LAGUNA 14 1 7 2007 12 LAGUNA 14 p.1 7 2007 1 1 2 3 4 1 Hugo Coops 5 Fossil benthic foraminifera from sediment core S1 of Lake Shinji, western Japan Hiroyuki Takata 1, Kazuyoshi Yamada 1, Kota Katsuki 2, Keiko Yamaguchi 3, Yasushi Miyamoto 4, Daisuke Nakayama 1 and Hugo Coops 5 Abstract: Fossil benthic foraminifera from a sediment core taken from central Lake Shinji, western Japan, were investigated as an indicator of paleoenvironmental change in the Shinjiko-Nakaumi lake system during the 20th century. A transition from dominance of Haplophragmoides canariensis to that of Ammonia beccarii forma 1 occurred in the middle 20th century. This faunal association and its transition are similar to those observed in previous studies of Lake Shinji and the Ohashi River. This faunal transition might be affected by not only environmental change in Lake Shinji but also that in the Ohashi River. Keywords: Lake Shinji, fossil benthic foraminifera, faunal transition in the 20th century 1995 6 20 Haplophragmoides canariensis Ammonia beccarii type 1 1998 1980 A. beccarii Ammonia event COD Nomura 2003 8 cm 10 1 2 3 4 5 Research Center for Coastal Lagoon Environments, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan. Division Earth Environmental Systems, Pusan National University, Pusan 609-735, Korea. Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan. Tottori Prefectural Institute of Public Health and Environmental Science, Tottori 682-0704, Japan. Institute for Inland Water Management and Waste Water Treatment RIZA, P.O.Box 17, 8200 AA Lelystad, Netherlands. 1
2 Hugo Coops 20 1995 1986 ; 1990 2004 210 79 km 2 6.4 m psu 2000 2006 2 S1a S1b 2004 9 1 S1a S1b 21 cm 17 cm 1 S1a S1b 210 S1a 1 cm 3 70 S1b 132 55' 133 00' 133 05' 133 10' 133 15' 133 20' 35 Sakai Strait 34' A Core S1 Hii River Lake Shinji B 0 5 10 15 Ohashi River Lake Nakaumi Ihnashi River Photo Lithology Description black mud Sea of Japan dark grey mud dark grey mud with lamination 1 A S1a, S1b B S1b Fig. 1. A Location of sediment cores S1a and S1b, B Columnar section of core S1b. 35 30' 35 25' X 1 cm S1a 63 μm 500 m 500 µm 63-500 μm 50
S1 3 1 S1b 210 6 Table 1. Pb-210 activity used for age estimation in core S1b depth Pb-210 (total) Pb-214 Pb-210 (excess) (cm) (dpm / g) (dpm / g) (dpm / g) 0.0-3.0 30.73 +/- 0.51 1.65 +/- 0.17 29.07 3.0-6.0 28.89 +/- 0.53 2.12 +/- 0.32 26.75 6.0-9.0 21.83 +/- 0.46 1.89 +/- 0.13 19.92 9.0-11.0 21.16 +/- 0.48 1.60 +/- 0.19 19.54 12.0-15.0 17.35 +/- 0.40 2.23 +/- 0.33 15.10 15.0-17.0 13.97 +/- 0.38 1.83 +/- 0.13 12.12 Sampei et al. 1997 S1a S1b 10 mg 110 1 mol l FISON CHNS E.A. 1108 BBOT 2, 5-bis- 5-tert-butyl-benzoxanzol-2yl -thiophen S1b 210 210 Pb ; 1995 1 6 210 Pb ex 214 Pb 210 Pb 214 Pb S1b 210 1 210 Pb ex 2 S1b 5.18 mm yr 210 Yamamuro and Kanai 2005 46 4 mm yr 3 Pb (ex) (dpm / g) 210 100 3 Mass depth (g / cm ) 0 5 Sedimentation rate: 0.518 (cm / yr) R = 0.98 10 0 5 10 15 20 2 S1b 210 Pb ex Fig. 2. 210 Pb ex activity in core S1b. S1a S1b S1a S1a S1b 3 S1a S1b 8.5 12.5 cm S1a S1b 8.5 11.5 cm 2.5 3.5cm S1a 2.5 8.5 cm S1b 3.5 11.5 12.5 cm S1b S1a 50 S1a 2 14.5 8.5 cm 7.5 5.5 cm Haplophragmoides canariensis d Orbigny Ammonia beccarii Linné forma 1 Miliammina fusca Brady Haynesina sp. 0.5 cm Elphidium somaense, Miliolinella spp., Uvigerinella glabra
