Blue Tide Research Articles

A practical pCO2 estimation and carbonate dynamics at an event of hypoxic water upwelling in Tokyo Bay

Urban bays have been considered to have a high CO2 absorption function due to the high nutrient load and resultant primary production. It is expected to enhance the function by promoting a blue carbon policy co-beneficial with strengthening ecosystem services such as fisheries. Estimates of CO2 absorption in urban bays have been based mostly on fragmentary information from shipboard observations, and an evaluation based on continuous observation of water quality is necessary considering the large spatiotemporal variability of such bay environment. In particular, Tokyo Bay has a specific feature of water pollution problem of hypoxia and anoxia leading to emitting high CO2. Bottom hypoxic and anoxic waters develop from early summer to autumn in the central part of the bay and enclosed areas such as navigation channels and borrow pits. It is known that pCO2 becomes very high in these waters, and their upwelling (called blue tide in the bay from the discoloration of the sea surface) is thought to cause high CO2 emissions; however, the actual situation is unknown. We developed a practical method for continuous estimation of pCO2 by appropriately combining continuous observation of water quality using sensors and measurements of carbonate parameters by water sampling. The results show that a highly reproducible and practical method for continuous estimation of pCO2 was possible by combining in situ salinity and pH meters and the total alkalinity and calc. pH measured by a total alkalinity titrator for water samples. This method was then applied to the duration of blue tide that occurred in the head of the bay in the summer and autumn of 2021. The pCO2 in the surface water was found to increase significantly and exceed 2000 µatm due to the upwelling of anoxic bottom water containing high pCO2. Mean CO2 emissions of approximately +2150 and +1540 µmol m-2 h-1 were observed at two stations during the upwelling period. The mean values rose to +2390 and +2190 µmol m-2h-1 with the blue tide and lowered to +810 and +1120 µmol m-2 h-1 without it, suggesting that high CO2 emissions may occur due to upwelling, especially with blue tides.

The Mystery of Milky Seas: Scientists are beginning to understand an eerie phenomenon that has bewildered seafarers for centuries.

The Mystery of Milky Seas: Scientists are beginning to understand an eerie phenomenon that has bewildered seafarers for centuries.

An effective process-based modeling approach for predicting hypoxia and blue tide in Tokyo Bay

ABSTRACT Hypoxia and blue tide are the most significant environmental issues in Tokyo Bay as they have been damaging fisheries for a long time. Although studies on modeling these two associated phenomena have been conducted for decades, the scarcity of relevant observational datasets has greatly hindered the progress, and no study has successfully reproduced the entire processes of blue tide or predicted the time and place of its outbreak. To address the problems from limited data, this study proposed a relatively conventional benthic flux model and developed a novel method that converts the total organic carbon content into the fluxes of sediment oxygen consumption and sulfide release to represent the spatial differences in benthic fluxes. A pelagic sulfur model with only three key chemical reactions of blue tide that includes the disproportionation of elemental sulfur was proposed. The method significantly improved the results of dissolved oxygen in bottom water, as seen by the root mean square error decreasing by 15.9% and 18.9% in two simulations with largely different forcings. The sulfur model also accurately predicted the outbreaks of blue tides in each simulation, which is significant to the stakeholders as it facilitates the forecast of blue tides in Tokyo Bay.

Diffusive methane burst during a blue tide, wind-driven event in a meromictic lake

Strong stratification has formed in Lake Abashiri, a typical meromictic lake in Hokkaido, in the subarctic zone in Japan. When the anoxic water of the lower layer is upwelled to the surface by a strong wind, fish and corbicula clams die due to a lack of dissolved oxygen. This event is called as blue tide. It was observed that the dissolved methane in the lake decreased more than 100 t after the blue tide which occurred in 2008. This is the discovery of the phenomenon that a large quantity of methane diffuses to the atmosphere caused by upwelling of anoxic water which contains dissolved methane. We named the event as “methane burst”. It is also the first report that the wind-driven upwelling is reproduced using a numerical analysis code and the methane burst is analyzed. During this blue tide, the methane flux was approximately 170 times greater than usual.

