Limitations of DSB's

[SPC]

Originally posted by mojoreef
Spanky I just want to congradulate you. This is the first time since I have known you that you have spoken common English in a thread that I can actually understand, lol you da man.

I think we might be turning him into a hobbest. Chris your next.


Mike

I think that "old dog" thing went right out the window .

Thanks for the excellent replys as usaual Jerel, but you know I'm not through being confused quite yet .
You wrote:
"If people are worried about organics and metals, then remove detritus. That's where all their problems are going to be. Not locked up in CaCo3, but in organics and bacteria."

So, in order to get the detritus out of the entire sand bed, one would have to either:
1. Remove sand bed and replace with new.
2. Remove sand bed and wash sand.
3. ?
I would presume that a deep vacuuming would be counterproductive as this would disturb the anaerobic zone thus rendering it useless? Or, could a small portion of the DSB be done this way at certain intervals, and keep enough of the anaerobic zone in tact.?
Steve

[Spanky]

One way to tell for sure, look at your sand critters through the side glass. When you start seeing them only active shallower and shallower in the sand bed, it's time to investigate. I would start by vacuuming out a small section that looks like it's giving you problems and wait and see.

Honestly there's no rule of thumb. It's all going to depend on how much you put in the system and how many different things and ways you take it out. Depending on the system and you, it might last forever or not so long.

Steve, I will answer your question, I'm just thinking. Here's what I do. Sometimes I just stir up the sand with my hands while I'm in the tank and let the skimmer take it out. Sometimes I take a gravel vac. Sometimes I siphon a section out into a tub when I'm doing a water change and put it back with a little new mixed in. Sometimes I just siphon it out, dump it, and replace that section.

[MJB]

If you're looking for a fairly straightforward treatment of the interaction between sediments and metals check out:
Louma,Samuel N. Can we determine the biological availability of sediment-bound trace elementts. Hydrobiologia 176/177 Pp.379-396. 1989. While its true that bacteria may make metals more biavailable its something of a stretch to suggest that as a rule they are not remineralized through other pathways. While I agree that ultimately organics may prove to be our worst enemy I don't think you can rule out metals toxicity either. Particularly if you're going to make the argument that the ultimate sink for metals is complexation with bacteria and organics.--MJB

[Spanky]

You're right, I just don't want to be the one to say it. I'm trying to keep this on organics and bacteria right now.
On that note:

http://nautarch.tamu.edu/class/anth605/File9.htm

Here's a interesting read. It's about recovering ship wrecks. I've snatched a few lines out that directly apply to this conversation.

>>Despite the fact that the corrosion processes are impeded by the formation of encrustation, metal deterioration can continue due to the presence of sulfate-reducing bacteria.

>>Sulfate-reducing bacteria, particularly the strains known as Sporovibrio desulphuricans (Pearson 1972a:35) and Desulphovibrio desulphuricans (Farrer et al. 1953:82) are commonly found in salt water,Sea water has a large supply of sulfates, and under aerobic conditions, these bacteria use hydrogen to reduce the sulfates (SO4)-2to sulfides (S-2) as a metabolic by-product according to the reaction:
H2SO4 + 8H >> H2S + 4H2O

>>In this process, the hydrogen that accumulates on the iron as a cathodic product polarizes the cathode in an oxygen-free environment. The polarization of the cathode ordinarily halts the electrochemical corrosion process. However, the utilization of hydrogen in the metabolism of the bacteria depolarizes the cathodic areas of the cell, allowing corrosion to continue unabated. In addition, the hydrogen sulfide formed as a metabolic by-product reacts not only with iron but with all of the metals of antiquity (except gold) and accelerates the corrosion process

>>The life cycle of sulfate-reducing bacteria stimulates both the cathodic and anodic reactions of the electrochemical corrosion process.

