siderophore-based iron uptake strategies problematic. However, many heterotrophic marine bacteria do produce siderophores, albeit with properties different from those produced by terrestrial organisms. Many marine siderophores are surface-active and tend to form molecular aggregates, for example aquachelins. The presence of the fatty acyl chain renders the molecules with a high surface activity and an ability to form micelles.[34] Thus, when secreted, these molecules bind to surfaces and to each other, thereby slowing the rate of diffusion away from the secreting organism and maintaining a relatively high local siderophore concentration. Phytoplankton have high iron requirements and yet the majority (and possibly all) do not produce siderophores . Phytoplankton can, however, obtain iron from siderophore complexes by the aid of membrane-bound reductases [35] and certainly from iron(II) generated via photochemical decomposition of iron(III) siderophores. Thus a large proportion of iron (possibly all iron) absorbed by phytoplankton is dependent on bacterial siderophore production.

That last line is pretty interesting.