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Organic-rich freshwater sediments formed from the remains of water plants, plankton and benthic organisms, which are transformed by microorganisms, and mixed with mineral components supplied from the lake basin, are known as gyttja (sapropel or dy). Gyttja is a valuable natural resource that can be used in various fields such as agriculture, forestry, construction, chemical industry, balneology and the latter ones are especially interested in chemical composition and safety of natural materials. The aim of the study was to investigate micro- and macro-element content of gyttja derived from lakes of eastern Latvia (north-east of Europe). Depending on composition, sediment samples were identified as peaty, various algae, green algae, diatom, carbonate and organic-silicate types of gyttja. Dried samples were wet-digested by heating in HNO3/H2O2 solution until complete mineralization. Sample solutions were analysed by atomic absorption spectrometry (AAS) to detect concentration of Ca, Fe, K, Mg, Mn, Na and Zn, but inductively coupled plasma mass spectrometry (ICP-MS) was applied for As, Ba, Cd, Co, Cr, Cu, Li, Ni, Pb, Rb, Se, Sr and V concentration measurements. Total content of elements was variable; higher macroelement concentration was detected for gyttja of carbonate type, but higher microelement concentration-for organic-silicate gyttja. As concentration of several elements was much lower than permitted by the European Union legislation, gyttja is not only safe, but also highly valuable resource applicable in organic agriculture. There is a potential to use gyttja as a peloid in health care, but element bioavailability should be estimated likewise.

This paper presents results of pollen and macroscopic analyses of a geological core from the village of Bulhary, at the north-eastern foot of the limestone Pavlovske vrchy hills, South Moravia, Czech Republic. The core reached down to about 10 m of aeolic loess layers and some 40–50 cm of compressed organogenic sediments. They accumulated around ca 25,000 years bp. The moss peat and algal gyttja we have analysed were deposited in an ox-bow of the past flood-plain of the river Dyje. The time of the sedimentation may be synchronous with the time when the northern foot of the Pavlovske vrchy hills was inhabited by upper Palaeolithic people of the Gravettian (Pavlovian) culture, dated generally to an Upper Wurmian interstadial. Archaeologists excavated their settlements in the villages of Dolni Věstonice and Pavlov, neighbouring our site of Bulhary. Our analyses permit the reconstruction of the vegetation of that time in the region but may also reveal the environment and living conditions of the Palaeolithic people. In our assemblages over 200 types of palynomorphs (pollen, spores, etc.) have been found, which indicates a very rich flora and vegetation growing in at least six different biotopes of the Pavlovske vrchy hills region: (1) Open, mostly coniferous stands with grass and herbaceous cover in their undergrowth. These were probably situated in the lowest parts of the territory and could also have dominated in the broader vicinity with loess cover. (2) Grass and herbaceous steppe-like vegetation probably occupied the belt above where the trees occurred but still within the loess zone. (3) The highest elevations of the hills and their limestone cliffs formed biotopes for a complex of subalpine (alpine) communities. (4) The flood plain was certainly occupied by very diversified tall-herb vegetation with scattered alder and willow trees or shrubs. (5) Aquatic communities of the infilled stages in the river ox-bows are well documented by microscopic and macroremain finds of water macrophytes, algae and mosses. (6) The presence of scattered spring outflows and their communities is indicated by pollen of typical spring plants, e.g. Chrysosplenium, Montia, Cardamine amara etc. The vegetation, especially that in the flood-plain, produced enough plant biomass to feed numerous herds of large herbivorous mammals, which were hunted by the Palaeolithic tribes. Also the climate was probably relatively suitable for the style of living at that time. It could have been similar to that of the present northern boreal zone of NE Scandinavia and N Russia or even milder.

This study presents a detailed analysis of geochemical and biotic proxies in a lake sediment profile to assess the effects of local and regional environmental drivers on the Holocene development of Lake Loitsana, situated in the northern boreal forest of NE Finland. Multi-proxy studies, in particular those that include a detailed plant macrofossil record, from the part of the northern boreal zone of Fennoscandia which has not been affected by treeline fluctuations, are scarce and few of these records date back to the earliest part of the Holocene. A 9-m sediment sequence of gyttja overlying silts representing the last c. 10,700 cal year, allowed for a high-resolution study with emphasis on the early to mid-Holocene lake history. The lacustrine sediments were studied using lithology, loss-on-ignition and C/N ratios, micro- and macro-fossils of aquatic and wetland taxa, diatoms, chironomids and accelerator mass spectrometry 14C dating on terrestrial plant macrofossils. Our study shows that the local development at Loitsana was complex and included a distinct glacial lake phase and subsequent drainage, a history of fluvial input affected by nearby wetland expansion, and lake infilling in an eventual esker-fed shallow lake. Enhanced trophic conditions, due to morphometric eutrophication, are recorded as Glacial Lake Sokli drained and open water conditions became restricted to a relatively small Lake Loitsana depression. pH appears to have been stable throughout the Holocene with a well-buffered lake due to the local carbonatite bedrock (Sokli Carbonatite Massif). The fossil assemblage changes are best explained by a complex mixture of drivers, including water-body conditions (i.e. depth, turbidity and turbulence), rate of sediment input, and the general infilling of the lake, highlighting the need to carefully evaluate the possible influence of such local factors as palaeoenvironmental conditions are reconstructed based on aquatic proxies.

