Periodic Occurrence of Diurnal Signal of ADCP Backscatter Strength in Uchiumi Bay, Japan

Kaneda, Atsushi; Takeoka, Hidetaka; Koizumi, Yoshitsugu

doi:10.1006/ecss.2001.0908

Cited by 15 publications

(6 citation statements)

References 10 publications

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“…Thus, a Kyucho contains scarce amounts of nutrients. Bottom intrusion is deep, cold water that slips through just above the continental shelf (Kaneda et al 2002a,b); this cold water contains a large amount of nitrates, phosphates, and silicates (Koizumi 1991, Koizumi & Kohno 1994, Koizumi et al 1997, Takeoka et al 2000, Kaneda et al 2002a. Koizumi et al (1997) noted that, after an occurrence of bottom intrusion, the cell density of diatoms in Shitaba Bay of the Uwa Sea increased with the use of the supplied nutrients.…”

Section: Introductionmentioning

confidence: 99%

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Katano¹,

Kaneda²,

Takeoka³

et al. 2005

Mar. Ecol. Prog. Ser.

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Uchiumi Bay experiences intermittent physical events of 'Kyucho ' and bottom intrusion.A Kyucho is an intrusion of warm surface water from the Kuroshio in the Pacific Ocean. Bottom intrusion, which contains a large amount of nitrates, phosphates, and silicates, slips through just above the continental shelf. We investigated seasonal changes in the abundance of Prochlorococcus, Synechococcus, and eukaryotic picophytoplankton while monitoring Kyucho and bottom intrusion from March to October 2002. Kyucho and bottom intrusion frequently occurred from June to September. Relatively high concentrations of nitrate + nitrite (> 0.8 µmol N l -1 ) and phosphate (> 0.1 µmol P l -1 ) were found when bottom intrusion occurred. The cell densities of Prochlorococcus were relatively high (>1 × 10 4 cells ml -1 ) when Kyucho occurred. Those of Synechococcus were high (2 to 30 × 10 4 cells ml -1 ) during the period of thermal stratification except in July, when bottom intrusion occurred. The cell densities of eukaryotic picophytoplankton were high (2 to 8 × 10 4 cells ml -1 ) in May and July. To examine the effects on picophytoplankton growth of the nutrients supplied by bottom intrusion, we conducted nutrient-enrichment experiments. The growth rates of Prochlorococcus and Synechococcus were not stimulated by the addition of any kinds of nutrients. The growth rates of Prochlorococcus were negative in most cases. In July, the growth rate of eukaryotic picophytoplankton was stimulated by nitrate and phosphate additions. Thus, Prochlorococcus detected in Uchiumi Bay might have been transported by Kyucho from the Pacific Ocean and could therefore not grow vigorously. Synechococcus may have been flushed out by bottom intrusion, and its growth was not limited by the nutrient concentrations. Eukaryotic picophytoplankton was abundant in spring, and its growth might have been limited by the nutrient concentrations in some cases. These results suggest that Kyucho and bottom intrusion have different effects on the abundance and growth rate of the 3 picophytoplankton groups.

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Section: Introductionmentioning

confidence: 99%

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Katano¹,

Kaneda²,

Takeoka³

et al. 2005

Mar. Ecol. Prog. Ser.

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“…The influence of ambient temperature on the backscatter calculation (Appendix B, Equation B1) was tested and found to be negligible (not shown). Many previous studies have used a similar approach (e.g., Ashjian et al, 2002;Bianchi and Mislan, 2016;Blanc et al, 2008;Chereskin and Tarling, 2007;Kaneda et al, 2002;Liljebladh and Thomasson, 2001;Radenac et al, 2010;Tarling et al, 2001).…”

Section: Acoustic Datamentioning

confidence: 99%

Micronekton distribution in the southwest Pacific (New Caledonia) inferred from shipboard-ADCP backscatter data

