Assessment of Caffeine and its metabolites on marine phytoplankton growth

This research aims to assess the influence of varying concentrations of caffeine (CA), one of the pharmaceutically active compounds, and its metabolites (i.e., paraxanthine (PX), theophylline (TP), and theobromine (TB)) on the growth of common marine phytoplankton ( Isochrysis galbana and Thalassiosira pseudonana) under controlled laboratory conditions. Additionally, the study estimates the daily discharge of CA into marine ecosystems utilizing a developed model. The most effective metabolite inhibiting the proliferation of I. galbana was determined as TP (68.5%) at a concentration of 500 mg/L, while it was CA (65.8%) at the same concentration for T. pseudonana. . After exposure to CA, the IC50 values for I. galbana and T. pseudonana were calculated as 107.3 mg/L and 136.8 mg/L, respectively after 96 hours. Furthermore, the lowest IC50 50 concentration was 7.4 mg/L in TP treatment in I. galbana. . Based on a computational model developed in the paper, in a province with about 2 million inhabitants, where all wastewater is treated in wastewater treatment plants (WWTP), the quantity of CA discharged into the sea was computed as 8.11 kg/day. The CA amounts reaching the sea were potentially increased in regions devoid of wastewater treatment infrastructure. Consequently, WWTPs should undergo expansion and enhancement of their capacity, including advanced treatment for chemical removal for sustainable marine life. Additionally, further studies are needed to elucidate the mechanisms underlying the inhibition effects of CA on phytoplankton.