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Peatlands form environmental archives of trace element deposition. In this regard they are particularly valuable for areas such as the Arctic, where regular pollution monitoring is either impossible or extremely costly. The aim of this study was to assess pollution in the Solovetsky Islands (65° 05' N, 35° 53' E) by examining the spatial variability in trace element content of the uppermost layer of peat, immediately below the surface layer of green vegetation. We evaluated Cr, Cd, Ni and Pb contents in samples taken from ombrotrophic (raised bog) and mesotrophic (transitional) mires and in different microtopographical settings (hummock/hollow), and calculated the following pollution indices: geoaccumulation index (Igeo), contamination factor (Cf) and degree of contamination (Cdeg). The contents of these elements were markedly lower in the Solovetsky Islands than reported from other parts of central and northern Europe. Depending on the pollution index considered, the studied peat samples could be classified as unpolluted to considerably polluted. The local spatial patterns showed the highest values of Cd in samples collected near the sea, while the highest contents of Cr and Ni were noted at sampling points located farther inland. Moreover, Cr and Pb concentrations were higher in raised bogs than in transitional mires, and this contrast was accentuated if raised bog was represented by hummocks alone. These patterns are consistent with the likely sources of Cr, Ni and Pb being atmospheric pollution; and with higher mobility of Cd in seawater, which periodically floods the transitional mires. Amongst the trace elements determined, the most consistent values across peat types and sampling locations were found for Ni, which could be successfully used for pollution monitoring even in transitional mires.

The coupling relationship between biogenic deposits and productivity may vary across different stages or regions. To explore the responses of biogenic deposits to productivity since the last glacial period, we analyzed multiproxy biogenic deposit data from Core YDY09 in the Bay of Bengal (BoB) spanning the past 30 ka. We first observed that the trends of biogenic depositional records (radiolarians, BSi, and CaCO 3) were in antiphase to that of the productivity of siliceous organisms in the overlying waters during the Last Glacial Maximum (LGM), Heinrich Stadial 1 (HS1) and late deglacial period (LdGp; 15–10 ka) in the northeastern Indian Ocean. We suggest that productivity variations were influenced mainly by the Indian summer monsoon (ISM) during the last deglaciation to glaciation. The decoupling between high productivity and low biogenic deposition during the LGM and LdGp was attributable to significant dilution by large-scale terrigenous inputs. Unlike the substantial inputs of terrestrial materials caused by low sea levels during the LGM period, the sea level rose rapidly during the LdGp period, suggesting that the intense ISM may have played a crucial role at that time. Conversely, the high amount of biogenic deposition during HS1 could be attributed to weak terrigenous dilution resulting from diminished rainfall in the Intertropical Convergence Zone (ITCZ). The strong terrigenous dilution observed during the LGM and weak terrigenous dilution during the HS1 in the BoB were consistent with findings in the northern South China Sea (SCS), except the unique LdGp period. Our findings will enhance the understanding of the decoupling mechanisms between biogenic deposits and productivity in global marginal seas. • Biogenic deposit records (Radiolaria, BSi) since the 30 ka from Bay of Bengal. • Indian summer monsoon modulates productivity pattern. • Biogenic deposition and productivity decouple during last deglaciation-glaciation. • Different mechanisms of terrigenous inputs during LGM and late deglaciation. • Reduced ITCZ rainfall weakened terrigenous inputs during Heinrich Stadial 1. [ABSTRACT FROM AUTHOR]

In the examined part of central Poland, there are numerous kettle-hole basins filled with mineral and biogenic sediments of the Eemian Interglacial and Early Weichselian. These basins are located in varied geological and geomorphological locations with variable thicknesses of the sediments and deposits. The infillings were investigated by lithological and palaeobotanic methods. Lithology of the biogenic sediments is diverse, primarily gyttja and peat, but also organic silt. A number of the documented sites contain a record of environmental changes throughout the glacial-interglacial cycle from the end of the Warta Stadial (Saalian) to Early Weichselian. Local geological, geomorphological and hydrological conditions influenced the possibility of continuous peat-lake accumulation and the timing of the completion of this accumulation. Biogenic sediments are covered with the Middle and Late Weichselian mineral sediments which indicate climatic changes and are the main reason for rapid and synchronic degradation of kettle-hole infillings.

The diversity of origins of peatland basins in Central Poland allowed the peatlands to be distinguished by location (in valleys or upland mires) and by the processes forming their basins (e.g. glacigenic, aeolian, fluvial or thermokarst processes). Peats prevail in the structure of the sediments in the analysed basins of peatlands; among them the most predominant are fens, whereas the amount of raised bogs is low. In parts of the analysed objects there are lake sediments, which usually form the bottom sections of the profiles of the biogenic sediments, and were usually deposited in the Late Vistulian. In the Holocene, peat series were accumulated. In the examined peatlands located on morainic uplands, lacustrine sediments of the Late Vistulian and Early Holocene covered by Late Holocene peats are documented. Peatlands located near aeolian forms do not show evidence of continuous accumulation of biogenic deposits. They are particularly sensitive to changes in humidity and they underwent frequent modifications during phases of aeolian activity. The sediments of valley peatlands are not suitable objects for stratigraphic analyses, but they are appropriate for reconstructions of short events that occurred in the river valleys.