This study uses the Holocene lake sediment of Lake Ķūži (Latvia, Vidzeme Heights) for environmental reconstruction with multi-proxy records including lithology, computerised axial tomography scan, grain-size analysis, geochemistry, diatoms and macrofossils, supported by AMS radiocarbon dating. Numerical analyses (PCA; CONISS) reveal three main phases in the development of the lake. Response to the Lateglacial–Holocene transition in Lake Ķūži took place around 11,300 cal. BP. Organogenic sedimentation started with distinctive 5-cm-thick peat layer and was followed by lacustrine sedimentation of carbonaceous gyttja. Several findings of the peat layer with similar dated age and position at different absolute altitudes indicate that lake basin was formed by glaciokarstic processes. In the Early Holocene (until around 8,500 cal. BP), the lake was shallow and holomictic, surrounded by unstable catchment with erosion and inflow events. Predominance of diatom species of Cyclotella and Tabellaria, large numbers of respiratory horns of phantom midge pupae (Chaoboridae), high Fe/Mn ratio, as well as the presence of laminated sediments indicates the transition to a dimictic and oligo-mesotrophic lake conditions with high water level, anoxia in the near-bottom and stable catchment in the Middle Holocene (8,500–2,000 cal. BP). This contrasts with many hydrologically sensitive lakes in Northern and Eastern Europe in which the water level fell several meters during this period. During the Late Holocene (from 2,000 cal. BP to the present), the lithological and biotic variables reveal major changes, such as the increase in erosion (coarser grain-size fraction) and eutrophication [diatoms Aulacoseira ambigua (Grun.) Sim., Stephanodiscus spp., Cyclostephanos dubius (Fricke) Round]. Characteristics of lake-catchment system during the Late Holocene reflect anthropogenic signal superimposed on the natural forcing factors. To date, the Late Quaternary palaeolimnological reconstructions using lake sediment has been limited in the Baltic region. Therefore, findings from Lake Ķūži provide important information about environmental and climatic changes that took place in this part of Eastern Europe. This study shows that the relative importance of climate and local factors has varied over the time and it is essential to consider the lake basin topography, catchment size and land cover as potential dominant forcing factors for changes in sedimentary signal.

Post-isolation (9,600 year BP) sedimentology in Lake Pyhajarvi, Finland, was studied using sub-bottom echo-sounding and sediment coring. The sediment sequence appeared in the echo-sounding profiles as two sections: (1) a lower section of homogenous, light grey gyttja clays, and (2) an upper section with dark layers of mainly clay gyttjas and gyttjas, here referred to as C_gyttja. We investigated the thickness and volume of sediments as well as their morphology and areas of accumulation. Approximately 77 % of the lake represents areas of accumulation, containing 34 and 1.3 million tons of dry matter and carbon, respectively. Spatial variability in sedimentological properties indicates that accumulation in the Kirkkoselka sub-basin was focused into the deepest areas since lake isolation. In the Isoselka sub-basin, however, accumulation was focused partially onto the flanks of the depression, whereas the deepest parts (23–27 m) of the sub-basin represent erosional areas. There appears to have also been sediment re-suspension and re-deposition, as indicated by erosion surfaces. This, combined with dune-like bottom morphology in the accumulation areas, provides evidence for the role of wind-driven bottom currents on sedimentation dynamics in the Isoselka sub-basin. Increases in Cu and Zn concentrations, driven by Pyhasalmi mining activities, were used as a geochemical marker for recent sedimentation (RS) between 1966 and 2008. As a consequence of wind-driven bottom currents, 60 % of the metals accumulated in the Kirkkoselka sub-basin and 40 % accumulated in the Isoselka sub-basin. There is a spatial correlation between amounts of C_gyttja and RS. In the middle of dune-like C_gyttja formations in the Isoselka sub-basin, the RS grain size is smaller than in other areas. Variations in RS are greatest along the borders of the accumulation area, likely a consequence of bottom currents in those areas.

Piston cores from deep-water bottom deposits in Lake Ontario contain shallow-water sediments such as, shell-rich sand and silt, marl, gyttja, and formerly exposed shore deposits including woody detritus, peat, sand and gravel, that are indicative of past periods of significantly lower water levels. These and other water-level indicators such as changes in rates of sedimentation, mollusc shells, pollen, and plant macrofossils were integrated to derive a new water-level history for Lake Ontario basin using an empirical model of isostatic adjustment for the Great Lakes basin to restore dated remnants of former lake levels to their original elevations. The earliest dated low-level feature is the Grimsby-Oakville bar which was constructed in the western end of the lake during a near stillstand at 11–10.4 (12.9–12.3 cal) ka BP when Early Lake Ontario was confluent with the Champlain Sea. Rising Lake Ontario basin outlet sills, a consequence of differential isostatic rebound, severed the connection with Champlain Sea and, in combination with the switch of inflowing Lake Algonquin drainage northward to Ottawa River valley via outlets near North Bay and an early Holocene dry climate with enhanced evaporation, forced Lake Ontario into a basin-wide lowstand between 10.4 and 7.5 (12.3 and 8.3 cal) ka BP. During this time, Lake Ontario operated as a closed basin with no outlets, and sites such as Hamilton Harbour, Bay of Quinte, Henderson Harbor, and a site near Amherst Island existed as small isolated basins above the main lake characterized by shallow-water, lagoonal or marsh deposits and fossils indicative of littoral habitats and newly exposed mudflats. Rising lake levels resulting from increased atmospheric water supply brought Lake Ontario above the outlet sills into an open, overflowing state ending the closed phase of the lake by ~7.5 (8.3 cal) ka BP. Lake levels continued to rise steadily above the Thousand Islands sill through mid-to-late Holocene time culminating at the level of modern Lake Ontario. The early and middle Holocene lake-level changes are supported by temperature and precipitation trends derived from pollen-climate transfer functions applied to Roblin Lake on the north side of Lake Ontario.

Pollen was analysed from a sediment sequence collected in the close vicinity of the Mesolithic settlement Tagerup, southern Sweden. Macroremains were also retrieved from numerous samples taken at the site of the archaeological excavations of Kongemose and Ertebolle settlement phases, 6700–6000 b.c. and 5500–4900 b.c. respectively. Plants and other organic remains were well preserved in the refuse layers from the settlements embedded in the gyttja. The pollen record includes no clear indications of human impact on the vegetation during the Mesolithic. The occurrence of charcoal particles and pollen of grass and herbs associated with nutrient-rich soils are contemporaneous with the Kongemose settlement. The Ertebolle settlement phase, although characterised by considerable dwelling activities less than a hundred metres from the pollen sampling site, is scarcely seen in the pollen data. Numerous finds of crushed dogwood stones from the Kongemose phase, often partly carbonised, suggest that these stones were used for the extraction of oil. Other plants found in the Kongemose refuse layers that may have been used are apples, cherries, raspberries, acorns and rowan-berries. Based on the abundance of hazelnut shells found at the studied site and in other studies of Mesolithic sites in southern Scandinavia it is proposed that these remains may testify to an important food supply rather than just use as a supplement to animal protein. It is also hypothesised that a regional decrease in hazel populations and thus hazelnut availability at the end of the Mesolithic may have motivated the adoption of Neolithic subsistence.

