A note on the growth-rate and year-class strength of bream, Abramis brama (L.), in three eutrophic lakes, England

In this study some comparative observations on the growth-rate and year-class strength of bream, Abramis brama , in three Shropshire-Cheshire meres are given. All populations are exposed to variable recruitment. The occurrence of four strong year-classes (1959, 1966, 1969,1973) suggests that climate is an important factor influencing spawning success. Water temperatures ≥16°C in July and August may be particularly important. All other intervening year-classes are absent. The growth-rate of bream in Tatton Mere and Ellesmere Mere is good ( L ∞= 541–561 mm) but comparatively poor ( L ∞= 448 mm) in Cole Mere. The significance of population density, food supply and parasitic infestation by Ligula intestinalis is discussed.     

The influence of land use on the sedimentation of the river delta in the Kyrönjoki drainage basin

Sediment surface samples (0–2 cm) from 66 sites, and longer cores (up to 540 cm) from 9 sites in the estuary of the river Kyrönjoki, Western Finland, were analysed for organic content, P, Fe, Mn, Pb, Cd, Cu and Zn. One core was dated on the basis of annual laminations.Chemical analyses of the cores showed that organic matter and heavy metal content have increased in recent decades. The heavy metal content was clearly lower than in areas polluted by industry. The sedimentation rate in the delta increased between the 1930s and 1950. It decreased in the 1960s, and has been below 1930s levels since 1970. The sedimentation rates of organic matter were fairly stable all through the period measured, even though the organic content increased.The increase in organic matter and the heavy metal content of the sediment in recent decades is evidently due to the increased intensity of agriculture, forestry and peat harvesting in the drainage basin. Drainage of peatlands in particular has increased erosion and the organic sediment load of the river. Reservoir building after 1970 has decreased the sedimentation rates in the delta.     

Paleolimnological studies of annually-laminated sediments in Loe Pool,Cornwall, U.K.

The sediments of Loe Pool, a eutrophic coastal lake in south west England, consist largely of laminated clays and clay-gyttjas. Studies of the diatom microstratigraphy of frozen sediment cores from the Pool indicate that the laminations are annual, and that they contain pairs of light and dark bands formed by seasonal variations in the supply of sediment to the Pool from its catchment. Analysis of the magnetic properties of individual laminations demonstrates the presence of physical and mineralogical microstratigraphic variations, which may also be related to seasonality. A varve chronology, which is confirmed by ¹³⁷Cs analysis and historical records, has been used to provide a timescale for the interpretation of data from other paleolimnological studies. A close agreement between variations in the abundance of sedimentary Sn, and the history of mining in the catchment, has been found. Similarly, analysis of total organic matter, total phosphorus, sedimentary chlorophyll a, sterols, diatoms and Cladocera in the uppermost sediments all indicate eutrophication of the Pool in the period AD 1940 to the present.     

The impact of the kelp (Laminaria hyperborea) forest on the organic matter content in sediment of the west coast of Norway

Sediment cores were collected from an area off the west coast of Norway, where a well-established kelp community made up mainly of Laminaria hyperborea is found. Chemical analyses of the sectioned sediment cores were made, which included organic carbon, carbohydrates and phenols. These were used to collate the sediments in order to establish whether the different sites had a common origin and if this was kelp-related. The organic matter content in the surface sediments appears to be related to the water depth, which determines the degree of perturbation at the sediment-water boundary and hence the sedimentation of the organic matter. The relation between carbohydrates and phenols in the sediment appears to indicate a common origin. However, the carbohydrate and phenol content in the sediment organic fraction appears to closely resemble (to be analogous) to that of the kelp Laminaria hyperborea. Although there are some diagenetic and decomposition changes in the subsurface (historical) organic matter (that may alter its findings), this study provides good evidence that the deposits were supplied by the kelp forest in the region. The sedimentation and export of kelp-derived material is of particular significance in terms of benthic ecology and production and may also play a significant role in the global carbon budget.     