Comparative study of the electrical characteristics of hydrate reservoirs before and after gas hydrate trial production in the Muli permafrost area of the Qilian Mountains, NW China

Natural gas hydrate (NGH) is considered one of the most promising alternative energy sources in the 21st century. The exploitation and decomposition of NGHs could cause geological disasters and eco-environmental problems related to climate warming, seawater blue tides, submarine landslides, drilling platform collapses, slope instability, etc. Thus, an investigation of the eco-environmental effects of NGH exploitation and decomposition has scientific and practical significance. In this paper, the electrical characteristics of NGH reservoirs before and after NGH trial production in the Muli permafrost area of the Qilian Mountains are comparatively examined for the first time. The electrical structure models before and after NGH trial production are obtained through two-dimensional and three-dimensional inversion of the NE audio-magnetotelluric (AMT) sounding profile around production test well SK2. Notably, the electrical structure of the NGH reservoir changes greatly. The research indicates that (1) after NGH trial production, the formation resistivity increases remarkably within 200 m and burial depths in the range of 120– 340 m around the production test well; (2) the main reason for the increasing resistivity after trial production is the Joule-Thomson effect caused by depressurization production and the endothermic effect of NGH decomposition, which lead to the formation of ice-bearing strata; afterwards, we explain the formation process of ice-bearing strata after NGH trial production; and (3) we speculate that the formation stability is not adversely affected after NGH trial production. These findings and research results can provide guidance for subsequent geoenvironmental safety risk assessments of NGH development in permafrost areas.

A Cooperação Sul-Sul no Mercosul

The United Nations (UN) recognized the interconnection between the development of South-South Cooperation (SSC) and the multiplication of regional integration mechanisms, mainly in Latin America and the Caribbean, since the first decade of the 21st century (A/66/229). In South America, this context coincided with the coming to power of progressive governments in several countries, which established SSC and Latin American regional integration as priorities in their foreign policy guidelines, with emphasis on the role of Mercosur. Although international cooperation has been present in Mercosur since its inception, it is in this political context that became known as the pink wave (2003-2015) that SSC became a priority within the bloc. This process led to the gradual institutionalization of SSC in Mercosur with the establishment, in 2008, of the High Level Group for the elaboration of a South-South Cooperation Program, whose mission was to elaborate the conceptual, methodological and operational bases of a program of cooperation in strategic sectors; in 2012 from the International Cooperation Group (GCI) to coordinate Mercosur's technical cooperation; in 2014, of the new International Cooperation Policy and; in 2018, of the Strategy on Cooperation in Mercosur for the period 2018-2021. However, this context has changed and, more recently, both phenomena in the region have lost priority in the political agenda of shift governments, without, however, being extinguished by the blue tide. This work aims to discuss the potentialities and limitations of SSC as a means for autonomous regional integration in Latin America, in this context of celebration of Mercosur's 30th anniversary.

Satellites Allow Scientists to Dive into Milky Seas

Satellites may finally be able to report the fleeting phenomena of milky seas in near-real time, allowing researchers to potentially study an ocean mystery that has survived more than 2 centuries.

Phytoplankton species abundance in Tokyo Bay (Japan) from 1998 to 2019

AbstractTokyo Bay is a semienclosed coastal system located in the center of Japan. Eutrophication has progressed since 1950, resulting in red tides and blue tides appearing frequently. This Data Paper reports the abundance of phytoplankton species sampled monthly from April 1998 to March 2019 at 17 stations in Tokyo Bay. Monitoring has been carried out by Chiba Prefectural Government. Phytoplankters were enumerated by microscopy as numbers of cells or colonies. The abundance of each species was expressed as cells per milliliter of seawater. The total cell density ranged from 102 to 106 cells·ml−1. The dominant taxa were diatoms, such as Chaetoceros spp., Skeletonema spp., and Thalassiosira spp. in most of the months. The dominant diatom species reached concentrations of 106 cells·ml−1. Microflagellates or Cryptomonadaceae were also abundant, especially in winter, reaching 106 cells·ml−1. These data can be used to appreciate how anthropogenic disturbances such as eutrophication and global warming affect the density and community composition of phytoplankton. The detailed Metadata for this abstract published in the Data Paper section of the journal is available in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2021-03.1/jalter-en.

Honing in on bioluminescent milky seas from space

Milky seas are a rare form of marine bioluminescence where the nocturnal ocean surface produces a widespread, uniform and steady whitish glow. Mariners have compared their appearance to a daylit snowfield that extends to all horizons. Encountered most often in remote waters of the northwest Indian Ocean and the Maritime Continent, milky seas have eluded rigorous scientific inquiry, and thus little is known about their composition, formation mechanism, and role within the marine ecosystem. The Day/Night Band (DNB), a new-generation spaceborne low-light imager, holds potential to detect milky seas, but the capability has yet to be demonstrated. Here, we show initial examples of DNB-detected milky seas based on a multi-year (2012–2021) search. The massive bodies of glowing ocean, sometimes exceeding 100,000 km2 in size, persist for days to weeks, drift within doldrums amidst the prevailing sea surface currents, and align with narrow ranges of sea surface temperature and biomass in a way that suggests water mass isolation. These findings show how spaceborne assets can now help guide research vessels toward active milky seas to learn more about them.

Shear Stress‐Responsive Polymersome Nanoreactors Inspired by the Marine Bioluminescence of Dinoflagellates

AbstractSome marine plankton called dinoflagellates emit light in response to the movement of surrounding water, resulting in a phenomenon called milky seas or sea sparkle. The underlying concept, a shear‐stress induced permeabilisation of biocatalytic reaction compartments, is transferred to polymer‐based nanoreactors. Amphiphilic block copolymers that carry nucleobases in their hydrophobic block are self‐assembled into polymersomes. The membrane of the vesicles can be transiently switched between an impermeable and a semipermeable state by shear forces occurring in flow or during turbulent mixing of polymersome dispersions. Nucleobase pairs in the hydrophobic leaflet separate when mechanical force is applied, exposing their hydrogen bonding motifs and therefore making the membrane less hydrophobic and more permeable for water soluble compounds. This polarity switch is used to release payload of the polymersomes on demand, and to activate biocatalytic reactions in the interior of the polymersomes.

Shear Stress-Responsive Polymersome Nanoreactors Inspired by the Marine Bioluminescence of Dinoflagellates.

Some marine plankton called dinoflagellates emit light in response to the movement of surrounding water, resulting in a phenomenon called milky seas or sea sparkle. The underlying concept, a shear‐stress induced permeabilisation of biocatalytic reaction compartments, is transferred to polymer‐based nanoreactors. Amphiphilic block copolymers that carry nucleobases in their hydrophobic block are self‐assembled into polymersomes. The membrane of the vesicles can be transiently switched between an impermeable and a semipermeable state by shear forces occurring in flow or during turbulent mixing of polymersome dispersions. Nucleobase pairs in the hydrophobic leaflet separate when mechanical force is applied, exposing their hydrogen bonding motifs and therefore making the membrane less hydrophobic and more permeable for water soluble compounds. This polarity switch is used to release payload of the polymersomes on demand, and to activate biocatalytic reactions in the interior of the polymersomes.

Puzathaer and Churning of the Milky Sea: Origins in Austronesian Southeast Asia

The similarities in Austronesian Puzathaer and Indian Churning of the Milky Sea point to a common source whether in South Asia or Southeast Asia. The paper argues the origin of both tales is in Southeast Asia, particularly Austronesian Southeast Asia. The arguments include linguistic, archaeological, historical, ethnological data and chronological precedence as evidence in favor of an Austronesian origin. The various details of the Indian tale provide clues as to its provenance. It is further argued that the Churning of the Milky Sea is a documentation of contact and growing trade between the two regions. The linguistic evidence further shows the impact of trading and seafaring activities of Austronesians on the civilization of India. The paper moreover ties Austronesians in Southern China, South Asia and Southeast Asia. Both tales have religious connotations albeit in a different context. Puzathaer is connected to ancestor worship whereas Churning of the Milky Sea is more philosophical.

An estimation method for blue tide distribution in Tokyo Bay based on sulfur concentrations using Geostationary Ocean Color Imager (GOCI)

Blue tide, which occurs in eutrophic semi-enclosed bays, is recognized as an important environmental problem because it causes mass mortality of fish and shellfish. In Tokyo Bay, which is a typical eutrophic semi-enclosed bay in Japan, fishery damage due to blue tide is frequently reported. Continuous monitoring is needed for effective water environment management and conservation because blue tides can be too short in duration to observe in the course of field observations. The aim of this study is to develop a model for estimating the distribution of blue tide based on sulfur concentration, which is a key element associated with blue tide. Using real-time data from the Geostationary Ocean Color Imager (GOCI) to estimate sulfur concentrations, we can clearly identify the spatial distributions of blue tides. We developed an empirical model using in situ measurement of sulfur and remote sensing reflectance to obtain sulfur concentration (R2 = 0.851). The developed model was applied to GOCI images acquired shortly after field observations during a blue tide on 24 August 2015 in Tokyo Bay in order to validate the accuracy of the sulfur estimation. Estimated and measured sulfur concentration showed less difference when the time between the start of field observations and GOCI image capture was comparatively small (R2 = 0.704). Further, the blue tide distributions could be estimated by applying the developed model to other images acquired during blue tide occurrences at other dates and years. In conclusion, spatial distributions of blue tide in Tokyo Bay can be adequately estimated based on sulfur concentration determined from GOCI images.

Complete Genome Sequences of Two Bioluminescent Vibrio campbellii Strains Isolated from Biofouling Communities in the Bay of Bengal.

ABSTRACTVibrio campbellii is a pathogen of aquatic animals and has been proposed as a bacterial partner in the formation of bioluminescent milky seas. We present here the complete genome sequences assembled from Illumina and Oxford Nanopore data for two bioluminescent Vibrio campbellii strains (BoB-53 and BoB-90) isolated from biofouled moorings in the Bay of Bengal.

