What you need to know about copper and coral

[IridescentLily]

Hi all,
Starting in December 2011, Reefkeeping Magazine will introduce a new 'Topic Thread'. This will be located in one of Reef Central's forum sections every month. The goal of each Topic Thread will be to share information between experienced and beginners in the hobby with emphasis on contributing interesting facts, ideas, scientific articles, and some question/answer type dialogue on the subject. Afterward, a short summary of the thread will be added to the monthly Reefkeeping Magazine home page.
This month our thread topic is Copper and will be located in The Reef Chemistry forum on Reef Central. Feel free to post, learn or share information regarding this topic written by Cliff Babcock (Highlandreefer).

What You Need To Know About Copper and Coral


For the average hobbyist this subject can get very complicated and the chemistry part can quickly go over their head. For this reason, I would like to try and bring this down to the average hobbyist's level of understanding.

Copper can take many chemical forms in our tank water. It is important that this is understood. Basically you have the inorganic (often more toxic) and organic forms (often less toxic). It is usually the inorganic forms we are most interested in. When the toxic copper is introduced into tank water it can be grabbed by the organics in the water and can therefore become less toxic. This may occur fairly quickly. Studies have shown however the toxic copper form can act quickly on our coral. If levels are high enough, it can damage coral within hours after it is introduced.

A little history may help understand the copper level in our tanks. Dr. Craig Bingman has studied this in the past. His findings were that our tanks range between 10 ppb - 80 ppb copper. Dr. Randy Holmes-Farley tested his tank and his copper level was around 15 ppb. Bingman's study on salt mixes years ago found they averaged around 7 ppb copper contrary to what some manufacturers claim. The copper form in salt mixes is a toxic inorganic form in most cases. Keep in mind we are talking ppb (part per billion), which is a very small amount, well below what we as hobbyists can measure. The ocean averages around 0.25 ppb total copper. This includes both the organic and inorganic forms of copper.




What levels of copper are toxic to coral?

Copper toxicity varies greatly depending on the coral species. From scientific research it can vary from 10 ppb - 100 ppb. Hmm, this is the level that many of us may find in our tanks. Why is it that our coral don't die off from this? Most likely due to the toxic copper binding with the organics in the tank water fairly quickly once it is introduced. This is an important aspect to remember down the road when you add supplements, food & other things that contain the toxic forms of copper. Further complicating matters, scientists have found that different heavy metals combined with copper will increase its toxicity.



Ok, how can we apply this knowledge in a reef tank?

Copper is in alkalinity, calcium & magnesium supplements used in Two-Part supplements. We don't want to add too much of these supplements at one time. This gives time for the organics in the water to attach the copper and make it less toxic. It also allows tome for the copper to bind to surfgaces like rock and sand, reducing its availability to most organisms. You want to use chemically pure supplements with the lowest levels of copper. Using deicers may be risky since we don't know their copper level. You do not want to increase the calcium and magnesium level by more than 100 ppm using Two-Part supplements due to this type of concern about impurities.

Using Lime water will reduce the amount of copper added, since at least some of it will precipitate out to the bottom of the reservoir which should not be dosed. Kalk reactors and calcium reactors will add all the copper in the material used, so you want to use the least contaminated material as possible. If you add vinegar to your kalk water, it may increase the level of copper in the limewater.

The foods you add contain copper, checking the copper content in the foods added is called for. Keep in mind copper will build-up in the food chain. Fish that eat high copper content algae will have higher levels. Fish that eat other fish can accumulate more copper in their bodies.

Copper is a micro-nutrient. Over the counter additives containing copper should be avoided. We have enough copper in our tanks already.

Tap water and well water contain copper. If you have copper pipes, this can add a lot of copper. Use RODI water at all times when adding water to your tank, mixing supplements or mixing salt mixes. It's not worth the risk.



What are the symptoms of copper toxicity in coral?

The coral will bleach out and show signs of tissue necrosis within one to two days if enough copper is added. Many things cause tissue necrosis and bleaching in corals, so keep copper in mind if you have problems. Chronic copper poisoning can show up as polyp retention.




An article you may find interesting:

Heavy Metal Levels and Their Potential Toxic Effect on Coral (2009)

© 2009 Academic Journals Inc.