4 Hugo Coops 2. S1a Table 2. Occurrence of fossil benthic foraminifera in core S1a 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 Ammonia beccarii (Linne) forma 1 7 5 7 23 38 154 37 8 8 14 Haplophragmoides canariensis (d'orbigny) 2 2 Elphidium excavatum (Terquem) forma selseyensis 1 Haynesina sp. Miliammina fusca (Brady) 3 1 1 1 1 Trochammina hadai Uchio 6 Total 9 8 8 24 46 154 38 8 9 15 Split 2 2 2 2 2 2 2 2 2 2 Sample weight (g) 13.45 17.65 16.64 19.23 17.34 23.46 19.16 21.62 24.40 24.84 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 Ammonia beccarii (Linne) forma 1 7 16 8 2 7 6 5 5 9 3 Haplophragmoides canariensis (d'orbigny) 2 2 12 15 21 30 27 34 Elphidium excavatum (Terquem) forma selseyensis Haynesina sp. 2 2 2 Miliammina fusca (Brady) 1 1 1 3 1 1 Trochammina hadai Uchio Total 7 19 11 3 19 21 29 37 39 40 Split 2 2 2 2 2 2 2 2 2 2 Sample weight (g) 26.70 27.41 27.65 30.15 31.36 29.36 27.94 30.85 38.90 25.46 Core S1B Core S1A Estimated age (AD) Water Total sulfur Water Total sulfur Estimated age (AD) 3 S1a S1b 2 S1b Fig. 3. Change in water and total sulfur of cores S1a and S1b. The sediment cores can be correlated at two horizons based on these indices. The chronology shown here was based on these correlations and the average sedimentation rate of core S1b. Nomura, 2003 S1 0.5 cm 20.5 15.5
S1 5 0 5 10 15 20 0 5 10 15 Ammonia beccarii forma 1 (# / g) 0 1 2 3 4 5 Haplophragmoides canariensis (# / g) ~1990 ~1980 ~1970 ~1960 4 S1a Fig. 4. Stratigraphic change in characteristic benthic foraminifera in core S1a. cm H. canariensis 7.5 4.5 cm A. beccarii forma 1 4 14.5 8.5 cm A. beccarii forma 1 S1a 1995 SI-4, 5 S1b S1a S1 2 S1a H. canariensis 1950 60 1952 1965 A. beccarii forma 1 1980 90 1986 1993 1995 1986 ; 1990 H. canariensis 1933 Ammonia beccarii type 1 A. beccarii forma 1 1980 H. canariensis 1995 1933 A. beccarii forma 1 1995 6 13 20 H. canariensis A. beccarii forma 1 1995 1998 1930 COD 1980 Nomura and Seto, 1992 ; 2000 H. canariensis 2007 2 H. canariensis 1998 1970 20 H. canariensis A. beccarii forma 1 Yamamuro and Kanai 2005 3 1950 1998 Ammonia COD
6 Hugo Coops 1. S1a Plate 1. Scanning electron micrographs of benthic foraminifera from core S1a. Scale bar=100 μm. 1a c. Ammonia beccarii Linné forma 1 2a, b. Haplophragmoides canariensis d Orbigny 3a, b. Haynesina sp. no.16201008 1995 210Pb 137Cs 46: 225 238 1986 5 1985 5: 11 18 Nomura, R. 2003 Assessing the roles of artificial vs. natural impacts on brackish lake environments: southwestern Japan. The Journal of the Geological Society of Japan, 109: 197 214. 1998 5 Ammonia event 2005 LAGUNA 5: 15 26 Nomura, R. and Seto, K. 1992 Benthic foraminifera
S1 7 from brackish Lake Nakaumi, San-in District, southwestern Honshu, Japan. In: Ishizaki, K. and Saito, T. eds., Centenary of Japanese Micropaleontology. Terra Scientific Publishing Company, Tokyo, pp. 227 240. 1995 : 2 1 29: 31 43 Sampei, Y., Matsumoto, E., Kamei, T. and Tokuoka, T. 1997 Sulfur and organic carbon relationship in sediment from coastal brackish lakes in the Shimane peninsula district, southwest Japan. Geochemical Journal, 31: 245 262. 2000 19: 65 76 2006 45: 375 390 2007 2007 220 1990 36: 15 34 Yamamuro, M. and Kanai, Y. 2005 A 200-year record of natural and anthropogenic changes in water quality from coastal lagoon sediments of Lake Shinji, Japan. Chemical Geology, 218: 51 61.