Buffers in daphnid culture and bioassay

✍ Scribed by Kathleen I. Keating; Paula B. Caffrey; Brenda C. Dagbusan

• Book ID: 102198122
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 86 KB
• Volume: 15
• Category: Article
• ISSN: 0730-7268
• DOI: 10.1002/etc.5620150319

✦ Synopsis

When an algal diet is employed, or precipitation of dissolved inorganics during autoclaving is likely, or test circumstances introduce pH changes, addition of a buffer to daphnid culture or bioassay media is appropriate. Glycylglycine, employed in our research for 20 years, is unsuitable for general use because it requires microbe-free cultures. In contrast, n-hydroxyethyl piperazine-n-2-propane sulfonic acid (HEPPSO) and N-2-hydroxyethyl piperazine-NЈ-2-ethane sulfonic acid (HEPES) offer safe and effective pH control at 300 ppm for animals, 400 ppm for algae (weight excludes Na), with no requirement for microbe-free cultures. No negative effects on fecundity, monitored in both single and multigeneration tests, or on vigor, measured by acute bioassay performance, were observed. The 48-h LC50 for glycylglycine is approximately 4,500 ppm. No deaths occur at or below 10,000 ppm of either HEPES or HEPPSO. When bioassayed against zinc (as chloride), animals reared in cultures buffered by HEPES, HEPPSO, or glycylglycine and tested in unfed acute bioassays performed similarly, allowing 100% survival in 1,000 ppb in 48 h with an LC50 of approximately 1,750 ppb.