acid rain

[k-bob]

striking to see how much pa trout streams seem to be affected by acid rain as buffered by various local geologies. potter county, with mostly high buffering bedrock, has about 100 class a streams (not counting streams listed across 2 counties, for example "mckean-potter"). forest county, with mostly low buffering bedrock has about 5. adjust for the larger size of potter, and 1000 sq miles of potter on average has ten times more class a streams vs 1000 sq mi of forest.

I am sure there are other things going on here, how much surveying done, etc., but if potter had forest's bedrock makeup things would be different there. Pa rain has become less acidic, but apparently stream water acid reductions have a lag time after this.

 

[lycoflyfisher]

Without referencing studies and on anecdotal evidence from first hand experience flipping rocks, the macro communities in well buffered watersheds with ph in the mid 6s compared to watersheds with lower buffering capacity and ph in the 5s are very different. The lower ph systems often seem to lack diversity and density. Flip rocks in the upper Tioga river watershed outside of the mining influences and then flip some rocks in the kettle creek drainage. The difference is is very noticeable.

Geology clearly plays an important roles in water quality and biological productivity.

 

[k-bob]

these acid rain effects are very local. swift run, snyder-middleswarth is impaired but a trib to it is not:

"Humans are also having impacts on the old-growth forest. Acid precipitation has seriously impacted the area by enhancing the acidity of soils and of Swift Run. The water that enters Swift Run moves through Tuscarora sandstone and soils derived from this hard sandstone. Because these substrates are unable to buffer the strongly acidic precipitation, the portion of Swift Run within the old-growth forest area has a pH too low for fish (e.g., the native brook trout) to survive (low pH releases aluminum, which in turn is toxic to fish and other aquatic organisms). The unnamed creek that joins Swift Run near the parking area has a substantially higher pH because its waters percolate through Juniata sandstone and its derived soil, which has greater buffering ability. As a result, fish such a brook trout do occur as far upstream as the confluence of these creeks."

https://tinyurl.com/ymp994ma

 

[troutbert]

k-bob wrote:
these acid rain effects are very local. swift run, snyder-middleswarth is impaired but a trib to it is not:

"Humans are also having impacts on the old-growth forest. Acid precipitation has seriously impacted the area by enhancing the acidity of soils and of Swift Run. The water that enters Swift Run moves through Tuscarora sandstone and soils derived from this hard sandstone. Because these substrates are unable to buffer the strongly acidic precipitation, the portion of Swift Run within the old-growth forest area has a pH too low for fish (e.g., the native brook trout) to survive (low pH releases aluminum, which in turn is toxic to fish and other aquatic organisms). The unnamed creek that joins Swift Run near the parking area has a substantially higher pH because its waters percolate through Juniata sandstone and its derived soil, which has greater buffering ability. As a result, fish such a brook trout do occur as far upstream as the confluence of these creeks."

https://tinyurl.com/ymp994ma

It's pretty interesting to go there. Downstream from the confluence of the trib, I caught small native brookies fairly readily. Then above the confluence, nothing, even though the stream looks nice.

Below the confluence, the stream was stocked when I was there, stocking right over the native brookies. I'm not sure if that is still the case or not.

 

[DGC]

I just looked at some ph data for Yellow Breeches. It seemed odd to me that morning ph has been very low, starting in the low to mid 6's and moving to 7's during the day. There was one day, probably a cloudy and rainy one, where ph was under 7 all day. Last year, March 15 to April 15, it was far more steady, and always above 7, day and night. I did not compare for other factors such as flow or temperature.

Not sure if there is anything to make of this for those who fish the lower Breeches. The station is at Lisburn.

I may go back and see if other streams show similar patterns.

 

[k-bob]

Hi pH is a log scale. I see the big swings, for ex 6.5 to 7.5 in one recent day, for yllw brches on the srbc site. Since it's a logarithmic scale that would have been ten times the acidity at 6.5 vs 7.5. I am guessing but maybe measurement off. For what it's worth I have found that simple chemical kits like the hach 17-f ones don't require the maintenance and calibration of electronic probes. (I tried multiple electronic pH gauges but maintenance and calibration were not what I really wanted)
But of course the chemical / color wheel type test can't be used continuously.

