Cold-water lakes situated in high latitudes and altitudes have pivotal socio-ecological importance both globally and locally. However, they are increasingly threatened by multiple anthropogenic stressors, such as climate change, hydropower and invasive species. The development of efficient management strategies is therefore urgently needed and requires a comprehensive understanding of the factors influencing the biodiversity and ecological processes of these ecosystems. We provide a holistic knowledge base for informed future research and management by addressing the interplay between local and global environmental drivers of food webs in Arctic charr (Salvelinus alpinus, Salmonidae) and brown trout (Salmo trutta, Salmonidae) dominated cold-water lakes in Fennoscandia. The trophic niche and population dynamics of these generalist top consumers provide extensive insights into the effects of natural and anthropogenic drivers on food webs in intensively studied Fennoscandian cold-water lakes, covering marked biogeographical gradients in abiotic and biotic conditions. Drawing on a synthesis of existing literature, our focus is on three pivotal drivers: (1) lake location and connectivity, (2) lake area and morphometry and (3) fish community composition. These drivers significantly influence the complexity and the origin and flow of energy in lake food webs, and ultimately the size structure of the charr and trout populations. Furthermore, we highlight ongoing environmental changes in Fennoscandian cold-water lakes caused by hydropower and invasive species. Finally, we identify crucial knowledge gaps and propose management actions for improving the future state of Fennoscandian cold-water lake ecosystems and their charr and trout populations.

The Food-Energy-Water nexus approach to resource governance is a paradigmshifting approach that moves away from “siloed” resource management and pursues integration and holistic planning between food, energy, and water governance. The Food-Energy-Water nexus approach carries the potential to increase synergies and reduce tradeoffs between the Sustainable Development Goals. However, theoretical challenges remain, and practical implementations of the nexus approach have lagged. The purpose of the article is to respond to the theoretical challenges and the need for practical implementations. The article first outlines the relationship between the Food-Energy-Water nexus approach and the Sustainable Development Goals. It then analyzes the relationship between the Sustainable Development Goals, human rights, and the capability approach, an influential account of wellbeing. I then discuss how the Food-Energy-Water nexus approach, in alignment with the capability approach, can contribute to trade-off reductions and synergies between the Sustainable Development Goals. I finally discuss an outline of a context-specific implementation model for a Food-Energy-Water nexus approach capable of mapping and quantifying carbon footprints creating synergies and reducing tradeoffs between the Sustainable Development Goals. A carbon capture and utilization project in the Arctic serves as a test case. Important policy implications of the study include a criterion for what it means to “optimize” the “output” of an algae cultivation system. This criterion is a tool for adjudication between stakeholders’ conflicting priorities.

Source at: <a href=http://doi.org/10.3354/meps12582> http://doi.org/10.3354/meps12582</a> | Understanding drivers of benthic-pelagic coupling in Arctic marine ecosystems is key to identifying benthic areas that may be sensitive to climate-driven changes in hydrography and surface production. We coupled algal biomass and sedimentary characteristics with stable isotope data for 113 fishes and invertebrates in the Canadian Beaufort Sea and Amundsen Gulf to examine how trophic structure was influenced by the vertical water mass structure and organic matter input regimes, from 20 to 1000 m depths. Indices of community-level trophic diversity (isotopic niche size, 13C enrichment relative to a pelagic baseline, and δ13C isotopic range) increased from west to east, coincident with the use of more diverse dietary carbon sources among benthic functional groups. Data suggested benthic-pelagic trophic coupling was strongest in the western study region where pelagic sinking flux is relatively high, intermediate in the central region dominated by riverine inputs of terrestrial organic matter, and weakest in the east where strong pelagic grazing is known to limit sinking flux. Differences in δ13C between pelagic and benthic functional groups (up to 5.7 ‰) increased from west to east, and from the nearshore shelf to the upper slope. On the upper slope, much of the sinking organic matter may be intercepted in the water column, and dynamic hydrography likely diversifies available food sources. In waters > 750 m, there were no clear trends in benthic-pelagic coupling or community-level trophic diversity. This study represents the first description of fish and invertebrate food web structure > 200 m in the Canadian Beaufort Sea.

Source at <a href=https://doi.org/10.3389/fmars.2019.00244>https://doi.org/10.3389/fmars.2019.00244</a>. | We used inverse modeling to reconstruct major planktonic food web carbon flows in the Atlantic Water inflow, east and north of Svalbard during spring (18–25 May) and summer (9–13 August), 2014. The model was based on three intensively sampled stations during both periods, corresponding to early, peak, and decline phases of a <i>Phaeocystis</i> and diatom dominated bloom (May), and flagellates dominated post bloom stages (August). The food web carbon flows were driven by primary production (290–2,850 mg C m^-2 d^-1), which was channeled through a network of planktonic compartments, and ultimately respired (180–1200 mg C m² d^-1), settled out of the euphotic zone as organic particles (145–530 mg C m^-2 d^-1), or accumulated in the water column in various organic pools. The accumulation of dissolved organic carbon was intense (1070 mg C m^-2 d^-1) during the early bloom stage, slowed down during the bloom peak (400 mg C m^-2 d^-1), and remained low during the rest of the season. The heterotrophic bacteria responded swiftly to the massive release of new DOC by high but decreasing carbon assimilation rates (from 534 to 330 mg C m^-2 d^-1) in May. The net bacterial production was low during the early and peak bloom (26–31 mg C m^-2 d^-1) but increased in the late and post bloom phases (>50 mg C m^-2 d^-1). The heterotrophic nanoflagellates did not respond predictably to the different bloom phases, with relatively modest carbon uptake, 30–170 mg C m² d^-1. In contrast, microzooplankton increased food intake from 160 to 380 mg C m² d^-1 during the buildup and decline phases, and highly variable carbon intake 46–624 mg C m² d^-1, during post bloom phases. Mesozooplankton had an initially high but decreasing carbon uptake in May (220–48 mg C m^-2 d^-1), followed by highly variable carbon consumption during the post bloom stages (40–190 mg C m^-2 d^-1). Both, micro- and mesozooplankton shifted from almost pure herbivory (92–97% of total food intake) during the early bloom phase to an herbivorous, detritovorous and carnivorous mixed diet as the season progressed. Our results indicate a temporal decoupling between the microbial and zooplankton dominated heterotrophic carbon flows during the course of the bloom in a highly productive Atlantic gateway to the Arctic Ocean.