Tidal Flat Sediments Research Articles

Pseudoruegeria insulae sp. nov., isolated from a tidal flat.

A Gram-stain-negative, aerobic, non-motile and ovoid or rod-shaped bacterial strain, designated BPTF-M20T, was isolated from tidal flat sediment in the Yellow Sea, Republic of Korea. Strain BPTF-M20T grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 2.0-3.0 % (w/v) NaCl. A neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain BPTF-M20T fell within the clade comprising the type strains of Pseudoruegeria species. Strain BPTF-M20T exhibited 16S rRNA gene sequence similarity values of 97.4-98.3 % to the type strains of Pseudoruegeria haliotis, Pseudoruegeria lutimaris, 'Pseudoruegeria litorisediminis' and Pseudoruegeria sabulilitoris and 96.4-96.9 % to the type strains of the other Pseudoruegeria species. Strain BPTF-M20T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids detected in strain BPTF-M20T were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminolipid and one unidentified glycolipid. The DNA G+C content of strain BPTF-M20T was 63.2 mol%. Mean DNA-DNA relatedness values of strain BPTF-M20T with the type strains of P. haliotis, P. lutimaris, P. sabulilitoris and 'P. litorisediminis' were 18-27 %. Differential phenotypic properties, together with the phylogenetic and genetic data, revealed that strain BPTF-M20T was separated from recognized Pseudoruegeria species. On the basis of the data presented here, strain BPTF-M20T is considered to represent a novel species of the genus Pseudoruegeria, for which the name Pseudoruegeriainsulae sp. nov. is proposed. The type strain is BPTF-M20T (=KACC 19614T=KCTC 62422T=NBRC 113188T).

Draft Genome Sequence of "Candidatus Izimaplasma sp." Strain ZiA1, Obtained from a Toluene-Degrading and Iron-Reducing Enrichment Culture.

Here, we report the draft genome sequence of "Candidatus Izimaplasma sp." strain ZiA1 (1.88 Mb and 29.6% G+C content). Strain ZiA1 was cocultured with iron-reducing and toluene-degrading bacteria in an enrichment culture from tidal flat sediment. Like the genomes of other strains of "Ca. Izimaplasma," the ZiA1 genome contained genes required for anaerobic fermentation.

Pseudopontivivens aestuariicola gen. nov., sp. nov., a Novel Bacterium of the Class Alphaproteobacteria Isolated from a Tidal Flat

A Gram-stain-negative, non-motile and coccoid, ovoid or rod-shaped bacterial strain, OITF-57T, which was isolated from a tidal flat sediment in South Korea, was characterized taxonomically. Strain OITF-57T grew optimally at 25°C, at pH 7.0-8.0 and in the presence of 2.0% (w/v) NaCl. Strain OITF-57T exhibited the highest 16S rRNA gene sequence similarity value (94.2%) to the type strain of Pontivivens insulae forming a cluster in the neighbour-joining phylogenetic tree. In the maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences and the phylogenetic tress based on gyrB sequences, strain OITF-57T formed evolutionary lineages independent of those of other taxa. Strain OITF-57T contained Q-10 as the predominant ubiquinone and C18:1 ω7c as the major fatty acid. The major polar lipids of strain OITF-57T were phosphatidylcholine and phosphatidylglycerol. The DNA G + C content of strain OITF-57T was 66.0mol%. The chemotaxonomic data and other differential phenotypic properties made it possible to distinguish strain OITF-57T from the genus Pontivivens and other phylogenetically related genera. On the basis of the data presented, strain OITF-57T constitutes a new genus and species within the class Alphaproteobacteria, for which the name Pseudopontivivens aestuariicola gen. nov., sp. nov. is proposed. The type strain is OITF-57T (= KACC 19570T = CGMCC 1.13481T).