Sediment geochemistry and lithology were studied in Gostyń Lake in the eastern part of the Myślibórz Lakeland (part of the Western Pomeranian Lake District). The research was undertaken because relatively shallow lake basins without ground supply contribute to the intensification of water circulation through evaporation. Late Glacial and Holocene phases in the evolution of Gostyń Lake were reconstructed based on selected geochemical indicators (Fe/Mn, S/Fe, Na/K, Mg/Ca, Cu/Zn, Na+K+Mg/Ca, Fe/Ca) as well as on the presence of human activity (Stone Age, Bronze Age, Early Iron Age and Roman Period). Also, the geochemical and archaeological data were correlated. Generally, the lithogeochemical composition variability in the Gostyń Lake deposits was found to be controlled by changes in: 1) the climate, related to the biogenic accumulation environment, 2) land cover in the Late Glacial and Holocene, and 3) human activities. Principal Component Analysis (PCA) revealed four major variable groups responsible for the changes: hydroclimatic variations which determined the type of sedimentary conditions during the Holocene climate optimum; changes in the organic matter provenance (along with conditions favouring sulphide precipitation); and denudation processes in the Gostyń Lake catchment. The methods used allowed the distribution of ancient settlement to be traced. Interpretation of the geochemical indicators (Fe/Mn, Cu/Zn, S/Fe, Ca/Fe) should involve many more factors which, in the relevant literature, are treated as measures of changes in redox conditions. [ABSTRACT FROM AUTHOR]

In the examined part of central Poland, there are numerous kettle-hole basins filled with mineral and biogenic sediments of the Eemian Interglacial and Early Weichselian. These basins are located in varied geological and geomorphological locations with variable thicknesses of the sediments and deposits. The infillings were investigated by lithological and palaeobotanic methods. Lithology of the biogenic sediments is diverse, primarily gyttja and peat, but also organic silt. A number of the documented sites contain a record of environmental changes throughout the glacial-interglacial cycle from the end of the Warta Stadial (Saalian) to Early Weichselian. Local geological, geomorphological and hydrological conditions influenced the possibility of continuous peat-lake accumulation and the timing of the completion of this accumulation. Biogenic sediments are covered with the Middle and Late Weichselian mineral sediments which indicate climatic changes and are the main reason for rapid and synchronic degradation of kettle-hole infillings. [ABSTRACT FROM AUTHOR]

The diversity of origins of peatland basins in Central Poland allowed the peatlands to be distinguished by location (in valleys or upland mires) and by the processes forming their basins (e.g. glacigenic, aeolian, fluvial or thermokarst processes). Peats prevail in the structure of the sediments in the analysed basins of peatlands; among them the most predominant are fens, whereas the amount of raised bogs is low. In parts of the analysed objects there are lake sediments, which usually form the bottom sections of the profiles of the biogenic sediments, and were usually deposited in the Late Vistulian. In the Holocene, peat series were accumulated. In the examined peatlands located on morainic uplands, lacustrine sediments of the Late Vistulian and Early Holocene covered by Late Holocene peats are documented. Peatlands located near aeolian forms do not show evidence of continuous accumulation of biogenic deposits. They are particularly sensitive to changes in humidity and they underwent frequent modifications during phases of aeolian activity. The sediments of valley peatlands are not suitable objects for stratigraphic analyses, but they are appropriate for reconstructions of short events that occurred in the river valleys. [ABSTRACT FROM AUTHOR]

A determination of the critical bed shear stress of maerl is a prerequisite for quantifying its mobility, rate of erosion and deposition in conservation management. The critical bed shear stress for incipient motion has been determined for the first time for samples from biogenic free-living maerl beds in three contrasting environments (open marine, intertidal and beach) in Galway Bay, west of Ireland. The bed shear stress was determined using two methods, Law of the Wall and Turbulent Kinetic Energy, in a rotating annular flume and in a linear flume. The velocity profile of flowing water above a bed of natural maerl grains was measured in four runs of progressively increasing flow velocity until the flow exceeded the critical shear stress of grains on the bed. The critical Shields parameter and the mobility number are estimated and compared with the equivalent curves for natural quartz sand. The critical Shields parameters for the maerl particles from all three environments fall below the Shields curve. Along with a previously reported correlation between maerl grain shape and settling velocity, these results suggest that the highly irregular shapes also allow maerl grains to be mobilised more easily than quartz grains with the same sieve diameter. The intertidal beds with the roughest particles exhibit the greatest critical shear stress because the particle thalli interlock and resist entrainment. In samples with a high percentage of maerl and low percentage of siliciclastic sand, the lower density, lower settling velocity and lower critical bed shear stress of maerl results in its preferential transport over the siliciclastic sediment. At velocities ∼10 cm s −1 higher than the threshold velocity of grain motion, rarely-documented subaqueous maerl dunes formed in the annular flume. [ABSTRACT FROM AUTHOR]