[mojoreef]

This might be interesting in regards to the carbonate not being available to the metals
here

and this was a good read to
thier are a few experiments that are interesting

mike

[Spanky]

I realize that last post of mine was a leap of faith (BTW Mike your HERE link doesn't work)

What is in a DSB that you don't want to stir up because it might kill everything in the tank? smells like rotten eggs? Called Hydrogen what?

sulfide - sulfates

Now read that last post of mine again and tell me where these bacteria will be found.....

and where the bacteria are, what will be found with them?

[mojoreef]

ok so you are saying dont stir to deep

[mojoreef]

American Mineralogist, Volume 86, pages 826–833, 2001
TEM analysis of microbial mediated sedimentation and lithification in modern marine
stromatolites
JOHN F. S TOLZ,1, * TIMOTHY N. FEINSTEIN,2, † JOSHUA SALSI,1 PIETER T. VISSCHER,3
AND R. PAMELA REID 4
1 Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, U.S.A.
2 Department of Biology, Colorado College, Colorado Springs, Colorado 80903, U.S.A.
3 Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340, U.S.A.
4 Division of Marine Geology and Geophysics, RSMAS, University of Miami, Miami, FL 33149, U.S.A.
ABSTRACT
Three sedimentary processes are involved in the growth of living stromatolites at Highborne Cay,
Bahamas: (1) trapping of oolitic sands, (2) formation of surface micritic crusts, and (3) formation of
fused-grain laminae. The microbial role in each process was investigated by examining the stroma-tolites
using transmission electron microscopy. Species composition and physiological state of the
bacteria were discerned by ultrastructure. A well-dispersed population of Schizothrix gebeleinii was
observed in rapidly accreting surface layers. Their filaments produce copious quantities of amor-phous
exopolymer and condensed sheath that surround individual, and pairs of cells. Both fresh and
degraded sheaths are, however, devoid of carbonate precipitates. This suggests that the primary roles
of S. gebeleinii are the trapping and binding of unconsolidated sediment and the production of extra-cellular
polymeric secretions. Surface micritic layers are composed primarily of needle-shaped crys-tals
of aragonite. The uppermost surface of the micritic crust is coated with a biofilm comprised
primarily of small Gram negative bacteria (i.e., sulfate reducing bacteria) that range in size from 250
to 500 nm in diameter and up to 1 µm in length. Empty cyanobacterial sheaths and occasional Gram
positive spores were also observed. Thin sections through resin-casts of ooid microborings in the
fused-grain laminae show cells of the endolithic cyanbacterium Solentia sp. and evidence of an
organic matrix. The micritic crusts and fused-grain layers became lithified laminae that were pre-served
at depth, although the organisms that formed them were not. This suggests that morphologi-cal
remains of these organisms (i.e., microfossils) in ancient stromatolites should not be expected.

[Spanky]

There's a lot of debate as to whether metals even collect in a DSB, much less where and by what process.

I'm showing a definite link between Sulfate-reducing bacteria, what they do, and where they are found in a reef tank.

Now if you want to stir it, go ahead.

Don't bother to test the calcium carbonate for metals, the metals are going to be found in that yellow looking bacterial bile that comes up when you stir a DSB. They are going to be in the bacteria.

[Jabel]

Sorry Guys, I've read about 4 pages and everyone seems to agree that DSB's aren't great. I'm here to disagree.

I've had a DSB in my tank for 7+ years with no problems. For the 1st 6 I never changed water and I added tap to replace evaporation. Now I change about 5% about every month or so and I ad ro/di. My nitrates have never gotten above 5 and the tank is running beautifully. I keep reading about this old tank syndrome but I'm skeptical. From my biochem background I know that things precipitate when thier concnetration getts to high. No matter how much you mix the sand up it will be hard to solubalize any more. So the idea that suddenly your tank will let all of these metals or salts back into solution is false. If they do then there is something else majorly wrong with you system.

DSB's might get clogged with detritus but having critters keeps the bed mixed. If it sinks into the bed then bacteria take care of the rest. Bacteria eat alot more than nitrogen products and I gaurantee there is a very large bacteria bioload in your tank to take care of it. In nature there a plenty of critters to eat everything so thats how the cycle goes.