Applying a Simple Analytical Solution to Modelling Wind-Driven Coastal Upwelling of Two-Layered Fluid at the Head of Tokyo Bay, Japan

Blue tides at the head of Tokyo Bay are a hydro-environmental phenomenon where seawater appears to be milky blue because of the reflection of the sunlight off surface water containing large amounts of sulphur particles. Its appearance is due to the coastal upwelling of bottom oxygen-depleted water induced by northeasterly wind-driven circulation. Blue tides cause the death of many shellfish and other aquatic animals across the head of Tokyo Bay and consequently result in substantial economic losses to coastal fisheries. This paper examines the occurrence of wind-driven blue tides in Tokyo Bay, based on a simplified hydrodynamic model and observational analysis. The model assumed a two-layer structure with a wind-driven upper layer and an oxygen-depleted lower layer. In this study, we derived a simple analytical solution to determine a critical wind condition for which the lower layer outcrops at the surface if the wind forcing is sufficiently strong, resulting in the mixing of the two layers and giving rise to blue tide. The results of sensitivity analyses of the analytical solution to all incorporated factors were found to be in accordance with a qualitative understanding of the blue tide phenomenon. More importantly, comparisons of observational data with real cases of blue tide during 1978–2016 and without blue tide during 2003–2016 suggested that this analytical solution was mostly valid. This study would be helpful for gaining a better understanding of the hydro-dynamical mechanism of blue tide.

A study on the transfer of blue tide and the relationship between high turbidity and sulfur in Tokyo Bay

A study on the transfer of blue tide and the relationship between high turbidity and sulfur in Tokyo Bay

Outline of the Large-scale Blue Tide Occurred at the Inner Part of Tokyo Bay in June 2017 and the Situation of Satellite Data Acquisition

Outline of the Large-scale Blue Tide Occurred at the Inner Part of Tokyo Bay in June 2017 and the Situation of Satellite Data Acquisition

A novel Vibrio beta-glucosidase (LamN) that hydrolyzes the algal storage polysaccharide laminarin.

The metabolic versatility, tractability and rapid growth potential of the Vibrio spp. have made them increasingly attractive systems for investigating carbon cycling in the marine environment. In this study, an in silico subtractive proteomic strategy was used to identify a novel 101 kDa GH3 family β-glucosidase (LamN) that was found in bioluminescent Vibrio campbellii strains capable of utilizing the algal storage glucan laminarin. A heterologous overexpression system verified the sequence-predicted function of LamN as it enabled the growth of Escherichia coli on laminarin as a sole carbon source. Quantitative reverse transcription PCR analyses revealed that V. campbellii grown on laminarin demonstrated a 4- to 314-fold induction of lamN gene expression when compared to the same strains grown on glucose or glycerol. Corresponding tandem mass spectrometric analyses detected LamN protein expression only in cells grown on laminarin. Heterologous expression, purification and biochemical characterization identified LamN as a heat stable laminarinase with β-1,3, β-1,4 and β-1,6 glucosidase activity. Collectively, these data identify an enzyme that may allow V. campbellii to exploit some of the most abundant polysaccharides associated with deteriorating phytoplankton blooms and provide support for the potential involvement of V. campbellii in the formation of bioluminescent milky seas.

Granulated Coal Ash – used Method for Remediation of Organic Matter Enriched Coastal Sediments

Fukuyama inner harbor is an enclosed bay located in the western Seto Inland Sea of Japan. This area has many serious problems, such as outbreak of malodorous gas, raw scum, eutrophication and blue tide. The purpose of this study is to propose a valuable method for remediation of organic matter enriched coastal sediments using granulated coal ash (GCA) for the restoration of water environment in the bay. Field experiments were carried out to evaluate the suppression of nutrients, malodorous gas, and raw scum by GCA, as well as to understand the restoration of biological environment. Covering layer of GCA on the sea bottom sediment of the harbor was constructed by a crane ship. Three experimental sites (each 1800m2) were constructed with different GCA layers (70cm, 50cm, and 30cm) and a control site was established. The improvement effects of covering layer made by GCA were evaluated by field observations. The number of outbreak of raw scum on the water surface decreased after covering GCA on the bottom sediment. It was also confirmed that the concentration of malodorous components gas of the experimental sites was lower than that of the control site. These suggest that GCA has a capability to reduce the malodorous components and raw scum. From our findings, it can be concluded that GCA covering work is valuable for improving water and sediment environments in the bay. And it provides an effect method to mitigate the organic matter enriched coastal sediment problems.

Numerical Simulation and Remote Sensing for the Analysis of Blue Tide Distribution in Tokyo Bay in September 2012

Numerical Simulation and Remote Sensing for the Analysis of Blue Tide Distribution in Tokyo Bay in September 2012