Relationship of Foraminifera and thecamoebian distributions to sediments contaminated by pulp mill effluent: Saguenay Fiord, Quebec, Canada

Gravity cores and grab samples collected in the Saguenay Fiord between 1976 and 1988 contain the record of a 20th century benthic marine environment contaminated primarily by organic matter discharges from several local pulp and paper mills.Spiroplectammina biformis is the dominant arenaceous species. Its living percent abundance decreases between 1982 and 1988 as a consequence of the apparent recolonization of the upper reaches of the fiord by several arenaceous taxa, the most important beingTextularia earlandi. Cassidulina reniforme, the dominant living calcareous species, shows about a three fold increase in relative abundance over the six year interval. Grab sample observations also suggest a recolonization of some formerly barren benthic environments near the head of the fiord by foraminiferal species between 1982 and 1988. This recolonization may reflect the combined effect of government regulations imposed on local industrial polluters in the early 1970's and the capping of a large area of contaminated sediment by a layer of clay that was transported to the basin at the head of the fiord as the result of a catastrophic landslide in 1971.X-radiographs of core sections from a basin at the head of the fiord show sharp laminations that reflect both the absence of bioturbators and the seasonal variation of fluvial depositional processes. Organic waste deposition from pulp and paper mill outfalls first increased around 1910 and shows a first order inverse relationship to benthonic foraminiferal assemblage diversity. The presence of only allochthonous thecamoebian and reworked planktonic Foraminifera tests in many benthonic Foraminifera-barren core intervals supports the idea that common indigenous estuarine species such asSpiroplectammina biformis were excluded from these areas at certain times as a consequence of pollution “stress” rather than having been removed from the sediment record as a result of post-depositional diagenetic effects. However, future studies of estuarine pollution history based on proxy foraminiferal data from cores must give greater emphasis to distinguishing ecological stress responses from diagenetic process (i.e. test dissolution effects) since both mechanisms can be reflected in the proxy pollution “signal” in a similar way.     

The laminated sediments of Loch Ness, Scotland: Preliminary report on the construction of a chronology of sedimentation and its potential use in assessing Holocene climatic variability

Two sediment cores, ca. 6 m long, have been recovered from the north basin of Loch Ness, Scotland. Each consists of ca. 4.5 m of laminated gyttja, terminating in a basal grey, unlaminated clay. A suite of three ¹⁴C AMS dates have been obtained, and place the base of the gyttja at ca. 9500 yr B.P. Investigations into the structure, composition and formation of the laminae are in progress. Analysis by Backscatter Scanning Electron Microscopy (BSEM) has demonstrated that they consist of couplets comprising dark, clay-rich sediments thought to be deposited from spring to autumn, and pale, silt-rich layers believed to represent sedimentation through winter. The laminae are thus thought to record incidence and intensity of streamflow into the Loch over the past nine millennia, and thus illustrate environmental change over the region for most of the Holocene. X-ray densitometry has been utilised in order to count the laminations and test the hypothesis that they are varves. It has, however, proved difficult to obtain a continuous sequence of countable laminations, although it has been possible to construct a fragmented, floating chronology which indicates that the hypothesis may be correct. Examination of lamination thickness reveals that although the average rate of sedimentation throughout the time periods studied seems to have remained fairly constant, significant variations have occurred. As Loch Ness is located on the northwest oceanic fringe of Europe, any climatic signal which the laminations contain will be closely related to even larger scale events over and within the North Atlantic Ocean, which is a major controller of global climate. Preliminary statistical investigation of sequences of laminae is being carried out in order to search for periodicity of sedimentation which may then be related to appropriate climatic indices.     

Comparison of the Vertical Distribution of Nematodes from Two Contrasting Abyssal Sites in the Northeast Atlantic Subject to Different Seasonal Inputs of Phytodetritus

The vertical distribution of nematodes in the sediments of three cores from the phytodetritus-influenced Porcupine Abyssal Plain station is compared with three cores from the Madeira Abyssal Plain station in the DEEPSEAS programme. Nematode vertical distributions are compared with sediment organic chemistry data sampled at the same time from the same sites. The results support the two hypotheses erected by Thiel (1983) that the penetration of meiofauna into deep-sea sediments might be correlated with the input of organic matter and that a greater biological activity of larger organisms would increase the penetration of nematodes into the sediment through increase downward transport of food material.     

