Phytoplankton are a key factor in primary production within pond ecosystems, yet their winter activity remains poorly understood in urban stormwater management ponds (SWMPs). In this research, we investigate the winter primary productivity of a Mississauga, Ontario SWMP and a nearby isolated control pond to examine spatial and temporal variations in ecosystem productivity. Continuous measurement of dissolved oxygen was made at surface and depth at a central location in both the SWMP and control pond. Weekly water samples were collected from three depths at four locations in each pond, alongside temperature, dissolved oxygen, and pH readings. From December, 2023 to March, 2024, samples were collected and compared with those taken from July to November, 2023 to examine variation in photosynthetic activity. Summer chlorophyll a mean concentration across all sites at mid-depth was 90.7 ± 9.4 mg/L in the SWMP and 46.1± 16.3 mg/L in the control pond on July 27 compared to ice-absent 59.9 ± 9.1 mg/L in the SWMP and 51.1 ± 11.4 mg/L in the control pond on December 12. Comparatively, chlorophyll a at mid-depth under ice averaged 26.1 ± 14.6 mg/L in the SWMP and 27.3 ± 10.4 mg/L in the control pond on January 24. Under ice, chlorophyll a peaked at 252.2 ± 15.0 mg/L at the surface in the SWMP and 247.9 ± 14.8 mg/L at depth in the control pond on January 19. The results provide evidence of substantial primary productivity in an urban stormwater management pond during winter, even under ice cover conditions.