SPS coral care

Discussion in 'SPS Corals' started by stoney waters, Apr 2, 2011.

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  1. Corailline

    Corailline Super Moderator Staff Member

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    It is a dry heat, yeah right !
    Alrighty then if you have higher values for phosphates and all around increased DOC, perhaps you are feeding the brown zooxanthellae.

    Maybe corals use the nutrition produced by the brown zooxanthellae more readily then the nutrition produced by the zooxanthellae that are providing protection from the UV/Sun rays.
     
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  3. stoney waters

    stoney waters Fire Shrimp

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    Inwall I found this post a while back that you made which might help people understand this more...It's not merely the amount or lack of zooxanthellae that controls coral coloration. As Dr. Fragenstein mention, the coral has it's own pigment that serve a variety of different purposes. These pigments reside within the tissue of the coral itself. These pigments do not have the ability to transfer light energy, but it has been found that in very deep waters they have the ability to alter particular color wave lengths. This is done by absorbing one color and the fluorescing a color the coral can use. SPS or shallow water corals produce large amounts of pigments under high lighting intensity.

    Most pigments in coral tissue are called pocilloporin and are categorized as either Brightly Colored Low Fluorescent Pocilloporins or as Highly Fluorescent Pocilloporins. Highly Fluorescent Pocilloporin pigments have the ability to absorb light with a specific wavelength and then fluoresce or emit this light into a different wavelength. Most of the highly flourescent variety act as UV protectorents. (I.e. Protecting the coral and algae from UV's and too much light). The lower fluorescent types tend to help the Zoox pigments reflect wavelengths they don't want and only absorb the wavelengths they do want. However, just to make things more difficult, there are also non-fluorescent proteins that provide coloration.

    These pigments absorb light basically with in the zone of 400 to 620 nm. violet to blue to some green and some yellow and some red. They absorb those light but fluoresce different colors back out. The colors that fluoresce out are the colors we see in our tanks.

    Further complicating matters is that corals eventually say to themselves, "Hey, I don't think we're in Kansas anymore". I've seen people say to themselves that since this is an SPS, I should put it up high in the tank under 400W MH's. Probably not a good idea if your coral is a deepwater acro. However, if acclimated slow enough, it will probably be fine. Zooxanthellae come in numerous clades and in a reef tank environment following a bleaching event, a coral might be reinfected by a different clade.
     
  4. m2434

    m2434 Giant Squid

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    Right, so zooxanthellae being an algae(actually, more specifically a dinoflagellate), will grow under any conditions that would promote algae growth. So, what conditions help dinos grow?


    However, the next level of complication occurs because the algae resides within the tissue of a coral. So, the coral controls access to the outside environment. Therefore, then the next question is how does the coral influence the environmental conditions for the algae? I'll hold off on this for now though, to focus on the first question, first.
     
  5. m2434

    m2434 Giant Squid

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    Well, no one else followed up on the question and I have to leave for the afternoon, so I'll start LOL. Some of the more important conditions required for algae to grow are.


    - Light
    - Inorganic phosphate
    - Inorganic Iron
    - Inroganic - Other trace elements
    - Inorganic nitrogen (i.e. ammonia/ammonium, nitrite, nitrate)
    - Dissolved Inorganic Carbon (DIC) - i.e. CO2


    Anything else I missed?


    - NOT Dissolved Organic Carbon (DOC) or other organic compounds for that matter. For our intents and purposes, algae is autotrophic, that more or less, means it produces organic compounds from light and inorganic compounds.


    Roughly stated, an organic compound, for example, could result from fish food or die-off organic dieoff as it starts to decay. As these sources break down, the resulting material will consist of Organic Carbon, Nitrogen, phosphate etc... This is still organic though because it is bound to carbon molecules. As it decays, or is consumed by hetrotropic bacteria etc... however, it can loose the carbon components and becomes "inorganic", and therefore accessible to the algae for nutrients.

    So, then the next question is, how can a coral regulate access to these requirements?
     
