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.


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).



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

Deep sea lithogenic weathering a source of iron colloids for the ocean

Homoky and co-workers determined the isotope composition of dissolved iron profiles in shallow surface sediments of the South Atlantic Uruguayan margin…


Science Highlights

Adding external sources allow a better simulation of the oceanic rare earth elements cycles

Oka and colleagues demonstrate that the global distribution of REE can be reproduced by considering the internal cycle associated with reversible scavenging and external REEs inputs around continental regions.


Science Highlights

First direct measurements of luxury iron uptake in natural phytoplankton communities: surprising results!

This study demonstrates the importance of biology and ecology to understanding iron biogeochemistry.


Science Highlights

Air-sea gas disequilibrium drove deoxygenation of the deep ice-age ocean

This study provides one of the first mechanistic explanations for Last Glacial Maximum deep ocean deoxygenation.