We present isotope, cladoceran and diatom results from investigations of Eemian sediments of the palaeolake at Ruszkowek, central Poland. Our analyses of the 15-m-thick sediments indicate that sandy silts occur on the bottom, followed by calcareous gyttja, interbedded with lake marl. The upper part of the sequence contains peat and peaty sands. Values of δ18O change from −9.4‰ to −3.3‰ and δ13C values oscillate between −3.2‰ and +7.0‰. Nine isotope zones (Is) were defined and characterized using stable isotope analysis of carbonates. Fifteen species of subfossil Cladocera were found and six faunal zones were distinguished (Cladocera zones). One hundred and twenty-three diatom taxa, representing 31 genera were identified, enabling us to discern six Diatom Assemblage Zones. The isotope, cladoceran, and diatom data correlate well with pollen data that define seven phases of evolution of the palaeolake at Ruszkowek. The palaeolake began during the final phase of the Wartanian (Late Saalian Glaciation). During the early Eemian, the palaeolake reached its maximum depth. During the Early Vistulian glaciation, the palaeolake declined. Changes in the cladoceran and diatom communities indicate initial oligotrophic conditions in the lake, then an increase to mesotrophy, and finally eutrophic conditions.

Two years of measurements are explored with a view to formulating an ecosystem model for Myall Lake. Stable physical characteristics, low catchment loads, low light attenuation, flat-bottomed hypsometry, and soft gyttja substrate allow stable charophyte biomass throughout the year in Myall Lake. Chara fibrosa dominates the total biomass and is abundant over the depth range 0.5–4 m. Nitella hyalina is found over the same depth range but has diminished biomass at depths greater than 2 m due to increased incidence of zero-biomass samples at depths greater than 1.5 m. Upper bounds for biomass densities were estimated for charophytes. Najas marina has great seasonal variability and meadows can have very high biomass in waters 1.5–2.7 m deep. High biomass of Najas marina is associated with low biomass of Nitella hyalina and may be a factor determining how the biomass of Nitella hyalina is distributed with respect to depth. Patchiness of Najas marina is particularly high. Temperature and light can support two growing seasons for Najas marina but mechanical disturbance is often high in spring and high biomass was only observed in late autumn during the present study. Less than 5% of the present-day production of submerged macrophytes would have been required to produce organic material of the gyttja over a 1,000-year period. The spatial distributions of gyttja and the dominant macrophytes are consistent with wind patterns. Down-lake limits on the distributions of charophytes and Najas marina are related to a gradient in the coefficient of light attenuation that is, in turn, related to proximity to the bulk of the catchment load.

During the Fennoscandian ice recession from the eastern Baltic area, the water level in the Lake Peipsi basin was decreasing and reached a minimum at the end of the Younger Dryas Chronozone. The low lake level episode is represented in the basal deposits by a ca. 0.8 m thick bed of coarse detritus gyttja dated to 9.6–9.1 ka 14C BP. The gyttja lies at an elevation of 20–21 m a.s.l., i.e. about 9 m below the present lake level (30 m a.s.l.), and is buried under a 1.5–2 m bed of fine to medium-grained sand. The overall pollen data indicate a shallow-water littoral environment during the gyttja accumulation in the area studied. The diatom flora in the gyttja is dominated by shallow-water benthic and epiphytic taxa, indicating eutrophic littoral conditions at the time of gyttja accumulation. In the uppermost portion of the gyttja sequence the pollen and diatom successions indicate a short period of land emergence when swampy conditions prevailed in the surroundings.

A comprehensive study (chronological, lithological and geochemical) of an 8.5 m postglacial sediment sequence from Lake Peipsi was conducted to elucidate the effects of lake-level changes on the sedimentary environment and biogeochemical dynamics in a large lake. Four lithological units were distinguished in the sediment sequence studied: clayey silt, slightly laminated greyish carbonaceous gyttja, brownish-grey gyttja and dark gyttja. These units indicate that large shifts in sedimentation processes occurred in the past. The sediment data show that fluctuations in water depth had a profound impact on the lake environment, recorded as changes in the lithological composition, phosphorus content of sediments and composition of diatom assemblages. The corresponding changes are best reflected in sediments accumulated during phases of regression when the lake area was also smaller. As the water depth and area of the lake increased, wave-induced erosion and resedimentation smoothed or even disturbed the initial information. The increase of phosphorus content in the unconsolidated, high-porosity surface sediments (0.5 m) is most probably connected with active diffusion and matter exchange between the water-sediment pools.

Increased concentrations of several trace elements have been observed in water draining areas with sulphidic sediments along the Baltic Sea coast of Sweden and Finland. Some of these elements are harmful to the water environment. The increased leaching of trace elements is often caused by antrophogenic activities, such as ditching, which cause oxidation of the sulphides and thereby acid soil conditions. It is therefore important to recognise areas with sulphidic sediments and, if possible, avoid land use, which causes sulphide oxidation. The aim of this study was to find time effective methods, which can be used to delineate areas with sulphidic sediments. Three areas in Sweden with known occurrences of sulphidic sediments were studied. Data obtained from the mapping program at the Geological Survey of Sweden (SGU) were first studied. Selected sites were thereafter visited and geoelectrical measurements were carried out by the use of several instruments. The results imply that areas with sulphidic sediments are reflected as areas with high trace element contents on SGUs biogeochemical maps, which are based on analyses of trace elements in aquatic plants. The same deposits are often shown as gyttja clay on the maps of Quaternary deposits. Furthermore models derived from airborne electromagnetic measurements show that areas with sulphidic sediments often have a lower electric resistivity than surrounding sediments. Also the results from ground geoelectrical measurements suggest that the sulphidic sediments have a lower resistivity than surrounding fine-grained deposits. That interpretation was verified after stratigraphical studies and analyses of the sulphur contents of the sediments. It is therefore suggested that data from ground geophysical measurements can be used for a detailed delineation of sulphidic sediments, whereas data obtained from airborne geophysical and geological maps give an overview over potential areas with these sediments. The absolute resistivity of the sulphidic sediments varies, however, between the three investigated areas. Complementary corings and stratigraphical descriptions are therefore always necessary to verify the occurrence of these sediments.