  6. stoney waters

    stoney waters Fire Shrimp

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    Not even sure on what to say haha...It would be nice to know though
     
  7. m2434

    m2434 Giant Squid

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    Some background info (or just see conclusion if preferred):

    So the algae is found in vacuoles (called symbiosomes) within the corals endodermal layer. Really all that matters is that the algae are contained within compartments in the corals tissue. I did a quick search, but couldn't find a great diagram. So, I've mentioned the specific terms in case someone else wants to do a search.

    I nature, corals live in very nutrient poor water. Again, the algae is photoautotrophic meaning it can synthesize it's own food from light and inorganic nutrients. The coral is heterotrophic meaning it requires organic compounds for growth. However, all inorganic substances must pass through the corals tissue to get to the algae. This can occur through diffusion or specialized transport mechanisms depending on the particular substance.

    Also, the coral produces some inorganic substances for the algae, such as CO2 from respiration. The algae in return provides fixed organic carbon to the host in forms such as glycerol, glucose, lipids, amino acids etc..

    As mentioned inorganic nitrogen appears to result in algae growth, suggesting that the algae growth is nitrogen limited. However, for whatever reason, it does not appear that corals regulate zoox via nitrate limitation. In nature nitrate concentrations are very low however, so this may be less of an issue though. It's possibly more of an issue in our tanks.

    Phosphate is another potential limitation, and there is some evidence that corals may regulate zoox through phosphate. A few experiments found that increasing external phosphate didn't actually lead to increased zoox density, whereas increased external nitrate did. This would suggest the corals may be able to regulate phosphate. However, since there appears to have been some debate on this though, and the mechanisms of phosphate transfer are still mostly unknown.

    Conclusion:

    The zooxanthellae is located within compartments in the corals tissue and the coral can regulate access to certain nutrients to promote or restrict algae growth. Regardless though, the under certain environmental conditions, the algae is able to bypass the coral and use nutrients such as nitrate directly from the water. When this occurs the algae can grow faster and the corals perceived coloration becomes browner.

    Next question:
    So, now stepping back a minute is a brown coral a bad thing? And why or why not? hint: what have I left out?
     
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  9. inwall75

    inwall75 Giant Squid

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    Sorry I've missed out on all of the fun.

    OK, we've established that browned out corals is largely in response to high nutrients in our tanks. I'm glad that m2434 made this comment.
    just to give an interesting factoid. It's not only the bacteria in your LR/LS that is converting Ammonia and Nitrite via electon exchange.....the zoox in your corals are actually ingesting them (along with nitrates). Betcha didn't know that. You don't have to remember these names but I want them out there in case anyone wants to do some in-depth study. This tight cycling of nutrients right within the coral itself is how both the coral and the algae manage to survive in oligotrophic (nutrient-poor) conditions.

    There's a number different ways. Corals basically "kick" them out on a limited basis whenever they are producing too much Oxygen. Think of trees and other algaes. They take in CO2, perform photosynthesis, and put out Oxygen and retain much of the Carbon. The algae is taking in CO2 and nitrogen from the polyp, performing photosynthesis, and returning Oxygen and sugars (Carbon) to the polyp. They regulate their numbers all day long. Think of this as a "controlled partial bleaching". The polyp can also close up and decide to not accept any of their food. However, the biggie is that they'll actually eat their "symbiont" and that's why I think this relationship should be classified as something other than endosymbiosis. Corals with "throw them under the bus" at the first hint of stress in any way. (However, I'm an accountant and not a biologist).

    I'm shocked that no one has mentioned that one can put a SPS frag that was brown under PC lighting, slowly light-acclimated it to MH or other forms of higher PAR lighting, and Ceteris paribus, the coral starts coloring up. Why is that?
     
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  10. m2434

    m2434 Giant Squid

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    Right, great points :)

    Also, here is some extra info, for anyone not suffering information overload:

    Although the exact mechanisms are largely unkown, we know that corals can regulate zooxanthellae growth, by regulating access to inorganic nutrients passing through the corals tissue to the zoox. For example there's evidence corals can divert CO2 to zooxanthellae in more productive areas of tissue, such as those areas that are better illuminated.

