Recent climate warming favours more specialized cladoceran taxa in western Canadian Arctic lakes

Abstract

Aim Shifts in the distribution of freshwater algal communities as a result of climate-related limnological changes are well documented; however, impacts on higher trophic levels have received less attention. For example, little is known about how Cladocera (Crustacea, Branchiopoda), often dominant invertebrates and key ecological indicators, have responded to recent warming on broad spatial and temporal scales. Here, we use lake sediment records to test the hypothesis that recent, intensive warming in the western Canadian Arctic has resulted in consistent shifts in the composition of cladoceran assemblages.Location Small, first-order lakes in the Mackenzie Delta region of the western Canadian Arctic.Methods Sediment cores representing the recent past (approximately 150-200 years) were obtained from five lakes spanning a strong climatic gradient. Subfossil remains of Cladocera were identified and enumerated and overall primary production was inferred using spectroscopic techniques. The habitat preferences and feeding strategy of each taxon were compared. Detrended canonical correspondence analysis was used to estimate compositional turnover since 1850, and compared with that of three cladoceran assemblages from Nova Scotia, to place high-latitude changes in context. ResultsCladoceran assemblage changes occurred coincident with the timing of known regional warming and were strongly linked to estimated changes in primary production. In the northern and deepest lakes, an increase in the planktonic, filter-feeding taxon Bosmina spp. coincided with a decrease in the generalist littoral taxa Chydorus cf. brevilabris and Alona circumfimbriata. In the more southern lakes, an increase in macrophyte-associated scrapers Acroperus harpae and Eurycercus spp. occurred concurrently with decreases in generalist taxa. In one lake, an increase in another specialist, an obligate mud-dwelling taxon, was observed.Main conclusions In the western Canadian Arctic, warming has resulted in an increase in cladoceran taxa occupying more specialized feeding and habitat niches. Generalist taxa capable of occupying multiple habitats and employing diverse feeding strategies have been systematically replaced by more specialist species. This response is analogous to what has been inferred for algal communities across the Northern Hemisphere, and represents the first evidence of consistent cladoceran changes to recent climate warming in high-latitude regions.

The response of Cladocerans to recent environmental forcing in an Alpine Lake on the SE Tibetan Plateau

“…The occurrence of these forms suggests that these littoral macrophyte-associated species were more competitive during the shorter growing seasons of summers in the LIA (Whiteside et al, 1978;Thienpont et al, 2015).…”

“…6) indicate the amelioration of the environment at Moon Lake (a longer growing season due to the longer ice-free period) due to the natural climate recovery. However, the remains of the cold-preferring cladocerans such as, A. harpae and C. sphaericus (Hofmann, 1987) continued to increase which may be related to increased input of snow-melt, which would reducing the surface water temperature of the lake combined with increased growth of littoral vegetation as the growing season lengthened (Whiteside et al, 1978;Saros et al, 2010;Thienpont et al, 2015).…”

“…The sedimentary profiles of biological remains collected from alpine lakes has been inferred to reflect the climatic forcing over the recent past (Lotter et al, 1997). In particular, over the last two centuries, ecosystems of many high mountain lakes across the world have shown different responses, such as loss of biodiversity and shift in biological assemblages, due to rapid changes in their physical environment Thienpont et al, 2015). Rise in temperature has also influenced the nutrient dynamics in alpine lakes; for example, regional warming in North America has enhanced nutrient release from the catchment influencing the lacustrine productivity (Saros et al, 2010).…”

Ecological Responses to Climate Change at Biogeographical Boundaries

“…Directional taxonomic shifts of the algal communities in the Northern Hemisphere have been observed by Ruhland et al [39], especially in the alpine regions and arctic zones with a tendency of an increase in specialized taxa which are replacing generalized species [40].…”

Trends in Ostracoda and Cladocera distribution and water chemistry in subarctic Canada: Churchill (Manitoba) lakes and ponds revisited

“…Despite single indicative species, overall it appears that waters in boreal settings have a higher alpha diversity in zooplankton, whereas waters in the shrub tundra display a higher diversity in benthos faunal assemblage. Further research is needed to monitor these trends and to specify implied consequences to the food web (Thienpont et al, 2015).…”