Assessing the toxic effects of dissolved copper on the Antarctic macroalga Desmarestia menziesii using chlorophyll fluorescence imaging in ecotoxicological tests

Abstract

Chlorophyll fluorescence was used to measure changes in the maximum fluorescence yield () and effective quantum yield (ΔF/) of Antarctic macroalgae in response to dissolved copper. Single-point measurements of ΔF/ of Desmarestia menziesii in concentration-response experiments were used to define the concentration where ΔF/ declined by 50% (EC₅₀) after 6 h of exposure (3.9 mg L⁻¹ ± 23% coefficient of variation (CV)). Fluorescence imaging experiments with the laminar algae Iridaea mawsonii and Himantothallus grandifolius neither showed any consistent pattern in spatial heterogeneity of fluorescence response, nor could EC₅₀ values be obtained. However, imaging experiments on the terete D. menziesii resolved heterogeneity in fluorescence responses to dissolved copper with parameters declining more rapidly for thin thalli than thick thalli. While ΔF/ of thick thalli declined significantly after 7 days and provided an EC₅₀ of 1.1 mg L⁻¹ ± 29% CV, declining provide a lower and more precise nominal EC₅₀ estimate after 7 days (0.061 mg L⁻¹ ± 1% CV). These results demonstrate the importance of spatial heterogeneity in fluorescence of terete algae and suggest as a sensitive measure of toxic effects.

Keywords:

• Antarctica
• copper
• ecotoxicology
• fluorescence imaging
• macroalgae
• photosynthesis

Acknowledgements

The authors thank the diving teams at Casey Station (summers of 2001–2002 and 2002–2003) for their support. This project was funded as part of ASAC grant 2201.