The profundal fauna of Llyn Tegid, North Wales

Benthic fauna samples were quantitatively collected each month from the 6 to 40 m depth zone of Llyn Tegid for a period of one year. The seasonal distribution, abundance and life cycles of the invertebrate species are discussed in addition to a general description of the physical and chemical environment in which they live. The abundance and composition of the profundal fauna is compared with that of a similar survey carried out by D. R. Dunn in 1951/2 and shows a fourfold increase in total numbers of animals. The contribution to the increased profundal fauna of all animals recorded in 1951/2 and of those that have colonized this zone since that time are discussed.