Autumn leaf subsidies influence spring dynamics of freshwater plankton communities
- 470 Downloads
While ecologists primarily focus on the immediate impact of ecological subsidies, understanding the importance of ecological subsidies requires quantifying the long-term temporal dynamics of subsidies on recipient ecosystems. Deciduous leaf litter transferred from terrestrial to aquatic ecosystems exerts both immediate and lasting effects on stream food webs. Recently, deciduous leaf additions have also been shown to be important subsidies for planktonic food webs in ponds during autumn; however, the inter-seasonal effects of autumn leaf subsidies on planktonic food webs have not been studied. We hypothesized that autumn leaf drop will affect the spring dynamics of freshwater pond food webs by altering the availability of resources, water transparency, and the metabolic state of ponds. We created leaf-added and no-leaf-added field mesocosms in autumn 2012, allowed mesocosms to ice-over for the winter, and began sampling the physical, chemical, and biological properties of mesocosms immediately following ice-off in spring 2013. At ice-off, leaf additions reduced dissolved oxygen, elevated total phosphorus concentrations and dissolved materials, and did not alter temperature or total nitrogen. These initial abiotic effects contributed to higher bacterial densities and lower chlorophyll concentrations, but by the end of spring, the abiotic environment, chlorophyll and bacterial densities converged. By contrast, zooplankton densities diverged between treatments during the spring, with leaf additions stimulating copepods but inhibiting cladocerans. We hypothesized that these differences between zooplankton orders resulted from resource shifts following leaf additions. These results suggest that leaf subsidies can alter both the short- and long-term dynamics of planktonic food webs, and highlight the importance of fully understanding how ecological subsidies are integrated into recipient food webs.
KeywordsTerrestrial-aquatic linkages Food webs Phenology Ponds Zooplankton
We thank A. L. Ritger, J. V. Trout-Haney, and R. L. Wood for field and laboratory assistance and S. Stokoe for management of the Dartmouth Organic Farm. Comments from J. J. Gilbert, R. O. Hall, E. T. Irwin, and two anonymous reviewers greatly improved this manuscript. An Environmental Protection Agency STAR Fellowship and James S. McDonnell Complexity Postdoctoral Fellowship to S. B. F. and National Science Foundation grants DEB-1110369 to S. B. F. and K. L. C. and EF-0842267 to K. L. C., EF-0842112 to H. A. Ewing, and EF-0842125 to K. C. Weathers funded this research.
- Benfield EF, Webster JR, Tank JL, Hutchens JJ (2001) Long-term patterns in leaf breakdown in streams in response to watershed logging. Int Rev Hydrobiol 86:467–474. doi: 10.1002/1522-2632(200107)86:4/5<467:AID-IROH467>3.0.CO;2-1 CrossRefGoogle Scholar
- Dzialowski AR, Rzepecki M, Kostrzewska-Szlakowska I, Kalinowska K, Palash A, Lennon JT (2014). Are the abiotic and biotic characteristics of aquatic mesocosms representative of in situ conditions? J Limnol 73 doi: 10.4081/jlimnol.2014.721
- Elser JJ, Bracken MES, Cleland EE, Gruner DS, Harpole WS, Hillebrand H, Ngai JT, Seabloom EW, Shurin JB, Smith JE (2007) Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems. Ecol Lett 10:1135–1142. doi: 10.1111/j.1461-0248.2007.01113.x PubMedCrossRefGoogle Scholar
- Fey SB, Mertens AN, Beversdorf LJ, McMahon KD, Cottingham KL (2015). Recognizing cross-ecosystem responses to changing temperatures: soil warming impacts pelagic food webs. Oikos doi: 10.1111/oik.01939
- Smith CR, Baco AR (2003) Ecology of whale falls at the deep-sea floor. Oceanogr Mar Biol Annu Rev 41:311–354Google Scholar
- Twiss MR, McKay RML, Bourbonniere RA, Bullerjahn GS, Carrick HJ, Smith REH, Winter JG, D’souza NA, Furey PC, Lashaway AR, Saxton MA, Wilhelm SW (2012) Diatoms abound in ice-covered Lake Erie: an investigation of offshore winter limnology in Lake Erie over the period 2007–2010. J Great Lakes Res 38:18–30. doi: 10.1016/j.jglr.2011.12.008 CrossRefGoogle Scholar
- Ueveges V, Tapolczai K, Krienitz L, Padisak J (2012) Photosynthetic characteristics and physiological plasticity of an Aphanizomenon flos-aquae (Cyanobacteria, Nostocaceae) winter bloom in a deep oligo-mesotrophic lake (Lake Stechlin, Germany). Hydrobiologia 698:263–272. doi: 10.1007/s10750-012-1103-3 CrossRefGoogle Scholar
- Williamson CE, Reid JW (2009) Copepoda. In: Thorp JH, Covich AP (eds) Ecology and classification of North American freshwater invertebrates. Academic Press, San DiegoGoogle Scholar