VERIFICATION OF THE PREDICTED SHIFT FROM DIATOMS TO FLAGELLATES IN COASTAL SEAS USING LARGE SCALE MESOCOSM DATA

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1 International Journal of Latest Research in Science and Technology Volume, Issue 1: Page No.11-1, January-February 15 ISSN (Online):7-599 VERIFICATION OF THE PREDICTED SHIFT FROM DIATOMS TO FLAGELLATES IN COASTAL SEAS USING LARGE SCALE MESOCOSM DATA 1 Shigeki Harada, 1 Toshiaki Aoki 1 Department of Environmental Sciences, Miyagi University, Japan Abstract- The shift of dominant species from diatoms to flagellates together with nutrient abundances was predicted and verified using data obtained from large scale mesocosm experiments. The prediction was done using a system dynamics model shown in authors previous study. With common parameters, most of the variables were predicted well. Some important factors such as wind mixing, migration by flaegllates, etc. were pointed out. Keywords Stella, System Dynamics Modeling, Diatom, Flagellates, Shift of Dominant Species, NIES Mesocosm I. INTRODUCTION Species transition with change of silica abundance keeps scientific attention [1]-[7]. According to Harashima [5][], the reduction of silica decides whether a fish or jellyfish to where an energy flow finally excel. The increase in jellyfish is really pointed out []. As for the cause of the increase in jellyfish, there is the indication that a change of the water temperature or the change of the shore environments, also, are related []. However, the importance to assess the effects of silica abundance on species changes still be remaining. Silica supplied conventionally from the forest and varied with the urbanization of the catchment and the construction of the dam. Thus, fundamentally, we have to be more careful to know the effect of silica decrease from catchments to coastal seas. In our previous study [9] we showed potential effects of silica decrease on species changes based on system dynamics (STELLA) modelling. In this study, we compared the modelling results (silica, dissolved inorganic nitrogen, diatom abundances and flagellate abundances) with actual data obtained through NIES (National Institute for Environmental Studies) mesocosm experiments [1][][1]-[13]. In these experiments, the effects of the variations in silica abundances were observed. And we can find discussion on the sift of ecosystems and resulting changes in the food chains. The mesocosm is 5m in diameter and 1 in depth, the huge test tube put up in the sea, suitable site to discuss the relationship between silica decrease and species changes. II. MATERIALS AND THE METHODS Data obtained in the experiments conducted in 199 [1][1][11] and 1991[1][][1][13] were used in this study. The structure of the mesocoms and variations in average concentrations of silica, dissolved inorganic nitrogen, diatom abundances and flagellate abundances in -5m layer are shown in Harada et al. (199) [1]. The reason why we used average concentration of silica, dissolved inorganic nitrogen, diatom abundances and flagellate abundances among -5m layer is the layer was well mixed [1]. The system dynamics model used in this study is mostly same as that shown in Harada & Aoki [9], the slight modifications are done on dissolved inorganic nitrogen flow. Parameters in the model were calibrated using the data obtained in the 1991 experiment and applied to the data obtained in the 199 experiment. Dissolved inorganic phosphorus was not considered in the model, because, phosphorus abundances mostly exceeded general half saturated constant of diatoms and flagellates. III. RESULTS Calibrated parameters are shown in Tab.1. The values are mostly common such as the ones shown in Amano et al. [11]. variations in silica and dissolved inorganic nitrogen agreed with the observed ones, generally (Figs.1-). But increases in silica and dissolved inorganic nitrogen were shown at the latter period in both 199 and 1991 experiments (Figs.1-). The variations in diatom abundances matched well (Figs. 5 & ). However, the variations in flagellate abundances did not match though the average abundances were in the same orders in both years (Figs. 7 & : see DISCUSSION). ISSN:

2 silicate (um) Fig. 1 and silicate in disolved inorganic nitrogen (um) Fig. and dissolved inorganic nitrogen in 1991 ISSN:

3 1 9 7 silicate (um) Fig.3 and silicate in disolved inorganic nitrogen (um) Fig. and dissolved inorganic nitrogen in 199 ISSN:

4 5 diatoms (cells/ml) Fig.5 and diatom abundances in diatoms (cells/ml) 1 1 Fig. and diatom abundances in 199 ISSN:

5 35 flagellates (cells/ml) Fig.7 and flagelaltes abundances in 1991 flagellates (cells/ml) Fig. and flagellates abundances in 199 ISSN:

6 TABLE I CALIBRATED PARAMETERS Parameters diatoms diatoms flagellates silica nitrogen nitrogen Vmax Ks ìmax 1..7 IV. DISCUSSION Factors affecting the increase in silica and dissolved inorganic nitrogen at the later period may be: 1) supply of them from deeper layer by wind mixing and ) supply of them via rapid regeneration within the -5m. The changes of vertical profiles of silica and dissolved inorganic nitrogen in 1991 experiment suggest the importance of the former factor (Figs. 9 & 1). Also Watanabe et al. (1995) indicated that strong wind mixing occurred at the later period in 199 [1]. The latter factor should be analysed more in the next step. Factors affecting the differences in the discrepancy between predicted and observed flagellate abundances may be migration of flagellates. The changes of vertical profiles of flagellates abundances (Figs. 11) indicates that flagellates concentrated at the surface. The meaning of our prediction (Figs. 7 & ) is that we could predict the potential transition from diatoms to flagellates as shown in Harada & Aoki (13) [9] using the common parameters (Tab.1). The real distribution of flagellates should be predicted considering the ability to migrate as shown in Amano et al. (199) [11]. Day Day Day Day Day Day1 Day1 Depth silica (um) Fig.9 vertical profiles of silica in 1991 ISSN:

