Composition, distribution and biomass of benthic macrophyte communities from lake Baciver, a spanish alpine lake in the central Pyrenees

Abstract

Species composition, distribution and biomass of benthic macrophyte communities have been studied in a high mountain, oligotrophic, softwater lake from the Central Pyrenees. Isoetids (Isoetes lacustris L., Isoetes setacea Lam., Subularia aquatica L. and Eleocharis acicularis (L.) Roemer & Schultes) are the dominant macrophytes in areas over 2-3 meters in depth. Natopotamids (Sparganium angustifolium Michx.) are restricted to shallow waters. Algae (Nitella gracilis (Smith) Agardh) only predominate in deep waters. Three main communities have been distinguished: the Sparganium angustifolium community (160 g dwt m -2 ), the Isoetes lacustris community (120-460 g dwt m -2 ) and the Nitella gracilis community (11 g dwt m -2 ). Biomass differences between shallow and deep water Isoetes populations have been attributed to ice-scour stress. Neither irradiance nor slope can explain the lower boundaries observed in the distribution of vascular plants; sediment features may be responsible for them. Mean lake macrophyte biomass amounts to 140 g dwt m -2 (20 g C -2 ), a very high value if compared with boreal lakes with similar limnological characteristics. © Masson, 1989.