Phosphorus- and nitrogen-limited photosynthesis and growth ofGracilaria tikvahiae(Rhodophyceae) in the Florida Keys: an experimental field study
✍ Scribed by B. E. Lapointe
- Book ID
- 104753248
- Publisher
- Springer-Verlag
- Year
- 1987
- Tongue
- English
- Weight
- 787 KB
- Volume
- 93
- Category
- Article
- ISSN
- 0025-3162
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✦ Synopsis
The relative effects of NH4 + (N) and PO~-(P) on growth rate, photosynthetic capacity (Pmax), and levels of chemical constituents of the red macroalga Gracilaria tikvahiae McLachlan were assayed during winter and summer, 1983 in inshore waters of the Florida Keys by using in-situ cage cultures. During winter, both N and P enrichment enhanced growth over that of ambient seawater; however, P rather than N accounted for more (60%) of the increased winter growth. During summer, P, but not N, enhanced growth over ambient seawater and accounted for 80% of increased growth. Similarly, Pmax was enhanced by both P and N during winter (but mostly by P) and only by P during summer. Elevated C:P, C:N and N:P ratios of G. tikvahiae tissue during winter, but only C:P and N:P ratios during summer, support the pattern of winter N and P limitation and summer P-limitation. This seasonal pattern of N vs P limited growth of G. tikvahiae appears to be a response to seasonally variable dissolved inorganic N (twofold greater concentrations of NH~-and NO~ during summer compared to winter) and constantly low to undetectable concentrations of PO]-. Mean C:P and N:P ratios of G. tikvahiae tissue during the study were 1 818 and 124, respectively, values among the highest reported for macroalgae.