Predicting the impacts of climate change on aquatic ecosystems in the Subarctic is challenging due to the presence of permafrost and the wide range of geomorphologic conditions found across this heterogeneous landscape. To accurately predict how fish and wildlife will be impacted by climate change, it is critical to identify the habitat requirements of important prey such as macroinvertebrates. To better understand spatial heterogeneity in macroinvertebrate populations and identify key habitat requirements, we compared taxonomic richness, relative abundance, and density of macroinvertebrate populations in seven different lake basin types, spanning a large latitudinal and elevational gradient of subarctic Alaska. We used nonparametric statistics and NMDS to relate macroinvertebrate community metrics to landscape characteristics such as sedimentary deposit type, permafrost extent, geomorphology, and lake basin type, as well as chemical conditions within the lakes. Macroinvertebrate richness was highest in areas with continuous permafrost, largely driven by richness in dipterans. Lake water chemistry influenced taxa richness, relative abundance, and densities of both macroinvertebrates and microcrustaceans. Invertebrate densities were greatest in regions (parks) with higher nutrient concentrations and specific conductance, with higher relative abundance of dipterans in older landscape terrains (Yedoma) while a higher relative abundance of microcrustaceans was found in landscapes with little peat accumulation (sand dunes). As climate-driven permafrost thaw continues across the subarctic, shifts in pH, specific conductance, and calcium are likely to occur due to changes in active layer thickness and surface and groundwater flow paths that drive nutrient and solute delivery. Changes in invertebrate relative abundance and density are most likely to occur in ETOC and Diptera, two of the most ecologically important invertebrate groups found in subarctic lakes.

Ongoing climate change threatens the biodiversity of glacier-fed river ecosystems worldwide through shifts in water availability and timing, temperature, chemistry, and channel stability. However, tropical glacier-fed rivers have received little attention compared to those in temperate and Arctic biomes, despite their unique biodiversity potentially responding differently due to additional stress from higher altitude locations thus lower oxygen availability, diurnal freeze-thaw cycles, and annual monsoon rainfall disturbances. However, tropical glacier-fed rivers have received little attention compared to those in temperate and Arctic biomes, despite their unique biodiversity potentially responding differently due to additional stress from higher altitude locations thus lower oxygen availability, diurnal freeze-thaw cycles, and annual monsoon rainfall disturbances. This study quantified aquatic biodiversity responses to decreasing glacier cover in the Cordillera Blanca range of the Peruvian Andes. Ten rivers were studied along a gradient of decreasing glacier cover in the Par & oacute;n, Huaytapallana, and Llanganuco basins, with a specific focus on macroinvertebrates and physicochemical parameters in both the dry and wet seasons. We found higher temperatures, more stable and lower turbidity rivers as glacier cover decreased, which were related significantly to higher local diversity and lower beta-diversity. Analysis of similarity revealed significant differences in the macroinvertebrate community among rivers with high, medium, or low glacier cover, illustrating turnover from specialists to generalists as glacial influence decreased. Redundancy analysis demonstrated that there were more species found to prefer stable beds and water temperatures in medium and low glacier cover in a catchment rivers. However, certain taxa in groups such as Paraheptagyia, Orthocladiinae, Anomalocosmoecus, and Limonia may be adapted to high glacial influence habitats and at risk of glacier retreat. Although species composition was different to other biomes, the Cordillera Blanca rivers showed similar benthic macroinvertebrate biodiversity responses to glacier retreat, supporting the hypothesis that climate change will have predictable effects on aquatic biodiversity in mountain ranges worldwide. Ongoing climate change threatens glacier-fed river ecosystems globally, impacting biodiversity through shifts in water availability, temperature, and chemistry. Tropical glacier-fed rivers, like those in the Peruvian Andes, are understudied despite unique stressors. This study examined biodiversity in 10 rivers along a glacier cover gradient. Results showed higher temperatures and stability as glacier cover decreased, correlating with increased local diversity. Analysis revealed turnover in macroinvertebrate communities with reduced glacial influence. Certain taxa may be vulnerable to glacier retreat. Despite differences from other regions, findings support predictable biodiversity responses to climate change in mountainous areas.image