Heavy Metal Levels and Their Potential Toxic Effect on Coral
Galaxeafascicularis from Java Sea, Indonesia
http://docsdrive.com/pdfs/academicjournals/rjes/2009/96-102.pdf


A. Sabdono
Department of Marine Science, Diponegoro University, Semarang, Indonesia


Abstract:

Specific aims of the study were to quantify heavy metal concentration in the coral
tissue and to determine the toxic effect of metal on coral Galaxea fascicularis. The
concentration of heavy metals in the coral tissues were assessed using Atomic Absorption Spectrophotometer (AAS) technique. Various oceanographic parameters were also measured on sampling sites. Controlled tolerance experiment testing copper were performed on coral organism. Series of exposures at different range concentrations (0.025, 0.050, 0.075 and 0.100 mg L-1 Cu) were conducted for 96 h LCso . Results indicated that low variation existed among some oceanographic parameter in depth. Higher concentrations ofPb and Fe were detected in coral tissues. Short duration (24 h) laboratory assay demonstrated dramatic effects (tissue bleaching and death) on coral at copper concentrations (0.1 mg L-1 Cu). The LCSO _96 was determined to be 0.032 mg L-1 Cu (II). The present experimental results demonstrated that heavy metals can have deleterious effect on coral animal, at relatively low concentrations and for brief exposures.


CONCLUSION

Variations of Zn, Cd, Cu, Fe, Pb and Cr concentrations in tissues of the scleractinian coral G. fascicularis were measured to provide information for designing bio-assay surveys involving this coral. Inter-colony variations were measured using single portions (tissue) from different colonies of a coral community. The application of tissues for heavy-metal bio-assays is compromised by consistent inter-colony variation. Comparisons with earlier studies show that G. fascicularis to be the more sensitive to heavy metal toxicity, however this organism could survive in higher
concentrations for longer periods of time than the other coral species. The finding of this study suggest that the metal concentrations in coral tissue might be sensitive to differences in environmental metal load. Future study will need to establish study for quantitatively assessing both the acute and chronic toxic influence of heavy metals on coral physiology from polluted and non-polluted sampling sites.





Copper in the Ocean Environment

http://www.google.com/url?sa=t&sour...o7GdBA&usg=AFQjCNHh0yF2q0dbArHiv_Fp5eR8UMDbrw

 

[HighlandReefer]

The Chemistry Forum continues to provide reef keeping hobbyists scientific knowledge with the purpose of helping those interested sort through the opinions prevailing in this hobby. This is in tune with Randy's initial intentions when he first started this forum 10 years ago on Dec 13th of this year.

Congratulations & many thanks Randy for all your efforts over the years to keep this wonderful Chemistry Forum going. I would like to thank all the scientists & other hobbyists who have added to the information available to hobbyists.

:thumbsup:

We look forward to providing more interest in upcoming months through the monthly threads as time progresses.

I would like to thank Dr. Randy Holmes-Farley for editing my statements noted in the original short article, "What you need to know about copper and coral".

A few additional comments:

There are methods to detect and reduce copper levels if one suspects this is a problem. The easiest would be to run a polyfilter in the system. A polyfilter will act as a crude device to detect copper levels perhaps around 30-40 ppb which is the high end as to what is normally recommend to allow copper levels to climb. A polyfilter will turn colors if copper is present at sufficiently high levels. Keep in mind hobby grade test kits will not detect copper at these levels, they will detect copper at levels more like 100 ppb which is really high for a reef tank. If hobby grade copper test kits detect any level of copper, you should take immediate action to lower the level.

 

[jeremy K]

Excellent information, thank you.

Would running carbon (such as in a phosban reactor) eliminate the excess copper, or must it actually be a polyfilter?

 

[HighlandReefer]

You're welcome.


Running GAC (granular activated carbon) will remove many dissolved organics in your tank water. Copper will attach to these dissolved organics over time. So, running GAC will help to remove copper from tank water. GAC will not likely remove much inorganic copper ions from tank water, which can be more toxic than the inorganic forms.

IMO, the major concern to hobbyists is the period of time it takes for the inorganic copper to convert to the organic forms of copper. For example, lets say you add a lot (over 100 ppm) of magnesium supplement at one time. The copper in the magnesium supplement is in the inorganic forms of copper. It will take a while for the copper to attach to the dissolved organics in your water column. During the period of time it takes for the copper to convert forms is where problems can occur to your coral. It only takes hours for the inorganic copper to cause problems for coral. If you add to much inorganic copper at once it will cause problems.

Keep in mind that the organic forms of copper are thought by some sources to be only be about 1/3 as toxic as the inorganic forms, so if the organic copper is not removed by GAC or other methods (perhaps bacterial break-down) then it too can cause problems. There is also the possibility of the combination of inorganic and organic copper adding up together causing possible problems.