Recent patterns of sediment accumulation in a small closed eutrophic lake revealed by the sediment records

A short-core palaeolimnological investigation was undertaken with the aim ofacquiring knowledge of sediment deposition. Analyses of the lithological composition of sediments from the whole-lake basin were performed on the small eutrophic L. Linajärv (northern Estonia) and the concentrations of mineral and organic matter were measured on 647 sub-samples from 14 sediment cores. The accumulation rate of the sediment sequences was established and C/N ratios of organic matter in some cores were recorded. Results indicate that the water depth, basin slopes and distance to the shore have the most important impact on the physical sediment properties. It was shown that variations in the mineral matter concentrations were influenced by the changes in deposition conditions in the areas with steep slopes. The study indicated that more objective information about the sedimentation mechanisms is obtained using analysis of the concentration ratio of mineral and organic matter since it reduces the implied role of diagenetic compaction.     

Late Quaternary fluctuations of palaeoproductivity in the Murray Canyons area, South Australian continental margin

Two sediment cores from the Murray Canyons area, south of Kangaroo Island, South Australia, were investigated for proxy-records to reconstruct past productivity of the surface waters in the area over the last 175 ka. The proxies used included concentrations of aragonite, low- and high-Mg calcite, total carbonate, total organic carbon, sulfur and δ¹³C of Globigerina bulloides. Cyclic increases in palaeoproductivity were observed to be in tune with insolation minima at 30°S.

The atmospheric conditions during insolation minima were comparable to present winter patterns, when strong westerly winds dominate over the area and bring dust from the central desert areas. During the last insolation minimum (last glacial maximum: LGM), the Murray Canyons laid directly under the “Eastern Australian Dust Plume”. Dust could have fertilized surface waters and initiated the observed productivity “increases” on a precessional time scale. The core from the more westerly canyons is richer in organic matter; this could be attributed to the influx of organic matter from shallower water, which is carried by an overflow of hypersaline water from the Spencer Gulf to the deep ocean, using the western canyons as conduits. There is no evidence that the “Palaeo-Murray River”, which debouches close to the core sites during sealevel lowstands, was a major source of nutrients for surface waters. Although total carbonate concentrations remained high, planktonic foraminifers were fewer in numbers during these periods, possibly due to reduced light penetration caused by suspended river material. A deglacial minimum in δ¹³C of Globigerina bulloides, observed in other cores from the southern hemisphere and attributed to a major hydrographic change south of the Polar Front, is also visible in our two cores, thus attesting to the global significance of the event.     

Formation of micro‐spherulitic barite in association with organic matter within sulfidized stromatolites of the 3.48 billion‐year‐old Dresser Formation,Pilbara Craton

The shallow marine and subaerial sedimentary and hydrothermal rocks of the ~3.48 billion‐year‐old Dresser Formation are host to some of Earth's oldest stromatolites and microbial remains. This study reports on texturally distinctive, spherulitic barite micro‐mineralization that occur in association with primary, autochthonous organic matter within exceptionally preserved, strongly sulfidized stromatolite samples obtained from drill cores. Spherulitic barite micro‐mineralization within the sulfidized stromatolites generally forms submicron‐scale aggregates that show gradations from hollow to densely crystallized, irregular to partially radiating crystalline interiors. Several barite micro‐spherulites show thin outer shells. Within stromatolites, barite micro‐spherulites are intimately associated with petrographically earliest dolomite and nano‐porous pyrite enriched in organic matter, the latter of which is a possible biosignature assemblage that hosts microbial remains. Barite spherulites are also observed within layered barite in proximity to stromatolite layers, where they are overgrown by compositionally distinct (Sr‐rich), coarsely crystalline barite that may have been sourced from hydrothermal veins at depth. Micro‐spherulitic barite, such as reported here, is not known from hydrothermal systems that exceed the upper temperature limit for life. Rather, barite with near‐identical morphology and micro‐texture is known from zones of high bio‐productivity under low‐temperature conditions in the modern oceans, where microbial activity and/or organic matter of degrading biomass controls the formation of spherulitic aggregates. Hence, the presence of micro‐spherulitic barite in the organic matter‐bearing Dresser Formation sulfidized stromatolites lend further support for a biogenic origin of these unusual, exceptionally well‐preserved, and very ancient microbialites.     

