Salinity Effects Of Small Variations

[Skim]

Some of this is straight goobly goop to me but got the basics and found it interesting and thought I would pass it on.
http://www.int-res.com/articles/meps/181/m181p309.pdf

 

[Skim]

OK I guess I will just state some of the things that I found interesting.
1. 38 psu now I they where dealing with Red Sea but stated that the region that they where dealing with would cover most of the Indo region which is where most of the SPS corals come from. I like the fact they used psu not S.G as psu and ppt are not affected by temp as is S.G.
2. 38 psu is 3 points higher then 99% of all written material talks about, standard being 35psu/ppt
3. When samples where put into an environment of 34,36 and 40 psu that in 3 to 4 weeks Corals died or showing signs of dying.
4. When samples where kept at 38 psu sample where healthy and produced the largest amount of Protein production.
5. Where talking about a 2 point variation and Corals are dying ( Bleaching ) in 3 to 4 weeks and most Tanks are being kept at 35 psu/ppt or less.
6. General question I come up with is should we be running at this much higher level to be more region accurate as 35 psu/ppt is a Global generalization average of open ocean levels.
7. When a new shipment arrives at a Dealer and transferred from shipping containers to holding tank or display tank could this be the beginning of doom for many of these Corals which are lost. How many of use have herd the saying " it is stressed from shipping ", or heard " you should have seen it when it got here it was beautiful but I guess the stress of shipping got to it ". The one factor that does not go back to say a tolerable level would be psu/ppt according to this study. Corals seem to be able to withstand large PH fluctuation in a everyday life and large temp fluctuation in a normal day but the one thing that would not change back to a tolerable level from the day removed from reef would be psu/ppt which we keep a standard of 35 psu/ppt.
Just a few points that make me go Hmmmmmmm.

Skim

 

[shamous113]

Well my brain hurts after reading that at this time of day... I found this quote interesting,

"The decrease in photosynthesis might be due to a contraction of polyps, which reduces the exposure of zooxanthellae to light
(Muth~ga & Szmant 1987). Such a mechanical response has already been described in other anthozoan species (Shumway 1978, Moberg et al. 1997). moreo over, since most
coe-lenterates are not able to control their osmotic pressure (Ranklin & Davenport 1981), a change in salinity may also induce tissue damage "

As I'm in the process of finally setting up a salt water tank I have been doing a lot of reading and I see a lot of new people having problems with their new coral purchases. and I have to wonder if this is the cause. some people measure their salinity at room temp and others at tank temp. how much of a difference does that make when you convert that # to PSU.

 

[Skim]

There is a formula but the thing is most of the Refractometers that are used do not read psu or ptt really, it will read ppt for the equivalent of S.G but S.G. is affected buy so if you read 1.026 it will read 35 ppt but if it at 80 F the ppt or psu will be less in reality. So now I know why I would get all kinds of mixed readings on my Milwaukee Salinity tester, I thought the thing was busted, but now I know how I would get 1.025 but have a psu or ppt reading of 32 or 30 or 33. So from now on I will be using the Milwaukee tester and not worrying about S.G but looking at psu and ptt.

 

[Pistol]

Good refractometers have temperature compensation, I have a sybon with atc and calibrate it with calibration fluid so I think it's pretty close, seems to me no matter what method or meter you use there will be a chance for error. Sometimes you can over analyse it.

 

[Skim]

Just thought you may want to know that the ATC is only good for a few degrees and that covers the difference between the calibration temp of the refractometer and the ambient temp. Most are calibrated for I believe 60 F, the only one I know that is not is the Red Sea Refractometer it is calibrated for 77 F and the Milwaukee which states ATC between 10 C to 40 C

 

[Pistol]

Just thought you may want to know that the ATC is only good for a few degrees and that covers the difference between the calibration temp of the refractometer and the ambient temp. Most are calibrated for I believe 60 F, the only one I know that is not is the Red Sea Refractometer it is calibrated for 77 F and the Milwaukee which states ATC between 10 C to 40 C

Sybon states ATC between 10 to 30C, I think consistency is more important than maintaining an exact psu, people have had successful reef tanks with hydrometers.

 

[shamous113]

@Skim did you increase your salinity to 38psu?

 

[Skim]

I have not checked it lately but I tend to keep it on the high range 35ppt to 38ppt. I can tell when it drops below I can see it in my Moorish Idol and Naso. the Colouring is not as rich and deep, it tends to lighten up and blend together in a way.