 

[HighlandReefer]

I would also add that the inorganic forms of copper are added in salt mixes, so doing combinations of things like a large water change, increasing your mag in large doses, increasing calcium in larger doses, adding high copper fish foods in larger amounts and adding micro-nutrients (which contain copper) in combinations can add up collectively and cause problems for your coral.

 

[RubberFrog]

Wow. How am I ever going to remember all of this? I better bookmark it and come back to it from time to time.

 

[disc1]

Nice Job Cliff! :thumbsup:


Here's some reading material. The first one has a lot of technical data to dig through, but the second one is a great read.


http://www.aslo.org/lo/toc/vol_33/issue_5/1084.pdf


Limnol. Oceanogr., 33(5), 1988, 1084-l 101
@ 1988, by the American Society of Limnology and Oceanography, Inc.


Copper complexation in the Northeast Pacific
Kenneth H. Coale' and Kenneth W. Bruland

Institute of Marine Sciences, University of California, Santa Cruz 95064

Abstract
Copper titrations were conducted at sea with differential pulse anodic stripping voltammetry to examine the degree to which copper was associated with organic ligands. Greater than 99.7% of the total dissolved copper in surface waters of the central Northeast Pacific shallower than 200 m was estimated to be associated with strong organic complexes. Below 200 m, increasing proportions of inorganic or labile copper spccics were observed. At middepths (1,000 m), about 50-70% of the total dissolved copper was in the organically complexed form. Whereas total copper varies by a factor of only three from the surface to middepths (0.6 - 1.8 nM), copper complexation gives rise to extremely low cupric ion activities in surface waters ({Cu2+} = 1.4 x 10^-14 M) and higher values at middepth ({Cu2+} = 10^-11 M)-a variation of three orders of magnitude. Two classes of copper- binding ligands were found to be responsible for this complexation: an extremely strong ligand class [log K' = 11.5 ] at low concentrations ( 1.8 nM) -which dominated copper complexation in the surface waters and decreased with depth, and a weaker class of ligands [log K' = 8.5] at higher concentrations (8-10 nM) which was observed throughout the water column and showed no apparent structure in its vertical distribution. These findings have significant implications concerning the toxicity and bioavailability of copper in open ocean systems.

It gets real technical, but if you don't mind hunting through it, there is a ton of info about organic ligands binding copper. One of the problems is that no one really knows exactly what molecules are binding the copper. There are a number of small organic ligands and some polypeptide type ligands, but their exact identities are a bit fuzzy.

Bruland describes at least two different classes of ligands for copper in seawater. There are stronger ligands which basically lock the copper away and detoxify it, and weaker ligands with lower affinity for copper.




Another interesting thing to me is that the cyanobacteria had already figured this problem out a billion years ago. In fact, the vast majority of the organic ligands that bind to copper are produced by the same cyano and algae and other photosynthetic organisms that we work so hard to fight back and keep out of our tanks.



From Chapter 2 of "The Oceans and Marine Geochemistry" Vol 6
(Available on the net: http://andrew.ucsd.edu/courses/sio263/downloads/brulandlohan-tog2003.pdf)

Read section 6.02.5 and section 6.02.5.1.

Copper provides an interesting example of a trace metal that is an essential, required element, but that can be toxic at relatively low concentrations. It can be considered the "œGoldilocks" metal. Surface-water concentrations in the open ocean are ,1 nmol/kg. Without organic complexation, the free copper concentration would be approximately a factor of 20 lower than the total dissolved concentration, with Cu(CO3) predicted to be the dominant species. This would yield [Cu2+] concentrations ,0.5 * 10^-10M or 10^-10.3 M. This concentration would be toxic to many oceanic phytoplankton, particularly the prokaryotic photosynthetic bacteria such as synechococcus (Brand et al., 1986). Figure 14(b) presents the actual vertical distribution of [Cu2+] in the upper 500 m of the Northeast Pacific. Coale and Bruland (1988, 1990) observed a slight excess of a strong copper-binding class of organic ligands, called L1. This class of strong copper binding ligands was found to occur in surface waters at concentrations of 1"“2 nmol / kg and its presence led to greater than 99.8% of the copper being chelated to this class of ligands. As a result, [Cu2+] was reduced by close to a factor of 1,000 and exists at concentrations ,10^-13 M, which is a concentration not toxic to phytoplankton. Moffett and Brand (1996) have shown that cyanobacteria when stressed with slightly elevated [Cu2+] can produce a ligand with a similar conditional stability constant. It appears that, somehow, the phytoplankton of the open ocean, particularly the prokaryotic phytoplankton, are controlling the external concentration of free copper by producing a strong copper-binding ligand that reduces the [Cu2+] to levels that are no longer toxic. As a result, the [Cu2+] in surface waters is buffered by the L1 class of ligands at a concentration that is "œnot too little" and "œnot too much," but "œjust right"; thus, the "œGoldilocks example." This buffering of [Cu2+] also influences its distribution and, because this chelated form is unavailable biologically, the dissolved copper is not depleted to a great degree in oceanic surface waters.

