Biogeochemical Methods Research Articles

Problems and Prospects of Botanical Methods of Mineral Exploration with Reference to India - an Appraisal

The present report attempts to evaluate the existing literature with regard to geobotanical and biogeochemical methods of investigation for mineral prospecting. The emphasis is laid o.i the validity of grouping of indicator plants into 'Universal' and 'Local' in the light of their limitations in application value. The report also stresses the essentiality of biosystematic studies prior to making any new reports from any mineralized areas. This suggestion is made taking in view the prevailing opinions on the evolution and adaptation of indicator plants. Moreover, few notable indicator species are now recognised as only ecotypes of the related species growing on unmineralised areas. A compilation of indicator plants is made and the scope of utilisation and profitable exploitation of these taxa is discussed. A few important aspects of biogeochemistry are also given which are necessary in systematic and effective orientation surveys. It was felt that instead of taking up this subject in the established line, the analysis of herbarium material, procured from different herbaria of the country would be of great use for a quick tracing and assessment of mineral rich areas in the country.

Identification of potential marker bacteria with metagenome data in boron mine detection

Mining exploration programmes are being expensive and risky due to the limitations of conventional prospecting methods in identifying desired mineralisation. Worldwide, mining exploration programmes have a success rate of approximately 0.7%. Bio-geochemical methods, a sub-branch of geochemical prospecting, are used to identify potential mineralisation areas by studying the distribution of plants containing certain metals. Turkey's leading position in the world in terms of boron reserves increases the strategic importance of boron. On the other hand, metagenome analysis is an important tool in scientific research for detecting microorganisms. Our study aims to develop a cost-effective and efficient biological alternative method for detecting boron mines. Metagenome analysis output showed correlation with the presence of Calothrix sp. NIES-3974, Snodgrassella alvi, Xanthomonas citri, X. citri pv. Fuscans, Pseudomonas viciae, and Aphanothecaceae bacteria and detecting of the potential boron traces in soil. Modelling studies were also conducted on aquaporin z protein, related to the boron uptake, that can be used for utilising from boron detection.

REVIEW OF IDENTIFIED SHORTCOMINGS IN AQUIFER VULNERABILITY ASSESSMENTS

Several studies have successfully carried out aquifer vulnerability evaluations using a combination of geophysical and biogeochemical methods. Unfortunately, some identified shortcomings have often led to inaccurate assessments. This review attempts to identify some of these drawbacks and suggest better ways to improve upon analysis and interpretation of results. Articles reviewed were sourced publicly and subjected to systematic analysis based on fundamental principles. The outcomes of each analysis were discussed, among which was a study that applied Ohmega Resistivity meter to acquire Self-Potential (SP) data without specifying the nature of electrode used. The result indicated large SP readings ≥200mV attributed to high fluid flow. According to analysis, when copper stakes are used, spurious SP readings occur in contrast to lower SP values of roughly 10 mV when suitable non-polarizable electrodes of Cu/CuSO4 porous pots are utilized to collect SP data. The review made clear the importance of providing detailed explanation of the nature of materials used. Another study solely collected samples for groundwater quality assessments during dry season, ignoring the effects of seasonal variation on water parameters. This must have had an impact on the results of the investigations. Research examined the aquifer problems in Gosa area of Abuja, utilizing only the Vertical Electrical Sounding (VES) technique. The study suggested basaltic intrusion as probable cause of borehole failures in the area. A different research which incorporated VES and data from the hill-shaded Shuttle Radar Topography Mission (SRTM), suggested insufficient interconnectivity within the fractures as conditions controlling groundwater occurrence in the area. The study illustrated the need for integrating geophysical methods for effective target detection. To map the infiltration of leachate into the subsurface, a study applied only the VES technique. Studies, however, showed that the VES method only provided average resistivity readings, suppressing some features. The study suggested the combination of VES and 2-D imaging for more accurate results. Another study obtained data via the ADMT Groundwater Detector. At the interpretation stage, the author interpreted ADMT data as VES, which was perceived as inaccurate as their principles and methodologies are different. Another study was noted to have presented results without categorizing the Aquifer Protective Capacity (APC) rating in percentages (%). It was assessed that a framework that accurately categorized the APC of each transversal using common statistics guidelines would have made it simpler to understand and aided decision-making. Future research is advised to take some of the noted flaws into account in order to enhance data processing and interpretation.

