Climate and productivity shape fish and invertebrate community structure in subarctic lakes

Abstract

Summary Climate change and land‐use intensification are increasing productivity in subarctic lakes. Simultaneously, fish and invertebrate species adapted to temperate conditions are expanding their range northwards into subarctic habitats. Community level studies are required to predict long‐term effects of these dual stressors on subarctic freshwater ecosystems. We conducted a space‐for‐time study examining the fish, benthic invertebrate and pelagic zooplankton communities in littoral, profundal and pelagic habitats in 19 subarctic lakes situated on a temperature, land‐use and productivity gradient in northern Europe. Fish density (ranging between 0.5 and 150.5 fish per net series h−1) and biomass (range between 92 and 5,147 g per net series h−1) increased significantly with increasing lake temperature and productivity. This was associated with significantly decreasing body size (26 to 12 cm total length; 174 to 19 g body mass) and a shift in fish community structure from salmonid (Arctic charr Salvelinus alpinus, whitefish Coregonus lavaretus), to percid (ruffe Gymnocephalus cernua, perch Perca fluviatilis) and ultimately cyprinid (roach Rutilus rutilus, bleak Alburnus alburnus) dominance. Changes in fish community composition were most apparent in littoral and pelagic zones. Benthic macroinvertebrate density peaked in mesotrophic lakes, zooplankton density was highest at either end of the gradient, indicating habitat specific differences in predation pressure and top‐down control. Body size of zooplankton and benthic macroinvertebrates was negatively related to temperature and productivity. These results suggest that climate change and intensification of land‐use practices are gradually turning subarctic lakes into warmer, less transparent and more productive systems harbouring abundant, small‐sized and warmer adapted communities.

Fish but Not Macroinvertebrates Promote Trophic Cascading Effects in High Density Submersed Plant Experimental Lake Food Webs in Two Contrasting Climate Regions

“…By contrast, in the fish treatments, a cascading effect was revealed by a major reduction of the zooplankton grazing potential and a significant increase in phytoplankton biomass in both climatic zones. Our findings confirm the occurrence of a fish predation-driven structure of zooplankton [2], as suggested also in previous works in subtropical, e.g., [19,26,32,[56][57][58][59][60], temperate, e.g., [61][62][63][64], and even sub-polar systems [65,66].…”

Potential climate change impacts on Arctic char Salvelinus alpinus L. in Ireland

“…salmonids). Hayden, Myllykangas, Rolls and Kahilainen () found significant positive associations of increasing fish density, decreasing body size, and shift in fish community structure (salmonid to percid to cyprinid) along a gradient of increasing temperature and land‐use in sub‐Arctic Europe. Species that occur in Britain and Ireland that are already at the edge of their thermal distribution and are unable to disperse will be the most affected.…”

From clear lakes to murky waters – tracing the functional response of high‐latitude lake communities to concurrent ‘greening’ and ‘browning’

“…, ; Hayden et al . ). However, the majority of data collected regarding these changes relates to shallow temperate lakes (Meerhoff et al .…”

“…) of these lakes, increasing the duration and intensity of pelagic production and creating a habitat for warmer adapted consumers which occupy distinct benthic and pelagic niches (Hayden et al . ). Evidence from marine systems indicates that increased pelagic productivity may also result in an increase in pelagic‐benthic coupling, whereby benthic communities are fuelled by pelagic detritus (Docmac et al .…”