We developed a new method for reconstructing millennia-long hurricane records from coastal environments that uses Organic Geochemical Proxies (OGPs) of organic carbon and nitrogen concentrations and their δ13C and δ15N compositions. The new method is independent of presence/absence of sand layers and improves significantly the severe-storm history resolution. The subject of this investigation is a 1.5 m long sediment core raised at 2.8 m water depth from the center of Lake Shelby, Alabama, a freshwater lake located approximately 250 m from the Gulf of Mexico, from which an overwash sand-layer based record was previously derived. The core contains two distinct sediment units; an upper 62 cm thick, fine-grained, organic-rich lacustrine sapropel (gyttja) that shows no visible structures except one sand lamina at 23.7 cm depth, and an underlying 90 cm thick, organic-poor lagoon/estuary clay unit. The sapropel unit was deposited over a 682 ± 30 cal year time interval (1320–2002 A.D.) with a mean sedimentation rate of 0.79 ± 0.04 mm/year. Lake Shelby’s water column exhibits two contrasting states based on water chemistry surveys (i) an “isolated”, stratified, mode under calm weather conditions with a relatively low trophic state, and (ii) a “flooded” mode occurring during storm surges when nutrient-rich seawater floods the lake. Statistically significant δ13C and δ15N positive excursions in organic matter, up to maximum values of −25 (‰ PDB) and 4 (‰ Air N2), respectively, are interpreted as geochemical responses to the marine intrusions that fertilize the lake, increase light availability, and cause eutrophication spikes. Detailed OGPs analyses crossing a sand layer that offers visual evidence of a catastrophic hurricane overwash event at 1717 A.D. exhibit large δ13C and δ15N positive shifts bounded by rapid returns to base values, thus confirming the validity of the hurricane identification by the OGPs model. Our data indicate that 11 catastrophic hurricanes hit the Alabama coast over the past 682 years with a rough recurrence interval of one in 62 years.

Phosphorus content in sediment, water and tissues of three macrophyte species growing in Myall Lake, Australia were studied from January to November, 2004. The sites investigated were North–West (NW), North–East (NE), South–West (SW) bays and Central deep area of the lake (CL). The objective of this study was to investigate how total phosphorus (TP) in plant tissues relate to phosphorus pools and the role played by the aquatic macrophyte species under investigation in phosphorus recycling in the lake. Of the four investigated sites of the lake, TP in plant tissues were significantly higher in North–West and South–West bays compared to the rest. Najas marina had significantly higher TP content (e.g., 1.55 and 1.44 mg/g dw.; P

The article presents the results of lithological and geochemical investigations of recent sediments of Lake Pusty Staw. The analysed sediments document about 300 years of the history of this lake. Historical materials indicate that significant changes in the catchment of the lake took place from the beginning of the 18th century (deforestation and afforestation) followed by 19th century tourist development, and 20th century industrialisation. The sediments were dated using the 210Pb and 137Cs method and core lithology. These made it possible to establish a reliable chronology to the year 1730. The calculated sedimentation rates ranged between 0.17 and 0.83 cm year−1. There was a period of intensified erosion caused by land clearance between 1734 and 1810, which resulted in an acceleration in sedimentation rate (0.36 cm year−1) and a change of lithological type of sediment from detritus gyttja to clayey gyttja. On the basis of Cu, Zn, Cd and Pb content in the sediments, it was determined that the beginning of pollution of the lake dates back to the 19th century and was caused probably by the existence of a health resort. A systematic increase in pollution occurred in the 20th century as a result of industrial plants. Normalised with respect to Al, the content of heavy metals in polluted sediments was from several to twenty times higher than in sediments of the preindustrial period, and a comparison of historical materials with changes of sediments in most cases made it possible to identify the direct causes of the increase in pollution.

Lake Vaha-Pitkusta is a 35-m deep meromictic kettle-hole lake in SW Finland. The topmost 15cm of the sediment stratigraphy consists of black gyttja, representing the last ca. 600years. A sediment core from the deepest point was examined with multi-proxy methods to determine the origin and evolution of the basin, the onset of the meromictic conditions and the primary factors that initiated the meromictic processes. The results indicate that Lake Vaha-Pitkusta became isolated from the Baltic basin during the Yoldia Sea stage. After initial unstable sedimentary conditions the development continued steadily until ca. 2500–2300 cal.BP when there is indication of lake level rise and/or increased surface runoff, probably resulting from a cooler and moister climate. The diatom and cladoceran results indicate only a slight rise in the trophic state following the increased erosion. Pollen evidence suggests weak anthropogenic activity in the catchment during the last 1000 years, and this had only little effect on the trophic state, which remained rather low. Thus, it is most unlikely that the trophic state was the primary reason for the origin of meromixis, although it may have contributed to it. We tentatively suggest that the primary reason was the peculiar morphometric dimensions of Lake Vaha-Pitkusta (small, deep, sheltered from winds) which made it very sensitive and that even a very slight increase in soluble electrolytes may push it over the edge into meromixation. It is possible that this did not occur during the cold/moist period around ca. 2300 cal.BP but during the Medieval Climate Anomaly. Studies on sediment geochemistry are needed to verify this assumption.

A sub-bottom acoustic survey of Devil Lake on the Canadian Shield in southern Ontario reveals three acoustic facies: (I) a moderately acoustically transparent, laminated sequence interpreted as a glacilacustrine deposit in glacial Lake Iroquois or a subsequent phase in water depths up to 200 m greater than at present, (II) a transitional more transparent, less layered facies interpreted as being deposited in a more distal glacial lake from erosion of sediment in the watershed exposed by the failure of the ice dam and lowering of the glacial lake before stabilization by the development of forests, and (III) an acoustically transparent facies with similar transmissivity to the water column, interpreted as Holocene gyttja. Each is spatially variable in extent and thickness in response to those processes. There is only a very weak relation between sediment thickness and the water depth in which it was deposited. Wave processes prevent deposition in water depths less than about 6 m and evidence of erosion to the greatest depths of the lake (>40 m) is pervasive. The data demonstrate the value of acoustic survey in assessing lacustrine processes and the history of lakes, and the significance of such documentation in planning a coring program and in interpreting the results.

