Climate change poses significant threats to freshwater ecosystems due to their vulnerability to environmental changes, limited species dispersal, and exposure to multiple stressors. Most studies have focused on individual or species-level responses, but understanding interactions across multiple levels of biological organization is crucial for predicting ecological consequences. Metabolic scaling, foraging theory, and ecological stoichiometry offer frameworks to analyze these interactions. For example, individual basal metabolic rate scales with body size and temperature, influencing food web structure and ecosystem processes. Rising atmospheric CO₂ may alter detrital nutrient ratios, affecting elemental fluxes in food webs. Climate change impacts temperature, hydrology, and atmospheric composition, interacting with other stressors to influence ecosystems. Freshwaters, being isolated and already stressed, are particularly vulnerable. Climate change may shift community structures, with smaller organisms dominating in warmer conditions, altering food web dynamics. Long-term studies in mesocosms and natural systems show warming effects on community composition and ecosystem functioning. Field experiments and natural experiments reveal temperature-dependent changes in species distribution and ecosystem processes. Palaeoecological data show long-term warming trends, with shifts in algal and invertebrate assemblages. Climate change may lead to non-random species changes, with higher trophic levels more vulnerable to extinction. Species may adapt, migrate, or perish, leading to food web restructuring. Latitudinal differences in warming effects are significant, with high-latitude systems experiencing greater changes. Glacier retreat creates new habitats but may also lead to extinctions of cold-adapted species. Linking individual metabolism to ecosystem responses is essential, with metabolic scaling, foraging theory, and ecological stoichiometry providing insights into how warming affects energy flow, resource use, and trophic interactions. Biodiversity-ecosystem functioning studies highlight the importance of species diversity in maintaining ecosystem services, but climate change threatens these relationships. Understanding these interactions is key to predicting and mitigating climate change impacts on freshwater ecosystems.Climate change poses significant threats to freshwater ecosystems due to their vulnerability to environmental changes, limited species dispersal, and exposure to multiple stressors. Most studies have focused on individual or species-level responses, but understanding interactions across multiple levels of biological organization is crucial for predicting ecological consequences. Metabolic scaling, foraging theory, and ecological stoichiometry offer frameworks to analyze these interactions. For example, individual basal metabolic rate scales with body size and temperature, influencing food web structure and ecosystem processes. Rising atmospheric CO₂ may alter detrital nutrient ratios, affecting elemental fluxes in food webs. Climate change impacts temperature, hydrology, and atmospheric composition, interacting with other stressors to influence ecosystems. Freshwaters, being isolated and already stressed, are particularly vulnerable. Climate change may shift community structures, with smaller organisms dominating in warmer conditions, altering food web dynamics. Long-term studies in mesocosms and natural systems show warming effects on community composition and ecosystem functioning. Field experiments and natural experiments reveal temperature-dependent changes in species distribution and ecosystem processes. Palaeoecological data show long-term warming trends, with shifts in algal and invertebrate assemblages. Climate change may lead to non-random species changes, with higher trophic levels more vulnerable to extinction. Species may adapt, migrate, or perish, leading to food web restructuring. Latitudinal differences in warming effects are significant, with high-latitude systems experiencing greater changes. Glacier retreat creates new habitats but may also lead to extinctions of cold-adapted species. Linking individual metabolism to ecosystem responses is essential, with metabolic scaling, foraging theory, and ecological stoichiometry providing insights into how warming affects energy flow, resource use, and trophic interactions. Biodiversity-ecosystem functioning studies highlight the importance of species diversity in maintaining ecosystem services, but climate change threatens these relationships. Understanding these interactions is key to predicting and mitigating climate change impacts on freshwater ecosystems.