I recently attended a Freshwater Invertebrate Survey set up by the RSPB at Coombes Valley Nature Reserve, Staffordshire.
The site is an oak woodland, located in the steep sided Coombes Valley, it attracts a variety of woodland breeding birds. Species include; flycatchers, redstarts and wood warblers. The site also has a small population of rare argent and sable moths, whose caterpillar larvae encase themselves in birch leaves (see photo below).
The caterpillar of the Argent and Sable moth encases itself in birch leaves:
The samples were taken from a stretch of the Coombes Brook as it passes through the nature reserve. They were collected using the ‘kick-sampling’ method, where the substrate is disturbed up stream of a hand net which collects any small invertebrates and everything else flowing down stream. The content of the net was spread out on a tray and any invertebrates carefully collected.
In the makeshift laboratory the collected samples were analysed and compared to known samples, paying close attention to the features that distinguish one family from another. The invertebrate larvae we hoped to identify were mayflies, Ephemeroptera, stoneflies, Plecoptera, caddisflies, Trichoptera and true flies, Diptera.
The samples collected were predominantly mayfly larvae, a few stonefly larvae and a single caddisfly larva. Identification of the mayfly larvae is relatively simple, they are identified by the presence of three tails. Identification to a family level involves analysis of the gill structure, the gill location, the location of the eyes, the body shape. This was done using a stereo microscope, the assistance of a freshwater invertebrate expert and invertebrate keys.
Section of Coombes brook where Kick-sampling took place:
Freshwater invertebrates are a good indicator of water quality, usually determined based on the species present and their levels. For example an abundance of stonefly and mayfly larvae suggests good oxygen levels and low levels of pollution. The study of freshwater invertebrates can be very useful in ecological surveys.
Despite the foggy weather it was a very rewarding day and I very much look forward to returning and observing the larvae through their development.
Karl Harrison
UES Graduate Ecologist
If you would like to see this blog in original format visit the United Environmental Services website.
http://www.ues.org.uk/news/2013/02/freshwater-invertebrates-survey-rspb-nature-reserve/