An Investigation of the Profundal and Sublittoral Fauna of Windermere

Abstract

A quantitative and qualitative study of the distribution of the macrofauna of the sublittoral and profundal regions of this oligotrophic ("Sergentia") English lake was carried out by means of a dredge and especially a Petersen Grab. Of the bottom or mud fauna, Pisidia, Chironomidae. and Oligochaeta only were abundant, but these were supplemented by Ephemeroptera, Trichoptera, Neurop-tera, and Hydracarina. A definite depth zonation of spp. was evident, of which 88% occurred in the sublittoral and 12% were truly profundal. The abundance decrease with depth, being most variable at 3 meters. The fauna shows seasonal variation in abundance with the maximum in the winter and the minimum in summer. With increase in depth the animals become more restricted to the surface of the mud. The lower layers of the mud at all depths contain less oxygen than the surface. The decrease in abundance with depth of water was believed due to decreasing coarseness of the mud. although the indirect influence of decreasing light through affecting the plant food supply may also be important.