<p>Global climate changes are significantly affecting ecosystems worldwide. Concurrently, potential geomagnetic field reversals could introduce additional environmental stressors as a reduction of geomagnetic field induction. We carried out a series of experiments to simulate global warming consequences (increased temperature, reduced dissolved oxygen, and increased salinity) under the geomagnetic field and hypomagnetic conditions to mimic possible future environmental scenarios. We utilized freshwater cladoceran <i>Daphnia magna</i>, a model organism in aquatic ecosystems with limited migration potential. Life history traits, morphometric characteristics, and α-amylase activity were evaluated after exposure to combined influences. Our results demonstrate that hypoxia affects the daphnid’s reproductive output more adversely than elevated temperatures and increased salinity. Hypomagnetic conditions exacerbated these effects. A significant reduction in α-amylase activity in <i>D. magna</i> was found under hypomagnetic conditions, more notably when combined with low dissolved oxygen, high temperature, or increased salinity. The reduction in α-amylase activity was accompanied by a decrease in female sizes. The findings highlight the importance of considering multiple environmental stressors when predicting the future impacts of climate and geophysical changes on biodiversity and ecosystem function. Further research is needed to explore the long-term ecological consequences of these combined stressors.</p>