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A fresh look at Freshwater life in Weardale

25th Aug 2021

The profile of industry in the North East has changed greatly since 1903 when it was reported that the River Wear, as a salmon river is 'ruined by pollution' so that 'there is nothing to be said about its angling.

Chapter 7, Freshwater Life, in the Natural History of Upper Weardale notes that there are a great many fish along the Wear today.

Image: Migratory Sea Trout (c) G M Heeley

These are at the top of the food chain, and this fascinating Chapter looks into the microscopic algae that is very much part of the aquatic ecosystem - yes, that is is 'slime' to the uninformed eye. Much of these tiny organisms form the base of many food chains that sustain aquatic animals.

The way that the river and tributaries are shaped by underlying geology is explained along with the contribution that water acidity and chemistry has on its ecology. The presence, diversity and distribution of invertebrates is greatly affected by the water quality. Although abandoned long ago, the lead mines of Weardale still have an impact on wildlife - there are fewer types of invertebrate and also fewer individuals of each type in the metal impacted streams.

A larva of the free-roaming predatory caddis fly Rhyacophila dorsalis (Rhycacophiidae). Note the tufted gills on the abdominal segments (Length: 1.5 cm) (c) Martyn Kelly

Moorland streams host 'shredders', invertebrates which feed on autumn-shed leaves and bankside plant detritus that has entered the channel. Freshwater shrimps such as Gammarus which would normally perform this role are sensitive to heavy metals, but the role is performed by metal-tolerant stoneflies.

Further down the Dale, more nutrients and a drop in zinc concentrations, results in a more diverse stonefly community including Dinocras cephalotes, a large predatory species which can be relatively abundant. As the river flows along, further invertebrate communities appear and all are food for other animals along the food chain, ending in fish.

A diorama in watercolour, pencil and pastel showing the filamentous green alga Ulothrix zonata with epiphytic diatoms, based on material collected from Bollihope Burn in May 2016. The foreground represents a width of about a tenth of a millimetre. (c) Martyn Kelly

In many ways this chapter brings together the many aspects of the book, the way in which land, water and creatures are connected through the ecosystem.

The Natural History of Upper Weardale online provides summaries and additional data, and has the ability to update the information from time to time. A print copy of the book is available from Durham Wildlife Trust. It is a wonderful handbook to the wonders of the region as we spend time exploring close to home in 2021.

Preparing for the online Chapters on Flora, Fauna and Freshwater Life we created a PDF reference list for the hundreds of species name-checked in the book. For this Chapter, entries for Freshwater Life are included in the FAUNA list, by both Vernacular and Scientific names, with hand links to what an internet search might add to wider information on each. A reminder that the same lists for Fauna, with Venacular and Scientific names are also available to download linked to Chapter 5.