Pam Petherbridge, is a local ecologist who is passionate about fresh water ecology. Last year she began sampling the Danes Stream, looking for and recording the creatures she finds, to get an idea of how clean the water actually is.
Here is her Report:
Since my retirement I have become passionate about protecting our natural environment. My particular interest is freshwater ecology and in order to broaden my knowledge I enrolled on a training course which taught me techniques for establishing the general health status of rivers.
There are two main methods. Chemical sampling using spot samples shows the water quality at the time of sampling of such parameters as nitrates and phosphates, which if too high have adverse effects on the health of the river, causing prolific alga growth at the expense of natural diversity.
The other method is biological sampling in the form of invertebrate monitoring. This technique has the advantage that it shows the overall health of the river over an extended period. Freshwater invertebrates living within the stream are abundant, not very mobile and carry out some or all of their life cycle within the stream and are therefore exposed to the quality of the water on a continuous basis. The type and abundance of invertebrates found will therefore directly relate to the water quality.
Some freshwater invertebrates are more tolerant to specific types of pollution than others. Worms, midge larvae, snails, and leeches are more tolerant of muddy streams than mayflies, caddisflies and stoneflies which need healthy lotic (flowing) water. Sewage spills, agricultural runoff and flash flooding associated with urban development and climate change are an ever increasing threat to our freshwater ecosystems.
Last June the Dane Stream became very turbid throughout the Pleasure Grounds. The source was traced back to a water main burst in a broad bean field off Hordle Lane. This resulted in a cascade of muddy water entering the watercourse. Damage to the ecology of the stream was fortunately limited but will have had a suffocating effect on some invertebrate species.
I did my monitoring of the Dane Stream in the Pleasure Grounds at Milford at a location known as Mervyn’s bench. I carried out a technique known as “kick-sampling” on a monthly basis from June to December 2022.
It is too early to draw firm conclusions, but to date the Dane Stream does not appear to be impacted by elevated levels of nitrates or phosphates, and is classed as having a mesotrophic (moderate) nutrient status. A biotic scoring system was used to record freshwater invertebrates and the Dane Stream is currently exhibiting a healthy ecosystem which requires generally good quality water.
My thanks go to the Parish Council for permission to do my sampling and the Milford Conservation Volunteers for their assistance with the surveys and getting me out of the mud!
Pam Petherbridge