Sentinel responses of Arctic freshwater systems to climate: linkages, evidence, and a roadmap for future research

Abstract

While the sentinel nature of freshwater systems is now well-recognized, widespread integration of freshwater processes and patterns into our understanding of broader climate-driven Arctic terrestrial ecosystem change has been slow. We review the current understanding across Arctic freshwater systems of key sentinel responses to climate, which are attributes of these systems with demonstrated and sensitive responses to climate forcing. These include ice regimes, temperature and thermal structure, river baseflow, lake area and water level, permafrost-derived dissolved ions and nutrients, carbon mobilization (dissolved organic carbon, greenhouse gases, and radiocarbon), dissolved oxygen concentrations, lake trophic state, various aquatic organisms and their traits, and invasive species. For each sentinel, our objectives are to clarify linkages to climate, describe key insights already gained, and provide suggestions for future research based on current knowledge gaps. We suggest that tracking key responses in Arctic freshwater systems will expand understanding of the breadth and depth of climate-driven Arctic ecosystem changes, provide early indicators of looming, broader changes across the landscape, and improve protection of freshwater biodiversity and resources.

Integrating hydrological connectivity and zooplankton composition in Arctic ponds and lakes

“…Arctic freshwaters, cladocerans, copepods, crustacean production, rotifers invasions of taxa previously unable to tolerate Arctic conditions (Saros et al, 2022;Wrona et al, 2006). The resulting alterations to aquatic biodiversity have the potential to produce major changes in the aquatic food webs that supply clean water (Ayala-Borda et al, 2021) and support exploited fish populations (Grosbois et al, 2022).…”

“…The breadth of freshwater surface coverage in the Arctic results in freshwater ecosystems that contribute significantly to Arctic biodiversity (Schartau et al, 2021). Given the predicted hydro‐geomorphic and hydro‐ecological shifts (Kokelj & Burn, 2003), biodiversity is expected to vary significantly as a result of changes in abiotic disturbance regimes and physical habitats that may exclude existing resident taxa and favour the invasions of taxa previously unable to tolerate Arctic conditions (Saros et al, 2022; Wrona et al, 2006). The resulting alterations to aquatic biodiversity have the potential to produce major changes in the aquatic food webs that supply clean water (Ayala‐Borda et al, 2021) and support exploited fish populations (Grosbois et al, 2022).…”

“…For example, shallow Arctic ponds and lakes are especially susceptible to the effects of climatic change because of their low water volumes and high surface area to depth ratios (Smith et al, 2005). Accordingly, Arctic pond and lake systems may be valuable sentinels of ecological change, particularly as Arctic systems appear to be highly sensitive to the threshold effects of small step changes in the prevailing environmental conditions and prone to cascading regime shifts (Saros et al, 2022). Studies have already shown phenological, distributional, and genetic changes in response to climate change among a wide variety of Arctic taxa, including plants, invertebrates, mammals, birds, and fish (Bradshaw & Holzapfel, 2006; Parmesan & Yohe, 2003; Power et al, 2022).…”

Hydrology Controls Dissolved Organic Carbon and Nitrogen Export and Post‐Storm Recovery in Two Arctic Headwaters

“…While systemic changes to Arctic ecosystems may have both antagonistic and synergistic effects on ecosystem structure and function, they manifest as alterations in water-mediated fluxes (Saros et al, 2022;Shogren et al, 2021;Tank et al, 2020;Vonk et al, 2019). The expression of changing river chemistry at the event scale can reflect the dominant sources and pathways of material as they are transferred from terrestrial zones to the stream channel (Godsey et al, 2009(Godsey et al, , 2019Moatar et al, 2017).…”

Oxygen Depletion in Arctic Lakes: Circumpolar Trends, Biogeochemical Processes, and Implications of Climate Change

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Surface freshwaters are pervasive across the Arctic, and the polar amplification of climate warming implies that numerous characteristics of these highly sensitive ecosystems are susceptible to change due to environmental forcings (Culp et al, 2022;Saros et al, 2022). Oxygen dynamics respond strongly to ongoing physical, chemical, and biological changes, and oxygen may therefore be considered an integrator of climate-mediated alterations in aquatic environments (Hanson et al, 2006).

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