| Popis: |
While the climate induced increase of allochthonous dissolved organic carbon ( input to freshwater ecosystems is well studied, however, the effects of different DOC sources and their impact on seston quality, and in turn on the food webs and particularly on zooplankton biomass and composition is poorly understood Accordingly, we tested the effects of recalcitrant and labile DOC pulse disturbances on zooplankton communities via outdoor mesocosm experiments for six weeks We expected that zooplankton community biomass would be enhanced with labile DOC source compared to the recalcitrant, and zooplankton community composition would differ between particular DOC sources Treatments included a single pulse of alder leaf leachate ( labile DOC), Huminfeed ( recalcitrant DOC) and both together ( compared to controls (no DOC) After day 10 of the experiment, relative to the control, zooplankton biomass increased in the L and HFL treatments but did not change in the HF treatment The highest biomass increase was observed in HFL Before the pulse, Ceriodaphnia spp dominated approximately 60 of the total zooplankton biomass At the end of the experiment, the community composition was different for L, HF and HFL Unlike control, Daphnia spp dominated (approx 90 biomass in L and HFL treatments, while Cyclopoid Copepoda and Diaphanosoma spp were together 50 in HF Despite the temporal variation, overall mean seston N P ratio in L ( std 105 5 47 1 and HFL 102 1 35 2 was lower relative to HF 256 8 117 9 and controls 208 4 108 7 Additional seston phosphorus coming from labile DOC source led to lower seston N P ( and in turn, may have favoured Daphnia spp in L and HFL Initial results demonstrated that labile DOC source could have major impacts on zooplankton biomass and composition, especially when it combined with recalcitrant DOC source. |
