# A question, dissolved oxygen and a pond



## dw1305 (15 Aug 2019)

Hi all,
I've been surveying, and doing some water quality work, on some of <"Bristol's pond and rivers"> over the last couple of weeks.

I had an interesting one today. I won't tell you the location, or context, but it was a pond and the water sample had a dissolved oxygen level of 180% (~20oC, 18mg/L DO) and a pH value of pH 10.5.  

Question is a really simple one: What did the pond look like?

Any suggestions welcomed, and I'll post the answer picture at some point.

cheers Darrel


----------



## Edvet (15 Aug 2019)

Densely planted and or lots of small waterfalls, or an aquifer.


----------



## papa_c (15 Aug 2019)

Here's my guess.....

Would suggest that it is choked full of algae, blanket or something slimy like BGA, due to a spike in ammonia, limited plant growth and rather smelly....

But thinking again as you are surveying it with interest it could be a thing of beauty and confound all expectations!

Interested to see your findings.


----------



## Zeus. (15 Aug 2019)

Oh a quiz 

Well lots of something growing OFC 

well seeing that Ed got the densely planted option and Papa got the algae one which is what I first thought 'algae' but then I thought a bit of my pond.

So Pond full of duckweed- as mine is doing so well ATM


----------



## Kalum (15 Aug 2019)

I'll give it a go...

Totally overgrown with either water features or a waterfall which might explain the high dissolved oxygen %

Concrete lined or some other sort of leaching of lime from either stone or man made materials around it to explain the high ph


----------



## dw1305 (15 Aug 2019)

Hi all,





Edvet said:


> Densely planted


Sort of.





papa_c said:


> Would suggest that it is choked full of algae, blanket or something slimy like BGA, due to a spike in ammonia, limited plant growth and rather smelly....


Some of that.





Zeus. said:


> So Pond full of duckweed


No Duckweed (or Ducks).

cheers Darrel


----------



## revans (16 Aug 2019)

Maybe a few shopping trolleys in there as it is Bristol 

Sent from my SM-G960F using Tapatalk


----------



## DeepMetropolis (16 Aug 2019)

A fountain, with invasive fish and plants?


----------



## zozo (16 Aug 2019)

Perfect parameters for biogenic decalcification on the aqautic plants..  Probably rather hard water with such high pH.

My guesss its packed with Hornwort and or potamogeton spp. (other suspects Calitriche and or Crasula spp.) and some floating blanket weed and cristal clear water.


----------



## dw1305 (16 Aug 2019)

Hi all, 





zozo said:


> Perfect parameters for biogenic decalcification on the aqautic plants..  Probably rather hard water with such high pH.
> 
> My guesss its packed with Hornwort and or potamogeton spp. (other suspects Calitriche and or Crasula spp.) and some floating blanket weed and cristal clear water.


This is <"the pond">, so I think that makes @papa_c the "winner".





About <"20 m long, 5 m wide, entirely surrounded by paving"> and around 60 cm deep. We sampled it pretty much at midday, and it was calm and sunny.

The pond was even greener than the photo, and a couple of fairly unhappy goldfish were just visible, hanging under the water surface.

When we sealed the water collection bottles (collected with a <"Phil sampler">) the green water algae were pearling very noticeably. The water, and sweep net samples, are in the lab. at the moment, so I will eventually have some invertebrate numbers and chlorophyll, NO3, NH3 and PO4 values.

The pH and supersaturation of oxygen were both caused by the phytoplankton bloom, and the total lack of water movement.

I would love to know what the dissolved oxygen and pH values were at two o'clock in the morning. It maybe that pH will remain high (because the CO2 depletion isn't being fully replenished), or it may fall as the CO2 levels rise through the night.

Eventually oxygen levels will fall (as the light levels decrease in the autumn), probably to levels that won't support life.

cheers Darrel


----------



## papa_c (16 Aug 2019)

YESSSS! 

Darrell, look forward to shortly receiving the prize of joining you on one of your future field trips....if only to carry all your gear!


----------



## dw1305 (17 Aug 2019)

Hi all,





papa_c said:


> look forward to shortly receiving the prize of joining you on one of your future field trips..


Back to Bristol on Monday and then probably for another two days later in the month, after that Swanage at the end of September and probably Keswick at the start of November (with the students).

I can sign you up for Swanage, a few days on the <"Dorset Heaths"> and not too strenuous. 

cheers Darrel


----------