Late Quaternary sedimentary evolution of the outer shelf of the East China Sea

This study investigated the late Quaternary sedimentary evolution of the outer shelf of the East China Sea (ECS) using borehole core data (DH02). Three unconformity-bounded sedimentary facies, namely, prodelta facies of marine isotopic stage (MIS) 3, intertidal to subtidal flat facies of the deglacial period, and offshore tidal sand ridge facies of the Holocene, were identified from the base upward according to combined evidence of lithology, microfossil assemblages, and geochronology. Through comparative analysis with other neighboring borehole cores, these three facies, along with the MIS 3 nearshore facies and the last glacial maximum (LGM) river facies, were found to constitute the late Quaternary sediment strata. Sedimentary processes of these five facies were interpreted based on a synthetic consideration of sea-level change, climate variation, paleotopographic setting, and paleoriver-sea interactions. In particular, the development of the delta was attributable to integration of the slow sea-level decline during the later stage of the MIS 3 and abundant sediment supply resulting from the warm-wet climate. The gentle shelf topography suggests the presence of shallow and wide rivers in the delta, and the lateral shift of river channels might have induced the local formation of nearshore facies at the abandoned river mouth. The LGM river facies, which was rarely observed (presumably due to marine erosion with deglacial transgression), was inferred to have been deposited during the latter half of the LGM in response to the rise in river base level. Occurrences of tidal flat facies imply the formation of a tide-dominated estuary with the deglacial transgression. Furthermore, tidal flat sediments were reworked by enhanced tidal currents in the estuary front environment, forming mud ridges during subsequent deglacial transgression. Formation of tidal sand ridges in offshore environments of the Holocene was attributable to the uneven base caused by the underlying estuarine erosion mud ridges, and this promoted the occurrence of tidal depositional processes. The sedimentary evolution in association with sea-level change was constructed using the above-mentioned results. Overall, this study systematically elucidates the late Quaternary sedimentary processes and evolution of the outer ECS shelf, and provides an insight into the sedimentary development of analogous shelves around the world.

Pseudoruegeria litorisediminis sp. nov., a novel lipolytic bacterium of the family Rhodobacteraceae isolated from a tidal flat.

A lipolytic bacterial strain, designated BPTF-M5T, was isolated from a tidal flat sediment of the Yellow Sea in Republic of Korea, and identified by a polyphasic taxonomic approach. It was Gram negative, aerobic, non-motile and rod shaped. Strain BPTF-M5T grew optimally at 30°C and in the presence of 2.0-3.0% (w/v) NaCl. A neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain BPTF-M5T fell within the clade comprising the type strains of Pseudoruegeria species. The novel strain exhibited the highest 16S rRNA gene sequence similarity value (98.6%) to Pseudoruegeria marinistellae SF-16T. Strain BPTF-M5T exhibited sequence similarities of 97.0-98.5% to the type strains of five other Pseudoruegeria species and of less than 96.1% to other recognized species. Strain BPTF-M5T contained Q-10 as the predominant ubiquinone and C18:1 ω7c as the major fatty acid. Phosphatidylglycerol, one unidentified aminolipid, one unidentified lipid and one unidentified glycolipid were detected as major polar lipids in the novel strain. The DNA G + C content of strain BPTF-M5T was 63.3mol%. DNA-DNA relatedness values between strain BPTF-M5T and the type strains of the six Pseudoruegeria species were 11.0-24.3%. The phenotypic properties of strain BPTF-M5T were clearly distinguished from those of the type strains of the six Pseudoruegeria species. Based on the polyphasic data presented, strain BPTF-M5T represents a novel species of the genus Pseudoruegeria, for which the name Pseudoruegeria litorisediminis sp. nov. is proposed. The type strain is BPTF-M5T (= KCTC 62420T = KACC 19613T = NBRC 113189T).

Sulfitobacter aestuarii sp. nov., a marine bacterium isolated from a tidal flat of the Yellow Sea.

A novel bacterial strain, designated hydD52T, was isolated from a sample of tidal flat sediment of the Yellow Sea in the Republic of Korea. The cells were motile, rod-shaped and Gram-stain-negative. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain hydD52T was a member of the genus Sulfitobacter and most closely related to Sulfitobacter dubius DSM 16472T (98.0 %), Sulfitobacter indolifex HEL-45T (97.8 %) and Sulfitobacter delicatus DSM 28223T (97.6 %). The major fatty acids (>5 %) of hydD52T were C18 : 1ω7c/C18 : 1ω6c, C16 : 0, C18 : 1ω7c 11-methyl and C19 : 0ω8c. The respiratory quinone of strain hydD52T was ubiquinone-10. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and an unidentified amino lipid. The G+C content of this strain was 64.0 mol%. The DNA-DNA relatedness values of hydD52T with the type strains of S. dubius, S. indolifex and S. delicatus were 18.8, 13.1 and 15.7 %, respectively. Based on the results of morphological, physiological and chemotaxonomic characterization, DNA-DNA hybridization relatedness, and 16S rRNA genes analysis, we concluded that strain hydD52T represents a novel species, for which the name Sulfitobacter aestuarii sp. nov. is proposed. The type strain is hydD52T (=KCTC 32982T=TISTR 2562T).

