Temperature, salinity and light duration dependence on the growth and cellular carbon and nitrogen contents of the epiphytic diatom,Achnanthes longipes Agardh | ||
| Egyptian Journal of Aquatic Biology and Fisheries | ||
| Article 12, Volume 12, Issue 4, September 2008, Pages 185-202 PDF (140.68 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ejabf.2008.2012 | ||
| Authors | ||
| Samia Mikhail1; Wagdy Gergis2 | ||
| 1National Institute of Oceanography and Fisheries, Alexandria, Egypt | ||
| 2National Institute of Oceanography and Fisheries, AleWagdy L. Gergisxandria, Egypt | ||
| Abstract | ||
| Achnanthes longipes Agardh cells were isolated from glass slides submerged in the Eastern Harbour of Alexandria. Addition of D-600 (10& 25 μM) and EDTA (10-3M) was sufficient to prevent adhesion and aggregation of A. longipes cells and get homogenous free cells inocula for culture experiments. The influence of 52 combinations of salinity (5-40 at 5 intervals) and temperature (10o-25oC, at 5oC intervals) under continuous light and 12:12 light/dark cycle on chlorophyll a content, the maximum doubling time, cellular carbon and nitrogen of Achnanthes longipes was examined under constant light intensity (70-80 μE m -2 S -1). No growth was detected at 5 salinity levels with all temperatures tested, and under the combination of 15oC-10 salinity. Maximum Chl. a content during the exponential phase was almost the same at the two light regimes (about 1.2 μg ml-1). Based on Chl. a variations by days, A. longipes showed its maximum growth rate and doubling time (1.18 and 0.82 d-1, respectively) at 20oC-30 salinity (continuous light) and 1.6 and 1.11 d-1, respectively at 20oC-25 salinity (light/dark cycle). A rising in temperature from 15oC to 20oC caused about 1.8 fold increases in the doubling time of Chl. a at the two light regimes. The results indicated that Chl. a and carbon proceeded in parallel during the exponential phase under the light regimes, and the increasing in carbon content and Chl. a content accompanied an increasing in temperature. The carbon content was consistently lower in continuous light cultures than in the corresponding light/dark cultures. No definite trend was found between nitrogen and changed temperature and salinity (continuous light), while nitrogen generally increased with increasing temperature under the light/dark cycle. The maximum carbon/nitrogen was measured at 25oC with salinity range of 35 - 40,it was about two-fold higher at the light/dark (40.03). The carbon: chlorophyll ratio showed a steady increase by days, and varied considerably with changed temperature. However, there was no characteristic relation between temperature,growth rate and carbon: chlorophyll. | ||
| Keywords | ||
| Achnanthes longipes; diatom; salinity; Temperature; growth rate | ||
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