Four sediment cores and twenty-five 14C ages from Ritterbush Pond in northern Vermont provide a detailed and continuous temporal record of Holocene lake and watershed dynamics. Using visual logs, carbon content, magnetic susceptibility, stable isotope signatures, and X-radiography, all measured at 1-cm scale, we identify and date discrete layers of terrestrially-derived sediment in the organic-rich, lacustrine gyttja. These inorganic layers range in thickness from 10 cm and range in grain size and sorting from homogeneous silt to graded sand. AMS radiocarbon ages both from macrofossils within the thickest layers, and gyttja bracketing these layers, provide the basis for correlation among the cores, the dating of 52 basin-wide sedimentation events, and the development of a detailed sedimentation chronology for the Holocene.

The sedimentology of an 8.22-m long core of late-Holocene deposits in the submerged Crescent Island Crater basin of Lake Naivasha, Kenya, is used to reconstruct decade-scale fluctuations in lake-surface elevation during the past 1800 yrs. Lake-depth inference for the past 1000 yrs is semi-quantitative, based on (1) relationships between lake level and bottom dynamics predicted by wave theory, and (2) historical validation of the effects of lake-level fluctuation and hydrologic closure on sediment composition in Crescent Island Crater and nearby Lake Oloidien. In these shallow fluctuating lakes, organic-carbon variation in a lithological sequence from clayey mud to algal gyttja is positively correlated with lake depth at the time of deposition, because the focusing of oxidized littoral sediments which dilute autochthonous organic matter before burial is reduced during highstands. The lake-level reconstruction for Lake Naivasha agrees with other adequately dated lake-level records from equatorial East Africa in its implication of dry climatic conditions during the Mediaeval Warm Period and generally wet conditions during the Little Ice Age. Crescent Island Crater survived widespread aridity in the early-19th century as a fresh weedy pond, while the main basin of Lake Naivasha and many other shallow East African lakes fell dry and truncated their sediment archive of Little Ice Age climatic variability.

A 341 cm long sediment sequence was recovered from the unofficially named Raffles So on Raffles O, outer Scoresby Sund region, East Greenland. The sediment sequence consists in the upper part (0–230 cm) of a stratified gyttja enriched in organic carbon and biogenic silica whereas the lower core part (235–341 cm) is composed of terrigenous, consolidated glacio-limnic sediments. 14C-AMS measurements indicate that the sediment sequence represents the entire Holocene lake history from 10,030 calibrated radiocarbon years. The geochemical parameters (opal, total organic carbon (TOC), total nitrogen (TN)) and the total diatom concentration show similar developments during the Holocene, and reflect changes in biological production and nutrient input into the lake. These records clearly reveal a broad Holocene TOC-opal-maximum interval between 5200 and 1800 cal. yrs BP. The diatom flora consisted of 66 taxa representing 20 genera but only seven taxa were abundant and, sometimes, these were monospecifically dominant during the Holocene. In the sediment core from Raffles So four successive stratigraphical zones can be distinguished. Accumulation of diatom valves began at 9900 cal. yrs BP with a Stephanodiscus minutulus (Kutz.) Cleve and Moller dominated assemblage (stratigraphic zone 1) followed by a diatom flora dominated by Cyclotella pseudostelligera Hustedt and, less frequently, by Diatoma tenuis Agardh (9400 until 5900 cal. yrs BP, zone 2). Cyclotella sp. A, a taxon which belongs to the Cyclotella rossii-comensis-tripartita-complex, was the dominant floral element between 5200 and 1800 cal. yrs BP (zone 3). From 1800 cal. yrs BP, the periphytic taxa Fragilaria capucina var. gracilis (Ostr.) Hustedt and F. capucina var. rumpens (Kutz.) Lange-Bertalot attained highest relative abundances, also almost monospecifically (zone 4). The distribution and composition of the diatom assemblages in the sediment record from Raffles So probably reflect past variations in the extent of the lake-ice cover during the growing season. More or less ice-free conditions during summer may have prevailed during the early Holocene until ca. 1800 cal. yrs BP, which allowed growth of planktonic diatoms (Cyclotella taxa) in the pelagic lake region. From 1800 cal. yrs BP, colder conditions lead to a perennial lake-ice cover with a small ice-free moat in summer which favored the growth of periphytic, littoral species (Fragilaria capucina varieties).

Freshwater bryozoans were investigated during field studies of 601 lakes and other surface water bodies throughout Norway from 1960 to 1978. The frequency of occurrence of the two Fredericella species was evaluated in relation to 12 environmental variables. Statistically significant deviations from the frequencies expected on the basis of random distribution were described using the categories preference, avoidance and absence. The typical European Fredericella sultana (with glossy statoblasts) occurred at 72 localities, north to 70° 25′ N (the northernmost record on a global scale). Its frequency dropped towards the north. Maximum elevation above sea level was 1097 m (maximum recorded for Northern Europe). Another species with pitted statoblasts, tentatively considered to be Fredericella indica, occurred at 50 localities, north to 71° 09′ N (the northernmost record reported to date). The geographical distribution reflected a typical northern cold-water species. One third of the 50 records were from lakes situated north of the Arctic Circle, and rich colonies were found on the North Cape plateau, as far north as possible on the European mainland. The few records from southeastern Norway were from high mountain lakes, up to 1397 m above sea level (highest record for Europe). This species was not found in any of the numerous lowland lakes investigated in southeastern Norway where F. sultana was common. Both species tolerated a cold climate, especially Fredericella indica, and they occurred in a wide range of environments. F. sultana preferred lakes with rather low elevation above sea level, rich vegetation with plant species typical for eutrophic environments, gyttja sediments and stony "hard" shores, some wave action, high content of calcium, and slightly coloured water. This species avoided ponds and was absent from ditches and mires, avoided dystrophic lakes surrounded by Sphagnum bog, with dy sediments and strongly coloured water, avoided sites with small wave action, was indifferent to magnesium and low concentrations of calcium, and was absent from lakes with pH below 5.4. F. indica was only recorded from lakes. It preferred rather low temperatures, oligotrophic conditions with poor aquatic vegetation and stony shores, some wave action, pH above 7.0, and low water colour (below 11 mg Pt l−1). This species avoided lakes with high temperatures and was absent above 20 °C, was absent where aquatic vegetation was rich or consisted of Sphagnum bog, avoided lakes with soft sediments of dygyttja and dy, places with small wave action, acid lakes, was absent at pH below 5.9, tended to avoid water with colour above 10 mg Pt l−1 and was absent in lakes with colour above 40 mg Pt l−1. F. sultana and F. indica occurred together in only six lakes, four in the north, and two in the southern mountain areas. The opposite sensitivity and reactions of the two species towards several environmental variables were supported by a logistic regression analysis. The main ecological difference between the two species is that F. indica appears to be more strongly dependent on climatic factors.