Pseudomaribius aestuariivivens gen. nov., sp. nov., isolated from a tidal flat sediment.

A Gram-stain-negative, non-motile and ovoid or rod-shaped bacterial strain, DBTF-15T, was isolated from a tidal flat sediment on the Yellow Sea in South Korea. Strain DBTF-15T grew optimally at 25-30 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences revealed that strain DBTF-15T joined the cluster comprising the type strains of species of the genus Palleronia. Strain DBTF-15T exhibited higher 16S rRNA gene sequence similarity values to the type strains (96.5-96.7 %) of Maribius pelagius and Maribius salinus than to those (94.6-96.1 %) of the three species of the genus Palleronia. It exhibited 16S rRNA gene sequence similarity values of less than 93.9 % to the type strains of the other recognized species. Strain DBTF-15T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids of strain DBTF-15T were phosphatidylcholine, phosphatidylglycerol and one unidentified aminolipid. The DNA G+C content of strain DBTF-15T was 68.7 mol%. The chemotaxonomic data and other differential phenotypic properties made it possible to distinguish strain DBTF-15T from the genera Maribius and Palleronia. On the basis of the data presented, strain DBTF-15T constitutes a novel genus and species within the class Alphaproteobacteria, for which the name Pseudomaribius aestuariivivens gen. nov., sp. nov. is proposed. The type strain is DBTF-15T (=KACC 19431T=NBRC 113039T).

Aestuariibius insulae gen. nov., sp. nov., isolated from a tidal flat sediment.

A Gram-stain-negative, non-motile and ovoid or rod-shaped bacterial strain, DBTF-13T, which was isolated from a tidal flat sediment of the Yellow Sea in South Korea, was characterized taxonomically. Strain DBTF-13T grew optimally at 25-30 °C and pH 7.0-8.0, and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences revealed that strain DBTF-13T formed an evolutionary lineage independent of other genera, including the genera Pseudooctadecabacter and Octadecabacter. Strain DBTF-13T exhibited 16S rRNA gene sequence similarity values of 96.9 % to the type strain of Pseudooctadecabacter jejudonensis, and of 95.8-96.5 % to the type strains of Octadecabacter species. Strain DBTF-13T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c and C16 : 0 as the major fatty acids. The major polar lipids of strain DBTF-13T were phosphatidylcholine, phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain DBTF-13T was 61.6 mol%. The chemotaxonomic data and other differential phenotypic properties made it reasonable to differentiate strain DBTF-13T from the genera Pseudooctadecabacter and Octadecabacter. On the basis of the data presented, strain DBTF-13T constitutes a new genus and species within the class Alphaproteobacteria, for which the name Aestuariibius insulae gen. nov., sp. nov. is proposed. The type strain is DBTF-13T (=KACC 19432T=NBRC 113038T).

Neotectonic Activity from the Upper Reaches of the Arabian Gulf and Possibilities of New Oil Fields

Upper reaches of the Arabian Gulf consist of different types of fine sediments including the vast Mesopotamia Plain sediments, tidal flat sediments and estuarine sabkha sediments. The height of the plain starts from zero meter and increases northwards to three meters with extremely gentle gradient. The vast plain to the north of the Arabian Gulf is drained by Shat Al-Arab (Shat means river in Iraqi slang language) and Khor Al-Zubair (Khor means estuary). The former drains the extreme eastern part of the plain; whereas, the latter drains the western part. Shat Al-Arab is the resultant of confluence of the Tigris and Euphrates rivers near Al-Qurna town; about 160 km north of the Arabian Gulf mouth at Al-Fao town; whereas, the length of Khor Al-Zubair is about 50 km; as measured from Um Qasir Harbor. The drainage system around Khor Al-Zubair is extremely fine dendritic; whereas around Shat Al-Arab is almost parallel running from both sides of the river towards the river; almost perpendicularly. The fine dendritic drainage around Khor Al-Zubair shows clear recent erosional activity, beside water divides, abandoned irrigation channels and dislocated irrigational channels and estuarine distributaries; all are good indication for a Neotectonic activity in the region. These may indicate the presence of subsurface anticlines, which may represent oil fields; since tens of subsurface anticlines occur in near surroundings, which are oil fields.

