TUMSAT-OACIS Repository - Tokyo
University of Marine Science and Technology(東京海洋大学)
第一部 海鷹丸航海調査報告 平成17年度(2005年度)
第18次航海報告
メタデータ

言語: Japanese
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公開日: 2008-04-15
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https://oacis.repo.nii.ac.jp/records/287

4.5.132006 年 Lützow-Holm 湾周辺海域における植物プランクトンの成長速度と動物プランクトンの捕食速度

堀本奈穂・井上孟・小野敦史・澤邊江梨子・山口征矢・石丸隆（東京海洋大学）

Phytoplankton growth rate and microzooplankton grazing rate around the Lützow-Holm Bay in 2006
Horimoto N., T. Inoue, A. Ono, E. Sawabe, Y. Yamaguchi, T. Ishimaru(Tokyo Univ. of Marine Science and Technology)

Introduction
To know regulate of variations in phytoplankton biomass are the difference between their growth and loss
processes which are due to grazing by zooplankton. Phytoplankton biomass and their productivity are afundamental biological property in the surface of the marine ecosystem. Most all of the estimates ofphytoplankton production have been obtained by the 14C (or 13C in Japan) tracer incubation technique(Steemann Nielsen, 1952), however it is necessary to know on heterotrophic grazing processes by
microzooplankton as mortality rate of the phytoplankton community. The dilution approach protocol(Landry & Hassett 1982) is based on the experimental determination of phytoplankton growth rate in adilution series. The dilution series is made up by combining the natural microbial community with seawaterthat has been filtered free of microbial components. The theoretical and practical considerations of thistechnique are fully described in Landry and Hassett (1982) and updated in Landry (1993). Essentially,
phytoplankton growth is assumed to be density independent with specific growth rates that are constant for all
dilution conditions.
Methods and preliminary results
All samples were collected in Niskin bottles that had been retrofitted with silicon o-rings and silicon tubes
as closing mechanisms. The seawater sample collected surface and Chlorophyll maximum depth (CMD)that confirmed in vivo chlorophyll fluorescence form CTD cast at Sta. S3, S4, S5, S6, S7, and S8. The
natural water sample has to be diluted with filtered water of the same origin to the following dilution steps:
0.25, 0.5, 0.75, and 1.00 (where 1.00 is undiluted). Dilution step is defined as the fraction of unfilteredwater. Filtered water can be acquired by means of Whatman GF/F filters. Filtered water should first bepoured into rinsed 500mL polycarbonate bottles, and then the remaining volume of unfiltered water is poured
in a gentle manner. Macro nutrients was not added to each bottle in this time because Antarctic Ocean isgenerally enough nutrients concentration as maintaining a constant maximal phytoplankton growth rateduring the incubation. For each dilution step at least two incubation bottles were taken as replicates for Sta.
S3, S4, S5, and S7 (however, Sta. S6 and S8 were singular). The initial Chl a concentration N0 as replicateswere measured for four dilution steps. A 500 ml water sample was filtered with a Whatman GF/F filter(25-mm-diameter) with <100 mmHg of vacuum pressure. Chlorophyll a was extracted from the filter in 6 mlof N,N-dimethylformamide in the dark at -20°C (Suzuki and Ishimaru, 1990). The Chl a concentration wasdetermined fluorometrically using a Turner Design Model 10R fluorometer (Parsons et al., 1984), which had
been calibrated with pure Chl a (Sigma Chemical Co.). The incubation had last a complete light–dark (24 h)period and then measured Chl a concentration as N24. After analysis of the samples, the growth rate andgrazing rate were calculated using the model proposed by Landry & Hassett (1982): Nt=N0 e(k g)t, where Nt is
the Chl a abundance at time t24, N0 the Chl a abundance at time t0, k the prey growth rate, and g the grazing
rate. In practice, the grazing rate g is equivalent to the negative slope of the linear regression between theapparent growth rate of heterotrophic prey calculated for each dilution using the generalized exponential
growth model and the proportion of seawater in the various dilutions.

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The regression lines at each station were showed in Figure 1. Initial conditions and results of dilution
experiments are summarized in Table 1. The estimation of phytoplankton growth rate and using dilution
theory gave almost similar values at all dilutions, that supports growth rates of phytoplankton aredensity-independent. However, it needs to determine some statistical analysis to clear significant differenceof each sample.
Table 1 Summary of observations
Lat. (S)GMTStation

Long. (E)2006/1/20 6:58 64 33.5835 60
2006/1/20 19:05 63 31.7115 66
2006/1/21 6:03 62 29.6651 70
2006/1/21 18:30 61 0.9608 75
2006/1/22 5:27 59 54.0036 79
2006/1/22 17:59 58 22.8197 84

S3
S4
S5
S6
S7
S8

0.6

13.97930.864349.7684
57.508936.1668
19.8619

Chl asurface
Chlorophyll
Chl a
CMD
Surfacesurface grazing
CMD temp
CMD grazing
concentration in growth rate
Maximum
concentration growth rate
temp (oC)mortality (d-1)(oC)
mortality (d-1)
Surface(ug/l)(d-1)
Depth (m)in CMD (ug/l)
(d-1)

0.03
0.52
0.77
0.98
1.50
1.77

0.14
0.90
0.57
0.20
0.45
0.53

0.09
0.23
0.08

0.01
0.15
-100
27
37
50
30
43

-0.68
0.43
0.59
-0.18
1.41
-0.19

0.20
1.14
0.44
0.24
0.26
0.81

0.6
S3-Chl Max

0.4

0.6
S3-0m
0.4

0.4

0.6
S5-0m
0.4

0.2

0.2

0.2

0.2

0.0

0.0

0.0

0.0

-0.2

-0.2

-0.2

-0.2

-0.4

-0.4

-0.6
0.6 0.0-0.6
0.6 0.0

0.5

1.0
S4-0m

-0.4
y = -0.2229x + 0.0042-0.6
0.5
1.00.6
S4-Chl Max 0.0

0.4

0.4

0.2

0.2

0.2

0.0

0.0

0.0

0.0

-0.2

-0.2

-0.2

-0.2

-0.4
-0.6
0.6 0.0

0.5

0.4

-0.4
y = 0.0924x - 0.049-0.6
1.0
0.60.0
S7-0m
0.4

-0.6
0.6
1.0
0.0
S7-Chl Max
0.4

-0.4
y = -0.1539x + 0.2324-0.6
0.6 0.0
0.5
1.0
S8-0m
0.4

0.2

0.2

0.2

0.0

0.00.0

0.0

-0.2

-0.2

-0.2

-0.2

-0.4

-0.4

-0.4

-0.4

-0.6

y = 0.0104x - 0.1092
-0.6

-0.6

0.2

-0.6
0.0

0.5

1.0

0.0

0.5

1.0

y = -0.1093x + 0.1064
0.5

1.0
S6-Chl Max

0.2

-0.4
y = -0.2013x + 0.1887
0.5

0.22
0.20
0.11
0.01
0.06

S5-Chl Max-0.4
y = -0.0143x + 0.0862
-0.6
0.6
0.0
0.5
1.0
S6-0m
0.4

0.4

0.00
0.19
0.11
-0.0

0.5

1.0

y = -0.0089x - 0.1285
0.5

1.0S8-Chl Max

y = -0.0644x - 0.0827
0.00.5Fraction of undiluted seawater
Figure 1 The relationship between apparent growth rate (d-1) phytoplankton anddegree of dilution of natural seawater with filtered seawater at each station.

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1.0