The biggest plus for DSB's is that they are cheap and easy to setup. Thier main job is to rid our tanks of Nitrates and they do that well.

I say switch everything over to DSB's, through out your skimmers and bring put back you bioball drip systems.

OOOOps maybe going off on a tangent.

Jeff!!

[galleon]

Only have a couple of minutes before a Marine Geology lecture, so I'll try to make a quick point since Jerel is trying to stay on organics. I think it may be time to go back to some basic principle

Reefs are not oligotrophic. They do not dwell in nutrient poor waters. The paradox is they are towers of DOM and labile organics in areas of generally oligotrophic waters, that outside of reefs support less than half the gross primary productivity compared to more temperate or better upwelled waters. Approaching the reef flat from all sides, the concentrations of suspended and dissolved organics increases exponentially. This is a fact. Crossland, Marshall, Gerber, etc. have all analysed reefs and surrounding waters in different areas and all established a remarkably similar gradient.

This organic matter stays suspended by surf/energies and what isn't DOM or in a dissolved state as labile OM is considered detritus, and its composition ranges from leaching from algal plastids (considering that algae dominate), the feces of all manner of plankton, nekton and benthic fecal matter, sedimentary biomass kicked up by surge.

Now...think, what are the dominant benthic animals on coral reefs adapted to do? If these particles are organic, they likely are made of what that these dominant animals could use as an energy source? I realize this covers POM/flocculated marine snow only. DOM and LOM are decomposed almost entirely by bacterioplankton. NOT sessile bacteria. Where do you think the inorganic material returned to solution by the bacterioplankton goes? I'll give you two hints. Its recycled back into DOM, LOM or POM, and its utilized in its inorganic form by the dominant organism on reefs.

Next comes flushing and flow. Most generally, it moves to lagoons, where seagrass and seagrass epiphytes and mangroves and bacteria can break the matter down and "sink" it, or it is sinked (eventually) to the abyssal plains

Now, if you can answer all these questions, you'll realize that there is no niche for organic material to sit in a reef sandbed and decay over a period of weeks/months/years down to its least common denominator.

[MJB]

I wouldn't disagree about the role of sediments near reef flats . However the point was made that they are vey good at denitrification something that seagrasses and mangroves don't really do very well (at least in dissolved form) although they may be the answer to keeping organics in the sediments low as they get their nutrients through well develped root systems. So while DSBs may be a liability with respect to accumulation of organics the answer may be to construct a remote lagoon system although it has been argued that efficiency of the bed will be impacted. And you still have the problem of what fills the role of primary producers especially when you start talking about a self sustaining ecosystem. I would like to add that OTS didn't just spring up last year although DSBs may exacerbate an existing problem.--MJB

[galleon]

I think you missed the point. The idea is that since these sediments aren't allowed to be degraded on reefs, they shouldn't be in our systems either. Since we don't have sinks involving transport through other ecosystems, DSB users choose to put the sink right in the tank. This completely goes against natural dynamics. Therefore, the ideal reef area system would be to have a system that pulls out organics at a very efficient rate (foam fractionation), as well as manual removal of settled detritus so it is not allowed to degrade. Very high in-tank circulation should be used in order to keep POM suspended as long as possible. Nobody has taken a stab at my questions yet, so I'll not yet reveal why they (POM) are such a good nutrition source. The remote lagoon system would be worthless due to its lack of volume and processing capability. In the least common denominator: We can't use nature as a model. We have to try to recreate conditions in nature, but we can't use nature's processes to do it. It doesn't work in closed systems.

[galleon]

"I think we might be turning him into a hobbest. Chris your next."

Does that mean its time for me to run away?

[galleon]

Just as a footnote to the metals discussion, detritus is arguable THE most important biogeochemical vehicle of metals in the oceanic/estuarine ecosystem, especially in terms of recycling. Assimilation potentials (efficiency) of metals are very high for nektonic organisms such as copepods. Copepods, to use as the idealized examply, actively seek and consume detrital material that contains algal remnants. This detritus will have complexed metals such as Zn from bacterial activity along with that which was actively held in the algal cells.