Arsenic detoxification by phytoplankton reveals that arsenic species could be good proxies of phosphorus limitation

Some phytoplankton species have the capacity to modify surface water arsenic speciation, inhibiting its toxicity. Such detoxification is operative in oligotrophic waters when phosphate concentrations are below those for arsenic (As). During the US GEOTRACES North Atlantic transect, fine determination of As speciation allowed establishing the potential use of these detoxification products as indicators of phosphorus (P) limitation. The new As indicator has been used to assess P-limitation in the North Atlantic, improving on the contradictory assessments using the conventional proxies. The coupled relationship between As and P is a classic example of a biogeochemical cycle, and how such relationship can be used as a tool in oceanography.

Wurl_low

Figure: Relationship between inorganic phosphate, arsenite (As3+) and alkaline phosphate activity (APA), the latter being an enzyme to cleave organic-bound phosphate and typically increasing with decreasing inorganic phosphate. Arsenate (As5+) uptake by phytoplankton increases under low phosphate availability due to the chemical similarities between them. Detoxification includes reduction and excretion of As3+, consequently indicating moderate (orange background) and extreme (red background) limitation of phosphate. No phosphate limitation occurs if As3+ levels are below 1 nmol L-1 (green background).

 

Reference:

Wurl, O., L. Zimmer, and G.A. Cutter. 2013. Arsenic and phosphorus biogeochemistry in the ocean: Arsenic species as proxies for P-limitation. Limnol. Oceanogr. 58: 729-740. Click here to access the paper.

Latest highlights

Science Highlights

Icebergs as sources of trace metals to the ocean: which impact?

Earth’s Ice Sheets are known to release significant quantities of lithogenic particles into the ocean every year, but how does this material affect trace metal availability in the ocean?

18.10.2021

Science Highlights

Microbial trace metal trafficking on marine particles

This study provides evidence for the processing of nine particulate trace metals in multiple manners by diverse microbial communities.

28.09.2021

Science Highlights

Volcanic emissions in the Southern Ocean: an efficient and unexpected source of iron for this remote area

This study suggests that volcanic emission can represent a significant source of bioavailable Fe to open ocean anaemic ecosystems.

20.09.2021

Science Highlights

Surprisingly heavy silicon isotopes in the surface and deep Arctic Ocean

Brzezinski and his colleagues report on a comprehensive study of the Arctic Ocean silicic acid concentrations and silicon isotopic composition…

14.09.2021

Rechercher