Watersheds are dynamic systems in which carbon and nutrient exports vary with hydrologic conditions and subcatchment characteristics, reflecting shifting connectivity between terrestrial sources and stream networks. Concentration-discharge (C-Q) relationships are widely used to examine these dynamics across spatial and temporal scales and infer whether solute export is controlled by transport/source limitation or hydrologic mixing. However, most C-Q frameworks are derived from event-focused studies, leaving uncertainty about how seasonal hydroclimate and landscape position regulate solute behaviour, particularly in low-gradient, subtropical Coastal Plain watersheds. Here, we examined seasonal and spatial variability in C-Q relationships for dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and phosphate (PO₄³-) across three nested subcatchments in the South Sandy watershed (~125 km²), in central Alabama, USA. We collected biweekly water samples paired with concurrent discharge measurements (June 2024-July 2025). We then fitted log-log C-Q regressions by site and seasonality to quantify slope magnitude and direction, enabling comparison across subcatchments and seasons. We found that DOC consistently enriched at high flows (positive C-Q slope), particularly during wet periods in spring, indicating transport-limited mobilization from organic-rich soil. In contrast, TDN and PO43- showed chemostatic (near-zero slopes) to negative values, reflecting source-limited behavior in higher flows. Differences among site pairs reflected landscape position, with headwater subcatchments showing stronger seasonal responses than the outlet, where hydrologic mixing neutralized C-Q signals. Results from our study will provide insight into solute source dynamics in low-relief Coastal Plain watersheds.