PARENT SESSION
Oral Session #56: Aquatic Ecology: Plankton. Presiding: N. Hairston.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas I.
Population synchrony in a hydrologically connected landscape: quantifying patterns and identifying processes.
RUSAK, JAMES1, BROCK, CURTIS1, LEAVITT, PETER1, YAN, N.2, 1 2
ABSTRACT-
Quantifying the degree and pattern of synchrony among populations connected in a landscape can identify the relative roles of local (lake-specific) and regional (climatic and hydrologic) factors influencing population abundance. We quantified the temporal coherence (degree of synchrony among populations in a region) of interannual zooplankton abundance in five lakes of the Qu'Appelle River Valley, Saskatchewan, Canada, from 1994 to 1999 for six common freshwater zooplankton (Diacyclops thomasi, Leptodiaptomus siciloides, Bosmina longirostris, Daphnia retrocurva, Daphnia pulex, Daphnia galeata mendotae). By regressing patterns of inter-lake synchrony against measures of lake separation, we tested for the relative influence of regional (spatially uniform patterns), landscape (spatially explicit) and local (spatially unstructured) controls on zooplankton abundance. Although the Qu'Appelle lakes are physically connected in the landscape, the biological responses varied widely. Overall, mainly lake-specific processes regulated zooplankton populations, resulting in high pairwise coherence only when lakes exhibited similar physical, chemical, or biological properties. However, the calanoid copepod Leptodiaptomus siciloides exhibited uniform and synchronous patterns, indicating that fluctuations in interannual abundance were determined by regional factors. This same genus has been previously identified as temporally coherent in boreal lakes. Populations in both areas were significantly correlated with the same regional climate signal (El Niño), suggesting strong density-independent population regulation and important implications for aquatic food webs under a changing climate.
KEY WORDS: synchrony, El Niño, landscape, zooplankton