PH in rainy season

[martin_c]

Hi all,
i know there are some people in this forum who have been to the amazon a lot, and also people who haven't but are smart anyway

Could somebody tell me if during rainy season the PH in rio negro and other south american black water streams actually goes up or down?
I always thought the rainy season would make PH go up, and during dry season it would be the lowest.
But lately i'm also reading other opinions saying PH would go down in rainy season due to increased organic stuff flushed into the rivers.

So which one is it? Would be really nice to know.

 

[MacZ]

Water values South America (Map pH) - Southamerica fans

To explain the markings on the map The color scale is based on the droplet tests for pH: red: appr. 4 to 5,5 yellow: appr. 6,0 three green: 6,5 7,0 and 7,5 blue appr. 8 to 9,5. Gray points stand for measurements without pH. For measurements where the exact location is known, the GPS data was

www.suedamerikafans.de

Have fun with that map. Just remember: Our summer is their wet season, our winter is their dry season. That way you can tell the readings apart.

It is also important to distinguish: Is it one of the main river channels or a smaller tributary. The bigger the less fluctuation.

But lately i'm also reading other opinions saying PH would go down in rainy season due to increased organic stuff flushed into the rivers.

That's simply how blackwater originates. The water has washed out the soil which is now basically inert, but the humic substances from the leaf litter are washed into the soil and once the water rises they are dissolved slowly into the water until it is gone again. Big question: Is the statement about river/stream main channels or is it about flooded forests like Igapó (blackwater) or Varzea (whitewater). In the latter case pH goes up because minerals are washed into the water instead of humic substances.

This article will also be helpful:

Junk, W.J., Piedade, M.T.F., Schöngart, J., Cohn-Haft, M., Adeney, J.M.
and Wittmann, FA., Classification of Major Naturally-Occurring
Amazonian Lowland Wetlands. Wetlands, 31, pp. 623–640, 2011

 

[martin_c]

Water values South America (Map pH) - Southamerica fans

To explain the markings on the map The color scale is based on the droplet tests for pH: red: appr. 4 to 5,5 yellow: appr. 6,0 three green: 6,5 7,0 and 7,5 blue appr. 8 to 9,5. Gray points stand for measurements without pH. For measurements where the exact location is known, the GPS data was

www.suedamerikafans.de

Thanks Mac.
Unfortunately only a few of the points provide the time of measurement, and i'd need a second measurement from the same spot at another time for comparison.

Is the statement about river/stream main channels or is it about flooded forests like Igapó (blackwater) or Varzea (whitewater).

I'm interested in Igapo because that's where i think that heckel discus breed. So i wonder if i should aim for 4.0 or rather 5.0 or even higher.
But simulating rainy season would be relevant for a lot of fishes.

This article will also be helpful:

Junk, W.J., Piedade, M.T.F., Schöngart, J., Cohn-Haft, M., Adeney, J.M.
and Wittmann, FA., Classification of Major Naturally-Occurring
Amazonian Lowland Wetlands. Wetlands, 31, pp. 623–640, 2011

That's an interesting publication. But at least from skipping threw it it doesn't seem to provide specific info about changes in PH in rainy or dry season.

 

[MacZ]

Unfortunately only a few of the points provide the time of measurement, and i'd need a second measurement from the same spot at another time for comparison.

Most have a source. So you'd have to follow the source link or look up the literature.

I'm interested in Igapo because that's where i think that heckel discus breed. So i wonder if i should aim for 4.0 or rather 5.0 or even higher.

Somewhere between 4 and 5 is all you need. At that low pH it doesn't really matter anymore. I'd rather make sure the EC stays under 20µS/cm.

That's an interesting publication. But at least from skipping threw it it doesn't seem to provide specific info about changes in PH in rainy or dry season.

But it provides the info you need to prove the statement you mentioned true or false. The study definitely explains what is washed into the water, how the soil is composed and other factors that will help you make an informed decision. Sorry I can't quote anything for you right, because I don't have the time to do any thorough editing.

 

[Apistoguy52]

When trying to spawn the “hard ones”, I’ve always tried to follow the advice of my friends from SA. pH tics up, temp tics down. .5 movement upward in the pH, and 5*f downward movement on the temp. While a big rainstorm can move the temp from the low 80’s to the high 60’s pretty quickly, I’ve noticed anything more than 5* will shut down a pair and their pre spawn activities pretty quick.