Water Quality Gradients across Albemarle-Pamlico Estuarine System: Seasonal Variations and Model Applications

Abstract The seasonal variations of water quality parameters as nitrite plus nitrate (NO−;x), total phosphate (PO3−4), chlorophyll a (chl a), and dissolved oxygen (DO) are analyzed across the Croatan-Roanoke-Albemarle-Pamlico-Core Sounds estuarine system (CAPES). Overall, several patterns are observed: The Chowan-Roanoke-Albemarle system is generally phosphorous limiting for phytoplankton growth, whereas both the Tar-Pamlico and the Neuse Rivers are generally nitrogen limiting. The largest PO3−4 gradients exist in the upstream portion of the Albemarle Sound, and the largest NO−x gradients exist in the lower Neuse and the Tar-Pamlico Rivers. Dissolved oxygen appears to have the strongest seasonal signal among the water quality variables, with highest DO values observed during winter (within the CAPES and in the nearshore area) or spring (in the continental shelf and deeper ocean) and lowest during summer. Chlorophyll a concentrations are highest during spring (within the CAPES) or winter (offshore). In con...