Why there is copper in phytoplankton culture medium

[capman]

Energy posted a message not too long ago as I recall about there being copper in the nutrient mix he was using to culture phytoplankton. I was talking to the plant biologist in my department the other day about why copper would be included, and his recollection was that copper is an essential cofactor for one of the enzymes involved in chlorophyll synthesis (I have not looked this up to verify that his memory was correct, but I think he probably knows what he is talking about). Translation...organisms (algae, plants, etc) cannot manufacture chlorophyll if they have no copper ...and if they cannont manufacture chlorophyll they cannot carry out photosynthesis. They only need very minute quanities of copper to do this (and if they have too much copper the copper becomes toxic of course), but if there is no copper at all they have a big problem.

I don't know my biochemistry all that well, but I would not be at all surprised if copper is a cofactor for some other essential enzymes involved in other biological processes as well.

In a normal aquarium situation where we add food there is probably enough copper (or more than enough) supplied to the system by the food. However, in a defined culture medium (presumably diluted to working strength using deionized water) a tiny bit of copper needs to be included, otherwise the algae will not be able to grow.

Just thought you might find this interesting.

Bill

[WildPraire]

Bill,

Being a plant freak in general... I know that copper is considered an essential micronutrient. It is needed at the cellular level in plants to activate enzymes, albeit at a very, very low levels.

Copper is also used to try to fight cyanobacteria in some bay areas. I find that kind of creepy, I wonder what all is killed off?

Phytoplanton would need sun or light, CO2, nitrogen, phosphorus, silicon and traces of cobalt, iron, zinc and copper. These are the substances that we know that they need. There could well be other minute traces that we don't really have a handle on yet. You probably already knew most of that. My plant expertise is mostly of the terrestrial type.

Sue

[Dwayne]

I agree it is important to know 'WHY' copper is in the culture medium.

More important, in my mind, is 'How much is too much?'. We know the phytoplankton uses the copper to grow, but what effect does it have on the tank? At what point does it become dangerous or toxic? Referring to the fact that the copper still exists in the tank, possibly in another form.

I have not 'seen' a negative reaction to feeding large amounts of phytoplankton to a reef tank for extended periods (few years). I'm sure after a couple of years dumping phyto in my tank there has to be some copper somewhere in the tank. Am I lucky or is the copper being utilized in such a way that makes it non toxic?

Just wondering.

Dwayne

[Energy]

The micro algae grow formula by Florida Aqua Farms contains the following:nitrates,phosphate,sodium,iron,maganese, cobalt,zinc,molybdate,sulfates,copper,thiamone,bio tin,cyanocobalamin,ascorbic acid,and EDTA in that order.

This is the situation which makes me believe some of these ingredients were making it into my tank. I had been dosing phyto plankton on a 24 hour drip for approximately one month. I had shut down the culture to refresh some of my batches before starting over again. At this time I had done a calerpa harvest from my refugium taking approximately 60% out. After giving the calerpa a few days to recover and begin to grow I restarted a very slow phyto drip. Within 5 days of starting the drip both of my cephlapods in different tanks started to show a loss of appetite. Although they are in different tanks it is still a connected system. A day later both cephlapods died. One was a cuttlefish the other an octopus. Everything else in all systems stayed healthy. The difference is cephlapods are extremely sensitive to heavy metals - especially copper. I realize it could be a number of factors but all other livestock were unaffected. Clams, anemones, sps, lps, softies etc are healthy. I believe the concentration of heavy metals increased to a toxic level for these extremely sensitive invertibrates.
I don't think it was the nitrates or phosphates which did it since everything else stayed the same and cephlapods aren't that sensitive to changes in either of those. That doesn't mean those two didn't increase it's just I don't think that was the killer component. I have also read that others who do phyto drips often have problems with their phosphate levels. There have been quite a few discussions on other boards about this topic with no resolution.
Either way I am done with the phyto-drip. It seems non-sensicle( is this a real word?) to introduce components into a closed system which are known to be destrucive and damaging.

[capman]

Here are some semi-random thoughts...no real answers though....no useful suggestions on how to deal with this situation.........

I'd bet the concentrations of everything in the phytoplankton culture medium are fairly high (in order to get the algae to grow really well, and to allow the culture to grow to high densities). However, assuming everything in the culture medium is in balance, in the proportions the algae use the various nutrients, I'd guess that a dense culture would use up everything in the culture medium (and yes, there would be a bit of copper in the algae, but minute quantities of copper are normal in any algal cells, and there is also going to be a tiny bit of copper in all the foods we feed).

