Estudio del fitoplancton de un lago somero y oligotróficoLoch Rusky (Escocia)

Resumen

The seasonal and depth distribution of phytoplankton in Loch Rusky, a shallow small oligotrophic lake in the central region of Scotland, is described. The diatoms Asterionella formosa Hass. and Melosira italica Müll, dominate the spring phytoplankton, under conditions of water turbulence, high nutrient levels and increasing light which facilítate their distribution and growth in the water column. Cryptomonas ovata Ehr. and Rhodomonas minuta var. nannoplanctica Skuja replace the diatoms in summer, under depleted nutrient levels and water stratification, and colonial blue-green algae dominate the autumn-winter phytoplankton. The minimum biomass was recorded in winter (25.000 ind/ml) and the maximum in July (700.000 ind/ml), when 90 % of the total biomass was concentrated in the upper one meter. A total of 85 phytoplanktonic species were identified. The maximum phytoplankton diversity, calculated by the Shannon-Weaver index, was recorded in January (between 3,9 and 4,6) and the minimum in July (between 0,2 and 0,3). The diversity of the phytoplankton calculated by this index was strongly influenced by the relative abundance of a few species.