New Zealand Journal of Marine and Freshwater Research abstracts
Growth responses of Alexandrium minutum (Dinophyceae)
as a function of three different nitrogen sources and irradiance
F. HOE CHANG
M. McCLEAN
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 14-901
Kilbirnie
Wellington, New Zealand
Abstract The growth response of the PSP-producing
dinoflagellate
Alexandrium minutum, cultured from a shellfish poisoning
outbreak in 1993 in the Bay of Plenty, was studied in semi-continuous cultures,
using 54 combinations of irradiance and different nitrogen (N) sources (nitrate
(NO3
-), ammonium (NH4
+), urea) and concentrations.
Irradiance had more influence on growth of
A. minutum cultures enriched
with NO3
- than on cultures enriched with either NH4
+ or
urea. At the high irradiance level (100 umol m
-2 s
-1),
the greatest growth (0.5 doubling d
-1) was recorded in cultures
enriched with NO3
-, followed by cultures enriched with
NH4
+ and urea, respectively. For cultures enriched with either
NH4
+ or urea, nutrient concentrations contributed to greater
variations in growth than irradiance. At high irradiance, growth of
A.
minutum peaked in cultures enriched with about 25 u
M of either
NH4
+-N or urea-N. Growth of
A. minutum was substantially
reduced when grown at 50 uM of either form of "recycled" N, and growth ceased
at concentrations >= 100 and >= 200 u
M of NH4
+-N and
urea-N, respectively. Growth of
A. minutum appeared to saturate at
relatively low irradiance (I
k < 40 umol m
-2
s
-1). These results imply that
A. minutum is able to substain
reasonably good growth rates, even in poorly illuminated depths within the
water column.
Keywords growth rates; nitrogen nutrients; NO3-;
NH4+; urea; irradiance; Alexandrium minutum
New Zealand Journal of Marine and Freshwater Research, 1997: Vol. 31:
1-7
0028-8330/97/3101-0001 $2.50/0 (c) The Royal Society of New Zealand
PDF file of entire paper: medium quality (498K); (scanned from paper original: notes about this process)
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