Assessment of Nutrient Contents in River Waters Introduced to Beni Haroun Dam, North East Algeria

The main objective of this study was to assess the hydrochemical water quality of the rivers that flowed into the Beni Haroun dam by integrating the use of biogeochemical and multivariate statistical investigation methods. Water samples were collected from the four principal rivers (Oued Rhumel, Oued Radjas, Oued Kebir and Oued El-Kotone rivers) flowing into the Beni Haroun dam in February 2020. Essential physical parameters (pH, Electric Conductivity (EC), Total Dissolved Solids (TDS) and Dissolved Oxygen (O2)) and nutrient contents (dissolved inorganic nitrogen (DIN: NH4, NO3 and NO2), phosphate (PO4) and silicates (SiO4) were analysed. The results of our study showed important variations in physical parameters according to the characteristics of each river; additionally, SiO2, NO3 and NO2 were found to be highly abundant in Oued Rhumel, Oued Radjas and Oued El-Kotone rivers. This abundance could be explained by the fact that these three rivers were more exposed to anthropogenic pollution principally due to agricultural activities compared to the Oued Kebir river. In contrast, NH4, as well as phosphate (PO4), was present at high concentrations in both Oued Rhumel and Oued Radjas rivers. These biogeochemical conditions would have severe impacts on the functioning and productivity of aquatic systems.

ANALYSIS OF ECOLOGICAL AND GEOCHEMICAL INDICES FOR PLANTS OF THE SPECIES POTENTILLA TANACETIFOLIA GROWING IN THE CONDITIONS OF THE CITY OF CHITA AND THE CHITA REGION

The use of biogeochemical research methods is necessary when studying the technogenic migration of toxic elements in urban ecosystems. Using the values of the ecological and geochemical indices, we assessed the degree of accumulation and movement of zinc, lead, cadmium, and copper from the soil to the organs of plants of the species Potentilla tanacetifolia. The content of elements was determined by the method of inverse voltammetry on a «TA-Universal» analyzer. According to the results of the studies and the values of environmental and geochemical coefficients, it was found that, according to the level of soil pollution, the studied areas of the city of Chita and the Chita region were classified as territories with a low level of pollution. According to the values of ecological and geochemical indices for plants of the P. tanacetifolia species, intense absorption of cadmium by the root system and active movement of zinc and copper from the root layer of soils were noted. The translocation coefficient (TF) values indicated the intake of copper, lead, and cadmium into the aboveground organs in almost all the studied sites. According to the value of the discrimination coefficient, it was found that this species intensively accumulates cadmium. The results presented by us indicate that plants of the P. tanacetifolia species can be attributed to accumulator species with a rather high degree of accumulation of heavy metals at a low concentration in the medium.

Olympia oyster, Ostrea lurida, in Puget Sound: stable isotope shell profiles as potential indicators of a changing climate

There is a need to monitor environmental changes in situ across aquatic ecosystems. Sclerochronology, a systematic biogeochemical method that assesses variations in the accretionary hard tissues of invertebrates, can be useful in studying these changes. Further studies are needed to evaluate whether an equilibrium relationship exists between seasonal annual temperature variations in bivalve shells of species with multiple geographic ranges. We present one of the first sclerochronology reports to characterize the δ18O and δ13C shell profiles of the Olympia oyster, Ostrea lurida Carpenter, 1864. We evaluated its utility as a proxy for past water temperature relating to seasonal cycles. The objectives were to: (1) assess shell δ18O and δ13C values from specimens sampled over time; and (2) evaluate whether δ18O shell profiles correlate with seasonal temperature patterns. Seven O. lurida specimens were collected, and measurements were taken across shell growth. Results from generalized linear mixed models (GLMM) showed that O. lurida produced δ18O profiles consistent with a sinusoidal time pattern. The δ18O values ranged from –2.74‰ to –1.05‰, and there was a significant third-order polynomial temporal relationship. Covariation between profiles of shell δ18O and δ13C values was observed over time. Two independently estimated measures of δ18Owater, accounting for salinity, temperature, and shell carbonate, were also positively correlated over time. Implications support the theory that O. lurida shell δ18O profiles may be in isotopic equilibrium with ambient water conditions with applications for monitoring programs.