Paenibacillus translucens sp. nov., isolated from tidal flat sediment.

A Gram-stain-variable, aerobic, rod-shaped, motile and spore-forming bacterial strain, designated CJ11T, was isolated from a tidal flat sediment sample from Ganghwa-do, Republic of Korea. Strain CJ11T grew optimally on R2A at 30 °C and pH 7.0. Sequencing results of the 16S rRNA gene revealed that strain CJ11T possesses two copies of the 16S rRNA gene varying at five nucleotide positions. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CJ11T belonged to the genus Paenibacillus within the family Paenibacillaceae and was most closely related to Paenibacillus lacus KCTC 33691T (99.36-99.15 % similarity). DNA-DNA relatedness levels of strain CJ11T was 41.7 % (reciprocal, 57.8 %) to P. lacus KCTC 33691T. The G+C content of the genomic DNA was 51.0 mol%. Strain CJ11Tcontained meso-diaminopimelic acid in the cell-wall peptidoglycan. The major isoprenoid quinone was menaquinone-7. The major cellular fatty acids were anteiso-C15 : 0, C16 : 0 and iso-C16 : 0. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids, an unidentified glycolipid and several unidentified lipids. On the basis of the polyphasic taxonomic study, strain CJ11T represents a novel species in the genus Paenibacillus, for which the name Paenibacillustranslucens sp. nov. is proposed. The type strain is CJ11T (=KACC 19304T=JCM 32080T).

Virus Dynamics Are Influenced by Season, Tides and Advective Transport in Intertidal, Permeable Sediments.

Sandy surface sediments of tidal flats exhibit high microbial activity due to the fast and deep-reaching transport of oxygen and nutrients by porewater advection. On the other hand during low tide, limited transport results in nutrient and oxygen depletion concomitant to the accumulation of microbial metabolites. This study represents the first attempt to use flow-through reactors to investigate virus production, virus transport and the impact of tides and season in permeable sediments. The reactors were filled with intertidal sands of two sites (North beach site and backbarrier sand flat of Spiekeroog island in the German Wadden Sea) to best simulate advective porewater transport through the sediments. Virus and cell release along with oxygen consumption were measured in the effluents of reactors during continuous flow of water through the sediments as well as in tidal simulation experiments where alternating cycles with and without water flow (each for 6 h) were operated. The results showed net rates of virus production (0.3–13.2 × 106 viruses cm−3 h−1) and prokaryotic cell production (0.3–10.0 × 105 cells cm−3 h−1) as well as oxygen consumption rates (56–737 μmol l−1 h−1) to be linearly correlated reflecting differences in activity, season and location of the sediments. Calculations show that total virus turnover was fast with 2 to 4 days, whereas virus-mediated cell turnover was calculated to range between 5–13 or 33–91 days depending on the assumed burst sizes (number of viruses released upon cell lysis) of 14 or 100 viruses, respectively. During the experiments, the homogenized sediments in the reactors became vertically structured with decreasing microbial activities and increasing impact of viruses on prokaryotic mortality with depth. Tidal simulation clearly showed a strong accumulation of viruses and cells in the top sections of the reactors when the flow was halted indicating a consistently high virus production during low tide. In conclusion, cell lysis products due to virus production may fuel microbial communities in the absence of advection-driven nutrient input, but are eventually washed off the surface sediment during high tide and being transported into deeper sediment layers or into the water column together with the produced viruses.

A Novel Halotolerant Thermoalkaliphilic Esterase from Marine Bacterium Erythrobacter seohaensis SW-135.

