Temporal dynamics of ecological networks: Deciphering changes in cladoceran assemblages over the past ~150 years in response to land-use development

Ecological networks serve as tools to infer community stability. Within these networks, species are depicted as nodes, interconnected by links representing observed or potential ecological interactions. Among the metrics used to evaluate network stability, connectance – the proportion of realized links over possible links – emerged as a key indicator to examine the impacts of global change on aquatic communities. Despite its significance, many gaps remain in network ecology including a lack of studies exploring patterns over extensive spatio-temporal scales. Paleolimnology can bridge this gap – as biological, chemical, and physical proxies preserved in sediments infer past environmental and ecological lake conditions. We focused on cladocerans, which leave subfossils in the sediment record and play a central role in lake food webs, to quantify how aquatic networks have altered between pre-industrial and modern times. Based on the correlation of taxa relative abundances across 101 Canadian lakes, we developed networks quantifying the potential interactions for different time periods and watershed land-use classes. We observed a 10% decline in connectance from pre-industrial to modern times in high human-impacted lakes, while networks generated from low impacted lakes remain unchanged. These patterns were verified by comparing observed networks with random network permutations. With this first Canada-wide study of zooplankton networks, we are developing powerful new insights into how aquatic ecosystem stability has changed over a period of accelerated anthropogenic change.

Primary Presenter: Jennifer Pham, McGill University (jennifer.pham@mail.mcgill.ca)

Authors:

Jennifer Pham, Department of Biology, McGill University; Interuniversity Research Group in Limnology (Groupe de recherche interuniversitaire en limnologie; GRIL), Montreal  (jennifer.pham@mail.mcgill.ca)

Zofia Taranu, Environment and Climate Change Canada, Aquatic Contaminants Research Division, Montreal; Department of Biology, McGill University; Interuniversity Research Group in Limnology (Groupe de recherche interuniversitaire en limnologie; GRIL), Montreal  (zofia.taranu@ec.gc.ca)

Madeleine Aucoin, Bieler School of Environment, McGill University, Montreal  (madeleine.aucoin@mail.mcgill.ca)

Zoë Rabinovitch, Department of Biology, McGill University; Interuniversity Research Group in Limnology (Groupe de recherche interuniversitaire en limnologie; GRIL), Montreal  (zoe.rabinovitch@mail.mcgill.ca)

Cindy Paquette, Dept of Environmental Sci, Univ of Quebec in Trois-Riviere; Dept of Biological Sci, Univ of Quebec in Montreal; Environment and Climate Change Canada, Aquatic Contaminants Research Div; Interuniversity Research Group in Limnology (GRIL)  (paquette.cindy@courrier.uqam.ca)

Beatrix Beisner, Department of Biological Sciences, University of Quebec at Montreal; Interuniversity Research Group in Limnology (Groupe de recherche interuniversitaire en limnologie; GRIL), Montreal  (beisner.beatrix@uqam.ca)

Irene Gregory-Eaves, Department of Biology, McGill University; Interuniversity Research Group in Limnology (Groupe de recherche interuniversitaire en limnologie; GRIL), Montreal  (irene.gregory-eaves@mcgill.ca)