Rhenium, osmium and nitrogen uptake in Phaephyceae macroalgae, Fucus vesiculosus

Abstract

Despite rhenium (Re) and osmium (Os) having no known biological role, living macroalgae concentrate Re and Os. Moreover, macroalgae nitrogen isotopes (d15N) are a powerful tool for monitoring water eutrophication, sewage influence and pollution. This study utilizes Fucus sp., brown macroalgae (Phaephyceae) to assess, on the one hand, Re and Os localization and uptake in the macroalgae biomass and, on the other hand, to understand the source of N of the river Tees and Staithes. The current study demonstrates that Os is evenly distributed within the macroalgae, but Re concentration varies within macroalgae structures. The uptake and tolerance of Re and Os was evaluated via Fucus sp. cultures grown in seawater of different Re or Os concentrations. A positive correlation between Re or Os concentration in doped seawater and the abundance of Re or
Os accumulated in the tips of the macroalgae is shown. Moreover, it was observed that metabolically inactivated Fucus sp. does not accumulate Re in oxic conditions, indicating that Re uptake is via syn-life bioadsorption/bioaccumulation. Thus, macroalgae may provide a source for Re phytomining and/or bioremediation. Furthermore, the strong correlation of Os isotopic composition in Fucus sp. and in the culture medium, strongly confirms the possible use of macroalgae as a biological proxy for the Os isotopic composition of seawater. The source of N in the River Tees and Staithes was evaluated
via in situ and ex situ tip cultures. Ex situ cultures were performed in seawater with different nitrate or ammonia concentrations and show a positive relation between the d15N of macroalgae and the d15N of the seawater doped. Therefore, a confirmation of the usefulness of Fucus sp. as an eutrophication or pollutant tracker is achieved. Thus, deciphering that River Tees most probable source of N is
NO3 from chemical plants nearby and Staithes most probable source of N is sewage waste