A novel esterase gene, e69, was cloned from Erythrobacter seohaensis SW-135, which was isolated from a tidal flat sediment of the Yellow Sea in Korea. This gene is 825 bp in length and codes for a 29.54 kDa protein containing 274 amino acids. Phylogenetic analysis showed that E69 is a new member of the bacterial lipolytic enzyme family IV. This enzyme exhibited the highest level of activity toward p-nitrophenyl (NP) butyrate but little or no activity toward the other p-NP esters tested. The optimum temperature and pH of the catalytic activity of E69 were 60°C and pH 10.5, respectively. The enzyme exhibited stable activity over a wide range of alkaline pH values (7.5–9.5). In addition, E69 was found to be a halotolerant esterase as it exhibited the highest hydrolytic activity in the presence of 0.5 M NaCl and was still active in the presence of 3 M NaCl. Moreover, it possessed some degree of tolerance to Triton X-100 and several organic solvents. Through homology modeling and comparison with other esterases, it was suggested that the absence of the cap domain and its narrow substrate-binding pocket might be responsible for its narrow substrate specificity. Sequence and structural analysis results suggested that its high ratio of negatively to positively charged residues, large hydrophobic surface area, and negative electrostatic potential on the surface may be responsible for its alkaline adaptation. The results of this study provide insight into marine alkaliphilic esterases, and the unique properties of E69 make it a promising candidate as a biocatalyst for industrial applications.

Determining the Effects of Major Cations (K , Na , Ca2 , Mg2 ) and pH on Scirpus mariqueter to Assess the Heavy Metal Biotoxicity of a Tidal Flat Ecosystem

ABSTRACT Dong, L.; Li, X.; Liu, X.; He, K., and Jiang, X., 2017. Determining the effects of major cations (K+, Na+, Ca2+, Mg2+) and pH on Scirpus mariqueter to assess the heavy metal biotoxicity of a tidal flat ecosystem. The biotic ligand model (BLM) as a mechanistic bioavailability model has been used to assess the risk of metals on various ecosystems. In this study, the effects of major cations (K+, Na+, Ca2+, Mg2+) and pH on root elongation of the salt marsh plant Scirpus mariqueter were investigated by laboratory experiments, and then a tidal flat sediment–BLM was developed successfully to assess heavy metal biotoxicity on a tidal flat ecosystem for the first time. The results showed that the increase of Na+ activities could decrease Cu2+ toxicity to S. mariqueter. A nonlinear relationship was observed between the median effective concentration (EC50) and H+ activity over the pH range (5.55–8.22). The results indicated that H+ did not compete with Cu2+ for the binding sites within the roots of S. mar...

The role of organominerals in the lithification of calcareous lumps within the intertidal sediments of Bubiyan Island, Kuwait, Arabian Gulf

Calcareous lumps of varying sizes and shapes are scattered on the landward part of the muddy intertidal flat along the southern coast of Bubiyan Island, northeast Kuwait. Two main lithotypes are recognized, namely, hard sandy crust fragments which are mostly formed of porous calcareous grainstone (bio-oosparite) and lithified muddy lumps that consist of calcareous wackestone (bio-micrite). They were originally eroded from the soft tidal flat sediments then lithified. Petrographic, mineralogical, and SEM/EDS examinations revealed that lithification of these calcareous lumps is attributed to cementation by biologically influenced organominerals, mainly high magnesium calcite and aragonite. The conditions responsible for the precipitation of these organominerals as well as variation in their mineralogy within each type of these calcareous lumps were discussed.

Rapid changes in phosphorus species in soils developed on reclaimed tidal flat sediments

Phosphorus (P) plays a key role in the global biogeochemical cycle. The dynamics of P in soils is of considerable importance to the management of soil fertility. However, little is known about P dynamics in reclaimed land at the centennial scale during the initial stage of soil development, when the ambient conditions undergo substantial changes. In this study, conducted in Eastern China, we used a sequential extraction method to analyze the changes in P species in sediments and soils in a coastal reclaimed area representing a sequence of soil ages. Significant accumulation of total P accompanied by organic matter enrichment, desalination, and decalcification were observed in the initial pedogenesis of reclaimed tidal flat sediments. A rapid change in top soil P species within a century of pedogenesis was revealed, which was characterized by a marked decline in P contained within primary minerals (DeP) and an increase in loosely absorbed P, Fe-bound P, authigenic P (CaP), and organic P. DeP decreased from 67.3% to 25.3% of total P, whereas CaP increased from 8.4% to 32.9% along the reclamation gradient. Dissolution of primary minerals and a high rate of fertilization were identified as the major causes of this P trajectory. A key factor controlling the evolution of soil P speciation is the marked change in ambient conditions following land conversion, resulting in a shift in anaerobic conditions, a decrease in pH, accumulation of organic matter, and depletion of carbonates. Under the strong interference of human activities, the P dynamics in soils derived from tidal flat sediments differ from those predicted by the Walker and Syers model. Our results indicate that current nutrient management practices in the studied area can not only avert soil P depletion but also increase P availability.