7 Day Day Day Day Day Day1 Day1 Depth dissolved inorganic nitrogen (um) Fig.1 vertical profiles of dissolved inorganic nitrogen in 1991 Depth Day Day Day Day Day Day1 Day flagellates abundance (cells/ml) Fig.11 vertical profiles of flagellates abundances in 1991 ISSN:

8 V. CONCLUSION AND THE FUTURE WORKS The potential shift of diatoms to flagellates accompanied with the decrease of silica abundance was reproduced with common parameters and verified by the NIES mesocosm data. The prediction should be expanded into the whole layer of the mesocosm and then some other factors such as regeneration of silica and inorganic nitrogen, migration of flagellates will make sense. Furthermore, more precise prediction on the performance of different species such as centric and pennate diatoms should be considered. Also the effects of the changes in zooplankton should be considered by taking into account the changes of loss parameters. ACKNOWLEDGMENT This study was supported by Miyagi University Research Fund. REFERENCES 1. Harada S., Watanabe, M., Kohata, K., Ioriya T., Kunugi, M, Kimura, T., Fujimori, S., Koshikawa, H., Sato, K. Analyses of planktonic ecosystem structure in coastal seas using a large-scale stratified mesocosm: a new approaches to understanding the effects of physical, biochemical and ecological factors on phytoplankton species succession, Wat. Sci. Tech., 3, Harada, S., Koshikawa, H., Watanabe, M., Ioriya, T., Implication for top-down control of phytoplankton species succession within a large coastal mesocosm, J. Global Environ. Eng., 11, Radach, G., Berg, J., Hagmeier, R., Long-term changes of the annual cycles of meteorological, hydrographic, nutrient and phytoplankton time series at Helgoland and at LV ELBE 1 in the German Bight. Continental Shelf Res. 1, 35-3, 199. Humborg, C. Ittekkot, A., Cociasu A, B, von Bodungen, Effect of Danube River Dam on Black Sea biogeochemistry and ecosystem structure, Nature, 7, 35-3, Harashima, A, Kimoto, T. Wakabayashi, T., Toshiyasu, T., Verrification of the silica-deficiency hypothesis based on biogeochemical trends in the Lake Biwa-Yodo River- Seto Inland Sea, Japan, Ambio, 35, 3-,. Harashima, A., Tsuda, R., Tanaka, Y. Kimoto, Y., Tatsuta, H.,Furusawa, K., Monitoring algal blooms and related biogeochemical changes with a flow-through system deployed on ferries in the adjacent seas of Japan. In: Kahru, M. et al. eds. Monitoring Algal Blooms: New Techniques for Detecting Large- Scale Environmental Change, 5-11, Springer New York, Richardson, A. J., A. Bakun, G. C. Hays and M. J. Gibbons, The Jellyfish Joyride: Cause, Consequences and Management Responses to a More Gelatinous Future, Cell Press, Vol., No. 5, pp.31-3, 9 9. Harada, S. and Aoki, T., Prediction of the shift of dominated phytoplankton species from diatoms to flagellates in accordance with decreasing silicate in the surface waters using a system dynamics model, I. J. L. R. S. T., Vol., pp. 7-73, Watanabe, M., Kohata, K., Kimura, T., Takamatsu, T., Yamaguchi, S., Ioriya, T., Generation of a Chattonella antiqua bloom by imposing a shallow nutricline in a mesocosm, Limnol.Oceanogr., Vol., No., pp. 17-1, Amano, K, Watanabe, M., Kohata, K. and Harada, S., Conditions necessary for Chattonella antiqua red tide outbreaks, Limnol.Oceanogr., Vol. 3, No.1, pp , Koshikawa, H., Harada, S., Watanabe, M., Sato, K., Akehata, K., Relative contribution of bacterial and photosynthetic production to metazooplankton as carbon sources, J. Plankton Res., Vol. 1, No. 1, pp.9-1, Koshikawa, H., Harada, S., Watanabe, M., Kogure, K., Ioriya, T., Kohata, K., Kimura, T., Sato, K., Akehata, T., Influence of plankton community structure on the contribution of bacterial production to metazooplankton in a coastal mesocosm, Mer. Ecol. Prog. Ser., Vol. 1, pp.31-, Harashima,A. Evaluating the Effects of Change in Input Ratio of N: P: Si to Coastal Marine Ecosysytem, J. Environmental Sciences for Sustainable Society, Vol. 1, pp.33-3, 7 ISSN: