Link between coral coloration and tank nutrient levels?

[Maxx]

I keep hearing about how corals will color up much more intensely in nutrient poor systems, BB tanks with heavy, wet skimming and Zeo-vit systems for example. But what is the mechanism for this color shift? How does it work?
I just got 3 frags which are all shades of brown. One is brown with green polyps, one is purple/brown, and the other is just tan.
I'm just curious about how this process works....

Nick

 

[NaH2O]

Nick - I believe the browning is due to the zoox (zoo = relationship with the animal, and xanth = gold), which is primarily brown in color. They have pigments of different chlorophylls (a=blue green and c2 = light green), peridinin (red), beta-carotene (orange), and diadinoxanthin (yellow), which make brown when they are combined......come on....get out your crayons. If you are feeding the zoox (algae - a dinoflagellate?) with excess nutrients, then you will see the more brown color. If I understand this correctly, the zoox cycle food to the coral (and zoox have controls they utilize), so, too many nutrients, then there would be an increase in growth of the zoox/algae....creating the brownish look. I noted this with an acro frag. Very brown after I placed it in my tank.....then it returned to its normal coloration. I have witnessed it cycle to a more brown color on two occasions, each followed later by the return to normal color. If I really look back, it may have been with the algae blooms I was experiencing. The frag looks great now, and has nice purple tips. Anyway - that is how I understand it - or at least have worked it out in my head as to what is going on. Hopefully, I have at least part of it right :lol:

 

[bc_slc]

wow.
Go nikki
its your birthday
were going to party like its your birthday.

 

[mojoreef]

Looks like you nailed it pretty darn good Nikki.!!!!!!! The colorful pigments that we love in sps are also in the tissue of the coral, now this tissue is only two cells deep so when you get a population increase of zoox it will cover the pigments that are in the tissue. Also those colorful pigments will ony be thier if the lighting is correct to.


Mike

 

[MarineDreamer]

I was thinking that it was also a response to spectrum (UV-A, UV-B) and intensity.

"Light also affects coral pigmentation. Corals from shallow, brightly illuminated water manufacture special pigments to absorb UV light…. The violet color is a means of reflecting or filtering excess ultraviolet light, and protects the coral from harmful UV wavelengths.” (Delbeek and Sprung, The Reef Aquarium, Volume One, Ricordea Publishing, 1994)

Borneman goes a lot deeper into this in his book, “Aquarium Corals: Selection, Husbandry, and Natural History” (T.F.H. Publications, 2001) but agrees with Debeek and Sprung as to the colors you can find in corals, and why they’re there.

So... as I’m reading this, I’m thinking that what Nikki’s saying is that the corals cannot control the growth of the algae, and when there’s excess nutrients in the water column the algae reproduce and we can see that in a color change, right?

If that be the case, and our aquariums tend to be nutrient rich rather poor (at least comparatively speaking to a reef,) why is it we get any color at all? If that’s not the case, will someone school me? I hate to buy a thousand dollar plus lighting system for my tank when all I really need is bigger, more efficient skimmer.

Trevor

 

[VINA DEL MAR]

Right on Nikki and Mike!It seems to me that the brownish coloration that SPS takes when the proper water conditions are not met(high nutrients) is more to protect themselfs from damage to their tissues.Are there any way of knowing how many layers of tissues SPS has?Perhaps it's just the outer layer that we see?And when proper conditionings are finally met SPS just shed the outer tissues and go on with their real coloration.
Good thread!Keep it going.

VINA

 

[NaH2O]

I hate to buy a thousand dollar plus lighting system for my tank when all I really need is bigger, more efficient skimmer.

No - there is more to it than a nutrient free environment (remember, we are talking SPS here...softies and LPS have different requirements). Photosynthesis makes up most of the coral's requirements, so if you create an environment with poor lighting and nutrient free living, I don't think you will be happy with your corals appearance either. Also, if you take a look back at the topic on Lighting in the great threads forum, it only takes a flash to get the process started for photosynthesis, but not too many of us would like a tank full of corals like that. Its the fluorescing pigments we like

Vina - I'm not sure if it is a protection thing, as much as it is just the way algae reacts to high nutrients - it blooms. The coral then can control the population of zoox, so it will regulate the populations based on available food.

The coloration I believe comes from the fluorescing pigments, and not necessarily the shedding of tissues. But here you are getting back into lighting, and not nutrient levels in the environment.

 

[dnjan]

Nick - I believe the browning is due to the zoox (zoo = relationship with the animal, and xanth = gold), which is primarily brown in color. They have pigments of different chlorophylls (a=blue green and c2 = light green), peridinin (red), beta-carotene (orange), and diadinoxanthin (yellow), which make brown when they are combined......come on....get out your crayons.

Does this mean that colors other than brown (-ish shades) can come directly from the zoox, and not from the coral tissue? I thought that SPS colors were from coral tissue trying to protect the zoox from too much light (at least too much in certain wavelengths). I hadn't realized that nice colors came from the zoox as well.