Oleiagrimonas citrea sp. nov., a marine bacterium isolated from tidal flat sediment and emended description of the genus Oleiagrimonas Fang et al. 2015 and Oleiagrimonas soli.

A Gram-stain-negative, aerobic, rod-shaped (1.4-3.6×0.4-0.6 µm) and motile marine bacterium, designated as MEBiC09124T, was isolated from tidal flat sediment of Suncheon Bay, South Korea. 16S rRNA gene sequence analysis revealed that strain MEBiC09124T showed high similarity to Oleiagrimonas soli 3.5XT (96.7 %). Growth was observed at 18-38 °C (optimum 30 °C), at pH 4.0-8.5 (optimum pH 7.5) and with 0-6 % (w/v) (optimum 2.5 %) NaCl. The predominant cellular fatty acids were iso-C15 : 0, iso-C16 : 0, iso-C17 : 0 and summed feature 9 (comprising 10-methyl C16 : 0 and/or iso-C17 : 1ω9c). The DNA G+C content was 66.1 mol%. The major respiratory quinone was Q-8. Biochemical characteristics such as production of acetoin and enzyme activities of trypsin, α-chymotrypsin and N-acetyl-β-glucosaminidase differentiated strain MEBiC09124T from O. soli 3.5XT. On the basis of data from this polyphasic taxonomic study, strain MEBiC09124T (=KCCM 43131T=JCM 30904T) is classified as the type strain of a novel species in the genus Oleiagrimonas, for which the name Oleiagrimonas citrea sp. nov. is proposed. Emended descriptions of the genus Oleiagrimonas and Oleiagrimonas soli are also given.

Comparative study on magnetic minerals of tidal flat deposits from different sediment sources in Jiangsu coast, Eastern China

Understanding the sources of sediments deposited in tidal flats is critical for reconstructing the evolution of coastal regions impacted by large rivers. Environmental magnetism can be an effective tool to track sediment sources and analyze the sediment properties. We evaluate several magnetic parameters from the tidal flat sediments along the Jiangsu coast. The results show that the sediments of Liandao Island have the lowest values of magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM) and saturation isothermal remanence magnetization (SIRM). In addition to these, the values of χ, ARM and SIRM display a generally increasing trend from the north to the south along the Jiangsu coast. The strong relations between χ, ARM and SIRM show that the changes of magnetization of the tidal flat sediments mainly reflect the changes of concentration rather than those in grain sizes of magnetic particles. The main magnetic phase is magnetite, with a small amount of hematite. The strong relationship between χ and the 2-16 μm grain-size fraction suggests that magnetite is enriched in the finer silt fraction. The sediment sources is the main factor that influences the magnetic properties of the tidal flat sediments from the Jiangsu coast. Combined with the previous studies, the results indicate that the tidal flat sediments of Liandao Island were mainly derived from the nearshore rock weathering. The Yellow River is the dominant supplier for the north of Dafeng, while the Yangtze River is the dominant supplier for the south of Rudong. The coast between Dafeng and Rudong is a transition zone influenced by both rivers. This study provides a basis against which possible future variations in sediment composition resulting from catchment changes can be assessed.

Fossil bog soils (‘dwog horizons’) and their relation to Holocene coastal changes in the Jade Weser region, southern North Sea, Germany

