Beyond the trends: The need to understand multiannual dynamics in aquatic ecosystems

Abstract

Interannual variability is a pervasive feature of aquatic ecosystems. This variability results from short-and long-term dynamics of biotic and abiotic origin, inclusive of multiannual variability and long-term trends. Although understanding short-term variability and forecasting directional change are important research efforts, far less attention has been paid to oscillatory, or wave-like dynamics that play out over multiple years, in aquatic ecosystems. In this essay, we argue that understanding these modes of variability-in addition to directional trends and intraannual patterns-and their underlying causes are necessary for understanding aquatic ecosystem functioning over long time periods for effective conservation and management. Fortunately, given the growing availability of multidecadal data, development of statistical tools, and the urgent need to forecast change, the field can readily adopt multiannual dynamic thinking into our understanding of aquatic ecosystems.

Climate Change and Teleconnections Amplify Lake Stratification With Differential Local Controls of Surface Water Warming and Deep Water Cooling

“…Teleconnections, recurring and cyclical large‐scale climate circulation patterns, link climatic variability in noncontiguous geographic regions and operate on multiannual timescales. Teleconnections can alter effects of climate change by modulating regional and local drivers and may account for a portion of variance around directional trends of stratification and aquatic ecosystem function controlled by climate change (Wilkinson et al., 2020). For example, while lakes in the northern hemisphere have shifted toward earlier ice‐free dates due to long‐term climate change (Sharma et al., 2019), variance around ice phenological trends can be attributed to teleconnections (NAO; Schmidt et al., 2019).…”

“…As a result, mixing regimes may shift from dimixis to monomixis in some lake ecosystems with the potential for increasing hypolimnetic hypoxia and radiating effects on biogeochemical processes and lake food webs (Ficker et al, 2017;Maberly et al, 2020;.Teleconnections, recurring and cyclical large-scale climate circulation patterns, link climatic variability in noncontiguous geographic regions and operate on multiannual timescales. Teleconnections can alter effects of climate change by modulating regional and local drivers and may account for a portion of variance around directional trends of stratification and aquatic ecosystem function controlled by climate change (Wilkinson et al, 2020). For example, while lakes in the northern hemisphere have shifted toward earlier…”

Sensitivity of plankton assemblages to hydroclimate variability in the Barents Sea

“…To date, most research into pelagic systems has described decadal (Beaugrand and Reid, 2003;Mutshinda et al, 2017) and seasonal (Arashkevich et al, 2002;Rat'kova and Wassmann, 2002) trends of plankton communities. Interannual variability over shorter time-periods (<10 years) and the underlying drivers of this variability are not well documented, and is vital for understanding longer-term (decadal) shifts in planktonic ecosystem functioning (Wilkinson et al, 2020). Variation of hydroclimatic variables over interannual time scales, such as SST, salinity, mixed layer depth and net primary production, can reach levels similar to their projected values for 2050 (Årthun et al, 2019;Lewis et al, 2020).…”

Forest defoliator outbreaks alter nutrient cycling in northern waters

“…Previous studies have focused at most on 1-2 defoliation events, all with single insect species, making it difficult to extract wider generalities [34][35][36][37][38] . Long-term studies are necessary 39 to separate within-and among-year environmental effects that can confound single defoliation studies. As northern catchments are expected to experience more insect outbreaks in the near future 40,41 , our work highlights the importance of terrestrial disturbances as a control of aquatic biogeochemical cycling.…”