A new radiolarian transfer function for the Pacific Ocean and application to fossil records: Assessing potential and limitations for the last glacial-interglacial cycle

Abstract Climatic and oceanographic processes in the Pacific Ocean have global implications. Reliable sedimentary proxies in this region are thus necessary to understand the magnitude of past climate variability. Radiolarian assemblages are of particular relevance in some regions of the Pacific Ocean where other proxies are either poorly preserved or are biased towards a specific season. Previously published radiolarian-based transfer functions in the Pacific Ocean did not cover some regions, such as the Western Pacific marginal seas or high-latitude Southwestern Pacific. Filling these gaps in sample distribution and using a thorough methodology for finding the most important variable for radiolarian assemblages in surface sediment are both essential steps in quantitative studies. In this study, we use published radiolarian census counts from 801 core-tops distributed across the Pacific Ocean, to investigate which environmental factors drive the assemblages. We harmonized taxonomically the modern microfossil dataset, and using multivariate statistical analyses, we determined that sea surface temperature at 10 m (SST10) is the most important variable influencing the changes observed in the radiolarian assemblages. The calibration method weighted-mean modern analogue technique with five analogs (WMAT-K5) corrected for autocorrelation using a cut-off distance of 500 km, showed a performance of R2cv = 0.83; RMSEP = 3.8 °C. This calibration method was then applied to taxonomically harmonized radiolarian census counts from 31 cores located in the Bering Sea, Western Pacific marginal seas, and Southwest and Eastern Equatorial Pacific, with some of these records covering at least the last 165 ka. We assessed the analogue quality and significance of the downcore SST10 reconstructions in all of them. We found that temperatures at 10 and 200 m were the most significant variables for the fossil assemblages. Finally, we compare the temperature reconstructions to previously published radiolarian-based SST estimates for the same cores, or to other SST records based on other methodologies. We find some differences between our new temperature estimates compared to existing ones, in particular in the Eastern Equatorial Pacific. Comparison to other methods in the Japan and Bering Sea and Sea of Okhotsk show that radiolarian-based reconstructions provide robust temperature estimates compared to biogeochemical methods, which showed SST overestimation during glacial periods.

Biological and biogeochemical methods for estimating bioirrigation: a case study in the Oosterschelde estuary

Abstract. Bioirrigation, the exchange of solutes between overlying water and sediment by benthic organisms, plays an important role in sediment biogeochemistry. Bioirrigation either is quantified based on tracer data or a community (bio)irrigation potential (IPc) can be derived based on biological traits. Both these techniques were applied in a seasonal study of bioirrigation in subtidal and intertidal habitats in a temperate estuary. The combination of a tracer time series with a high temporal resolution and a mechanistic model allowed for us to simultaneously estimate the pumping rate and the sediment attenuation, a parameter that determines irrigation depth. We show that, although the total pumping rate is similar in both intertidal and subtidal areas, there is deeper bioirrigation in intertidal areas. This is explained by higher densities of bioirrigators such as Corophium sp., Heteromastus filiformis and Arenicola marina in the intertidal, as opposed to the subtidal, areas. The IPc correlated more strongly with the attenuation coefficient than the pumping rate, which highlights that the IPc index reflects more the bioirrigation depth than the rate.

Biogeochemical evidence for residence, diet, and health of theWoman in the Iron Coffin(Queens, New York City)

AbstractIn 2011, the mummified body of a Black adult female was discovered in a mid‐19th‐century Fisk iron coffin buried in Queens, New York City. Archival research points to the identity of the woman as Martha Peterson, a domestic worker who lived in the home of William Raymond, the business partner and neighbour of Almond Fisk, the coffin inventor and manufacturer. Here, we apply biogeochemical methods to provide information about theWoman in the Iron Coffin's (WIC's) residence, diet, and health to complement the biological profile and test the archival‐based interpretation of identity. We conducted stable isotopic (δ13C, δ15N, δ18O,87Sr/86Sr, and206Pb/207Pb) and elemental (As, Sr, and Pb) concentration analyses of a second premolar and one strand of hair to characterize her lifeways during middle childhood and near the time of death. We interpret WIC's geographic location during the time of tooth formation as local to the New York region, compared with established δ18O and87Sr/86Sr isoscapes of the United States and206Pb/207Pb values of regional coal and ore. WIC's δ13C and δ15N values indicate a mixed diet similar to contemporaneous peoples from other Mid‐Atlantic States. Pb concentrations are potentially indicative of acute Pb‐caused health problems in a period of ~1 year during middle childhood. Our biogeochemical results bolster archival‐based interpretations of WIC's identity as a member of the Peterson's, a local free Black family, and provide a glimpse into the life of a Black woman in 19th‐century New York City.

