Is this pollution

[Paul Bullinger]

Just back from fishing the Wye for a week.
Spent a day catching very little except a small barbel and few chublets.
I wandered upstream and saw this in the water. Is it pollution? Could it have put the fish off from feeding?
The weed on the river bed was covered in brown sludge as were the rocks.

 

[Rhys Perry]

I would say yes, but I bet if you asked the EA they would come out with some BS about it being a natural occurrence, just like they do with the white foam.

 

[Stephen Crowhurst]

Looks like organic film, was this below some riffles or an area of high surface agitation by any a chance? Basically the excess air sticks to organics and they in turn stick to other organics and it creates a slime or foam. You see the same on the beach sometimes.

Where the organic material came from to create that is a different question, could be natural, might not. You’d expect to see this earlier in year below willows that are pumping out pollen or later when nutrients are being washed in from surface run off and high flow.

The brown sludge, you’d need to look closer but stuff growing on the weed and rocks as a slime or tufts is probably a mixture of bacterial growth and algaes. The bacteria in particular excel at growing in environments rich in phosphate but at a disbalance with nitrate, it can grow when more complex life like plants and higher algae cannot.

In short we can guess but from the photograph it is incredibly difficult to say what that is and why it occurred. If that was an isolated area, even more so. Going on a limb I’d guess it’s a combination of nutrient sources and really just a general indication of water condition, even that’s a stretch.

 

[Paul Bullinger]

Looks like organic film, was this below some riffles or an area of high surface agitation by any a chance? Basically the excess air sticks to organics and they in turn stick to other organics and it creates a slime or foam. You see the same on the beach sometimes.

Where the organic material came from to create that is a different question, could be natural, might not. You’d expect to see this earlier in year below willows that are pumping out pollen or later when nutrients are being washed in from surface run off and high flow.

The brown sludge, you’d need to look closer but stuff growing on the weed and rocks as a slime or tufts is probably a mixture of bacterial growth and algaes. The bacteria in particular excel at growing in environments rich in phosphate but at a disbalance with nitrate, it can grow when more complex life like plants and higher algae cannot.

In short we can guess but from the photograph it is incredibly difficult to say what that is and why it occurred. If that was an isolated area, even more so. Going on a limb I’d guess it’s a combination of nutrient sources and really just a general indication of water condition, even that’s a stretch.

Thanks Stephen. I seem to recall that when I first started fishing the Wye some 15+ years ago, the weed growth that was visible in the water was always green (as you would expect) but the weed that can be observed has a brown "sludge" on it and I wondered if it was this "covering" that had drifted off the weeds and floated to the surface?
Phosphates and nitrates are a big problem here in Norfolk as they are used extensively in agriculture and get washed into our watercourses.