Coatham Marsh and an Invasive Aquatic Plant

Last Friday I visited Coatham Marsh - a nature reserve managed by the Tees Valley Wildlife Trust. It is an area of open water, reed-beds, and brownfield land situated just back from the coast between Redcar and the South Gare.

This is the approximate outline of Coatham Marsh Nature Reserve
- I don't know where the exact boundaries are

This wasn't the first time I had been there but on previous occasions I had mostly stayed near the entrance, where the main ponds can be viewed fairly easily. This time I explored a bit further, and even crossed the railway line (on a footbridge - I didn't risk getting a £1000 fine for trespassing on the railway).

Most of the birds I saw were on the two ponds nearest the entrance and on the channel that runs through the middle of the reserve from west to east - 66 Gadwall and 5 Shoveler (two kinds of duck), plus a few Coots, Moorhens, Little Grebe, Mute Swans and a Grey Heron. Away from the watery habitats are several little hills, which are actually mounds of slag from the furnaces of the nearby steelworks. I can imagine that these are botanically quite interesting during the spring and summer, but I was there a little late in the season to see many of the plant species that flower there (including a few species of orchids, apparently). I'm already planning a few visits next year, when I might also see (and hear) some of the other birds that breed there - including Reed and Sedge Warblers.

The channel in the middle of the reserve - apparently it's called a 'fleet'.
Some of the reed-beds can be seen behind it

One thing that I was quite sad to see was a large amount of a plant species called Floating Pennywort (Hydrocotyle ranunculoides). This is an aquatic species which is native to North and South America and was brought to the UK as an ornamental species for aquaria and garden ponds - from these it escaped into the wild - possibly by small fragments of the plant being carried by wild birds. It was first seen in the wild in the UK in 1990 in Essex and from there it has spread across south-east England and the Midlands, with small pockets in other parts of the country (including Coatham Marsh unfortunately). It is one of five species of aquatic plants that were banned from sale in the UK in 2014 because of their negative effects on native habitats and species.

Floating Pennywort, unlike its close relative, the native Marsh Pennywort (Hydrocotyle vulgaris), forms dense mats of vegetation floating on the surface of the water in canals, ditches and slow-moving rivers - the negative effects of the species in the UK include changing the oxygen availability in the water, threatening populations of fish and invertebrates, blocking up drainage systems and out-competing the native plant species. For more information on it, visit this website - http://www.nonnativespecies.org/factsheet/downloadFactsheet.cfm?speciesId=1766

Floating Pennywort

And a closer view

Looking west from one of the bridges across the central 'fleet'
The mass of pale-green vegetation at the water's edge is all Floating Pennywort