Climate and lake development history in the south of West Siberia

There is a huge number of small lakes in south of West Siberia and such lakes are very useful local for climate and environmental reconstructions. The previously studied objects in the area are mostly peat-bogs and geologic sections; the lake history and natural interactions between paleoenvironmental and climate changes in the region are understudied. Here we present results of multiproxy investigation of three lakes located in different parts of the Baraba forest-steppe region along a 300km north-south transect: Bolshie Toroki, Chany (Yarkov subbasin), and Malye Chany. Vibrational drilling technology method was used to recover undisturbed columns of lake sediments and penetrate to non-lacustrine substrata. The obtained cores were investigated basically by sedimentological and palynological analyses (with the reconstruction of vegetational cover) and radiocarbon dating, additionally we used other paleontological (diatom, ostracod, chironomid analyses), geophysical, and biogeochemical methods to obtain information about environmental and climate changes, as well as lake level, biotic, ecosystem, and geochemical changes. This and our previous studies showed complicated picture of lake evolution histories and climate change in the south of West Siberia. According to our data most of investigated lakes (Chany, Malye Chany, Beloye, Minzelinskoye, Bolshie Toroki, and Kirek) are very young and started to form in the middle Holocene or later as marshy lowland with peaty sediments. Then they became deeper with mostly sapropel sediments.

The Effect of Chironomid Larvae on Nitrogen Cycling and Microbial Communities in Soft Sediments

The combination of biogeochemical methods and molecular techniques has the potential to uncover the black-box of the nitrogen (N) cycle in bioturbated sediments. Advanced biogeochemical methods allow the quantification of the process rates of different microbial processes, whereas molecular tools allow the analysis of microbial diversity (16S rRNA metabarcoding) and activity (marker genes and transcripts) in biogeochemical hot-spots such as the burrow wall or macrofauna guts. By combining biogeochemical and molecular techniques, we analyzed the role of tube-dwelling Chironomus plumosus (Insecta, Diptera) larvae on nitrification and nitrate reduction processes in a laboratory experiment with reconstructed sediments. We hypothesized that chironomid larvae stimulate these processes and host bacteria actively involved in N-cycling. Our results suggest that chironomid larvae significantly enhance the recycling of ammonium (80.5 ± 48.7 µmol m−2 h−1) and the production of dinitrogen (420.2 ± 21.4 µmol m−2 h−1) via coupled nitrification–denitrification and the consumption of water column nitrates. Besides creating oxygen microniches in ammonium-rich subsurface sediments via burrow digging and ventilation, chironomid larvae serve as hot-spots of microbial communities involved in N-cycling. The quantification of functional genes showed a significantly higher potential for microbial denitrification and nitrate ammonification in larvae as compared to surrounding sediments. Future studies may further scrutinize N transformation rates associated with intimate macrofaunal–bacteria associations.

Biogeochemical Differentiation of Living Matter and Biodiversity in the Ardon Polymetallic Subregion of the Biosphere

Specific responses of plants and animals to changes in the contents of microelements (Pb, Cd, Cu, Zn, As, Se, etc.) in abiotic environmental components of the Ardon River Basin (North Ossetia) were studied by new biogeochemical indication methods. In comparison to background areas, a local increase in the Pb, Cd, Cu, Zn, and As contents in soils and organisms occurs under the impact of natural and technogenic factors. The heavy metal contents in Ardon River water are generally within hygienic norms. Activation of sulfurcontaining synthesis in the leaves of willow, sea buckthorn, and coltsfoot was revealed for the maximum heavy metal content in soils. On plots adjacent to the Unal tailing dump, the contents of pigments and their proportions in leaves of coltsfoot, dandelion, and willow do not differ from those in less contaminated areas. On technogenic plots, the species richness of plants decreases, as well as the mowed biomass and projective cover of herbaceous plants (to 40%); inhibition of plant growth, chlorosis, necrosis, and lamina deformation are observed. A new metallophyte species (Cladochaeta candidissima M. Bieb.) was revealed. The increase in lead and arsenic contents in soils and plants of the Ardon floodplain is accompanied by an increase in their concentrations in the blood and hair of animals.

Geophysical characterisation of the groundwater–surface water interface

Interactions between groundwater (GW) and surface water (SW) have important implications for water quantity, water quality, and ecological health. The subsurface region proximal to SW bodies, the GW–SW interface, is crucial as it actively regulates the transfer of nutrients, contaminants, and water between GW systems and SW environments. However, geological, hydrological, and biogeochemical heterogeneity in the GW–SW interface makes it difficult to characterise with direct observations. Over the past two decades geophysics has been increasingly used to characterise spatial and temporal variability throughout the GW–SW interface. Geophysics is a powerful tool in evaluating structural heterogeneity, revealing zones of GW discharge, and monitoring hydrological processes. Geophysics should be used alongside traditional hydrological and biogeochemical methods to provide additional information about the subsurface. Further integration of commonly used geophysical techniques, and adoption of emerging techniques, has the potential to improve understanding of the properties and processes of the GW–SW interface, and ultimately the implications for water quality and environmental health.

