Phosphorus utilization by phytoplankton in the Yellow Sea during spring bloom: Cell surface adsorption and intracellular accumulation

Phosphorus (P) is frequently considered the limiting nutrient for marine phytoplankton growth and primary production in oceans. To explore P utilization by phytoplankton during spring blooms, field observations and incubation experiments were conducted during a cruise in the Yellow Sea (YS). In particular, phytoplankton cell-associated P pools were identified as intracellular P pool (P-intracellular) and cell surface-adsorbed P pool (P-surface). Both P-intracellular and P-surface varied in a wide range of 9.0-125.7 and 0.5-93.3 mu mol g(-1), respectively, in the YS. Pintracellular was frequently dominant in the total cellular P pool (contributing to 46-96%). Variation in the cell-associated P content was observed at different bloom stages, probably depending on phytoplankton species and seawater parameters. Cell-associated P enrichment was associated with a decrease in phosphate and increase in chlorophyll a, suggesting that the phytoplankton assimilated phosphate from the seawater and stored P in both cell interior and surface. This process supported the rapid biomass accumulation during the spring blooms. Incubation experiments further indicated that the accumulation rate of P-intracellular and P-surface was positively correlated with the phosphate removal rate in the seawater. Phytoplankton luxury P consumption could enhance both P-intracellular and P-surface mass content. P-surface, as a bioavailable P pool on the cell surface, could be internalized by the phytoplankton during active growth. Our study on the P assimilation mechanism involved in cell surface adsorption and intracellular accumulation enhanced the understanding of the dynamics of spring bloom.

Automated summary

Phosphorus utilization by phytoplankton in the Yellow Sea involves intracellular storage and cell surface adsorption, contributing to rapid biomass accumulation during spring blooms. Variations in cell-associated P content depend on phytoplankton species and seawater parameters. Luxury P consumption enhances P accumulation and internalization of bioavailable P pools during active growth.