 

[jeremy K]

Not to try to oversimplify here, but would it then be reasonable to suggest constantly having a polyfilter pad in the sump, or at least running one every regular interval (weekly, monthly, etc.)? I mean, if we are constantly releasing inorganic copper by doing large water changes (as some of us do), or with 2 part additives, why not just run a polyfilter pad in the sump either all the time, or when doing such additions?

I am asking because I recently had an RTN event of 6 of my SPS corals, and I am looking for explanations. I wondered if copper might have somehow played a role...

Does running polyfilter have negative effects on the tank such as removing necessary trace elements?

 

[kgross]

Not to try to oversimplify here, but would it then be reasonable to suggest constantly having a polyfilter pad in the sump, or at least running one every regular interval (weekly, monthly, etc.)? I mean, if we are constantly releasing inorganic copper by doing large water changes (as some of us do), or with 2 part additives, why not just run a polyfilter pad in the sump either all the time, or when doing such additions?

I am asking because I recently had an RTN event of 6 of my SPS corals, and I am looking for explanations. I wondered if copper might have somehow played a role...

Does running polyfilter have negative effects on the tank such as removing necessary trace elements?

This is something I suggest to all of my customers. I have had many customers with problems with heavy metal poisoning from one source or another so suggest polyfilters as a good insurance policy.

Now from my experience copper poisoning or some other heavy metal poisoning seems to effect snails first. If your snails start getting lethargic and dieing for no apparent reason. Get a poly filter and keep it in your system.

 

[HighlandReefer]

Does running polyfilter have negative effects on the tank such as removing necessary trace elements?

IMHO, I don't believe running a polyfilter will have negative effects by removing too many trace elements (including copper).

It is my understanding from posts previously made here in the Chemistry Forum that polyfilters designed for aquarium use likely will only reduce copper down to around 30 - 40 ppb. Polyfilters can be designed in different ways to remove heavy metals (copper) including organic matter. My concern is if reducing copper down to this level by a polyfilter is enough, especially if copper in your tank is in the ionic, more toxic form.

From my understanding, it is believed that resins like those used in Cuprisorb will reduce copper levels lower which may be of some value to hobbyists. I seriously doubt IMO, that both a polyfiter and running Cuprisorb would lower copper levels below that found in the ocean (around 0.25 ppb), keeping in mind that copper is being constantly added to one's tank.

 

[HighlandReefer]

Nice Job Cliff! :thumbsup:

Thanks David.

Informative articles. Thanks

 

[Randy Holmes-Farley]

It is no longer clear to me how Polyfilters are made or if they are pretreated with copper. They claimed to in the past when binding was deemed undesirable. I have no idea what happens now.

 

[tmz]

That's an eye opener Randy, I assume you mean they add it to limit adsorbiton by ployfilters to the 40ppb level or is it more of a concern than that? Do you think it will release free copper to an aquarium?

FWIW, I run small amounts some polyfilter and cuprisorb continuously without any noticeable ill effects over the years;perhaps I should stop.

 

[HighlandReefer]

Randy, do you believe the information provided in your article below is still valid?

After reading the manufacturers sight, they simply state they have made improvements, but nothing to the effect that more copper or heavy metals are removed. The information from their site provides little if any specifics.

FWIW, Randy's article below provides many more details regarding copper and other heavy metals in the reef aquarium. For those hobbyists who do read this article and have questions for Randy, Now Is A Good Time to Ask.


Reef Aquaria with Low Soluble Metals (By Randy)
http://www.reefkeeping.com/issues/2003-04/rhf/feature/index.php

from it:

"Export of Metals: Poly-Filters

Many aquarists have heard that Poly-Filters (made by Poly-Bio-Marine) absorb copper and other heavy metals. Poly-Filters are essentially comprised of an organic polymer that is designed to bind to a wide variety of chemical compounds in aquaria. As with all materials that bind metals, the higher the concentration of metal in solution, the more metal will be bound. Unfortunately, this fact has lead many aquarists to misunderstand whether Poly-Filters might actually help them reduce metal levels below that present in typical reef aquaria (10-40 ppb). In this section I am not discussing whether one can make a polymer that will bind copper and other heavy metals from aquarium water (that's a different discussion for elsewhere in this paper and others, but it is possible that modified Poly-Filters might work in that context). What we are interested here is in whether there is any information to suggest that currently available Poly-Filters are effective at reducing the copper concentrations below the 10-40 ppb copper reported for all of the marine aquaria in Shimek's study, and in my own aquarium (10-13 ppb copper).