Leachate from Municipal Waste Landfill and Its Natural Degradation-A Case Study of Zubří, Zlín Region.

This work deals with the natural degradation of leachate from an old reclaimed landfill by means of a biological pond. Hamra is a municipal waste landfill with a limited formation of leachate, which has already been reclaimed. Leachate in this location is disposed of using natural biogeochemical method, and it is subsequently discharged into a surface stream. The main issue dealt with here is the long-term effectiveness of natural degradation of leachate and the limits of its use. The solutions of these fundamental questions took advantage of a database of analytical assessments collected during a long-term monitoring of the landfill site. The primary degradation trends and the long-term development have been revealed and described on the basis of these assessments. The main benefit of the biological pond is the dilution of the dominant contaminants, especially of inorganic character. In the case of ammonium ions, they show nitrification caused by their transition from the reduction into oxidizing environment. From a long term point of view, the disadvantage of natural degradation of leachate can be seen in the gradual reduction in efficiency due to the concentration of the substances or an undesired growth of water plants, which can be successfully eliminated, for example, by means of targeted aeration and by maintaining vegetation in the pond and its surroundings. The biological potential of the locality is very favorable and, despite its anthropogenic load, it creates a location with suitable living conditions for many water animals and plants. That is why it can be concluded that the efficiency of the natural biochemical cleaning elements can be considered as sufficient, taking into account the nature of the deposited waste, the quantity and quality of leachate, as well as the climate character of the locality.

Reconstruction of breastfeeding and weaning practices using stable isotope and trace element analyses: A review.

Biogeochemical methods using stable isotopes and trace elements have been increasingly developed and applied to reconstruct modern and ancient breastfeeding and weaning practices of mammals, including humans, because they offer direct proxies for the dietary intake of subadults. Carbon, nitrogen, and oxygen isotopes have been used to evaluate breast milk lipid, protein, and water intake, respectively. Carbon and sulfur isotopes have been used to estimate the content of weaning foods. The elemental concentrations of Sr and Ba in subadult tissues differ because of the dietary change during the weaning process. For analyses, various tissues have been used, such as hair, nail, blood, and feces for modern mammals and bone and teeth for ancient ones. Of these, trace element analysis of tooth enamel offers a good opportunity for the reconstruction of breastfeeding and weaning practices of the more distant past at finer resolution, although further understanding of the metabolism of trace elements is necessary. There are various tissue- and element-specific advantages and disadvantages, and a combination of different proxies can illuminate practices from various viewpoints. Finally, applying the geochemical reconstruction of breastfeeding and weaning practices to human ecology, primatology, and paleoanthropology is important; basic studies of the underlying physiological mechanisms and technical improvements in the analyses will further highlight avenues for future research.

The metabolic pathways and environmental controls of hydrocarbon biodegradation in marine ecosystems.

The metabolic pathways and environmental controls of hydrocarbon biodegradation in marine ecosystems.

A Bioarchaeological and Biogeochemical Study of Warfare and Mobility in Andahuaylas, Peru (ca. ad 1160–1260)

AbstractWarfare impacts how people and populations can move about the landscape. Ethnographers have posited that internal warfare, conflict that takes place within a single society, is strongly associated with female abduction. In contrast, external warfare, combat between different societies, is often accompanied by the in‐migration of men for purposes of defence. To test this assertion, we evaluate human remains from one of the most violent eras in Andean prehistory, the Late Intermediate Period (ad 1000–1400). In the south‐central highlands of Andahuaylas, Peru, this era witnessed the coalescence of two formidable polities, the Chanka and the Quichua. Ethnohistoric accounts describe internal warfare among the Chanka and external warfare between the Quichua and their neighbours. In this study, bioarchaeological and biogeochemical methods are marshalled to elucidate ancient patterns of violence and mobility with greater nuance. We employ strontium isotope analysis of tooth enamel apatite to inform on residential origin, and we reconstruct patterns of violent conflict through analysis of cranial trauma. In all, 265 crania were excavated from 17 cave ossuaries at two Chanka sites and one Quichua site. Data were collected on age, sex and cranial modification—an indicator of social identity and cranial trauma. A representative subsample of molars from 34 individuals subjected to strontium isotope analysis demonstrates that among the Chanka, violence was significantly directed towards social groups within society, marked by modified crania. The presence of two nonlocal women with signs of increased morbidity and mistreatment points to possible mobility‐by‐abduction. In contrast, among the Quichua, men have significantly more trauma, and wounds are concentrated on the anterior. Trauma on women is lower, nonlethal, and concentrated on the posterior. This divergent pattern is commonly observed in external warfare (raids and community defence), where men face attackers and women escape them. The presence of two nonlocal men supports a mobility model of strategic in‐migration. In sum, osteological and isotopic data sets are shown to reveal divergent life‐course experiences not captured by the archaeological data or historic records alone. Copyright © 2014 John Wiley & Sons, Ltd.

