Numerical modeling of the slow-growing, motile harmful alga Gymnodinium catenatum in Inokushi Bay, a small inlet in southern Japan

Transcription

1 Numerical modeling of the slow-growing, motile harmful alga Gymnodinium catenatum in Inokushi Bay, a small inlet in southern Japan G. catenatum Tamiji YAMAMOTO and Ryoko AKAI Graduate chool of Biosphere cience, Hiroshima niversity, Japan

2 Inokushi Bay, Japan Honshu N Kyushu Bungo Chan hikoku Inokushi Bay km Toxification of noble scallops and other shellfish

3 Cell density of G. catenatum in Inokushi Bay, Japan Gymnodinium catenatum 細胞密度 Cell density cells/l cell density cells l J F M A M J J A O N D 観測日 Month Oita Pref. Fish. Res. Inst.

4 Purpose μ =0.3/day 5 o C, 30 psu Yamaguchi, pers. comm. Question: Why is this species able to form blooms in Inokushi Bay with such a low growth rate? To understand the bloom forming mechanisms of G. catenatum in Inokushi Bay using a numerical model

5 Methods Arrangement of boxes BOX 3 a 4 Inokushi Bay 蒲江湾 N <Observation> 5 Nov 003- Apr 004 <Parameters> Temperature alinity Nutrients Cell density Current velocity <tations> t.-5 t.a 5 BOX sizes BOX upper BOX lower BOX 0 m urface area.94 km.36 km Depth 0-0 m 0-7 m BOX 7 m Area of cross section 5,600 m 3,90 m

6 In Out mm/sec Current velocity t.a, Doppler Current Meter Abo pers. comm. Running mean of 5 hrs. 004 年 3 月 Mar m 5m 4m 3m m m 0m 9m 8m 7m 6m 5m 4m 3m m -50 When the water comes in to the upper layer 0-0 m, the water of lower layer 0 m-b is pushed out of the bay.

7 Meteorological data used Light Precipitation Jan Dec 00 Ic=0.5 I 0 exp-k Dc 5 Nov 003- Apr 004 Fukuoka Met. Agency Nobeoka Met. Agency Evaporation 5 Nov 003- Apr 004 Nobeoka Met. Agency Daily temp., wind vel., vapor pressure E m Es = 3 / day = 30 E E W exp s a A 4 9 T T Es: saturated vapor pressure at the water temp. mb Ea: atmospheric vapor pres. mb W: wind vel. m/s A: surface area km T 6 T Kurata and Okada 984

8 dt Diffusion coefficients Z a out = Kh Ah Kv Av h Ah h v Av v P E X a dt = Kh out X Ah Kv Z Av h Ah h v Av v Horizontal dif. coef..0~.00 3 m sec - ertical dif. coef ~.00-3 m sec - alinity salinity psu psu salinity salinity obs_salinity obs_salinity cal_salinity cal_salinity 30.0 /5 /5 /4 /4 /3 3/4 3/4 日 Date MM/DD

9 Framework of ecosystem model BOX precipitation G. c. Diatoms DIM BOX DOM Det swimming G. c. sinking diffusion ection sinking Diatoms sinking DIM DOM Det sinking release release

10 Time change in DIP Time change in Diatoms Time change in G. catenatum L O L gdip d DIP DIP Z K A DIP DIP X KH AH DIP DIP D DOP P C PP P P dt ddip = ρ ρ 3 L O L Pd Z K A X KH AH A ink A dt d = μ L O L Pg g gdop gdip Z K A X KH AH A wim A dt d = μ μ Time change in DOP Time change in Det-P L O L gdop DOP DOP Z K A DOP DOP X KH AH DOP DOP D DOP P PP C P dt ddop = ρ L L O PP g d DetP DetP DetP DetP Z K A DetP DetP X KH AH P DetP A ink P DetP C P C DetP P A P A dt ddetp 3 3 = Mass balance P, upper layer

11 Temp. & al. G. catenatum Diatom. costatum Light G. catenatum μ i = μ ' Biological processes μ = st T 0.06 T T T T Yamaguchi, pers. comm. I 0 I 3. μ = T t μ = s 0.65 T Tsuruta et al., 985 Diatom. costatum I 5.43 μ i = μ' I 5.43 Yamamoto et al., 00 Langdon,987 Nutrient uptake ρ = ρ G. catenatum K Dugdale, 967 Diatom. costatum μ = μ' e Q min / Q e Droop, 973 μ' Q = Q μ' μ min Morel,987 ρ ρ lo = ρ hi = μ' ρ hi Q ρ Q lo Q Q Q Q min min min Grover, 99

12 Biological processes cont d Growth rate G. catenatum Diatom. costatum μ = μ' min f e, f i μ μ t s μ = μ e μ t μ μ μst μ' μ T i i Motality rate A = exp k 3 M po MPT Decomposition rate of PP to DIP and DOP C C = = PI PO exp exp k PI T k PO T Decomposition rate of DOP to DIP D = DIP exp k DI T

