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あきみすえたけ
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1 Influence of river discharge with rain on the formation of the red tide and hypoxic water in the eastern Mikawa Bay (Atsumi Bay). TSUGE Asataro *1, OHASHI Akihiko *2, YAMADA Satoshi *1, IWATA Yasuhiro *1 and ISHIDA Motoo *1 Abstract :We investigated the influence of the river discharge with rain on the distribution of chlorophyll a and nutrients at offshore area of Toyo River mouth in Atsumi Bay during summer season in 2009 and DIN and DSi concentrations increased in the northern part of Atsumi Bay where salinity was low, two days after the rain. Because of the increase of nutrients supply, chlorophyll a concentrations were increased by the phytoplankton bloom in the same area, so that nutrient concentrations were quickly decreased. Dissolved oxygen in the bottom layer was increased after the rain. This may be due to vertical mixture of waters induced by the wind that increased in the period of rain. Dissolved oxygen in the bottom layer quickly declined to the same level as that before rain in five days after the rain. It might be suggested that oxygen consumption rate was accelerated by the increase of mineralization of particulate organic matter derived from the phytoplankton bloom.,2001 1),, 2-3) 2009, , 4-5) , 8 26, ,2010,9, 7,9 10, ) 1 18,, 7-10),,(:DIN, T-N :DIP,(2010 ):DSi) 66%,T-P 77% 11) a,, ( 1m),,,, (SeaBird,19plus V2)DIN,DIP,DSi a (Whatman GF/C),, AAC

2 S5 9 1 S1 4 7 S8 2 3 S2 S3 S S7 S mm mm mm mm S(Bran+Luebbe ), a,, 1mL, 7,,,,,,,,, 51%, 77 km, 724 km 2,27 12) 21 BOD 0.8 mg/l, A 13

3 m 3 /s m 3 /s () (m/s) () 2009() (m/s) , 46 mm, 49.5 mm mm, 14.5 mm 9 15, mm, 47.5 mm , 8 11,12 2, 49.5 mm, 79mm mm, 29.5 mm 9 16, , m 3 /s, 2, m 3 /s 50 m 3 /s,10 m 3 /s, m 3 /s m 3 /s, 2 50 m 3 /s m 3 /s, 50 m 3 /s, m 3 /s, (24 ) m/s , 7 m/s 2010, m/s , 7 m/s ,, 2010, ,2010,2009 2

5 S1 S3 S2 4 S4 5 6 S5 7 8 S7 S6 9 S ,2010 6, ,2009 1,S2,5,6 4,2010 1,2,S3, , ,2010 2m, ,,,2010 5,, 9,5, DIN DIN, 50 g/l g/l, DIN, 100 g/l 2 DIN,2009, 418 g/l, , 53 g/l, DIN DIN g/l, DIN 2, DIP DIP DIN, DIP, g/l, DIP, 2 DIP,2009,2010 DIP 2009, DIP 2, 2, DIP DIP, 2 DIP 9 DIP, DSi DSi, 60 g/l, DSi 250 g/l 1000 g/l 2 DSi, DSi 5 DSi, DSi 9 DSi DSi DIN:DIP,,DIN:DIP Redfield , DIN 16 2 DIN,DIN:DIP DIN DIN:DIP, DIN:DIP DIN:DIP,DIN, 16 2 DIN:DIP DIN, DIN:DIP 16 DIN:DIP 16,DSi,DSi:DIP Redfield 16,DSi:DIN Redfield

7 g/L g/L DIN

8 g/L g/L DIP

9 g/L DSi a,, a 30 mg/m 3 a, a 2,, mg/m 3, Leptocylindrus danicus Pseudo-nitzschia spp., a a, Chaetoceros spp. Leptocylindrus danicus, a a, 2 a,2 9 a, a , 2, , , DIN,DIP 2009, ( 8,9), a 10 mg/m 3 ( 11),,,,,

10 mg/m mg/m a

11 1 DIN:DIP16,,,, 2009,2010 a ( 8-11), 2 ( 12)2009,, , m, ( 7)

12 10% 10,30% % 10,30%

13 ( 1, 7) m/s,, ),,, 2,, 5,, 16-19), 2 DIN, Redfield 2009, 2 DIN,2010,2010 DIN 20 g/l, N:P,2009,2010 2, a, DIN:DIP Redfield Fisher et al. 20, DIN, N:P DIN 75.7M,DIP 1.2 M DINDIP 63 Redfield 16 ( ), Redfield 16,,N:P, 2010 DSi DSi, 21-22),, DSi DIN DIP, 23-24) 25), DSi DSi:DIN, 26), 27) DSi, 28) DSi,, 2 M 56 g/l 29-30), 1 DSi:DIN , DSi DIN, DSi:DIN 1 DIP DSi:DIP 16,DSi 56 g/l 5,DSi DIN, 2010, 2,, a 5 a, 2,5 9, 2 DIN,DIP 2, 5,9,,,,,

14 a 13 mg/m 3, 5 mg/m 3, mg/m 3 7), a, 1 6),, a 6 a, a,,, 1030 mm 25, 337 mm 10, mm, 15, 2,, ,2010,, a DIN,DIP %(4.4 mg/l), %(0.8 mg/l) mg/l, 1.2 mg/l/d 32) DO,DO, 0.59 mg/l/d, 33) 6, mg/l/d, 0.08 mg/l/d 1.2 mg/l/d 2, 10, 34-35), 36),, 1,,,,,, ha 37),,,,,,,,, 2 m,, 2,, 5 9, 7,(B-0908), -

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