Phytoplankton Biological Pump Controls the Spatiotemporal Bioaccumulation and Trophic Transfer of Antibiotics in a Large Subtropical River

Abstract

The spatiotemporal bioaccumulation, trophic transfer of antibiotics, and regulation of the phytoplankton biological pump were quantitatively evaluated in the Pearl River, South China. The occurrence of antibiotics in organisms indicated a significant spatiotemporal trend associated with the life cycle of phytoplankton. Higher temporal bioaccumulation factors (BAFs) were found in phytoplankton at the bloom site, while lower BAFs of antibiotics in organisms could not be explained by phytoplankton biomass dilution but were attributed to the low bioavailability of antibiotics, which was highly associated with distribution coefficients (R 2 = 0.480–0.595, p < 0.05). Such lower BAFs of antibiotics in phytoplankton at higher biomass sites hampered the entry of antibiotics into food webs, and trophic dilutions were subsequently observed for antibiotics except for ciprofloxacin (CFX) and sulfamerazine (SMZ) at sites with blooms in all seasons. Distribution of CFX, norfloxacin (NFX), and sulfapyridine (SPD) showed further significant positive relationships with the plasma protein fraction (R 2 = 0.275–0.216, p < 0.05). Both mean BAFs and trophic magnification factors (TMFs) were significantly negatively correlated with phytoplankton biomass (R 2 = 0.661–0.741, p < 0.05). This study highlights the importance of the biological pump in the regulation of spatiotemporal variations in bioaccumulation and trophic transfer of antibiotics in anthropogenic-impacted eutrophic rivers in subtropical regions.

Indirect Impact of Eutrophication on Occurrence, Air–Water Exchange, and Vertical Sinking Fluxes of Antibiotics in a Subtropical River

“…Moreover, a disparity in dominant phytoplankton species was found between the current study and prior studies , and others conducted in deep oligotrophic regions. The Pearl River is a shallow eutrophic river dominated by Cyanophyta, Chlorophyta, and Bacillariophyta. , In those deep oligotrophic and mesotrophic regions, diatoms typically dominate the phytoplankton community. , The results of previous work has indicated that cyanobacteria is the most sensitive group to lincomycin followed by chlorophytes and diatoms . Consequently, exposure to antibiotics often leads to reduced photosynthesis in cyanobacteria, which is considered a common response .…”