There is a massive hundred fifty plus page "yellow breeches Creek Watershed" assessment online that gives pH for ybc and many tribs.

 

[Mike]

DGC,
That’s the natural cycle of photosynthesis and respiration. As photosynthesis picks up during the day, CO2 is removed from the water column. It is removed at a slower pace when it is overcast. CO2 is generated at night as plants respire.

Even if rainfall pH is slightly higher than it was a few decades ago, the limited natural buffering capacity may have been used up from certain geological formations at that time. Additionally, there are other natural contributors to low pH in streams, such as bogs. Sinking Ck above Colyer Lk in Centre Co is a good example. Farther downstream (not too far) and before it gets to the sink hole it supports an attractive wild brown trout population with some better than average specimens.

 

[k-bob]

Mike if I'm reading this correctly, the ybc data on srbc site shows 6.5pH 6 am yesterday to 7.5 about 2pm....that great a change?

 

[Mike]

Yes, I think a full unit is possible; I think I have seen data like that in the past. I have seen very little of the Breeches except by Huntsdale Hatchery. If it is somewhat typical limestoner or typical low gradient stream in Pa and there are fair to lush amounts of vascular aquatic plants and/filamentous algae, a one unit change would not surprise me. In other streams, such as true freestoners, in-stream primary productivity comes from diatoms and even they will drive at least a minor pH change. (Note: Technically, in those streams primary productivity is mainly generated externally from leaf matter). If you find that I am wrong about the Breeches or some other fairly low gradient limestoner regarding pH swings from just before daylight to mid-afternoon on a bright, sunny day, let me know.

 

[k-bob]

Thanks that's interesting... I usually fish for brookies and mostly in tiny infertile streams, and often steep ones, not limestoners, and I don't think there's a withinday pH movement of that size. (If there were swings of more than 1 pH unit in a day, then unadjusted single readings made at different times would not be useful.) The minor changes you note in a non Limestone/steeper stream probably wouldn't overwhelm the pH differences between such streams by geology. I also often take the pH of two nearby streams only an hour or two apart; sometimes less when choosing where to fish. Cool explanation: 24 hr pH range moderated by stream type and even the weather. thanks again.

 

[k-bob]

When I do fish a long day on one stream, can sometimes compare an early am to quitting time pair of pH readings at same location. I often seek small/ brook not brown/ highly shaded streams, which would be quite different vegetation wise vs a limestoner, so may have smaller w/in day range, but ez enough to do.

 

[DGC]

Mike, thanks. I am aware of the photosynthesis angle. It does not seem plausible to me that there has been that much plant growth to explain the difference from last year's numbers. But maybe so.

 

[troutbert]

k-bob wrote:
Thanks that's interesting... I usually fish for brookies and mostly in tiny infertile streams, and often steep ones, not limestoners, and I don't think there's a withinday pH movement of that size. (If there were swings of more than 1 pH unit in a day, then unadjusted single readings made at different times would not be useful.)

Someone, I think a PFBC biologist in my region, told me years ago that pH readings are not that useful, because of the swings being described, and the difficulties of getting accurate readings with different technologies.

He said he relied more on alkalinity than pH to gauge where a stream is at.

But I think alkalinity can vary with high vs low flows, so...

Another approach is the biological approach, i.e. going by what life is found in the stream.

In freestone watersheds, I think of these basic categories:

1) Too infertile for any fish to survive, including brookies. And bug life is very sparse.

2) Fertile enough that brookies can survive, but not fertile enough for brown trout. These streams also have low bug life, but more than category 1.

3) Fertile freestoners. Support brown trout, and lots of bugs.

And, yes, you can correlate these pretty well with bedrock layers.

 

[k-bob]

tb:"In freestone watersheds, I think of these basic categories:

1) Too infertile for any fish to survive, including brookies. And bug life is very sparse.

2) Fertile enough that brookies can survive, but not fertile enough for brown trout. These streams also have low bug life, but more than category 1.

