Differential effects of warming and nutrient loading on the timing and size of the spring zooplankton peak - an experimental approach with hypertrophic freshwater mesocosms

Heidrun Feuchtmayr (1) , Brian Moss (2) , Ian Harvey (3) , Rebecca Moran (3) , Keith Hatton (3) , Leslie Connor (3) , David Atkinson (3)

1 Lake Ecosystem Group
2 Integrated Management and Ecosystem Research
3 Biosciences

1. 2. We present results of warming (4°C above ambient) and increased nutrient loading on plankton communities in 48 outdoor mesocosms, simulating fishless, hypertrophic ponds. 3. The timing of the chlorophyll a peak and crustacean zooplankton peak abundance, dominated by Daphnia pulex, responded strongly to temperature and nutrient addition. Daphnia numbers reached peaks 22 to 24 days earlier in heated than in unheated mesocosms. The chlorophyll a peak abundance advanced by 15 to 19 days with heating. 4. Phytoplankton, total zooplankton and D. pulex reached peak abundance 12 to 19 days later when doses of nitrogen and phosphorus were added; this finding contradicts predicted earlier phytoplankton and zooplankton spring peak abundances with nutrient enrichment. 5. Peak zooplankton and D. pulex abundances did not differ with temperature treatment, against our expectations, but peak abundances occurred at similar actual temperatures. Nutrient additions had no effect on the peak zooplankton and D. pulex abundances in our mesocosms. 6. Overall, climate warming is likely to advance plankton phenology in fishless ponds, however this advance could be dampened in systems with high nutrient concentration. We found very high zooplankton abundances with warming and high nutrient loadings, inducing a clear water state in all our tanks by heavy zooplankton grazing despite high nutrient concentrations.

Mots clés: Life Sciences

Heidrun Feuchtmayr, Brian Moss, Ian Harvey, Rebecca Moran, Keith Hatton, et al.. Differential effects of warming and nutrient loading on the timing and size of the spring zooplankton peak - an experimental approach with hypertrophic freshwater mesocosms. Journal of Plankton Research, 2010, ⟨10.1093/plankt/FBQ087⟩. ⟨hal-00612384⟩