Soil Phosphorus Fractionation during Forest Development on Landslide Scars in the Luquillo Mountains,Puerto Rico1

Mineral soils from a chronosequence of landslide scars ranging in age from 1 to more than 55 years in a subtropical montane rain forest of eastern Puerto Rico were used to determine the rate at which labile P capital recovers during primary succession. Nine organic and inorganic soil P fractions were measured using the Hedley sequential extraction procedure. Deep soil cores (9 m) from a nearby site were also analyzed to determine the distribution of P fractions below the solum. Litterfall P was measured for two years in the landslide scars to estimate allochthonous litter P inputs, and published precipitation data were used to estimate annual atmospheric inputs of P to the recovering forests. In the upper solum (0–10 cm), organic matter increased with landslide age, as did resin‐Pi, labile P (defined here as resin‐Pi + HCO₃‐Pi + HCO₃‐Po) and total organic P. Occluded P decreased with increasing landslide age. No significant changes in P concentrations or pools were observed in 10 to 35 or in 35 to 60 cm depth intervals across the chronosequence. Labile soil P increased to approximately two‐thirds of the pre‐disturbance levels in the oldest landslide scar (>55 yr). Thus, plants, their associated microflora/fauna, and P inputs from off‐site substantially altered the distribution of soil P fractions during forest recovery. Across the chronosequence, the increase in labile P accumulated in soil and biomass appeared to be greater than the estimated allochthonous inputs from litter and precipitation, indicating that as the forest developed, some occluded P may have been released for use by soil biota. Resin‐Pi and labile P were correlated with soil organic matter content, suggesting, as in other highly weathered soils, organic matter accumulation and turnover are important in maintaining labile P pools. Primary mineral P (apatite) was scarce, even in deep soil cores.     

Characterization of sources and temporal variation in the organic matter input indicated by n-alkanols and sterols in sediment cores from Admiralty Bay,King George Island,Antarctica

The Antarctic continent is one of the most protected areas on the planet, but is dynamically responding to environmental change on a global scale. Change in the air temperature may affect the organic matter production in the area. Biomarkers such as sterols, n-alkanols and phytol in three sediment cores from Admiralty Bay, Antarctica, were determined to identify the type of organic matter, variation in input and possible relationship with general temperature changes over the past decades. The concentrations ranged from 0.91 to 13.99 μg g^?1 (dry weight) of total sterols, 0.20–2.14 μg g^?1 of total n-alkanols and 0.13–2.38 μg g^?1 of phytol. Cholest-5-en-3β-ol was the most abundant sterol. The fecal sterols, 5β-cholestan-3β-ol and 5β-cholestan-3α-ol, occurred at low concentration (<0.01–0.15 μg g^?1), below the baseline values for this region. The lower carbon chain n-alkanols were more abundant, which suggested that algae, bacteria and zooplankton were the primary sources of the sedimentary organic matter. Phytol exhibited little variation across all of the cores, which appears to be the result of degradation. Variation in the concentration of compounds in one core was compared with the variation in mean air temperature (MAT) over time; this preliminary association showed a tendency toward increased concentration during the period in which the MAT was more elevated.     

Mid- and late-Holocene vegetation history of Quidenham Mere,Norfolk, UK interpreted using recurrent groups of taxa

The results of pollen analyses from the top 8 m of sediment retrieved from Quidenham Mere, Norfolk, UK are presented. These, together with the results of charcoal analyses and the numerical classification of the pollen and spore taxa into ‘recurrent groups’ using simple discriminant function analysis, are used to reconstruct the vegetation history of the Quidenham Mere catchment over approximately the last 8000 years and to infer anthropogenic effects on the landscape. After some minor woodland clearance in the Bronze Age and further clearance in the Iron Age, it was only in the Anglo-Saxon period that most of the woodland was cleared. Although arable farming was important, it appears that there was also a considerable amount of land used for grazing, with grazed woodland and wood pasture. Towards the top of the sequence, within the past 200 years, there is evidence of the foundation and development of the Quidenham Hall parkland adjacent to the site, with the planting of native and exotic species of trees. A comparison is made between the vegetation histories and anthropogenic effects on the landscapes of Quidenham Mere and Diss Mere, a similar lake about 10 km from Quidenham. Both sites reflect the agricultural practices occurring in their catchments from early times. Exceptionally high values of Cannabaceae grains are indicative of retting of hemp during the past 1500 years. Rarefaction analysis is used to compare the pollen richness of the two sites.     

