【POSTER】🧐 Spatial-temporal distribution and source of regulation of microbial pteridines in the euphotic layer of South China Sea

Abstract

Originally discovered in photoautotrophic cyanobacteria, microbial pteridines are precursors involved in the metabolism of carbon and nitrogen cycles, and participate in phototaxis signal transduction (as photoreceptor), photochemical redox reaction, solar energy capture and ultraviolet radiation protection as coenzymes or cofactors. In this study, the vertical distribution of biogenic microbial pteridines in the euphotic layer of the South China Sea Basin was reported for the first time, and the marine environmental concentrations of neopterin (NP), biopterin (BP) and isoxanthopterin (IP) were determined by high performance liquid chromatography fluorescence detector (HPLC-FLD), and the detection limits were NP: 0.48 nM, BP: 0.72 nM, and IP：0.22 nM respectively. The results showed that the pteridines was mainly enriched in the surface layer (within 100 m), and the subsurface layer (at 100-200 m) was mostly below the detection limits. Noteworthily, NP was not detected in all samples, and the concentration of water column profile distribution of BP (0.01–0.6 pM) and IP (0.01–3 pM) was strongly negatively correlated with the nutrients at each station, indicating biomass-dependent attributes. Around the maximum layer depth of chlorophyll a, it was found that the corresponding depth IP content response value was high, and the geographical distribution of BP and IP was positively correlated with the abundance of cyanobacteria Synechococcus and Prochlorococcus, which may indicate that Synechococcus is an important source of BP contribution. In terms of seasonal distribution, the abundance of pteridines in the surface layer in summer was significantly higher than that measured in spring. The detection of pteridines in euphotic layer has the potential to reveal the biogeochemical cycling processes occurring in marine microbial communities and their biological roles.