The marine polychaete Arenicola marina: its unusual arsenic compound pattern and its uptake of arsenate from seawater

Arsenic compounds in the marine polychaete Arenicola marina collected from Odense Fjord, Denmark were determined by HPLC–ICPMS. In contrast to most other marine animals, A. marina contained most of its water soluble arsenic as inorganic forms, arsenite (58%) and arsenate (16%), and arsenobetaine was present as a minor constituent (6%) only. Other arsenic compounds detected in A. marina were dimethylarsinate (4%), two arsenosugars (1 and 3%), tetramethylarsonium ion (1.5%), and arsenocholine (<1%). A new arsenobetaine — trimethylarsoniopropionate—previously only reported in fish, was also present at trace levels (<1%), and an unknown anionic arsenical ( 10%) remains unidentified. When A. marina was exposed in laboratory experiments to different concentrations of arsenate in seawater (10, 50, 100, 500 and 1000 μg As l−1) the polychaetes accumulated arsenic in a dose dependent, non-linear manner. Most of the accumulated arsenic was biotransformed to arsenite and dimethylarsinate, with the remainder being accumulated as unchanged arsenate. None of the other arsenic compounds naturally present in A. marina increased in concentration following arsenate exposure.