Calcification of Hard Corals...

[Joe_P]

Hi Advanced Reefers ,

We were having a discussion regards the validity of CO2 cylinders when a point by a fellow reefer was brought up and that is the usage of timers to stop the input of CO2 feeding Calcium Reactors... esp when pH of the main reef is low.... eg during lights out period...

That brought up a question and that is does Hard corals (SPS) perform calcification during lights off??

Is the requirement of light neccessary for calcification or is the lights neccesary to provide the food to sustain the hard corals and at the same time allow the corals the energy for development.....

Please advise.....

[yazid]

I read that coralline does not require direct light. It grows better in the shady area.

So does that mean calcification does not require light.

[Joe_P]

I read that coralline does not require direct light. It grows better in the shady area.

So does that mean calcification does not require light.

Yap, similar thoughts here since there are hard corals which do not rely on photosythesis for survival.... so they somehow must have acquired the growth rates from somewhere???

Ever since the introduction of SPS into SGreef, many reefers have strongly mentioned the benefits and requirement of strong lightings, leading reefers to believe that corals only perform calcification during photoperiod....

another question would also be .... Is the rate of calcification reduced during non photoperiod??

Anyone out ther can help put some light here???

[SharkBait]

Calcification do occur at night but it does not lead to skeletogenesis.

[Joe_P]

Calcification do occur at night but it does not lead to skeletogenesis.

Hmmm... maybe a little bit of explaination would help here...

don't understand why there isn't any CACO3 build up since clacification takes place....

[Achilles Tang]

Read this.

[SharkBait]

The reactions that calcification is involve in seems to differ by day and night and different in photosynthtic species and non-photosynthetic species

[Achilles Tang]

Simply put, most corals will calcify & build their skeletons during the day and rest at night.

So in theory, you can switch off your CR at night but you have to pump up the CO2 and speed up the effluent rate.

This is PROVIDED you have an extremely LARGE reactor to produce that much calcium during the 'DAY' hours or risk going back to Square 1 and having to dose manually to supplement your CR.

[bawater]

some links based on hard corals.photosynthetic species

Abstract from the link below :

"Coral polyps absorb calcium ions from seawater and are transferred by both diffusion and an active pump mechanism that ends at the area being calcified. This is important because calcium is used in cell metabolism for regulation. The calcium concentrations must be low or else it will interfere with coral tissue functions. The concentration of free calcium ions is lower in corals than in seawater because the calcium ions stick to membranes or organic molecules. Lothar Böhm at the University of the West Indies in Jamaica showed through his studies that calcium has a high turnover rate.

The process in which the skeleton is made takes place during the day with great intensity. At night skeleton growth abates and slows down. The growth depends also on the season of the year, age and shape of corals. Young corals grow much faster than old corals, sphere corals grow slower than corals which have branched shape. A fact of particular interest is that corals are able to change their shape during their life to aid in sunlight retrieval. Temperature is also very important, for corals grow best in temperatures between 25-27oC.

Factors Influencing Calcification

It seems pretty obvious that light is important in coral calcification because corals need light for photosynthesis. It makes sense that growth decreases when there are drugs present that inhibit photosynthesis. As a matter of fact, corals grow 14 times faster under light than in the dark. For example, calcium uptake is highest at mid-day on a clear sunny day. On a cloudy day, the rate is 50% lower, and in darkness, the rate is 90% lower. The calcium deposition rate rapidly decreases as depth increases.

Why Do These Factors Depend on Zooxanthellae?

There are few relationships as close and tight as that between coral and zooxanthellae. As one might suspect, it is crucial to take zooxanthellae into account when looking at how reef calcification occurs."

http://library.thinkquest.org/25713/reefs_....html?tqskip1=1

Research on the subject:

http://www.geos.ed.ac.uk/facilities/ionprobe/Nicky.pdf

http://www.whoi.edu/GG/science/people/acoh.../chemistry1.pdf

Reduction of calcification from lowered pH and CO32- was greater than reduction from nitrate additions. Corals in low pH treatments recovered their initial calcification rates within 2 d of re-introduction to ambient seawater, indicating the effects of CO2 chemistry are immediate and reversible. Changes in calcification from increases in atmospheric CO2, and hence decreases in CO32-, may be larger than local effects from elevated nutrients.

There are various articles on increased CO2 levels affecting growth rates in the wild- this is just one.

http://www.int-res.com/abstracts/meps/v188/p117-121.html

I think for sps night is more dedicated to food capture,but that's another subject altogether.

[FuEl]

I read that coralline does not require direct light. It grows better in the shady area.

So does that mean calcification does not require light.

Seems true in my setup...pink coralline algae seems to prefer growing in my I-box rather than in my main tank. Think I wun be able to see thru my I-box soon if this continues.... My I-box does'nt get much light at all and yet the coralline growth is insane.

[BarraCudaTM]

coralline algae are suckers for plastic surfaces