Nutrient status of Otsuchi Bay (northeastern Japan) following the 2011 off the Pacific coast of Tohoku Earthquake

Fukuda, Hideki; Katayama, Ryosuke; Yang, Yanhui; Takasu, Hiroyuki; Nishibe, Yuichiro; Tsuda, Atsushi; Nagata, Toshi

doi:10.1007/s10872-015-0296-2

Cited by 31 publications

(25 citation statements)

References 37 publications

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“…Approximately 55% of the freshwater entering the bay comes from the Unosumai River, with 30 and 15% freshwater coming from the Otsuchi and Kozuchi Rivers, respectively (Anbo et al, 2005). Water exchange between the bay and coastal ocean is rapid, with water residence time within the bay estimated to be on the order of a week to a month based on the residual current (3-5 cm s −1 ; Otobe et al, 2009) and the physical dimensions of the bay (length 7 km; wide 2-4 km; Fukuda et al, 2015). Water circulation changes on a seasonal basis in Otsuchi Bay.…”

Section: Study Area and Sampling Overviewmentioning

confidence: 99%

“…The density current is affected by river discharge, tide-induced residual current and seasonal changes in wind (Otobe et al, 2009). Fukuda et al (2015) recently investigated nutrient dynamics in the water column following the 2011 Tohoku earthquake and noticed 3 distinct periods: (1) a stratified period (stratification between Tsugaru current with high salinity and river water: May-September), (2) a mixing period (October-January), and (3) an Oyashio current intrusion period (low salinity and low temperature: February-April).…”

Section: Study Area and Sampling Overviewmentioning

confidence: 99%

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Sources and Transformations of Dissolved Lignin Phenols and Chromophoric Dissolved Organic Matter in Otsuchi Bay, Japan

Benner

Fichot

et al. 2016

Front. Mar. Sci.

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Dissolved lignin phenols and optical properties of dissolved organic matter (DOM) were measured to investigate the sources and transformations of terrigenous DOM (tDOM) in Otsuchi Bay, Japan. Three rivers discharge into the bay, and relatively high values of syringyl:vanillyl phenols (0.73 ± 0.07) and cinnamyl:vanillyl phenols (0.33 ± 0.10) indicated large contributions of non-woody angiosperm tissues to lignin and tDOM. The physical mixing of river and seawater played an important role in controlling the concentrations and distributions of lignin phenols and chromophoric DOM (CDOM) optical properties in the bay. Lignin phenol concentrations and the CDOM absorption coefficient at 350 nm, a(350), were strongly correlated in river and bay waters. Measurements of lignin phenols and CDOM in bay waters indicated a variety of photochemical and biological transformations of tDOM, including oxidation reactions, photobleaching and a decrease in molecular weight. Photodegradation and biodegradation of lignin and CDOM were investigated in decomposition experiments with river water and native microbial assemblages exposed to natural sunlight or kept in the dark. There was a rapid and substantial removal of lignin phenols and CDOM during the first few days in the light treatment, indicating transformations of tDOM and CDOM can occur soon after discharge of buoyant river water into the bay. The removal of lignin phenols was slightly greater in the dark (34%) than in the light (30%) during the remaining 59 days of the incubation. Comparison of the light and dark treatments indicated biodegradation was responsible for 67% of total lignin phenols removal during the 62-day incubation exposed to natural sunlight, indicating biodegradation is a dominant removal process in Otsuchi Bay.

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Section: Study Area and Sampling Overviewmentioning

confidence: 99%

Section: Study Area and Sampling Overviewmentioning

confidence: 99%

Sources and Transformations of Dissolved Lignin Phenols and Chromophoric Dissolved Organic Matter in Otsuchi Bay, Japan

Benner

Fichot

et al. 2016

Front. Mar. Sci.

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“…Water samples for nutrient analysis were collected in acid-cleaned polypropylene tubes and stored at −20°C for further analysis. Ammonia, nitrate, nitrite, phosphate, and silicate concentrations were determined by an autoanalyzer (AACS II or AACS III; Bran+Luebbe, Germany) as previously described ( Fukuda et al, 2016 ). Particulate organic carbon (POC) and nitrogen (PON) were determined as previously described ( Miyajima et al, 1998 ).…”

