Effect of gold(III) on the fouling diatom amphora coffeaeformis: Uptake, toxicity and interactions with copper

Tetrachloroaurate (AuCl^‐ ₄) was evaluated for its toxicity to the common marine fouling diatom Amphora coffeaeformis in the presence and absence of the widely used algicide Cu²⁺. AuCl₄ ^‐ was found to be toxic at concentrations above 0.5 μM, but cells were able to recover at concentrations below 5 M due to cellular and photoreduction of the AuCl₄ ^‐. In the presence of Cu²⁺, they did not recover. Other growth effects, such as inoculum level, dark toxicity, and recovery with cysteine, were also examined. Physiological measurements revealed that chlorophyll, photosynthetic rate and thiols were depressed by AuCl₄ ^‐, and AuCl₄ ^‐ uptake was greater than that of copper at the same ambient concentration. When both AuCl₄ ^‐ and copper were present, the uptake of both metals, but particularly of AuCl₄ ^‐, was increased. ATP was not required for uptake. Both live and dead cells, as well as their extracellular mucilage, were able to reduce AuCl₄ ^‐ to Au(0) which formed visible grains in and around the cells.

Key words:

• Amphora
• diatom
• toxicity
• copper
• gold

Notes

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