Correlation of vanadium content to the occurrence of halogenated organic compounds in Rhodophyta species of the Baltic Sea

Abstract

Halogenated organic compounds (HOCs) occur naturally in marine environments, and red algae are known producers, often via vanadium-dependent haloperoxidases (V-HPOs). The aim of this study was to investigate whether the red algae Palmaria palmata and Chondrus crispus sampled from the Baltic Sea possess the biochemical prerequisites for HOC formation, additionally a correlation between the vanadium content and the abundance of HOCs in algae samples was to be studied. A HR-CS-GFAAS method was established and validated for vanadium determination, showing excellent sensitivity and accuracy. Using this method, P. palmata consistently exhibited high vanadium contents (up to ~38 μg/g dry weight), while C. crispus contained considerably lower levels (~9 μg/g dry weight), suggesting strong species dependence. Comparisons between fresh and dried samples, as well as different digestion and extraction approaches, demonstrated that sample preparation had a major impact on measured vanadium levels. Further experiments focused on the enrichment of potential V-HPOs. Ammonium sulfate precipitation was not as effective in concentrating vanadium-associated proteins, whereas ion exchange chromatography of P. palmata extracts revealed vanadium enrichment in specific fractions, indicating moderate binding of vanadium-containing proteins. SDS-PAGE only provide clear protein band evidence for V-HPOs in C. crispus. Overall, this study demonstrates that P. palmata and C. crispus could be promising candidates for vanadium-dependent halogenation in the Baltic Sea. The validated method and initial enrichment steps provide a foundation for future studies linking vanadium to enzyme activity and HOC production.