Polyp Extension = Happy Corals?

[reedman]

Typically as the temperature of the tank increases and the calcium and alk necessary for calcification are available the corals will increase their growth rates. There is obviously an upper limit to this, as very high temps will cause bleaching events. There are some other chemical reactions that can increase the growth rates as well, but I am not well enough versed in these to elaborate.

 

[bobgoode]

Good question, Maxx. Sudden increases in dKH/Ca above NSW levels can supercharge the zoox's active transport system resulting in zoox. expulsion & bleaching. Sudden changes in irradiation can change the zoox. population to cause bleaching. Bob

 

[NaH2O]

I love this Media Review by Charles Delbeek. He reviews two studies on coral bleaching. This is a quote from: Media Review

One of the theories of coral bleaching states that coral bleaching begins when CO2 fixation under high temperature and irradiance begins to break down and toxic oxygen radicals and their derivatives begin to accumulate in the zooxanthellae. This leads to damaged pigments and proteins that results in to the inactivation of photosynthesis and brings about bleaching. The removal of these derivatives by diffusion before they can cause damage could be the result of high water flows that compress the boundary layer, enhance diffusion rates, and hence, mass transfer rates.

Not sure how much it pertains, but since we touched on bleaching I thought I'd toss this out there.

 

[bobgoode]

Well, Nikki, I caught it :razz: One of the interesting reviews on this forum eluded to irradiation intensity's effect on each coral's zoox. population/expulsion & bleaching effect. If I recall correctly[remember Mike, I'm still in my flame-proof bunker :lol: ] tank-water energy did not cause a change in the zoox. re-populating but did provide means of waste removal/nutrient gathering, etc. & prevent super-oxidating radicals from damaging the zoox.

 

[marinelife]

Let me open this thread back, has anyone changed there mind on this topic. I can say i have had corals growing one day and dead the next. To me polyps are out to feed

 

[Curtswearing]

You ought to read Sorokin. Most people wouldn't really desire this book. It is written by a scientist for scientists. He's the grand daddy of our understanding of coral reefs. He's the person who figured out the role of bacteria in terms of coral food. If you want to understand the nitty gritty details of corals, sandbeds, plankton, the Nitrogen Cycle, bacteria, etc., then this is a good book for you.

Eric Borneman did a write up of some of his research on this link.
http://www.reefs.org/library/talklog/e_borneman_051098.html

Indeed, corals do actively feed on bacteria in the mucus, in the water, and attached to particulate matter. They typically utilize them for 5% of their diet, by weight. This is on an efficiency level on par with many of the specialized filter feeders and sponges. Sorokin found that, in general, bacterioplankton ingestion alone can provide from 8-25% of the coral’s respiratory demands. This amount is the equivlent of 1-10% of the animals total biomass per day...from bacterioplankton!! Its assimilation index by nutritional content is the equivalent to the nutrition acquired by the capture of small crustaceans (which are by weight, much greater and a greater energy expenditure to capture). Phosphorus, a normally limiting resource in coral reefs, is found in the cell walls of bacteria. Coral consumption of bacterioplankton provides them with a more easily assimilated source of phosphorous than from the uptake of inorganic phosphate contained in the water.

If you read the whole article, WHICH I HIGHLY RECOMMEND, you can hit [CTRL] F to pull up the "find" dialog box and punch in Sorokin. However, the whole article is based on his work. Eric really brushes over some things in it (because his article would have to be a book then) but there are some things that the boards rarely discuss, AEROBIC denitrification, the fact that there are more than 80 strains of bacteria doing things in our tank, etc. Just in the paragraph I paraphrased above, it shows that corals do not like to capture pods because of the energy expenditure....they like to capture bacteria in mucous nets. Not only that, they "farm and raise" bacteria for their food needs. These things are rarely discussed on the reef boards.

Here's how a bookstore describes the book

Coral reef communities are among the most complex, mature and productive ecosystems on earth. Their activity resulted in the creation of vast lime constructions. Being extremely productive and having the function of a powerful biofilter, coral reefs play an important role in global biogeochemical processes and in the reproduction of food resources in tropical marine regions. All aspects of coral reef science are covered systematically and on the basis of a holistic ecosystem approach. The geological history of coral reefs, their geomorphology as well as biology including community structure of reef biota, their functional characteristics, physiological aspects, biogeochemical metabolism, energy balance, environmental problems and management of resources are treated in detail.

