Effects of the algal cellular nitrogen status on the defence against copper toxicity were studied in batch cultures of the coastal diatom Thalassiosira pseudonana, grown in coastal seawater (Oosterschelde, SW Netherlands; 30 parts per thousand salinity). The media represented nutrient-poor (summer) and nutrient-rich (winter) conditions, both without and with additional nitrate, respectively. In the summer series, initial inorganic N:P ratios were 1.5 and 7.1. In the winter series, N:P ratios were 12.2 and 18.4. Cu was added at five levels (0- 315 nM). We expected a low cellular nitrogen status to limit the synthesis of metal-binding peptides (phytochelatins). In N- enriched summer media phytochelatins were detectable (HPLC) only at the upper Cu level. In N-enriched winter media phytochelatins were detectable (14.6 mu M SH) even without additional Cu (pCu similar to 14; pZn similar to 8), whilst in low-nitrate winter media, phytochelatins were induced at somewhat higher Cu additions; cellular Cu concentrations were similar in both cases (similar to 25 mu M). In general, cells accumulated more Cu, Mn and Zn (summer and winter series) in N- enriched media, compared to low-nitrate media. In the low N:P media (summer) division rates were hardly affected by Cu. At N:P 12.2 and N:P 18.4, at cellular metal levels identical to those in low N:P media. T. pseudonana proved to be more Cu sensitive. In these nitrogen-rich winter conditions, phosphorus deficiency could have played a role. It was discussed that a P limitation might result in an impaired exclusion/export of copper. Phytochelatins appeared in T. pseudonana at cellular atomic C:N ratios lower than similar to 15, and at ambient inorganic N:P ratios higher than the Redfield ratio (similar to 16). Phytochelatins indicate metal toxicity (sensitivity) rather than available metal concentrations in the coastal marine environment, and will not be detectable at natural background concentrations of Cu and Zn under a nitrogen limitation. [KEYWORDS: C : N ratio; copper; detoxification; diatom; glutathione; phytochelatin Ditylum-brightwellii; chemical speciation; nutrient limitation; silene-vulgaris; maize seedlings; hplc analysis; heavy-metals;cadmium; toxicity; zinc]
Original languageEnglish
JournalAquatic Toxicology
Journal publication date1998

ID: 277771