Growth and production of aquatic mosses in acidified lakes of Karelia Republic, Russia

Three small acidified lakes (pH of water 5.3-5.9) in Karelia Republic, northwestern Russia, were studied in respect to species composition, phytomass, and morphometric characteristics of aquatic mosses in their dense carpet. The dense moss carpet in lake L-1 (mainly, Sphagnum denticulatum Bird.) occurred at a depth of 5.0-7.5 m and covered about 50% of the bottom area. The monospecific moss carpets occurred in lake L2 (Warnstorfia exannulata s. lato) and lake L3 (Fontinalis hypnoides Hartm.) at depths of 5.0-7.0 m and 4.5-5.5 m and covered 20 and 13% of the bottom, respectively. The moss phytomass was 43-53 g air-dry mass m(-)2 in the lake L2 and lake L3, while it was much higher in lake L1 - 293 g m(-2). Seasonal changes in shoot morphology of S. denticulatum, W. exannulata s. lato and in size and density of leaves along the shoot axis of F. hypnoides allowed to reconstruct the annual growth and to estimate of growth rates of the mosses in their natural habitat within dense carpet. The absolutely net production of the mosses was estimated on the basis of these data. In two lakes (L2 and L3), the annual means of absolutely net production of the aquatic mosses were 32-41 g air-dry mass m(-)2 yr (-1), while in the third lake (L1) they were markedly higher - 157 g m(-2). The obtained results and characteristics of aquatic mosses are compared with those for mosses in acidified Lake Grane Langso in Denmark.