Here's how a scientist I know describes the book

bacteria and microalgal interrelationships in benthic sediments and give a great deal of detail on the relationships of these nutrient cycles with theperiphytonic communities of algal turfs and pelagic bacterial and phytoplanktonic populations.

 

[ldrhawke]

Recent DNA analysis of bacteria in soil has shown that scientists have been badly underestimating it's diversity. There is no reason not to believe the same biodeversity will not be found on reef's when tested for under advanced DNA methods.

1 million different species of bacteria per gram of soil.

The World's No.1 Science & Technology News Service

Millions of bacterial species revealed underfoot
. 19:00 25 August 2005
. NewScientist.com news service
. Jon Copley
Related Articles
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. 16 April 2005
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. 27 May 2004
. Search New Scientist
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Web Links
. Los Alamos National Laboratory
. Ruth-Anne Sandaa, University of Bergen
. Science

The soil beneath our feet may be teeming with a hundred times more species of bacteria than previously thought, according to biologists in New Mexico, US. Their calculations reveal that one gram of dirt can harbour a million microbial species - and that metal pollution kills 99% of these as-yet unknown germs.

Measuring the bacterial biodiversity of soil is difficult because only a few species can be cultured in the lab, according to Jason Gans of Los Alamos National Laboratory, California, US. Fortunately, biologists can also estimate biodiversity using a technique called DNA reassociation. This involves chemically unzipping the two strands of all the bacterial DNA in a sample, mixing them up and seeing how long they take to join up again with matching partners.

If all the DNA strands were the same, they would find matching partners very quickly. But the more diverse the DNA strands, the longer this match-making takes, allowing researchers to estimate how many different species there are in the sample.

When this technique was applied to soils in the late 1990s, it suggested that a gram of dirt contained about 16,000 species. But this estimate assumed that the populations of all the different species in the soil were roughly equal in size. So Gans and his colleagues have developed new equations to reanalyse the same DNA reassociation data but without this size assumption.

Their results reveal that there are a few very common species in soil but lots of rare species. "There is a very large number of low abundance species," says Gans. So many rare species, in fact, that the estimate of bacterial biodiversity rises to one million species per gram of soil.

Sewage sludge
These rare species appear to be absent in soil contaminated with heavy metals, however. The team also reanalysed the DNA reassociation pattern of soil experimentally polluted with metal-rich sewage sludge. Gans suggests that the contamination may have killed 99% of the bacterial species. But the consequences of losing so much bacterial biodiversity in polluted plots of land are unknown. "Now that we have a way to measure it, the next thing is to correlate species diversity with how well plants grow," he says.

As the new calculations reveal far more bacterial species in soil than anyone realised, the next challenge is to identify those species and the roles that they play in ecosystems.

"They might have some key functions that are known, or even unknown," says Ruth-Anne Sandaa of the University of Bergen in Norway, who measured the original DNA reassociation patterns used in Gans' analysis.
Journal reference: Science (vol 309 p 1387)

 

[Scooterman]

Now that's gotta be difficult to count
Nice info!

 

[ethanriley]

I've read over and over people saying, "I have good polyp extension, so my corals are happy" (I'm talking mainly SPS here). Does polyp extension really equate to "happy corals"? I thought polyps extend from chemical stimulus in the area, so why would this mean they are happy?

Nikki I went back to this orignal thought Extended Polyps= Happy corals and relying on my experiences with snorkeling both at night and in the day in the Bahamas came up with the hypothesis that coral extension doesn't necessarily indicate happiness but it IMO does indicate the following:

1) The coral is looking for something prompted by a shift in flow a shift in light a shift in PH or some other chemical stimulus.
2) I think this formula works A fully extended coral= a hungry coral

Hungry either for calcium, magnesium, strontium or food. Clearly if polyp extension declines you do have an unhappy coral that is missing something it needs light, ph, chemicals or food. Interesting thing is we in the hobby reduce flow when polyps are feeding yet polyps on most wild corals I have seen are at their best when flow is the strongest!
__________________

 

[crazzyreefer]

I can agree with that... but how about color... does the amount of food...and chemicals increase or decrease the amount of color... we all know light has the most impact, but what about the other varibles?