13 Parameters used in this model symbols values unit references Gymnodinium catenatum μ 0.3 d - Kann 000 μ' P 0.53 d - yamaguchi K s DIP 3.4 μm Kataoka 00 K s DOP 7.6 μm Oh00 hi ρ DIP.4 pmol cell - h - Kataoka 00 hi ρ DOP 3.38 pmol cell - h - Oh00 lo ρ P 0.5 pmol cell - h - * Q 0 P.44 pmol cell - yamaguchi Q P 3.43 pmol cell - * W dinoflagellate 4.88 m day - Anderson and tolzenbach985 keletonema costatum μ 0.96 d - yamaguchi μ' P.5 d - tarutani and yamamoto994 K s DIP 0.68 μm tarutani and yamamoto994 hi ρ DIP pmol cell - h - tarutani and yamamoto994 ρ lop 0.0 pmol cell - h - * Q 0 P pmol cell - tarutani and yamamoto994 Q P 0.0 pmol cell - * inking 0.7 m day - mayda970 *: calculate with μ = ρ lo / Q -Q 0 *: calculate with Q = μ Qmin / μ - μ

14 70000 Results primary calculation: with no physical processes Cell density G.catenatum of の細胞密度 G. catenatum Cell density cells/l cell density cells/l obsgc obsgc calgc calgc Gcout Gcout 0 /5 /6 /6 /6 3/8 日 Date MM/DD. High growth potential/no extinction. Timing of the bloom

15 Examination of biological factors Growth rate of G. catenatum growth rate /day pper box G.catenatum の増殖速度 上層 /6 /7 /7 /7 3/9 日 Total 増殖速度リン DIP 水温 塩分光強度 Temp & al Light temperature Temperature temperature pper Lower 上層下層 growth rate /day G.catenatum の増殖速度 下層 Lower box /6 /7 /7 /7 3/9 日 Total 増殖速度リン DIP 水温 塩分光強度 Temp & al Light 5 /5 /5 /4 /4 /3 3/4 3/ Temperature is possible

16 Examination of biological/physical factors cells/day pper box /3 /3 /3 3/4 3/4 3/4 4/3 growth mortality swimming diffusion_out- ection_out- diffution_- ection_- sum cells/day Lower box /3 /3 /3 3/4 3/4 3/4 4/ Date MM/DD growth mortality swimming diffusion_out- ection_out- diffusion_- ection_- sum Changing rate day - =flow cells/day/cell densitycells/m 3 /box volumem 3. Physical factors ection and diffusion are deterministic,. Motility swimming is the second effective.

17 Cell density cells/l cell density cells/l Comparison of with/without motility Cell density of G. catenatum G.catenatum の細胞密度 obsgc obsgc calgc calgc Gcout Gcout Flow pattern in winter Inverse estuarine circulation Cooling Abo and Miyamura 005 BOX Warm water Cell density cells/l cell density cells/l 0 /5 /5 /4 /4 /3 3/4 3/4 G.catenatumday の細胞密度 Date MM/DD /5 /5 /4 /4 /3 3/4 3/4 Date MM/DD obsgc obsgc calgc calgc Gcout Gcout BOX Avg velocity ca. 0 m day - < wimming speed of G.catenatum 4.88 m day - Anderson and tolzenbach, 985 Fraga et al. 988, Fermin et al. 996 Ria de igo, pain

18 5.00E3 Examination of motility Without 移流 拡散による細胞の流入と流出 swimming Out In Out In cells/day cells/day cells/day cells/day 4.00E3 3.00E3.00E3.00E3 0.00E00 /5 -.00E3 /6 /6 /7 /7 3/9 3/ E3-3.00E3-4.00E3-5.00E3-6.00E3 5.00E3 4.00E3 3.00E3.00E3.00E3 0.00E00 With swimming 移流に逆らって鉛直移動させたときの移流 拡散による細胞の流入と流出 /5 -.00E3 /6 /6 /7 /7 3/9 3/ E3-3.00E3-4.00E3-5.00E3-6.00E3 gc_difout gc_out gc_difout gc_out gc_difout gc_out gc_difout gc_out pward swimming behavior of Gc plays an important role to decrease the loss of cells from the lower box to out.

19 Conclusions. Temperature is a possible factor to accelerate a growth rate at the time of the bloom.. Physical processes are the most effective to determine the bloom formation/dissipation of G. catenatum in Inokushi Bay. 3. wimming behavior is likely to be important for G. catenatum to maintain their cell density during the period of inverse estuarine circulation.

20 Acknowledgements This study was financially supported by Fisheries Agency of Japan. We thank to Dr. K. Abo for providing physical data, and thanks are also to Dr. K. Miyamura for field data collection.