Plankton dynamics in a high mountain lake (Las Yeguas, Sierra Nevada, Spain). Indirect evidence of ciliates as food source for zooplankton
✍ Scribed by L. Cruz-Pizarro; I. Reche; P. Carrillo
- Publisher
- Springer
- Year
- 1994
- Tongue
- English
- Weight
- 518 KB
- Volume
- 274
- Category
- Article
- ISSN
- 1573-5141
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✦ Synopsis
A detailed sampling programme during the ice-free season (July-September) in the oligotrophic lake Las Yeguas (Southern Spain) has shown a well-defined time lag between phytoplankton and zooplankton maximum standing stocks, the former displaying a peak (23 plgC -') just after the ice-melting, and the latter by the end of September (80 pgC 1-).
A ratio of autotrophs to heterotrophs lower than 1 which lasted more than two thirds of the study period may suggest a high algal productivity per unit of biomass. The estimated strong top-down regulation of phytoplankton by zooplankton indicates an efficient utilization of resources.
A comparative analysis between the available food supply and the critical food concentration that is necessary to maintain the population of Daphnia pulicaria (which constitutes up to 98 % of the heterotrophic biomass) proves this species to be food-limited in the lake under study.
To explain the dominance (and development) of such large-bodied cladoceran population, we discuss the possibility of the utilization of naked protozoan ciliates (Oligotrichidae) as a complementary high quality food source, and the exploitation of benthic resources through a coupled daily migration behaviour.