As(V) was the dominant arsenic species present in the water-soluble cell fractions of all D. tertiolecta cultures.
Under high PO4 3− concentrations As(V) accounted for greater than 93% of the extractable water-soluble arsenic,
with As(III) the only other species detected. Conversely, under low PO4 3 − concentrations As(V) accounted for
between 66 and 71% of the extractable arsenic with As(III) (16–26%) and PO4-riboside (8–13%) present.
Under high As(V):high PO4 3− concentrations As(V)was themajor arsenic species in hydrolysed lipid extracts accounting
for approximately 56% of the extractable arsenic, with Gly-riboside (26%), PO4-riboside (13%) and
As(III) (5%) also present. Under low As(V):high PO4 3 − conditions As(V) only accounted for approximately 18%
of the extractable arsenicwith Gly-riboside (44%) and PO4-riboside (38%)more prominent. Under lowPO4 3− conditions
Gly-riboside was themajor arsenic species (84–92%) irrespective of As(V) exposure with As(V) (8–10%)
and PO4-riboside (6%) also present.