Oral

IAPSO

P02 - Physics and Biogeochemestry of Semi-Enclosed, Shelf Seas and Coastal Zones

Distribution of Limiting Factors in the Yellow Sea Marine Ecosystem

Understanding ecological dynamics and identifying limiting factors in marine environments are essential for ecosystem management. This study investigates the spatiotemporal variation of limiting factors across three-dimensional ecological zones in the Yellow Sea (YS) using a coupled physical-biogeochemical numerical model as well asin-situ and satellite data from 2008 to 2010. Ecological zones were categorized into five distinct regions based on chlorophyll-a concentration gradients: (1) the offshore surface layer (OS, 0-15 m), (2) the subsurface chlorophyll maximum layer (SCML, 15-30 m), (3) the deep layer (DL, >30 m), (4) the western Yellow Sea (WYS), and (5) the eastern Yellow Sea (EYS). Horizontal boundaries corresponded to tidal fronts, while vertical separations were determined by the thermocline. Seasonal variation of chlorophyll-a concentration revealed distinct blooming patterns. The OS exhibited a spring bloom (March-April) with a peak concentration exceeding 3 mg/m3, followed by nutrient depletion. However, the SCML experienced a delayed maximum (June-July) due to reduced surface light attenuation after the spring bloom. Chlorophyll-a concentration in the DL remained low year-round due to light limitation, whereas the WYS and EYS sustained relatively high chlorophyll-a levels through vertical mixing and nutrient supply. This study highlights phosphate limitation as a key driver of phytoplankton growth from analysis of the nitrogen-to-phosphorus (N:P) ratio. Spatial correlation analysis between chlorophyll-a, nutrients, irradiation, and stability further demonstrated the controlling factors in each region. Phosphate was the dominant limiting factor in the OS and SCML during summer, whereas light limitation played a major role in the DL. Both the WYS and EYS sustained high productivity through continuous nutrient replenishment. This study provides critical insights into the spatial and temporal distribution of limiting factors in the YS, emphasizing the necessity of region-specific management strategies for sustainable marine ecosystem conservation.