The Distribution and Fate of Nutrients in Sagami Bay

Kamatani, Akiyoshi; Oku, Osamu; Tsuji, Hisae; Maeda, Masaru; Yamada, Yoshiaki

doi:10.2331/suisan.66.70

Cited by 12 publications

(6 citation statements)

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“…Therefore, diatoms dominate the phytoplankton community in the coastal regions of the Sagami Bay. The results of this study agree with the consideration by Kamatani et al (2000) that the sufficient supply of silicate by the upwelling of sub-surface waters and/or by the riverine waters is favorable for the maintenance of diatom ecosystems in the Sagami Bay. However, in the present study, regardless of the high silicate concentration, the phytoplankton assemblages in phase II, when maximum Chl a concentration was encountered, were dominated by dinoflagellates, Ceratium furca and Ceratium fusus.…”

Section: Discussionsupporting

confidence: 90%

“…The ratios of nutrients supplied to the regions through the upwelling of deep seawaters were approximately 25:15:1 (Si:N:P) (Kamatani et al 1977(Kamatani et al , 2000. Thus, nitrate was the most deficient nutrient during the main growth period of phytoplankton.…”

Section: Discussionmentioning

confidence: 99%

“…The counterclockwise currents along the coast are dominant in the bay, although the circulation patterns change rapidly corresponding to the distribution of the Kuroshio Current (Hirano et al 1977, Iwata 1985. Kamatani et al (2000) reported that the concentrations and ratios of nitrate, phosphate and silicate measured in the middle of the Sagami Bay from 1993 to 1994 were similar to those observed in 1978. Hence, they concluded that the increase in nutrients due to coastal eutrophication is washed out to the open ocean by the presence of strong currents in the bay.…”

Section: Introductionmentioning

confidence: 88%

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Phosphorus limitation of primary productivity during the spring-summer blooms in Sagami Bay, Japan

Fujiki¹,

Toda

Kikuchi³

et al. 2004

Mar. Ecol. Prog. Ser.

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In coastal regions of Sagami Bay, Japan, we examined the nutrient limitations of primary productivity of phytoplankton blooms during spring to summer 2000, using 2 approaches; (1) dissolved nutrient concentrations and ratios, and (2) bioassay experiments. During the study period, maximum concentration of nitrate + nitrite (19.2 µM) and silicate (31.2 µM) were measured on July 10 after heavy rainfalls, where the supplies of nitrate, nitrite and silicate to the coastal regions primarily related to the increase in freshwater discharge by precipitation. However, such relationships were not found regarding the phosphate concentration. Chlorophyll (Chl) a concentration increased after the increase in freshwater discharge and Chl a peaks over 10 mg m -3 were observed 5 times. Phosphate concentration observed at the depth of the 5 Chl a peaks was low enough to indicate probable P limitation based on criteria of nutrient concentrations and ratios. Bioassay experiments were carried out 12 times, every 8 d from May 1 to July 28. Primary productivities following nitrate and silicate additions showed no response compared to the controls. However, phosphate additions in the post-bloom period caused a significant increase in the primary productivity. On May 25, the primary productivity increased 51% relative to the control. These results suggest that phytoplankton productivity was limited by phosphate during the spring-summer blooms, and that phosphate availability in the Sagami Bay is an important factor in the termination of the blooms.KEY WORDS: Bioassay · Coastal ecosystem · Nutrient · P limitation · Phytoplankton bloom · Primary productivity Resale or republication not permitted without written consent of the publisher

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 88%

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Phosphorus limitation of primary productivity during the spring-summer blooms in Sagami Bay, Japan

Fujiki¹,

Toda

Kikuchi³

et al. 2004

Mar. Ecol. Prog. Ser.

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“…Redfield ratio: Si : N : P=16 : 16 : 1) in February-March of each year (Fig. 13, Redfield et al 1963, Brzezinski 1985, Justić et al 1995, Kamatani et al 2000, Ara et al 2011a). In addition, the timing of the first phytoplankton peak followed the dates when SR exceeded ca.…”

Section: Seasonal Variations In Nutrients Chl-a and Phytoplankton Bimentioning

confidence: 92%

Seasonal variability in phytoplankton carbon biomass and primary production, and their contribution to particulate carbon in the neritic area of Sagami Bay, Japan

