Phytoremediation with Algae:
Although little
research has been conducted in the area, some algal species may be able to
serve as phytoremediators. Due to their close evolutionary relationship
with plants, it is reasonable to hypothesize that algae may use many of the
same mechanisms of metal hyperaccumulation. In fact, they may be able
to accumulate more metals per biomass because soil particles can bind cations,
making them less bioavailable in soil than in an aquatic or agar-based medium9.
Crist, et al. long ago demonstrated that algae adsorb metals rapidly to
carboxylate anions of pectin at the cell surface, and then slowly absorb
the cations into the cytoplasm in a slower reaction15.
Algae are also capable of synthesizing MTs and PCs, in addition to organic
acids. Chlorella species have been shown to synthesize increased amounts
of proline as a defense against high concentrations of Cu16.
Applied to the Berkeley Pit Lake scenario, this mechanism of increased tolerance
could allow an increase in biomass and thus increase available carbon, O2,
and photosynthate concentrations for other organisms. More recently,
the group at the Sayre lab at Ohio State University has investigated the
role of metallothionines in Chlamydomonas reinhardtii hyperaccumulation of
Cd17. ::
Image from the Sayre lab website showing algae
binding heavy metals17