Section: Methodsmentioning

confidence: 99%

Distribution of Dimethylsulfoniopropionate Degradation Genes Reflects Strong Water Current Dependencies in the Sanriku Coastal Region in Japan: From Mesocosm to Field Study

et al. 2020

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Dimethyl sulfide (DMS) is an important component of the global sulfur cycle as it is the most abundant sulfur compound that is emitted via the ocean surface to the atmosphere. Dimethylsulfoniopropionate (DMSP), the precursor of DMS, is mainly produced by phytoplankton and is degraded by marine bacteria. To reveal the role of bacteria in the regulation of DMSP degradation and DMS production, mesocosm and field studies were performed in the Sanriku Coast on the Pacific Ocean in northeast Japan. The responsible bacteria for the transformation of DMSP to DMS and the assimilation of DMSP were monitored, and the genes encoding DMSP lyase ( dddD and dddP ) and DMSP demethylase ( dmdA ) were analyzed. The mesocosm study showed that the dmdA subclade D was the dominant DMSP degradation gene in the free-living (FL) and particle-associated (PA) fractions. The dddD gene was found in higher abundance than the dddP gene in all the tested samples. Most importantly, DMS concentration was positively correlated with the abundance of the dddD gene. These results indicated that bacteria possessing dmdA and dddD genes were the major contributors to the DMSP degradation and DMS production, respectively. The genes dmdA subclade D and dddP were abundant in the Tsugaru Warm (TW) Current, while the dmdA subclade C/2 and dddD genes were dominant in the Oyashio (OY) Current. Functional gene network analysis also showed that the DMSP degradation genes were divided into OY and TW Current-related modules, and genes sharing similar functions were clustered in the same module. Our data suggest that environmental fluctuations resulted in habitat filtering and niche partitioning of bacteria possessing DMSP degradation genes. Overall, our findings provide novel insights into the distribution and abundance of DMSP degradation genes in a coastal region with different water current systems.

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“…1a). In this region, coastal currents, such as the Tsugaru Warm Current and Oyashio Current, affect the physical and biogeochemical environment of the coastal embayment (e.g., Fukuda et al 2016; Ishizu et al 2017). Notably, the Oyashio Current supplies large amounts of offshore nutrients to the coastal embayment (e.g., Furuya et al 1993; Sawada and Hayakawa 1997).…”

Section: Figurementioning

confidence: 99%

Nutrient fluxes from rivers, groundwater, and the ocean into the coastal embayment along the Sanriku ria coast, Japan

Nakajima

Sugimoto

Kusunoki

et al. 2021

Limnology & Oceanography

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External nutrient supply from the land and ocean is crucial for sustaining high primary productivity in coastal seas. Submarine groundwater discharge (SGD) is recognized as one of the most important sources of terrestrial nutrients. However, the relative importance of SGD-derived nutrients from different sources in coastal ecosystems controlled by offshore exchange has not been well quantified. Here, we assessed water and nutrient budgets in the semi-enclosed bay along the Sanriku ria coast, where the intrusion of nutrient-enriched oceanic water is substantial. We conducted seasonal sampling campaigns and monitored the groundwater level throughout the year. Water and nutrient fluxes from fresh groundwater, saline groundwater, river water, and oceanic water were estimated using a hydrological method and radium (Ra) mass balance model. The results indicated that oceanic water was a dominant source, accounting for 99.5%, 86%, 97%, and 84% of the total influx of water, dissolved inorganic nitrogen, dissolved inorganic phosphorus, and dissolved silica, respectively. Although the mean fluxes of land-derived nutrients were small, the contribution increased to 28-59% in October, when nutrient fluxes of oceanic water weakened. Of the terrestrial sources, SGD dominated (41-94%), particularly saline SGD (>99% of total SGD). We concluded that an efficient supply of the primary limiting nutrient from land to the coastal ecosystem can accelerate coastal primary production during certain seasons, even if oceanic nutrients are typically the dominant source.Coastal seas are among the most productive regions of the Earth's biosphere, wherein land and ocean physical and biogeochemical processes interact (Jickells 1998). The external supply of nutrients is essential for sustaining the high primary productivity of coastal seas. Offshore seawater serves as a significant nutrient source in coastal seas (Kobayashi and Fujiwara 2008;Sugimoto et al. 2016). The magnitude and timing of oceanic nutrient flux is greatly influenced by physical processes, such as the movement of ocean current paths (e.g., Yoder et al. 1981;Sugimoto et al. 2009), wind intensity (e.g., Graham and Largier 1997;Carstensen and Conley 2004), and river discharge (e.g., Schubel and Pritchard 1986;Watanabe et al. 2017). Nutrient inputs from land via rivers and groundwater can also fertilize coastal ecosystems (Valiela et al. 1990).

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Nutrient status of Otsuchi Bay (northeastern Japan) following the 2011 off the Pacific coast of Tohoku Earthquake

Cited by 31 publications

References 37 publications

Sources and Transformations of Dissolved Lignin Phenols and Chromophoric Dissolved Organic Matter in Otsuchi Bay, Japan

Sources and Transformations of Dissolved Lignin Phenols and Chromophoric Dissolved Organic Matter in Otsuchi Bay, Japan

Distribution of Dimethylsulfoniopropionate Degradation Genes Reflects Strong Water Current Dependencies in the Sanriku Coastal Region in Japan: From Mesocosm to Field Study

Nutrient fluxes from rivers, groundwater, and the ocean into the coastal embayment along the Sanriku ria coast, Japan

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