Sediment cores recovered from Lago di Mezzano, central Italy, were petrographically and geochemically (dry densitity, total organic carbon) investigated. A floating chronology was established with sedimentation rates derived from varve thickness measurements, and this chronology was both supported and extrapolated with calibrated AMS-14C-datings. The profile has a length of 29.7 m and comprises a total of 34,000 years. Late Pleistocene sediments consist of minerogenic-organic mud with few benthic diatoms and an organic carbon content of 2%, thus suggesting a high allochthonous input. The onset of the Late Glacial at 14,580 cal BP is documented by a lithologic change to more organic-dominated sedimentation. The Younger Dryas cold event is recorded between 12,650 and 11,400 cal BP and exhibits higher dry densities and minerogenic input. These dates agree with records from other lacustrine archives in Europe and the Greenland ice cores. The early Holocene comprises a laminated organic diatom gyttja deposited at a time of climatic amelioration and increased primary productivity. The establishment of an anoxic hypolimnion enhanced the varve and organic matter preservation. Since 3700 varve years BP the sedimentation pattern has been strongly influenced by human impact, as documented by the increase in minerogenic sediments and turbidites as well as higher sedimention rates. The onset of this influence coincides with a Bronze Age settlement at the lake shore.

We studied Holocene lake-level fluctuations from a small lake, Iso Lehmalampi, southern Finland, utilizing cladoceran and diatom analyses. We report data from a sediment core (A) taken from the deepest part of the lake (8.1 m) where two layers of moss, mixed with gyttja, were found. These layers were formed in situ during the early Holocene (1. ca. 8100-7900, 2. ca. 7300 BP). Lake-level fluctuations were inferred also from another core C, which did not have moss layers. According to the ratio of planktonic/littoral Cladocera, the water level was high around 9000 BP and started to fall before 8000 BP. The lowering continued until 7000 BP and the moss layers were formed during this lowering. Water level was high again ca. 6000 BP and lowered towards ca. 4000 BP. The late Holocene is characterized by several rapid fluctuations of lake-level. The ratio of planktonic/littoral Cladocera and the diatom species composition in core A showed drastic changes between the moss layers and the non-moss gyttja sections of the core. We suggest that they reflect changes in sedimentary facies between the local moss environment and the pelagic bottom. Thus, cores which contain moss layers may lead to erroneous interpretations of lake-level fluctuations.

The accumulation of heavy metals and trace elements has been investigated in a well laminated sequence of Holocene and late Pleistocene lake sediments composed of diatomaceous gyttja, tuff and silt and clay sediments. Varve chronology of the annually deposited gyttja yielded a continuous high-resolution time sequence and allowed the absolute age dating of the sediment. Fluxes of elements remained largely uniform from the late Pleistocene into the Holocene. Higher trace element and heavy metal fluxes occur from 2322 to 862 VT years ago (VT: varve time, years before 1950) and reached their maxima in the uppermost sediments (

Methanogenesis was measured during the summer of 1994, in sediment coresand bulk samples from a Phragmites australis wetland in northern Jutland,Denmark. We compared sediment from healthy reed and dying-back reed, andan open lagoon resulting from die-back. Cores revealed variability withdepth and between sites, with the highest rates coinciding with layers oforganic gyttja, and negligible methane production from the underlying sandbase. Methanogenesis rates in the lagoon and die back sites were higher(up to 100–150 nmol h-1 g-1dry wt. sediment) than in the healthy reed (50–80 nmolh-1 g-1), with the highest rates being recordedfrom May to July. At these times, methanogenesis was markedly temperature-limited; samples incubated at 30 °C anon-limiting temperature, gave rates as high as 200–400nmol h-1 g-1 for the lagoon and die-backareas and 150 nmol h-1 g-1 for the healthyarea. Addition of 8 mM acetate and H2/CO2headspace suggested that both acetate-fermenting andCO2-reducing bacteria were present. Acetate additions suggested some co-limitation by substrate availability, with acetate limitation occurring in the healthy site during July and in the die-back site during August. Lower rates during August, especially in the healthy area, were associated with low water levels which resulted in more oxidized sediments. The data reveal highly variable methanogenesis in the sediment which, when considered with sediment depths, indicates that sites of Phragmites die-back have significantly greater rates of anaerobic mineralization than surrounding healthy wetland, and may be intense sources of methane.

As many as 2500 interdune lakes lie within the Nebraska Sand Hills, a 50 000 km stabilized sand sea. The few published data on cores from these lakes indicate they are typically underlain by less than two m of Holocene lacustrine sediments. However, three lakes in the southwestern Sand Hills, Swan, Blue, and Crescent, contain anomalously thick marsh (peat) and lacustrine (gyttja) sediments. Swan Lake basin contains as much as 8 m of peat, which was deposited between about 9000 and 3300 years ago. This peat is conformably overlain by as much as 10.5 m of gyttja. The sediment record in Blue lake, which is 3 km downgradient from Swan lake, dates back to only about 6000 years ago. Less than two m of peat, which was deposited from 6000 to 5000 years ago, is overlain by 12 m of gyttja deposited in the last 4300 years. Crescent Lake basin, one km downgradient from Blue Lake, has a similar sediment history except for a lack of known peat deposits. Recently, a 8-km long segment of a paleovalley was documented running beneath the three lakes and connecting to the head of Blue Creek Valley. Blockage of this paleovalley by dune sand during two arid intervals, one shortly before 10 500 yr BP and one in the mid-Holocene, has resulted in a 25 m rise in the regional water table. This made possible the deposition of organic-rich sediment in all three lakes. Although these lakes, especially Swan, would seem ideal places to look for a nearly complete record of Holocene climatic fluctuations, the paleoclimatic record is confounded by the effect dune dams have on the water table. In Swan Lake, the abrupt conversion from marsh to lacustrine deposition 3300 years ago does not simply record the change to a wetter regional climate; it reflects the complex local hydrologic changes surrounding the emplacement and sealing of dune dams, as well as regional climate.

