Use of 14C carbon dating to determine feeding behaviour of enchytraeids

There is a lack of information about the trophic position of enchytraeid species, and it is unknown whether their vertical distribution in the soil corresponds to different feeding strategies. This study, for the first time, employs radiocarbon techniques to investigate the in situ feeding behaviour of enchytraeids. Soil cores including the associated vegetation were taken from a cambic stagnohumic gley near the summit of Great Dun Fell (845 m) in 1996. Since enchytraeid populations are known to be affected by changes in temperature and moisture regimes in upland soils, additional sampling was carried out at the soil warming experiment at the same site. Soil cores were also taken from a blanket bog on Hard Hill (560 m) at Moor House National Nature Reserve in 1998. All cores were sliced in the field into five layers, each of 2 cm, to a total depth of 10 cm. A subsample of each layer was used for animal extraction, and a parallel soil sample was used for 14C isotope analysis. Results indicate that enchytraeids assimilate carbon components which are predominantly of material that is ca. 5–10 years old. The vertical movements of the worms due to changing abiotic factors do not affect this as they show similar values at all depths. However, in response to warming, they could have changed their C source as a lower 14C enrichment with depth was observed in the heated samples.