Marine algae are an important primary producer in the marine food chain, and affect the biogeochemical cycle of arsenic in the marine ecosystem. Marine algae have the capacity to accumulate 1000 times more arsenic than its concentration in the surrounding sea water. Marine algae are an important primary producer in the marine food chain, and affect the biogeochemical cycle of arsenic in the marine ecosystem. Marine algae have the capacity to accumulate 1000 times more arsenic than its concentration in the surrounding sea water. This may contribute to the trophic transfer of arsenic to higher levels of the marine food chain and thus may pose a threat to human health. Much of the organoarsenicals present in the tissues of marine animals are derived directly or indirectly from consumption of marine algae. Zooxanthellae (algae), symbiotically present in clam mantle tissues, accumulate arsenate from the sea water and convert it to organic forms such as arsenoribosides and arsenotaurine, and pass the arsenic to the host. In marine algae, inorganic arsenic accounts for between 1 and 50% of total arsenic and the remainder is present in different organoarsenical forms.