ROTIFERS of the Afon Mynach

• PlaceAfon Mynach
• Coordinates52° 57'N, 3° 38'W
• Type
  • 2nd order gravel stream
  • median grain-size: 9.1 mm
  • pH: circumneutral

The Afon Mynach, second order stream, located close to Bala in North Wales, drains hilly pasture land and patches of dense riparian vegetation consisting of ash, sycamore, alder and oak. The streambed surface and subsurface is inhabited by 260 invertebrate species1,2, brown trout and salmon.

This gravel stream is characterized by an abundant rotifer assemblage, with 29 monogonont and 20 bdelloid species1. Monogonont and bdelloid rotifers display density maxima during the autumn and spring period, respectively.

A rare record for stream systems is the rotifer species Microcodides chlaena (Gosse), which was found within the interstitial of subsurface sediments (15 cm depth) of the Mynach. In this stream, the monogonont rotifer Proales theodora (Gosse) showed a maximum density peak in autumn, while the bdelloid Dissotrocha macrostyla (Ehrb.) peaked in spring.

The stream sediments, which are mostly composed of mudstone, have a median grain-size of 9.1 mm and a mean porosity of 29%. Freeze-core sampling in the Afon Mynach revealed a significant link between sediment depth, bacterial activity and body-size related distribution patterns of meio-and macrobenthic invertebrate3.

More benthic research