Wildlife pond water quality

[jpscloud]

Can anyone advise me about water quality when the water gets a lot of bird droppings in a small pond? The droppings come from a colony of house sparrows who roost in the bamboo that overhangs the pond, and hang out there during the day to launch onto the bird feeders. I can usually see plenty of droppings in the water.

There are a few frogs in the water and there was a large amount of spawn a few weeks ago, but it seemed to completely disappear. I haven't seen tadpoles this year, but I have seen a very large amount of midge/mosquito larvae and other tiny critters.

The water soldier plants are thriving, and other water plants doing fine too.

I think the water quality was very poor after winter, and I don't know what effect the bird droppings are having now. Could that have been a reason for the disappearance of the spawn/loss of tadpoles?

[wanlock dod]

Therer are two likely effects, an increase in nutrient levels, and a reduction in oxygen levels.

The main nutirent is likely to be phosphate, which is usually considered to be the limiting nutrient in many systems. This could result in increased plant growth.

The reduction in oxygen levels is due to the biochemical oxygen demand of the material, and is likley to be a transient effect, unless there is a continuous input.

The magnitude of any effects (if there ar eany at all) will depend on the size of the pond and the mass input of droppings.

It is my understanding that the presence of midge larvae indicate little or nothing other than that the water is wet.

Dod

[tom00_uk]

you should get some excellent plant growth if your ponds getting topped up with nutrients

[jpscloud]

Thanks both - I am hoping the only worry I will have is to routinely take out some plant growth if it gets out of control - would the water quality (if affected by the droppings) have any effect on my chances of getting dragonfly/damselfly breeding and newts in the pond?

I have a feeling I might have asked these questions somewhere before but can't remember if it was here! Sorry if I'm repeating myself.

[King Edward]

I doubt that nutrient enrichment would have any direct effects on the animal unless it reached quite a high level (sorry if that's a bit vague). Much more important are the effects on plant/algal growth. In particular, high nutrient levels can cause excessive algal growth (especially filamentous blanketweed, and also Duckweed), overwhelming submerged aquatics. It can also cause one or two particularly vigorous plant species to take over, excluding other species.

In the autumn/winter, large amounts of plants/algae can die off and cause pollution / oxygen depletion as they decay (threatening hibernating frogs).

From the sound of it, your aquatic plants are doing OK so far so there isn't too much to worry about. I wouldn't remove them at this time of year, but if there are a lot then you could take some out in the autumn before they start to decay. As far as newts/damselflies/most other water creatures are concerned, these will prefer ponds with plenty of underwater vegetation, rather than open water.

[wanlock dod]

The right habitat conditions are probably generally more important than the water quality (provided it isn't too bad)