The knock-on effect of low phytoplankton diversity contributes to low herbivorous zooplankton diversity, but which includes the crustacean Diaptomus, Cyclops and Daphnia (water fleas). Zooplankton species that predate on the herbivorous zooplankton include Leptodora, Polyphemus and Bythotrephes.
Species found in the open water and on the bottom to depths descending to 300m include naidid worms, which is distantly related to the earthworm; the pea mussel, which is an arctic species and a relic of the loch’s ice age; as well as Copepods and ostracods, both of which are typical freshwater crustaceans; and the chironomid larvae of the midge. (ref. Shine, A. 1983. New Scientist). At depths of 200m in Loch Morar the fauna is limited to lumbriculid worms, including Lumbriculus variegatus and Stylodrilus heringianus (Martin, S. et al. The Profundal Fauna of Loch Ness and Loch Morar. Scottish Naturalist Vol.105), whose presence indicates that there is oxygen present from the surface to the bottom of the loch and therefore no stagnant zones.