The Wykehamist
to support biodiversity and maintain the habitats of the remarkable flora and fauna that reside there. Among its wide array of species, Fallodon is a refuge for kingfishers, grey heron, and other populations of breeding wetland birds like sedge and reed warblers. Frequent sightings by members of the NHS demonstrate Fallodon’ s long-lasting success and the benefits the project still provides even now- our most recent excitement being an inquisitive otter caught on our wildlife cameras! Some of us are also fortunate enough to have spotted water vole along the bank of the Itchen despite their scarcity due to predation by the American Mink since its introduction in the 1920s.
More recently, the NHS has been at work monitoring the health of the River Itchen that passes through the Fallodon reserve. The Itchen is an example of a globally rare chalk stream environment. In fact, more than half of the world’ s chalk streams are found in Southern England alone. After growing concerns of possible contamination of the Itchen River Catchment, our attention was drawn to assessing the stretch accessible on school land. Contamination sometimes occurs when storm overflow water containing sewage is purposefully discharged into nearby rivers. Spending an afternoon working with the Wessex River Trust, we learnt about the Riverfly Monitoring Initiative and how to carry out surveys to evaluate the health of an area of river. Essentially, the project involves using mayflies and other aquatic invertebrates as indicator species that allow river health to be gauged from the type of species present and overall biodiversity. Equipped with nets and waders, we carried out a series of threeminute kick samples to disturb the riverbed, followed by a one-minute hand search in each location for anything collected in the nets. To get a fair representation, we sampled as
many spots along the riverbed as possible to reach different habitats and get an unbiased coverage of the stretch of river.
Over the past two years our surveys have produced encouraging results. On an average survey we usually find an abundance of common mayflies, cased caddisflies, uncased caddisflies and usually an army of freshwater shrimp. Occasionally, we also encounter aquatic worms, dragonfly larvae and— my personal favourite— the Flatbodied Upwing, a rare mayfly that looks like an alien from a science fiction movie.
Together, all these organisms illustrate a thriving chalk stream biome making use of a breadth of ecological niches. Fortunately, we scarcely find many worms, leeches or blackfly larvae. These species are indicative of unhealthy water conditions as they are pollution-tolerant and therefore more common in urbanised areas.
To investigate further we also tested nutrient levels in the River Itchen to assess the water quality. We found that phosphate levels were stable at around 0.02 to 0.05 mg / L but nitrate levels were shown to be much higher than the average at values above 10 mg / L. The unusual nitrate levels are most likely caused by agricultural run-off and the overuse of fertilisers and pesticides. This can in turn lead to the development of harmful algal blooms and by consequence eutrophication can also occur.
It is hoped that, with the continued dedication of the NHS and support of the college, Fallodon will endure as a haven for nature— a landscape teeming with life, where those of us lucky enough to visit will take the time to explore it.
Harry Tang( A, 2021-)
Flat-bodied Upwing Mayfly— Credit Harry Tang( A, 2021-)
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