    Also, there are cases where regulation doesn't happen, or happens too efficiently and zoox proliferates. However, I left out a few important parts, which Inwall75 mostly mentioned.

    Zoox produces oxygen, but also along with this, some byproducts such as Reactive Oxygen Species (ROS) and also Reactive Nitrogen Species such as NO. These byproducts can damage the host tissue. So, the host and symbiont have mechanisms to remove this stuff and/or break it down, in order to maintain their relationship. There are cases though, where the alga proliferates so fast that the mechanisms become ineffective. However, as Inwall75 mentioned, in these cases, the host can often eliminate some of the algae through various means.

    For example, this diagram from V. Weis ( 2008 ) "Cellular mechanisms of Cnidarian bleaching: stress causes the collapse of symbiosis" shows 5 different documented methods of zoox elimination, ranging from in-situ degradation/digestion to full-blown necrosis of the host cell.

    [​IMG]

    While it isn't exactly known, which stressors and at which levels cause these various outcomes, it can be inferred that more drastic outcomes are the result of more immediate threats to the host organism.

    All in all, though, mainly through these various methods, it appears that in most cases, the coral can largely control the algae population density. If a coral is brown, due to lack of light for example, it seems that the coral is allowing the algae to proliferate, in order for the coral to receive the necessary nutrients to survive. So, in this case, the browning is sort of a good thing as it is helping the coral adapt to otherwise insufficient lighting.

    Similarly, while light can reduce the zoox density, so can food. You could also argue that the coral requires more light because it isn't getting enough food. There seems to be some truth to this, as the availability of food is fairly low, in our systems compared to nature and average light levels over the course of the day are fairly high. (Actually, on a side note, this is somewhat of a fine balance, as there is a limit to how much light zoox can utilize and how much stress from zooxanthellae byproducts the coral can tolerate. This brings up another key component of SPS care; food!)

    When browning does become a problem, it's when the zoox still can't keep up with the corals demands, or when the coral looses control over it's zoox. These also happen.

    When a coral looses control however, it appears to be the result of synergistic effects of multiple stressors, not just a single stressor such as increase nitrate. For example, there are cases where a coral could turn brown when lighting is too high. I could hypothesize that this could occur if we have an old bulb, which has lost a lot of intensity, and in the meantime, nitrate levels have increased allowing the zoox density to increase. However, what we don't see is that the zoox density is being limited by lack of available light. However, now we replace the bulb and the algae takes off due to the increased intensity.

    It happens fast enough, that the coral doesn’t limit it's growth through nutrient regulation fast enough, but if the stress isn't too much for the coral, it is not necessarily an issue and over time, the coral will regain it's coloration.

    However, depending on the stress, it may need to expel some zoox, but if the stress is too great, it may even have trouble expelling the zoox fast enough. If the coral is able to restore balance, through these methods though, eventually, coloration will return. If not, some of the more extreme methods of zoox elimination may occur and the odds of survival decrease. If the stress is great enough however, it may just go strait to necrosis. There brings up another limitation of SPS corals BTW. Corals such as LPS corals can inflate and deflate to regulate their available surface area. So, in a situation such as this, they may buy some time by deflating and decreasing photosynthesis that way. An SPS coral can't do this.
     
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  11. stoney waters

    stoney waters Fire Shrimp

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    Very nice info right their thanks. I actually have never even thought about using a less intense light, I guess if you dont have one, you would have to go buy another fixture, which would pretty much waste your money, most ppl just raise thier lighting(that is if you can).
     
  12. stoney waters

    stoney waters Fire Shrimp

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    Wow....That was A LOT to take in, I had to read that three times to take it all in. I really thank you and inwall for all of the information you are giving me, and who ever else is reading this, where are you getting all of this cause I cant find anything like that?