A biogeochemical orientation survey around a low-grade uranium deposit in black shale in the Goesan district, Korea

Biogeochemical methods have been widely applied for uranium mineral exploration, but there have been few applications for low-grade uranium deposits. This paper describes a biogeochemical method of exploration for U in black shale areas. Sampling was performed in October 2010 and the following May along three survey lines at 15 sampling points 30 m apart. Daimyo oak ( Quercus dentata ) leaves and twigs, Japanese red pine ( Pinus densiflora ) twigs, and soils were collected at each sampling site, and the same suite of samples from five sites in a control area. Soil samples were analysed by INAA and four-acid digestion ICP-AES, and plant samples by ICP-MS after ashing to calculate values levelled to a dry-weight basis. The range of U in soils is from 2.7 to 694 ppm (mean 91.8 ppm; median 34.5 ppm); in plant samples, the ranges in Quercus dentata leaves and twigs, and Pinus densiflora twigs are from 0.007 to 2.687 ppm (mean 0.160 ppm; median 0.063 ppm), from 0.002 to 0.53 ppm (mean 0.037 ppm; median 0.012 ppm), and from 0.002 to 0.2 ppm (mean 0.014 ppm; median 0.009 ppm), respectively. In general, profiles of U concentrations in soil and plant samples coincide relatively well with the mineralized zone, although an inferior relationship at some sites may be due to down-slope displacement of soil. Quercus dentata twigs are considered to be useful as a biogeochemical medium to explore for low-grade U deposits in the study area.

Improving Intercomparability of Marine Biogeochemical Time Series

Shipboard biogeochemical time series represent one of the most valuable tools scientists have to quantify marine elemental fluxes and associated biogeochemical processes and to understand their links to changing climate. They provide the long, temporally resolved data sets needed to characterize ocean climate, biogeochemistry, and ecosystem variability and change. However, to monitor and differentiate natural cycles and human‐driven changes in the global oceans, time series methodologies must be transparent and intercomparable when possible. To review current shipboard biogeochemical time series sampling and analytical methods, the International Ocean Carbon Coordination Project (IOCCP; http://www.ioccp.org/) and the Ocean Carbon and Biogeochemistry Program (http://www.us‐ocb.org/) convened an international ocean time series workshop at the Bermuda Institute for Ocean Sciences.

Adaptation of spherical multicellular magnetotactic prokaryotes to the geochemically variable habitat of an intertidal zone

A combination of microscopic, molecular and biogeochemical methods was used to study the structure, phylogenetics and vertical distribution of spherical multicellular magnetotactic prokaryotes (MMPs) of intertidal sediments in the Yellow Sea. These MMPs were 5.5 μm in diameter and composed of approximately 15-30 cells. They synthesized bullet-shaped magnetites in chains or clusters. Phylogenetic analysis of 16S rRNA gene sequences suggested that these MMPs represent a novel species affiliated to the Deltaproteobacteria. To study their vertical distribution and the relationship to geochemical parameters, sediment cores were collected after the redox potential was measured in situ. The sediments were composed of yellow, grey and black layers from the surface to depth. The spherical MMPs were concentrated near the grey-black layer transition at a depth of 8-12 cm, while coccoid-shaped magnetotactic bacteria near the yellow-grey layer transition at a depth of 3-5 cm. The intertidal MMPs showed a deeper distribution at more reduced environments than coccoid-shaped magnetotactic bacteria, and MMPs in lagoon sediments. Additionally the MMPs were concentrated significantly in layers with high proportion of fine sand and total organic carbon, rich in leachable iron but poor in nitrate. These results show an adaptation of spherical MMPs to the peculiar intertidal sediment habitat.