A changing menu in a changing climate: Using experimental and long‐term data to predict invertebrate prey biomass and availability in lakes of arctic Alaska

Abstract

Changes in seasonality associated with climate warming (e.g. temperature, growing season duration) are likely to alter invertebrate prey biomass and availability in aquatic ecosystems through direct and indirect influences on physiology and phenology, particularly in arctic lakes. However, despite warmer thermal regimes, photoperiod will remain unchanged such that potential shifts resulting from longer and warmer growing seasons could be limited by availability of sunlight, especially at lower trophic levels. Thus, a better understanding of warming effects on invertebrate prey throughout the growing season (e.g. early, peak, late) is important to understand arctic lake food‐web dynamics in a changing climate. Here, we use a multifaceted approach to evaluate prey availability to predators in lakes of arctic Alaska. In a laboratory mesocosm experiment, we measured different metrics of abundance for snails (Lymnaea elodes) and zooplankton (Daphnia middendorffiana) across three time periods (early, mid‐ and late growing season) and across three temperature and photoperiod treatments (control, increased temperature and increased temperature × photoperiod). Additionally, we used generalised additive models and generalised additive mixed‐effects models to relate long‐term empirical observations of zooplankton biomass (1983–2015) to observed temperature regimes in an arctic lake. We then simulated zooplankton biomass for the warmest temperature observations across the growing season to inform likely zooplankton biomass regimes under future change. We observed variable responses by snails and zooplankton across experiments and treatments. Early in the growing season, snail development was accelerated at multiple life stages (e.g. egg and juvenile). In mid‐season, in accordance with warmer temperatures, we observed significantly increased Daphnia abundances. However, in the late season, Daphnia appeared to be limited by photoperiod. Confirming our experimental results, our models of zooplankton biomass showed an increase of nearly 20% in warmer years. Further, these model estimates could be conservative as the consumptive demand of fishes may increase in warmer years as well. Overall, our results highlight the importance of interactive effects of temperature and seasonality. Based primarily on temperature, we can readily predict the response of fish metabolism in warmer temperatures. However, in this context, we generally require a better understanding of climate‐driven responses of important invertebrate prey resources. Our results suggest invertebrate prey biomass and availability are likely to respond positively with climate change based on temperature and seasonality, as well as proportionally to the metabolic requirements of fish predators. While further research is necessary to understand how other food‐web components will respond climate change, our findings suggest that the fish community at the top of arctic lake food webs will have adequate prey base in a warming climate.

Ecosystem response to earlier ice break‐up date: Climate‐driven changes to water temperature, lake‐habitat‐specific production, and trout habitat and resource use

“…Lake‐specific effects can also be an important component in models predicting responses of zooplankton to water temperature or ice out; thus, it is possible that the differences in our results compared to those in Alaskan lakes could be explained by an unmeasured variable (e.g. watershed size, predatory community) between our study system and others (Carter & Schindler, 2012; Klobucar et al., 2018). Phytoplankton community succession may be accelerated under warming scenarios providing a lower quality food resources such as cyanobacteria for zooplankton and limiting their production in extremely warm years (Jassby et al., 1990; Park et al., 2004; Sommer et al., 2012).…”

“…Lake-specific effects can also be an important component in models predicting responses of zooplankton to water temperature or ice out; thus, it is possible that the differences in our results compared to those in Alaskan lakes could be explained by an unmeasured variable (e.g. watershed size, predatory community) between our study system and others (Carter & Schindler, 2012;Klobucar et al, 2018).…”

“…(2004) data. For example, de Senerpont Domis, Mooij, Hülsmann, van Nes, and Scheffer (2007) found only in extreme warming scenarios were zooplankton decoupled from algal food resources, and Klobucar, Gaeta, and Budy (2018) manipulated water temperature and found that later in the season under higher temperatures Daphnia abundance was reduced relative to control conditions. Lake‐specific effects can also be an important component in models predicting responses of zooplankton to water temperature or ice out; thus, it is possible that the differences in our results compared to those in Alaskan lakes could be explained by an unmeasured variable (e.g.…”

Effects of increased temperature on arctic slimy sculpin Cottus cognatus is mediated by food availability: Implications for climate change

“…Generally, aquatic ecosystems in the Arctic are predicted to become more productive with future warming (Levine & Whalen, 2001; Prowse et al., 2006; Vucic et al., 2020). For instance, zooplankton biomass is expected to increase in arctic lakes with increases in temperature and longer ice‐free periods (Klobucar et al., 2018), and these predicted increases fall within the range of increased consumptive demand predicted for fish species, such as Arctic char (Budy & Luecke, 2014). Additionally, growth rates of chironomids, the main prey source of slimy sculpin in arctic lakes, increase with temperature and peak near 20°C (Reynolds & Benke, 2005).…”

Are different benthic communities in Arctic delta lakes distinguishable along a hydrological connectivity gradient using a rapid bioassessment approach?

“…The western Canadian Arctic has experienced increases in mean annual temperature of 2-3°C and in winter temperature of 3-4°C over the past six decades, which are projected to rise a further 3-4°C and 7°C, respectively, by the end of the 21 st century (ACIA 2005). Climate change is likely to have effects on the water balance (MacDonald et al 2017), hydrology (Krogh and Pomeroy 2018;Lafrenière and Lamoureux 2019;Lininger and Wohl 2019), productivity (Kendrick et al 2018), and community structure (Laske et al 2016;Klobucar et al 2018) of aquatic ecosystems, but considerable uncertainty exists in projections of factors such as precipitation, discharge, evapotranspiration rates, and ice dynamics, such that the direction and magnitude of ecosystem changes are difficult to predict (ACIA 2005). Prediction of the ecological effects of these physical changes is more difficult still due to the complexity of ecological interactions (Kharouba et al 2018) and region-or lake-specific differences in trajectories of change (Rouse et al 1997;Lesack and Marsh 2010;Vonk et al 2015).…”