i just tried to find some previous information that i read that stated SPS corals grow out
their skeletons mostly at night but failed. So i do not have a reference. I am unsure if I read it
in one of my books or online.
Perhaps someone can chime in here about what i recall if it is correct or not. I will try to
find it later.
+1 they grow and to complete respiration needs at night.
-------------------
Taken from post by Martyn in another forum....
http://www.ultimatereef.net/forums/archive/index.php/t-180286.html
....."Closed systems are high in nutrients and for the most part are perfectly capable of supporting them without direct feeding.
when does the actual growth of the coral take place ?
The majority of the coral's extension growth occurs at night....."
--Full Post--
"I talk here mostly about Acroporids as these are what I mostly keep.
Many Acropora in the wild do not have there polyps extended much during the day.
But extend there polyp's fully during the night and may feed on plankton as it rises up through the reef at night.
In the aquarium there are many factors different to on the reefs.
There is likely more food available (feeding fish and some keepers feed there corals and some do it during the day) in the aquarium during the day (lighted period) than on the reefs this is available for the polyps to expand during the day if they do not recieve enough light.
Also, closed systems are often high in nutrients which Also may give allow the polyps to expand and feed during the day if needed.
Lighting:
This may effect polyp extension if the acropora does not recieve enough light it may reoganise its zooanthellae to adapt too a different lighting parameter from what it was adapted to on the reef.
By taking in zooanthellae that is in the water ejected by the older existing corals that are in the system.
It may need more zooanthellae in less intence lighting and may need too change type of zooanthellae and may need to feed on whats in the water to suppliment for any less light it recieves to what it needs.
I wonder how much the zooanthellae has to play in the adaption of wild imported acropora's to less intence lighted aquariums.
The degree to which corals need to feed heterotrophically to supplement the carbon translocated from their symbionts depends on how actively the symbionts are photosynthesizing.
If photosynthesis by the zooxanthellae exceeds the respiration requirements of both the coral host and its zooxanthellae the coral is fully autotrophic and requires no supplementary feeding. When photosynthesis drops, the coral requires an additional food source.
Water movement:
May play a part in how food is carried to and through the Acropora branches as the coral grew and formed its structure and shape on the reef to the water movement and enviroment there.
Then has to be able too adapt too a closed system too a different water movement and light it recieves then.
Some other things I look for too judge the health of an Acropora is look at the tip growth if the tips are growing they are most often a different colour to the rest of the branches.
And the edge of the bases of a Acropora display growth like the tips.
If I get no polyp extention at night over a period of time I am worried something is not correct and if I have no tip growth this also may mean something is not correct.
So long as you have polyp extention at night and tip growth then most likely the Acropora is doing well.
Respiration
Polyp extension in SPS is primarily related to respiration needs by the coral.
Corals need to "breathe" at night and the polyp has the most surface area. Very little gas exchange occurs accross the tissue
Varying the degrees of polyp extension helps them regulate their metabolism better than constantly varying the amount of zoox in the tissue.
It's not that they are programmed to open at night, it's that they are programmed to close when the coral has had enough light. They tend to be open early in the morning, closed during the day, and open again late in the afternoon and through the night.
During light periods, zoox are metabolizing and producing oxygen. Corals will close because they can get too much, or can't excrete the wastes fast enough.
Remember they have to maintain a "average" of zoox. Enough for early morning, late afternoon, cloudy days too. It's easier for them to close than shed and regrow.
We're talking typical SPS here - Acroporids, Pocilloporids, Porites mainly,
So we cant look at the corals polyp as just a food capturing device, it has alot of functions beyond that of capturing food.
Food availability and predation by coral-eating fish may be of minor issue,
Then you move on to feeding corals a lot of controversial views here lol.
SPS corals are mostly a thin skin adhering to a dead internal skeleton.
There's not a lot of meat on a SPS coral to support = not a lot of food needed.
SPS aren't that good at capturing prey.
You have to distingish between coral types to what its food requirements are,
An Acropora has evolved to have a highly developed ability to make its own food with the use of its zoox.
Closed systems are high in nutrients and for the most part are perfectly capable of supporting them without direct feeding.
when does the actual growth of the coral take place ?
The majority of the coral's extension growth occurs at night.
http://www.aims.gov.au/pages/laser2.html
Checking the effects of light, temperature, water movement and human impact on the growth of coral will not only allow researchers to better understand factors effecting coral health and growth in nature, but will also potentially make maintaining and culturing corals in laboratories and aquariums easier.
Martyn."
