Long term plankton community dynamics in the face of climate change

• Elizabeth M. Wolkovich

Abstract
Changing climate has brought earlier springs and later winters to most regions of the globe, with associated changes documented in many ecological communities. Research primarily has examined these community shifts in light of individual species’ environmental tolerances, and interspecific interactions. However, changes to dynamic links between spatially or temporally linked food webs may also be critical to understanding community-scale responses to climate change. Across systems winter food webs - under ice or snow - can provide key trophic links to the food webs of warmer months, usually supplying critical basal resources early in the warm season. For example, in alpine communities complex under-snow soil food webs develop, then degrade with snow melt, providing a critical pulse of nutrients to the summer plant communities. In marine Antarctic systems under-ice phytoplankton provide an important base to the pelagic web. Such critical links may be disrupted with climate change, as winter food webs have less time to develop and spring assemblages establish increasingly earlier. Using several long-term year-round plankton community datasets I will study how climate may alter dynamic, cross-seasonal links in freshwater food webs. Datasets include that maintained by Lyubov Izmest’eva (Irkutsk State University, Russia) for Lake Baikal, the world’s largest lake, located in subarctic Siberia. In Lake Baikal, under-ice development of diatoms provides a critical resource base to the benthic food web and potentially the pelagic ice-free food web in subsequent months. I will examine how these dynamic spatial and temporal links have changed with the onset of shorter winters and earlier springs in the 60 years of data for Lake Baikal, and in other freshwater systems with longer ice-free seasons. In addition to providing basic ecological knowledge on how spatially and temporally coupled food webs may influence trophic structure and stability, this research may allow us to predict ecological responses to changing climate at the level of the food web, in addition to that of the species.