Arctic marine ecosystems are experiencing unprecedented environmental changes due to rising sea surface temperatures, with potentially significant impacts on global carbon cycling. Diatoms, which contribute approximately 20% of annual global carbon fixation, are experiencing shifts in bloom dynamics that may affect their carbon sequestration capacity. This study presents a novel systems biology approach using dynamic flux balance analysis (dFBA) to model how these critical climate-responsive microorganisms adapt to changing conditions. We developed two interlinked dFBA models utilizing surrogate genome-scale metabolic networks to represent Arctic diatoms (Thalassiosira sp. and Chaetoceros sp.) and their symbiotic cyanobacteria partners, with temperature-dependent reaction kinetics, light-responsive carbon storage, and interspecies nutrient exchange. The models successfully reproduce observed seasonal succession patterns from early-blooming Thalassiosira to later-blooming, symbiotic Chaetoceros without prior parameterization to force this behavior. Our simulations predict that increasing temperatures will lead to earlier, shorter, and more intense diatom blooms across Arctic latitudes (55°N-85°N), resulting in reduced carbon fixation in non-symbiotic species. However, diatom-cyanobacterial symbiosis emerges as a critical resilience mechanism, with symbiotic communities maintaining relatively consistent carbon fixation rates across temperature gradients. The model predicts a shift from nitrogen to iron limitation when symbiotic associations dominate, aligning with field observations. These findings illustrate how a systems biology approach can mechanistically link environmental drivers, metabolic responses, and ecosystem-level carbon cycling. By capturing multi-scale interactions from enzyme kinetics to community dynamics, our model offers a framework for understanding how Arctic phytoplankton communities may respond to ongoing environmental changes, with implications for future carbon sequestration and potential feedback effects on global climate systems.