I'd be surprised if everthing is so perfectly balanced though....so, the most likely situation is that the algae will grow until one of the nutrients essential for thier growth is used up. If copper is not the first limiting nutrient, then there would be some copper left over and in solution at this point.

Even if the nutrients were perfectly balanced, if the algae cultures are not really dense and if they are still growing, then there will probably be available nutrients left in the culture medium, which will go into the tank. I would be surprised if the cultures are always grown to the point where growth stops (and the nutrients are all used up) before the algae are fed to the tank (because I'd guess that cultures might have a tendency to crash if they are grown for too long without replenishing nutrients????). So, with the nutrients well balanced or not, I think we are likely to be dumping nutrients from the culture medium into our tanks if we dump in phytoplankton cultures. Most of these nutrients will probably be snarfed up by organisms in our systems, but if something like copper is too concentrated there would be potential for it to build up beyond the concentrations that the organisms in our systems could make use of for their normal metabolic needs. If this was the case, then levels would gradually rise.

One way to minimize the amount of extra nutrients being added with the algae would be to centrifuge the algae down, dump out the liquid, and resuspend the pellet of algae in tank water. Since most aquarists don't have centrifuges in their homes, this is not going to be easy for most folks to do (and even if you did have a centrifuge, this would be a bit of a hassle to to every day).

I'd bet that as long as you are not keeping ultrasensitive animals like cephalopods, things would probably be fine in a system fed cultured phytoplankton as long as you have a significant amount of biomass harvest (e.g. Caulerpa, Xenia, turf algae, etc) as part of your nutrient export system. This is just a guess on my part though.

[capman]

Energy,

By the way, the anemone is doing well. It has attached its base inside a small depression in the side of a rock. It is inflating well, and it has a very impressive feeding response!

Thanks. I'm looking forward to seeing what it looks like as it grows larger.

[Toyfreek]

Bill,
I was wondering, I really don't know much about phytoplankton's life cycle and or it's biological processes. Would the chealation process (like in simple/macro algae) propose those needs for heavy metals, or is this simply a side effect of another needed process, or does this not apply to phytoplankton.
I was thinking that the heavy metals might be tied up with the phyto and then ingested by the feeding animals in a harmless form?
Or am I waay off base here.
Thanks,
Matt

[Energy]

Even if most of the metals get tied up in the animals that digest them what happens to the undigested material? It seems almost impossible to optimize the delivery time to when most of the growth influencing material is gone. Therefore some of the pure phosphate,nitrate ect. is going back into the system. On a 24/7 delivery schedule this can began to add up. I do believe that much of pure stuff will get gobbled up immediately but in my case, after such a large Calerpa harvest, my system was not ready for the excess nutrients. If excess nutrients are making there way back in so are the metals.

[capman]

Matt,
I don't know.

Energy,
Yes, I agree.

[capman]

An interesting additional note about copper...

I'm teaching an invertebrate biology course at the moment and I was just studying the text we are using and reading about respiratory pigments.

Respiratory pigments are molecules like hemoglobin (the stuff that makes our blood red), which is a special sort of protein that contains an iron atom at the center. The function of hemoglobin is to bind to oxygen (the iron is directly involved here), and thus increase the oxygen-carrying capacity of the blood When the blood flows to parts of the body where oxygen levels are lower (due to oxygen consumption), the oxygen is released by the hemoglobin, so hemoglobin is also an effective oxygen transporter. Hemoglobin is found in vertebrates and many invertebrates (the freshwater blood worms (chironomid midge larvae...tiny aquatic fly larvae) that are sold as fishfood are just packed with hemoglobin, which allows them to grab the little bits of oxygen that are present in the muddy, stagnant habitats they prefer). A form of hemoglobin is even found in some plants (in legume root nodules).

So, what does this all have to do with copper? Well, many invertebrates do not have hemoglobin. Instead, many of them (in particular a lot of the arthropods and molluscs) have a different respiratory pigment that uses a pair of copper atoms (rather than an iron atom) to bind to the oxygen (and interestingly, their blood turns blue when oxygenated).

I think it is rather ironic that rather small doses of copper can be so toxic to the very same invertebrates for whom minute quantities are absolutely essential.

I know, there are lots of things like this, where a little is good, and a lot is dangerous, but I thought some of you might find this essential role of copper interesting.

Don't start dosing your tanks with copper though...remember, in anything but minute quantities, copper is very toxic.

Bill