Ara

Fukuyama

Okutsu

et al. 2019

Plankton Benthos Res

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Seasonal variations in environmental variables, chlorophyll a (Chl-a), particulate carbon and nitrogen (PC and PN, respectively), phytoplankton carbon biomass (Ph-C) and primary production were investigated at a neritic station in Sagami Bay, Kanagawa, from January 2008 to December 2013. Size-fractionated Ph-C was converted from cell volume by microscopic observation, adding valuable data for this area. During spring blooms, the micro-size fraction (>20 µm) comprised the majority of the total Chl-a and total Ph-C, whereas during other periods the pico-and nanosize fraction (<20 µm) comprised a larger proportion, indicating that phytoplankton standing crops were affected by sunlight conditions and physicochemical properties of the water. In February-March, phytoplankton biomass increased and formed the first peak of spring blooms under increasing sunlight intensities (>15.7 MJ m −2 d −1 ), high nutrient concentrations and balanced molar ratios. From the regression equations of size-fractionated Ph-C-Chl-a relationships, the mean Ph-C/Chl-a ratio was 5.3-7.7, 29.2-32.6 and 22.1-25.1 for the <20 µm, >20 µm and total fraction, respectively. The Ph-C/Chl-a ratio (1.8-128.8) was regulated by irradiance and nutrients. Growth rate (ca. 0-3.7 d −1 ) was positively correlated with irradiance and assimilation number, and negatively with the Ph-C/Chl-a ratio. The depth-integrated primary production (DIPP) was 0.15-5.43 g C m −2 d −1 . On the basis of the 0-50 m depth-integrated values, the total Ph-C and DIPP accounted for 1.3-34.4% and 1.3-30.9% d −1 of PC, respectively, indicating that PC variations depended on the total Ph-C and DIPP.

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“…For diatom growth, it is necessary for ambient seawater to maintain both nutrient concentrations higher than the lower limits for growth of the diatoms as well as a balanced molar ratio of the nutrients. In the present study, we assessed single and/or combinations of elements that may serve as a limiting factor for diatom growth at our study site (threshold concentration: DINϭ1 mM, DIPϭ0.1 mM and DSiϭ3 mM, Justić et al 1995, Kamatani et al 2000 and stoichiometric nutrient limitation (nutrient uptake ratio: N : Pϭ16, Si : Pϭ16, Si : Nϭ1, Redfield et al 1963, Brzezinski 1985, Brzezinski & Nelson 1995. As shown for the earlier period (2001)(2002)(2003)(2004)(2005) by Ara & Hiromi (2008), the nutrient-environment background for phytoplankton (diatom) growth at our study site was characterized by no or little N limitation throughout the study period: DIN concentrations were higher than the threshold value on all occasions (0-50 m depth) in winter (December-February) and autumn (October-November) and below the photic zone in spring (March-May), and on 99.6% of occasions in the photic zone in spring (March-May), and 96.7% in the photic zone and 99.0% below the photic zone in summer (June-September) (Fig.…”

Section: Nutrient-environmental Backgroundmentioning

confidence: 99%

Seasonal and year-on-year variability in chlorophyll a and microphytoplankton assemblages for 9 years (2001^|^ndash;2009) in the neritic area of Sagami Bay, Japan

Ara

Fukuyama

Tashiro

et al. 2011

Plankton Benthos Res

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Seasonal and year-on-year variations in physicochemical properties (i.e. temperature, salinity, dissolved inorganic nutrient concentration), chlorophyll a (Chl-a) concentration, Chl-a size composition and abundance of microphytoplankton (Ͼ63 mm) assemblages were investigated at a neritic survey station in Sagami Bay, Kanagawa, Japan, from January 2001 to December 2009. These abiotic/biotic variables varied seasonally in an essentially similar way during the 9 year period. During spring blooms (February-May), the micro-size fraction (Ͼ20 µm) comprised a greater proportion of the total Chl-a, whereas during other periods the pico-and nano-size fraction (Ͻ20 µm) comprised a large portion. Larger diatoms (e.g. Eucampia zodiacus, Coscinodiscus spp.), which dominated the microphytoplankton during the initial-mid stage of spring blooms, were substituted by smaller ones (e.g. Chaetoceros spp., Pseudo-nitzchia pungens, Skeletonema spp.) during the final stage of spring blooms, and then these smaller diatoms continued to be dominant in summer. Dinoflagellates (e.g. Ceratium fusus, C. furca) increased their population densities after the decline of spring diatom blooms, maintained their abundance in spring-summer and became sporadically dominant in the microphytoplankton in summer. The deficiencies in concentration and molar ratio of Si, P and Si-P together in seawater in spring, especially in the photic zone, induce the final stage of spring blooms and lead to the variations in Chl-a concentration, Chl-a size composition and microphytoplankton abundance and species (size) composition. The year-onyear variations in Chl-a and abundance of microphytoplankton assemblages are correlated weakly with the temporal variations in physicochemical properties in relation to water conditions.

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The Distribution and Fate of Nutrients in Sagami Bay

Cited by 12 publications

References 0 publications

Phosphorus limitation of primary productivity during the spring-summer blooms in Sagami Bay, Japan

Phosphorus limitation of primary productivity during the spring-summer blooms in Sagami Bay, Japan

Seasonal variability in phytoplankton carbon biomass and primary production, and their contribution to particulate carbon in the neritic area of Sagami Bay, Japan

Seasonal and year-on-year variability in chlorophyll a and microphytoplankton assemblages for 9 years (2001^|^ndash;2009) in the neritic area of Sagami Bay, Japan

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