It turns out that, unlike most manufacturers, Poly-Bio-Marine provides some nice data and makes the results especially clear for us. Unfortunately, what they say is that it won't work for many metals in artificial seawater. In fact, they have specifically designed these filters to not take out copper below 30 ppb. Here's a series of quotes from their website:

ASTM Standard D 1141 lists only six (6) trace elements which are : Barium (99.4 mg/L), Manganese (34.0 mg/L), Copper (30.8 mg/L), Zinc (9.6 mg/L), Lead (6.6 mg/L) and Silver (0.49 mg/L).?

Note: ug/L is the same as ppb (parts per billion)

Then they note:

"Our next section will go into details of how Poly-Bio-Marine, Inc.'s special manufacturing process prevents Poly-Filter from sorbing those trace elements and other major or minor synthetic seasalt components."

"In order to make a Poly-Filter not capable of sorbing trace elements we must first saturate each Poly-Filter with the trace elements found in synthetic seawater."

"Upon completion Poly-Filter will not sorb trace elements nor calcium, magnesium, strontium or fluoride."

So they add the metals listed above to the Poly-Filters during manufacturing in order to prevent them from bringing down these metal concentrations when used in aquaria. In reality, I don't know whether their statements are accurate or not in relation to real aquaria, because all of the tests were in freshwater and synthetic seawater, not in aquaria where some of these metals (especially copper) will be largely bound to organics. Nevertheless, taking their claims at face value, one is forced to conclude that Poly-Filters will not be generally useful in reducing metal concentrations below the levels shown in Table 8 when used in raw artificial seawater. In this case, only zinc appears to be at a level such that Poly-Filters will remove substantial amounts from aquaria.

It is entirely possible that these filters will be more effective than described below at removing metals when the metals are bound to organics in real aquaria. After all, these filters claim to remove organics as well. However, it is also possible that they won't be effective, and testing them under actual reef aquarium conditions is something that I hope to provide in future articles."

 

[jeremy K]

Fascinating! Again, thanks for this. So basically, the only use for a polyfilter would perhaps be for aquaria where we were doing large water changes or adding large amounts of additives with metalic impurities. Any idea of how low Seachem's Cuprisorb can realistically lower our copper levels? Perhaps it is best to run polyfilter and cuprisorb together, as TMZ suggested above?

 

[Randy Holmes-Farley]

The info in my article was accurate as of when the Polyfilter folks posted that info. I do not know if it has changed or not. I've not heard it has, but I also have not noticed them make those claims publicly recently.

If what they posted is correct, it would add copper to my tank system (the last time I measured copper, around 10-15 ppb), but not to tank with substantially higher copper.

 

[HighlandReefer]

If what they posted is correct, it would add copper to my tank system (the last time I measured copper, around 10-15 ppb), but not to tank with substantially higher copper.

If I understand you correctly Randy:

If the manufacturer of the Polyfilter adds copper to prevent it from reducing copper below say 30 ppb and if the tank water is below this level, then the copper in the Polyfilter will go into the tank water, increasing the copper level until the copper in the Polyfilter is exhausted or reaches the 30 ppb level. If the copper in the polyfilter becomes exhausted, will it pull more copper out at that point and reduce the tank copper level below the 30 ppb level? Would there be potentially a significant amount of copper in this Polyfilter? Is the copper in the polyfilter chelated or in the ionic form? Personally, I don't understand this copper balancing procedure in a polyfilter & if chelated copper and ionic copper can come to a total copper equilibrium or if it is an equilibrium of just ionic copper forms and how the different organic forms of copper can come to an equilibrium (I hope this makes sense).

 

[tmz]

I understand your questions Cliff ;I must have a strange aging brain. If it's organically bound copper ,40 or 30ppb is not likely to be higher than the bound copper in the tank. If free copper leaches , I'm concerned. I must say though I 've usedit in small amounts for years without discerniblle issues.

 

[IridescentLily]

I'm going to ask the mods to "sticky" this thread up top in this section.

 

[Ralph ATL]

whooooa! editor? congrats!