Profiles of percent carbon and nitrogen, carbon/nitrogen (C/N) ratios and stable carbon (δ13C), and nitrogen (δ15N) isotopic ratios in organic matter from an 11.6 m core were used to reconstruct environments of deposition in the Swan Lake basin during the past 5300 YBP. The upper 6.5 m consisted of gyttja containing variable amounts of reddish brown-colored fine organic matter and calcium carbonate. It was followed by a 0.5 m sandy silt, which was followed by a 3.6 m reduced layer characterized by large quantities of black organic plant remains, sapropel, and then by another sapropel layer consisting mainly of well-sorted sapropelic sand with relatively low organic matter content. The C- and N-contents in the organic matter in the sediment profile ranged from 0.5 to 23% and from 0.02 to 2%, respectively. Carbon content were positively correlated to both N and clay content while carbon content was negatively correlated to sand content. Two major environmental phases in Swan Lake were apparent from large differences in the C and N data of the sediment organic matter. These include the sapropel (marsh) stage that stretched from approximately 5330 to 3930 YBP, and the following gyttja (open water stage). During the sapropel marsh plants identified in a previous pollen study as cattails and sedges proliferated and produced copious amounts of well-preserved organic matter. C/N ratios, δ13C values, and δ15N values in the sapropel were significantly different from those that characterized organic matter in the gyttja. During the gyttja δ13C values indicated that deep primary producers have dominated lake biomass. By utilizing bicarbonate as their C-source, the accumulating biomass became relatively enriched δ13C values. The presence of high sediment CaCO3 contents indicated more alkaline and deeper water conditions prevailed during the gyttja. Further refinement of the data suggested that each major phase initially contained an identifiable transition stage. During the sapropelic (initial marsh stage) which occurred before 5330 YBP, sand content gradually decreased as organic matter increased. As reflected by high C/N ratios and slightly enriched δ13C values, these sands appear to have contained sufficient permeability to promote partial mineralization of accumulated organic-N containing compounds. A short initial gyttja transition period from about 3930–3830 YBP occurred in which the sediment silt content was anomalously high relative that measured in the surrounding layers. The silt content suggests that this turbid transition layer can not be completely explained by sediment mixing via bioturbation. The silts appeared to have been associated with the sharp climate change that resulted in higher water-table conditions during the gyttja stage.

Methods of preparative centrifugation eliminate many of the difficulties involved in preparing pollen concentrates from deposits rich in resistant organic material. Density centrifugation for the separation of pollen from a gyttja sample rich in resistant organic matter was tested. Combining centrifugations in two CsCl solutions, one of higher density and one of lower density than pollen, a pure pollen fraction was successfully prepared. Data on the isodensity and sedimentation rate of ‘fossilized’ recent pollen from twelve tree taxa are also presented, and the potential for separating a single taxon from pollen assemblages is demonstrated.

Pollen analysis was carried out on gyttja from the small lake Femtingagolen in the Smaland Uplands, southern Sweden. The interpretation of the pollen diagram focused on land-use history and comparisons were made to archaeological and historical information from the area. An absolute chronology, based on AMS dates from terrestrial plant macrofossils, was complemented by inferred dates. The pollen analytical data suggest interference with the woodland cover from ca. 1700 B.C. onwards. Intensified grazing and forest clearances resulted in semi-open pastures between ca. A.D. 400–600 which was followed by forest regeneration (chronology based on AMS 14C dates and cross-correlation with other well dated profiles). The landscape became more open again between A.D. 800 and 1400. Animal husbandry was complemented by small-scale shifting cultivation during the Iron Age. Permanent arable fields were probably not introduced until the Late Iron Age or the Middle Ages. Hordeum and Triticum were grown during the Iron Age, Hordeum, Triticum, Secale and Cannabis sativa during the Middle Ages and early Modern time, and Hordeum and Avena in the recent past. Sandy and silty soils, where stone clearance was not necessary, have probably been used for cereal growing in prehistoric and historic time.

Phosphorus (P) reactivity and bioavailability in lake sediments may be determined by different forms of P and their distribution. Reactive and nonreactive P pools in two shallow subtropical lake sediments (Lake Apopka and Lake Okeechobee) were determined by sequential chemical extraction using 1 M NH4Cl (pH 7.0), 0.1 M NaOH, and 0.5 M HCl, reportedly representing loosely-bound P, Fe- and Al-bound P, and Ca- and Mg-bound P respectively. The sequential P fractionation was tested using pure P compounds and selected P minerals. The scheme effectively separated Fe- and Al-P from Ca-P fractions in an FePO4-AlPO4-Ca3(PO4)2 mixture. Readily available P, defined as the sum of water-soluble P and NH4Cl-extractable P, in the unconsolidated gyttja (UCG) layer (surface 0–30 cm) of Lake Apopka sediments accounted for 10.1 to 23.7% of total P (TP). This sediment P fraction constitutes a large reservoir which may act as a source of P to the overlying water. In subsurface marl layers (134–148 cm depth) of Lake Apopka, NH4Cl-P constituted

The purpose of this paper is to present the results of tests on the shear strength and compressibility of an organic-calcareous lacustrine deposit (gyttja). Physical and chemical properties of the detrital-calcareous gyttja of Grabowo are described herein. A ternary solid phase and colloidal liquid phase is a characteristic of gyttja.

