Acropora sp. Bleaching event

[CurvBall]

Hi Anthony,

I had 4-5 colonies of acropora that bleached in my tank. These corals are often seen inhabiting tidepools along the coast here where I live.

From all the research I've done, it seems as if the high water temperatures affected my corals. It seemed as if the corals were affected by RTN, as a colony would be fine in the morning but when I got home after work, the coral had completely lost all it's flesh leaving behind a white skeleton. The last piece to go was one that had begun to encrust around it's base. From what I've also read is that RTN spreads from coral to coral very quickly.

Now my actual question, if these corals are subject to such high temperatures in the tidalpool, how came the corals bleached in my tank?

I know there are many factors that influence these situations but everything was doing so well, they were in my tank for just over a month.

I do weekly water changes with NSW. No other corals were affected, I was really worried about loosing my montipora capricornis, but it seems to be fine.

 

[NaH2O]

CurvBall - just a couple of questions before Anthony jumps on here. What kind of temperatures were you experiencing? What type of lighting set-up do you have? How about the flow in your system?

 

[Anthony Calfo]

without much information and a symptom so general as RTN or the like, the possibilities are numerous as you might imagine.

To your question, though... the wild in situ corals either do not suffer fast spikes in water temp (if below the intertidal line) as the rise in temp is more gradual indeed for the volume of the ocean, or... if they are intertidal - then they are stimulated and conditioned to produce protective mucus (and have been feeding on adequate marine plankton, etc to be able to even produce the mucus, for which our corals in the aquarium do not do either

Aquarium corals neither receive adequate food/plankton, nor are they stimulated naturally to produce mucus by intertidal events, but instead suffer spikes in water temp more suddenly and while fully submerged. The latter point being an underrated issue as intertidal species at low tide are not suffering from the dissolved "pollution" of other neighboring corals (and later receive massive dilution via the rising tide) whereas aquarium corals must suffer the waste, mucus, increasing bacteria/DOCs, allelopathy, etc of other stressed corals in the small volume of water as they sit trapped in submerged water of increasing temperature.

When the natural mechanisms described above fail to occur in the wild, we do indeed see bleaching events, as you know.

Hmmm... I'm not sure if that helps

Ooh, BTW - I am staunchly against using NSW for many, many reasons (beyond concern for pathogens). If interested, please do read my passage on the subject in my Book of Coral Propagation or any of a number of threads/archives at wetwebmedia.com (do a google search on that homepage). I have written at length on the subject. The bottom line though is that it is not adequately consistent or safe unless you are collecting it from a very far distance off shore (closer to 10 miles than 2 miles).

NSW is not the problem here though.

best regards, my friend

Anthony

 

[CurvBall]

without much information and a symptom so general as RTN or the like, the possibilities are numerous as you might imagine.

Thanks for the quick answer, sorry I didn't provide more details regarding my tank, the light isn't always on upstairs

Here are my specs:
- 85 litre system
- In sump DSB/refugium on reverse lighting growing caulerpa sp.
- Sump return roughly 1800lph after head loss etc
- Sump return goes through SWCD wavemaking unit
- Roughly 12kg's live rock
- Venturi skimmer rated for 400litres
- lighting is 4 x 20w NO flourscent, recently added 150w 4200K HQI halide (this was added after the corals started their downward spiral, the tank was adjusted to the halide over a month period.)

Since this event has occured in my tank, I've taken to extensive researching on the net. Due to my findings, I've since added 3 x powerheads totally 1400lph for more circulation. My total circulation is now at about 3200lph.

My tanks temperature did rise but did not go above 81 degrees, I was cooling the system using a 30cm fan on full speed. All evaporated water is replaced with kalk/RO water, this is dripped into the sump.

The corals in question were actually collected from the aboved mentioned pool in my first post. This tidal pool is subject terrestial run off as it sits at the base of a very steep bank, many of the edges of the pool are staind red with surface skum clearly visible. Water movement is absent in this tidal pool expect on high tide when water washes over the wall into the pool. The temperature of the water in the pool was very high, close to 81 degrees. But sudden temp changes would happen when new water enters at high tide? The 'fresh sea water' was at least 3-4 degrees cooler. I do agree with many of your points but it seemed as if the corals could grow and flourish in this pool, then they would do well in my tank? When the corals started loosing their colour (turning brown) I thought it was the lack of light, but have since found out browning of corals is due to excess nutrients.

Thanks for your feedback again, and although I did loose these corals, I have learned and gained so much.

I will look up your NSW article and read over it. I still really need to get a copy of your book though, I know of only one other reefer here in South Africa that has a copy and there isn't a chance in hell he's going to lend it to me, and I don't blame him. :lol:

Thanks again for your time.

 

[damer]

curvball,

the browning of sps corals can be a result of many things, one is not enough light. if you collected the corals from the tide pool which would have been subjected to lots of light, and then put them under 4 NO tubes, i am reasonably confident that they are definately going to turn brown, and probably do very very poorly.

does the 85 litre system include the sump? what size tank do you have and how far down did you place the corals?

what are your water test results like? ie specific gravity, alk, ph, calcium, nitrate, and phosphate.

 

[Anthony Calfo]

bleaching from temp spikes are most always from increases (not decreases) and with differences of more than 4F. And so, when the tidal creatures are exposed at high tide, their mucus protects them and the cooler seawater is not a problem. Coral bleaching is by far more severe in areas corals below the intertidal zone enduring high temps as submerged.

In fact, most corals can take a sudden drop in temp much better than a like value increase.

As for books, I dearly wish I could hand deliver one to you I dream of seeing parts of Africa one day

Until then, perhaps you can get mail faster/easier from Europe? I have distributors in England, German and even Portugal (Italy now too). Mail from the US to SA is dreadfully slow

with kind regards,

Anthony