After the deceleration of the postglacial marine transgression, the German North Sea coast was subject to deposition of a complex pattern of subtidal to terrestrial facies. This study aims at reconstructing these facies changes in the ‘Land Wursten’ region (Lower Saxony) by focussing on so-called dwog horizons (incipient soil horizons of the pre-engineered salt marshes). We explore their implications for relative sea-level reconstructions and their indication for early settlement activities. Archive drilling data (1960, provided by the ‘Landesamt fur Bergbau, Energie und Geologie’) were analysed to create five high-resolution stratigraphic cross sections. Three new drilling records were subjected to sedimentological and microfaunal investigations and interpreted to verify and calibrate the archive data. Two dwog horizons were found and 14C-AMS dated. We found basal salt marsh deposits inundated by a high-energy event and covered by tidal flat sediments. The thick tidal flat unit is again overlain by salt marsh deposits indicating the transition from a shallow marine to a terrestrial environment where dwogs were developed and covered by episodic marine incursions. The ages of the dwogs (1128–969 cal BC; cal AD 1426–1467) do not correlate with known layers of adjacent settlement sites and are critically discussed. However, we show that they correlate with phases of stagnant regional relative sea level (RSL) and can be used as RSL indicators. The combined archive and modern data provide valuable information for the RSL reconstruction and palaeoenvironmental changes. However, further research is recommended to accomplish more detailed information about coastal response during the Holocene sea-level changes and implications for settlement dynamics.

Korean indigenous bacterial species with valid names belonging to the phylum Actinobacteria.

To understand the isolation and classification state of actinobacterial species with valid names for Korean indigenous isolates, isolation source, regional origin, and taxonomic affiliation of the isolates were studied. At the time of this writing, the phylum Actinobacteria consisted of only one class, Actinobacteria, including five subclasses, 10 orders, 56 families, and 330 genera. Moreover, new taxa of this phylum continue to be discovered. Korean actinobacterial species with a valid name has been reported from 1995 as Tsukamurella inchonensis isolated from a clinical specimen. In 1997, Streptomyces seoulensis was validated with the isolate from the natural Korean environment. Until Feb. 2016, 256 actinobacterial species with valid names originated from Korean territory were listed on LPSN. The species were affiliated with three subclasses (Acidimicrobidae, Actinobacteridae, and Rubrobacteridae), four orders (Acidimicrobiales, Actinomycetales, Bifidobacteriales, and Solirubrobacterales), 12 suborders, 36 families, and 93 genera. Most of the species belonged to the subclass Actinobacteridae, and almost of the members of this subclass were affiliated with the order Actinomycetales. A number of novel isolates belonged to the families Nocardioidaceae, Microbacteriaceae, Intrasporangiaceae, and Streptomycetaceae as well as the genera Nocardioides, Streptomyces, and Microbacterium. Twenty-six novel genera and one novel family, Motilibacteraceae, were created first with Korean indigenous isolates. Most of the Korean indigenous actionobacterial species were isolated from natural environments such as soil, seawater, tidal flat sediment, and fresh-water. A considerable number of species were isolated from artificial resources such as fermented foods, wastewater, compost, biofilm, and water-cooling systems or clinical specimens. Korean indigenous actinobacterial species were isolated from whole territory of Korea, and especially a large number of species were from Jeju, Gyeonggi, Jeonnam, Daejeon, and Chungnam. A large number of novel actinobacterial species continue to be discovered since the Korean government is encouraging the search for new bacterial species and researchers are endeavoring to find out novel strains from extreme or untapped environments.

Effects of watershed land-cover on the biogeochemical properties of estuarine tidal flat sediments: A test in a densely-populated subtropical island

The effects of watershed land cover on the biogeochemical properties of estuarine tidal flat sediment were examined in estuarine tidal flats of 16 watersheds in a densely populated, subtropical island of Japan. Despite the small sizes of the watersheds (<16.5 km2), a redundancy analysis showed that river water quality explained 62% of the cross-estuary variation in the biogeochemical properties of estuarine tidal flat sediment by the first two ordination axes. We also found that the dissolved nutrient concentrations of river water and pheophytin a content of tidal flat sediment were positively related to agricultural and urbanized land cover in the watersheds. These results indicate that human nutrient inputs significantly increase algae-derived deposits in estuaries with relatively more developed watersheds. The δ13C of particulate organic matter (POM) was negatively related to watershed forest cover. This suggests that terrestrially derived-origin POM deposits are substantial in the estuaries connected to watersheds with relatively high forest cover. However, the chemical properties of tidal flat sediment were not related to chemical indicators of POM in the base flow. We hypothesize that substantial terrestrially derived POM is discharged to estuaries of high-forest-cover watersheds during high flow, and this partially controls the chemical properties of estuarine sediments. Our results demonstrate that the chemical properties of estuarine tidal flats are associated with watershed land cover, and that the dominant processes controlling estuarine sediment properties differ among watersheds depending on land cover composition.