Pond Life

During the workday on 18th August, a group of volunteers carried out a survey of the Dewy Pond. This was completed a little later than usual and unfortunately the amount of pond weed made it difficult to see the organisms in the water. The sampling technique is familiar to anyone who has done pond dipping, as it involves scooping a sample into a white plastic tray of water and studying what might be there.   

 

Thanks to volunteer Kate Lake for leading the survey, then processing and analysing the data. 

Observations

1. There was only one predator species found, which was identified as a Small Flat Diving Beetle.

The diving beetle found in the Dewey Pond. Photo David Ward

2. It was significant that no dragonfly larvae were found as usually they are fairly abundant, nor were there any water boatmen. 

 

3. Daphnia or water fleas were numerous and in some samples, they were teeming. Furthermore, their colouration was red, which suggests low oxygen levels in the water. 

 

4. The scarcity of dragonfly larvae and mayflies and the relative abundance of shrimps, water lice and daphnia all indicate low oxygen levels. This is due to nitrogen enrichment of the water, a process known as eutrophication. As the pond accumulates dead vegetation, the process of aerobic decomposition consumes oxygen and reduces its availability for invertebrates and amphibians. 

5. Two flatworms were found, which is the first time they have been seen in the pond, although no major conclusions can be drawn by a one-off sighting. 

 

6. A developing newt, known as an eft was found in a sample. 

 

 

Elsewhere in the Wood, a small group of volunteers worked on building some new dead-hedges to protect the railway embankment from erosion as well as attending to path edging.