Abstract Effects of nitrogen to phosphorous (N/P) ratios of two nitrogen sources (nitrate and ammonium) on growth and toxin production
of a tropical estuarine dinoflagellate, Alexandrium minutum Halim, were examined using a strain isolated from a bloom at Tumpat Estuary, Malaysia in September 2001. Experiments were
carried out in batch cultures, using either nitrate (N-NO3) or ammonium (N-NH4) as the nitrogen source at a constant amount, and with initial N/P ratios ranging from 5 to 500. Cell density, residual N
and P in the medium, cellular toxin quota (Q
t), and toxin composition were analyzed throughout the growths. Our results showed that cell densities and growth rates of
A. minutum were severely suppressed under high N/P ratios (>100) in both N-NO3 and N-NH4 treatments. Cells tended to be larger at lower growth rate and P-limited cultures. Toxin profile was relatively constant
throughout the experiments, with GTX4/GTX1 as the dominant toxin congeners. Cellular toxin quota (Q
t) increased with elevated N/P ratios in both N-NO3 and N-NH4 treatments. Toxin production rate, R
tox, however was enhanced in N-NH4-grown cultures when P was limited, but showed no difference between N-NO3- and N-NH4-grown cultures when P was replete. Our results clearly showed that N/P ratios as well as the nitrogen compounds not only
affected the growth of A. minutum, but also the cellular toxin quota and its toxin production rate.
of a tropical estuarine dinoflagellate, Alexandrium minutum Halim, were examined using a strain isolated from a bloom at Tumpat Estuary, Malaysia in September 2001. Experiments were
carried out in batch cultures, using either nitrate (N-NO3) or ammonium (N-NH4) as the nitrogen source at a constant amount, and with initial N/P ratios ranging from 5 to 500. Cell density, residual N
and P in the medium, cellular toxin quota (Q
t), and toxin composition were analyzed throughout the growths. Our results showed that cell densities and growth rates of
A. minutum were severely suppressed under high N/P ratios (>100) in both N-NO3 and N-NH4 treatments. Cells tended to be larger at lower growth rate and P-limited cultures. Toxin profile was relatively constant
throughout the experiments, with GTX4/GTX1 as the dominant toxin congeners. Cellular toxin quota (Q
t) increased with elevated N/P ratios in both N-NO3 and N-NH4 treatments. Toxin production rate, R
tox, however was enhanced in N-NH4-grown cultures when P was limited, but showed no difference between N-NO3- and N-NH4-grown cultures when P was replete. Our results clearly showed that N/P ratios as well as the nitrogen compounds not only
affected the growth of A. minutum, but also the cellular toxin quota and its toxin production rate.
- Content Type Journal Article
- DOI 10.1007/s10811-009-9443-8
- Authors
- Po-Teen Lim, Universiti Malaysia Sarawak Faculty of Resource Science and Technology Kota Samarahan Sarawak 94300 Malaysia
- Chui-Pin Leaw, Universiti Malaysia Sarawak Institute of Biodiversity and Environmental Conservation Kota Samarahan Sarawak 94300 Malaysia
- Atsushi Kobiyama, Kitasato University School of Fisheries Science Sanriku Ofunato Iwate 022-0101 Japan
- Takehiko Ogata, Kitasato University School of Fisheries Science Sanriku Ofunato Iwate 022-0101 Japan
- Journal Journal of Applied Phycology
- Online ISSN 1573-5176
- Print ISSN 0921-8971
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