3) Fertile freestoners. Support brown trout, and lots of bugs.

And, yes, you can correlate these pretty well with bedrock layers."

I agree, interesting that a very good brookie stream can sometimes be right next to a stream too acidic to have any trout at all. this is more likely in places such some parts of central pa with patchy smaller areas of various bedrocks with variation in buffering.

As mike's remarks above suggest, pH movements within a day that doesn't have rain are probably bigger on a fertile limestoner than a shaded steep, little mountain brookie stream.

Alkalinity might be better to measure than pH, but a $90 hach pH kit works well for many tests and I think alkalinity's tougher to assess.

(hach 17f water ph kit has 100ml solution, =2000 drops, 8 drops/test, sometimes goof, = maybe 170 tests... what did we do without internet calculators? )

 

[k-bob]

TB: "Someone, I think a PFBC biologist in my region, told me years ago that pH readings are not that useful, because of the swings being described, and the difficulties of getting accurate readings with different technologies. ... He said he relied more on alkalinity than pH to gauge where a stream is at."

Image from kirby groundtruthing paper... the solid lines are lab tests... to fish little headwaters brookie streams, think I would rather have the pH numbers (means: tuscarora 4.8, shwngnk 5.7, nontuscrra 6.3) than the alkalinities (medians: tuscarora 0, shwngnk .5, nontusc 2.1)...

For example given the low alkalinity number, I think I would have passed up on the shwngnk streams and actually they did okay in terms of fish caught (6/6 had fish vs 9/28 tuscarora).

https://pubmed.ncbi.nlm.nih.gov/18258282/

 

[Mike]

k-bob,
That’s right. The low pH streams at the extreme do not have any trout. The low alkalinity streams may support a Class A biomass of ST. Such Class A streams exist in SE Pa. The most extreme ones have summer total alkalinities of 2 mg/l down to less than 1 mg/l. In the latter case, one drop of sulfuric acid turns the indicator pink (pH 4.6 color change) in 100 ml of H2O. That single drop lowers the pH from say 5.8 down to 4.6. Talk about little to no buffering capacity.

Another similar stream in in a mining area in SE Pa. It has moderately low pH, little or no alkalinity, but no iron problems. It is beginning to have an extremely low density of ST just a few hundred meters up from its confluence with the Schuylkill R. My crew and I discovered this stream’s conditions some yrs ago and followed up more recently, revealing the wild ST in the lower end. We encouraged the Schuylkill Co Conservation District to look into mitigating the mildly acidic conditions and now the Delaware Riverkeeper Network has become interested as well. There may be a future for wild ST to this stream’s headwaters since without any help it seems to be at the tipping point for supporting a population. It is a very interesting case. Most interesting is that t alk is less than 1 mg/l, yet the stream supports Gammarids (scuds). Where do they get the Ca for their exoskeletons?...must be highly efficient in grabbing the Ca from this infertile environment on a mountain top.

 

[k-bob]

Mike thanks again lots of great info

 

[Baron]

Very interesting Mike. I'm a bit naive is guess but what is wild ST? This is a fascinating subject.
Isn't this the same problem that some of the shallow high mountain ponds have in North central pa?
What type of mediation tool could be used to stabilize pH?

 

[k-bob]

As Mike already knew, can be a wave effect in the daily pH of a stream like the yellow breeches given plants and sun, but not so much in one like Kitchen Creek.. Kitchen Creek surveyed here at 20 square miles drainage is still a lot bigger than what I usually deal with... thanks again

srbc data.

 

[k-bob]

For brookie headwater summer stream choice, pH and dissolved aluminium can both be measured with simple kits ... given charts below, pH seems more useful.

pH kit might signal few or no fish at 5 or lower, and also more fish w/ higher pH numbers. Dissolved aluminium seems effective at signaling no fish at .065 mg/l or above, but lower aluminum scores may not really signal more fish.

(a figure from c kirby groundtruthing paper for pH and brookie #s; data on brookie # s x disslvd alumnm replotted) (all #s from low summer flows; higher flows or snowmelt may lower pH/increase alum)