Stalactites and moonmilk from Sahastradhara caves in Siwalik Himalayas were studied to understand the role of microbes in their genesis. Fourier spectroscopy in the moonmilk indicates a complex milieu of organic compounds that is unusual for inorganic formations. Stable C and O isotopes show trends in the moonmilk and stalactite, which suggest biogenic input; the geochemical inference is consistent with evidence from microscopy and laboratory-based microbial cultures. Light microscopy of moonmilk samples show the presence of a number of microbial forms similar to Cyanobacteria, and scanning electron microscope (SEM) images show microbial structures similar to Spirulina. The total number of microbial cells using SYBR Gold is 6.5 × 105cells, g sed−1in moonmilk and 3.2 × 105cells, g sed−1in stalactites. FISH indicates approximately 3.5 × 105cells, g sed−1in moonmilk and 2 × 105cells, g sed−1in stalactites. SEM images of the moonmilk indicate a large network of microbial filaments along with minerals, which are identified as calcite based on their x-ray diffraction pattern. In vitro laboratory cultures with pure monogenic strains isolated from the moonmilk and stalactites raise pH in the medium, which facilitate calcite precipitation. The mineral precipitating isolates were identified as:Bacillus pumilis, B. cereus,B. anthracis,B. lentus, B. sphaericus,B. circulansandActinomycetes. The Sahastradhara moonmilk and statactites are colonized by a diverse microbial community and the isolated bacterial strains induce biomineralization on different nutrient media, supporting their biogenic origin. [ABSTRACT FROM AUTHOR]

Heavy metals in the surface sediments and sediment core from the Xiangshan Bay, a mariculture base on the coast of the East China Sea, were determined by inductively coupled plasma mass spectrometry (ICP-MS) in order to evaluate their levels and sources. The results showed that the levels of Cu, Pb, Zn, and Cr in the sediments of the bay have been generally influenced by anthropogenic inputs since the founding of the People's Republic of China. In particular, Cu and Zn were polluted to some extent, as evidenced by high enrichment factors. Organic matter, grain size, wastewater discharge, and low energy hydrodynamic environment played dominant roles in the heavy metal enrichment in the sediments. The ratio of terrigenous source to marine biogenic deposit of trace metals in the sediments was calculated, revealing that terrigenous inputs were the main source of Cu, Pb, and Zn, while biological pellets contributed much more to the enrichment of Cr and Cd. Considering the influence of biological sources on the enrichment of Cd and Cr, and the fact that the sediment has been polluted by Cu and Zn, the development of mariculture and discharge of wastewater into the Bay should be restricted. [ABSTRACT FROM AUTHOR]

Abstract: The reef-forming polychaete Ficopomatus enigmaticus is the main benthic suspension-feeding species of the Mar Chiquita lagoon (37° 40′ S, 57° 23′ W; Argentina) and exerts a strong top-down control on phytoplankton biomass. A large portion of the ingested material is rejected as faeces, and a fraction of the material filtered is packed and discarded as pseudofaeces, which could be deposited on the sediment or horizontally displaced by water flow. In this work we evaluate the effect of this biodeposition on the organic matter (OM) content and productivity of the sediment between reefs. Laboratory experiments show that the OM from biodeposition was 21 times higher than the sediment between reefs and with low C per mg matter/N per mg matter. Sediment traps underneath live reefs showed higher OM content compared to traps underneath dead reefs but only in areas with low water currents, suggesting the importance of hydrodynamic conditions for this process. In situ mesocosms showed that F. enigmaticus decreased up to 45% the phytoplankton biomass, up to 50% the turbidity and up to 20% the particulate OM of the water column and, consequently enhanced up to 50% the OM deposited on the bottom. But there were no differences in the OM of sediment with increased distance from the reefs. Sediment gross primary production was lower in the sediment closer to reefs, but when adults of the high-density local crab that live underneath reefs were excluded, the productivity increased, suggesting that the activity of the crabs could be counteracting the reef effect on sediment. In summary, biodeposits of F. enigmaticus can enrich the sediment, but crab activity and water currents can disperse the suspended and/or deposited material, decreasing the OM content of sediment close to the reefs. However, these effects (suspension feeding and biodeposition) are linked, and could increase flux of particles from water column to the bottom of the lagoon, increasing the benthic–pelagic coupling. [Copyright &y& Elsevier]