Receveur

Kestenare

Allain

et al. 2020

Deep Sea Research Part I: Oceanographic Research Papers

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Acoustic data are invaluable information sources for characterizing the distribution and abundance of midtrophic-level organisms (micronekton). These organisms play a pivotal role in the ecosystem as prey of top predators and as predators of low-trophic-level organisms. Although shipboard-ADCP (acoustic Doppler current profiler) acoustic backscatter signal intensity cannot provide an absolute biomass estimate, it may be a useful proxy to investigate variability in the distribution and relative density of micronekton. This study used acoustic recordings data spread across 19 years (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) from 54 ADCP cruises in New Caledonia's subtropical EEZ (exclusive economic zone) to assess seasonal and interannual variabilities and spatial distribution of micronekton. The dataset was composed of two different ADCPs: 150 kHz for the first period, followed by 75 kHz for more recent years. We examined the 20-120 m averaged scattering layer. Using the few cruises with concurrent EK60 measurements, we proposed that the backscatter from the ADCPs and 70 kHz EK60 were sufficiently closely linked to allow the use of the backscatter signal from the ADCPs in a combined dataset over the full time series. We then designed a GAMM (generalized additive mixed model) model that takes into account the two ADCP devices as well as temporal variability. After accounting for the effect of the devices, we showed that the acoustic signal was mainly driven by diel vertical migration, season, year, and ENSO (El Niño-Southern Oscillation). In a second step, a consensus model between two statistical approaches (GAMM and SVM) (support vector machine) was constructed, linking the nighttime 20-120 m backscatter to the oceanographic and geographic environment. This model showed that sea surface temperature was the main factor driving backscatter variability in the EEZ, with intensified backscatter during the austral summer (December to May) in the northern part of the EEZ. We showed that acoustic density differed significantly, spatially and temporally from micronekton biomass predicted for the same period by the SEAPODYM-MTL (mid-trophic level) ecosystem model. The seasonal cycle given by ADCP data lagged behind the SEAPODYM-MTL Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.seasonal cycle by around three months. Reasons to explain these differences and further needs in observation and modeling were explored in the discussion. In addition to providing new insights for micronekton dynamics in this EEZ (i.e., the science needed for ecosystem-based fisheries management), the data should help improve our ability to model this key trophic component. Highlights► 20 years of ADCP acoustic data give insights on spatiotemporal micronekton dynamics. ► Sea-surface temperature is the main factor driving the backsca...

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“…Kyucho is an intrusion of warm, oligotrophic surface water from the south of the Bungo Channel to the west coast of Shikoku Island (Takeoka & Yoshimura 1988, Takeoka et al 1993. Bottom intrusion consists of deep, cold, nutrient-rich water that flows just over the continental shelf (Takeoka et al 2000, Kaneda et al 2002a, serving as the major nutrient input to the coastal areas (Koizumi 1991, Koizumi & Kohno 1994, Koizumi et al 1997, Takeoka et al 2000. While the effect of Kyucho on phytoplankton growth is negligible, diatom blooms have been observed to be promoted by nutrient inputs by bottom intrusion (Koizumi & Kohno 1994, Koizumi et al 1997.…”

Section: Monthly Monitoring Of Physicochemical and Biological Parametmentioning

confidence: 99%

Effects of nutrient supplies on the growth rates of planktonic bacteria in Uchiumi Bay, Japan

Ichinotsuka¹,

Katano²,

Takeoka³

et al. 2010

Aquat. Biol.

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In the oligo-to mesotrophic waters of Uchiumi Bay, Japan, there is an intermittent physical event which supplies nutrients to the sea: bottom intrusion of deep, cool, nutrient-rich water that slides through just above the continental shelf. To determine the effects of nutrients supplied by this bottom intrusion on bacterial growth, we monitored seasonal changes in bacterial growth rates and conducted nutrient amendment experiments with single or mixed-nutrient additions of N and P. In addition, we examined the importance of organic matter supply for bacterial growth rates using glucose. Bacterioplankton bulk growth rates ranged between 0.37 and 1.86 d -1 , with relatively high growth rates during the period of strong thermal stratification. Neither positive nor negative effects on bacterial growth rates were detected by amendments of nutrients or glucose. A significant positive relationship (p < 0.001) between cell density and production of bacteria was found, though the regression slope of bacterial cell density on bacterial production was relatively low (0.34). Our results suggested that bacterial growth rates in Uchiumi Bay are nearly saturated at ambient levels of nutrients and/or organic matter, and that bacterial abundance is subject to relatively weak bottom-up control.

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Periodic Occurrence of Diurnal Signal of ADCP Backscatter Strength in Uchiumi Bay, Japan

Cited by 15 publications

References 10 publications

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Micronekton distribution in the southwest Pacific (New Caledonia) inferred from shipboard-ADCP backscatter data

Effects of nutrient supplies on the growth rates of planktonic bacteria in Uchiumi Bay, Japan

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Periodic Occurrence of Diurnal Signal of ADCP Backscatter Strength in Uchiumi Bay, Japan

Cited by 15 publications

References 10 publications

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Micronekton distribution in the southwest Pacific (New Caledonia) inferred from shipboard-ADCP backscatter data

Effects of nutrient supplies on the growth rates of planktonic bacteria in Uchiumi Bay, Japan

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Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan

Seasonal changes in the abundance and composition of picophytoplankton in relation to the occurrence of Kyucho and bottom intrusion in Uchiumi Bay, Japan