The present Special Issue “Processes, Mechanisms and Utilization of Organic Soils” contains selected papers presented in a special session at the European Geosciences Union (EGU) General Assembly held in Vienna, Austria in April 2007. The goal of this session was to discuss natural organic soils and sediments, peatlands (fens and raised bogs), mires, gyttja, as well as mucks, their main physico-chemical processes and their utilization. Peat is a highly organic sediment (less than 25% of ash) whose physical, chemical and biological composition hardly depends on climate, topography, hydrology and geology. Humus in organic soils is composed of known and unknown chemical structures, whose impact on the physico-chemical properties (e.g., cation retention, metal chelation, hydrophobic interactions) and processes is of paramount importance. Peat is of interest to scientists in a variety of disciplines, such as plant ecology, organic geochemistry, soil science, coal geology, agronomy, and environmental sciences. Even though this topic was often considered in most of the agrochemistry, ecology, organic substrates, humic substances, landscape ecology and soil science meetings all around the world, the EGU meeting in Vienna has been the occasion to organize, for the first time ever, a specific comprehensive session on different aspects and approaches, with contributions from renowned experts of peat and organic soils sciences. Further, several young scientists involved in poster and oral presentations participated in very active and live debates during the meeting, promoting the session as a permanent forum of discussion, cooperation and exchange of scientific and professional experiences. During this session, the most recent progress and advancement in soil physics, soil chemistry, soil biochemistry, and soil microbiology of organic soils and their interactions with various components (organic vs. inorganic, natural vs. anthropogenic) have been extensively discussed. The papers that emerged from the meeting in Vienna reveal that peat comprises either relatively unstable substances, whose reactivity contributes to its usefulness, or highly stable, recalcitrant fractions, both involved in the fate of organic and inorganic pollutants. Some investigations described the physiological activity of peat in stimulating and promoting plant growth. Among other topics raised and discussed were: changes of the carbon cycle in oligotrophic bogs in Western Siberia due to climate change Plant Soil (2009) 315:1–2 DOI 10.1007/s11104-008-9825-8

Lake Balboa is a deep sinkhole lake in south Georgia. Subbottom acoustic profiling and long sediment cores reveal four stratigraphic units within >20 m of lacustrine fill above acoustically stratified and faulted Miocene/Pliocene overburden and basement Eocene limestone which hosts the Floridan Aquifer system (FAS). Fill consists of thin, rhythmically bedded, peaty sediments (Unit I), indicative of slow sedimentation in a shallow swamp until 13,110–12,680 cal BP, a mix of desiccated and over-consolidated clay and silty sand (Unit II) implying periodic subaerial exposure of the lake bed until 9470–9025 cal BP, and gyttja associated with a rapid 8 m rise in water level by 9120–9020 cal BP (Unit III), as well as an additional rise of 10 m to modern lake levels (Unit IV). Accumulation of nearly 4.5 m of low permeability gyttja, and higher lake levels have fundamentally changed exchange between surface water and groundwater, reducing by 40% or more the rate of vertical leakage to the FAS and increasing shallow aquifer discharge to the lake.

The longest continuous Amazonian palynological record (ca 7010 yrs B.P. to present) from Lake Ayauchi, Ecuador, reveals species-by-species abundance changes during a period of climatic change. Pollen influx from a wet tropical rain forest was found to be high, 1×104−105 grains cm-2 yr-1, although mature forest taxa were poorly represented. Horizons of laminated sediments and weathered gyttja, dated to ca 4200–3150 B.P., evidence a period of reduced net water availability. During this period Ficus, Alchornea and Palmae pollen representation appears to decline, although there is no evidence of a major forest compositional change. The lake was reduced to a shallow, possibly seasonal, pool. Zea cultivation was recorded between ca 2850 B.P., (the earliest paleoecological record to date in the Amazon basin) and ca 800 B.P. It is suggested that Zea was cultivated on exposed lake sediment within the crater at times of low water levels. The abandonment of Zea cultivation may have been due to rising water levels or social unrest.

Close study of past interglacials might indicate how and when the present interglacial will end and whether the limit is heading towards a warming or a cooling. No certain prediction has been possible because of man's interference with the environment. But it is reported that when exploring the records of past temperate intervals frequent signs of abrupt changes of local environment were observed. In particular, abrupt shifts in forest composition end each Pleistocene interglacial whose record was studied in detail. In Grand Pile (north-east France), the Eemian (s.s.) (oxygen isotope substage 5e) temperate forest was replaced by a pine-spruce-birch taiga within ~150+/-75 yr. These results are based on rich pollen content of continuously deposited laminated gyttja and on the assumption of a constant sedimentation rate during the last 11000-yr long interglacial.

Langsee lies in the southern Austrian alps and exhibits permanent meromixis. The lake sediment profile consists of a layer of glacial clay, then gyttja and an upper layer of sapropel. The 7 m core was analyzed for 24 metallic and 4 biophilic elements. The geochemical principles of isomorphism and atomic substitution were used to explain the association of chemically dissimilar element pairs such as K, Ba and Mg, Ni. High concentrations of S early in the gyttja zone indicate that meromixis occurred early in the history of the lake.

Etwa 100 000 Jahre alte, interglaziale Gyttja aus Rodebak im westlichen Danemark (Riss-Wurm-Interglazialzeit) wurde mit Ather extrahiert und die Extrakte mittels Papierchromatographie getrennt und untersucht. Es wurden grune, gelbe und rote Pigmente gefunden. Aus den Absorptionsspektren und der Fluoreszenz dieser Stoffe ergibt sich, dass die grunen Pigmente Chlorophyllderivate, die gelben (sowie wenigstens eines der roten) Karotinoide sind. Die Gyttja enthielt schr wenige bestimmbare Pflanzenreste, hauptsachlich nur Pollen und Diatomeen. Die Farbstoffe mussen von lebenden Pflanzen im interglazialen See, in erster Linie Algen, herruhren, und haben infolge Lichtabschluss und niedrigem Redoxpotential sowie niedriger Temperatur ausserordentlich gute Aufbewahrungsbedingungen gefunden; normalerweise werden solche Stoffe schnell abgebaut.

AS part of the joint study on the palaeolimnology of Lake Biwa-ko and the Japanese Pleistocene, a core 197.2 m long was taken at a point 65.2 m deep in the central region of the lake. The core, containing about forty thin layers of volcanic ashes, is composed chiefly of gyttja and fine clay and is now being analysed in various ways, for example palaeomagnetically. A continuous series of almost 10,000 oriented specimens (each 2×2×2 cm) was taken along the central axis of the core for palaeomagnetic investigations.