Hydrolytic Enzyme Activities in Bottom Sediment Cores from the Norwegian Sea and Statistical Analysis of Their Distribution

Proteinase and amylase activities were evaluated in bottom sediment cores from the Norwegian Sea collected along a transect from the summit plane of the Voring Plateau on the east to fault uplifts of the Yan-Mayen transform zone perpendicular to the present-day Norwegian Current. A spotted vertical distribution of hydrolytic enzyme activities by the location and depth of the cores and specificity in the distribution of proteinase and amylase activities have been revealed in four bottom sediment cores (up to 300 cm; 5 cm resolution). Specific activity distribution has been revealed for different types of enzyme-sorbing bottom sediments. Modern methods of statistical analysis and mathematical modeling were applied to reveal the relationship between enzymatic degradation of protein and polysaccharide organic compounds and the content of carbonates and organic matter in bottom sediments.     

Recent variations in sediment organic carbon content in Lake Soyang (Korea)

Four gravity cores were taken from Lake Soyang, which was created by the construction of an artificial dam in 1973. The variation of organic carbon content of the bottom sediments since the construction was interpreted using a variety of sedimentological and geochemical measurements. Based on the textural properties of sediments and the total organic carbon (TOC) content, it is clear that sediment organic carbon has been deposited very consistently throughout the postconstruction period, except for local sudden inputs caused by summer flooding events near fish farms or farmland areas. The autochthonous input resulting from the enhanced primary production led by phytoplanktons each year is likely to become a major problem at downstream sites within Lake Soyang. The vertical variation of δ¹³C values of sediment organic matter also reflects the fact that the level of autochthonous supply of organic carbon becomes high downstream.An erratum to this article can be found at .     

Water salinity and inundation control soil carbon decomposition during salt marsh restoration: An incubation experiment

Coastal wetlands are a significant carbon (C) sink since they store carbon in anoxic soils. This ecosystem service is impacted by hydrologic alteration and management of these coastal habitats. Efforts to restore tidal flow to former salt marshes have increased in recent decades and are generally associated with alteration of water inundation levels and salinity. This study examined the effect of water level and salinity changes on soil organic matter decomposition during a 60‐day incubation period. Intact soil cores from impounded fresh water marsh and salt marsh were incubated after addition of either sea water or fresh water under flooded and drained water levels. Elevating fresh water marsh salinity to 6 to 9 ppt enhanced CO₂ emission by 50%?80% and most typically decreased CH₄ emissions, whereas, decreasing the salinity from 26 ppt to 19 ppt in salt marsh soils had no effect on CO₂ or CH₄ fluxes. The effect from altering water levels was more pronounced with drained soil cores emitting ~10‐fold more CO₂ than the flooded treatment in both marsh sediments. Draining soil cores also increased dissolved organic carbon (DOC) concentrations. Stable carbon isotope analysis of CO₂ generated during the incubations of fresh water marsh cores in drained soils demonstrates that relict peat OC that accumulated when the marsh was saline was preferentially oxidized when sea water was introduced. This study suggests that restoration of tidal flow that raises the water level from drained conditions would decrease aerobic decomposition and enhance C sequestration. It is also possible that the restoration would increase soil C decomposition of deeper deposits by anaerobic oxidation, however this impact would be minimal compared to lower emissions expected due to the return of flooding conditions.     

Sediment distribution and accumulation in lagoons of the Southern Mediterranean Region (the MELMARINA Project) with special reference to environmental change and aquatic ecosystems

Surface sediments and sediment cores were collected from coastal lagoons and lakes located in the Southern Mediterranean Region (SMR) as part of the MELMARINA Project which involved integrated eco-hydrological monitoring and modelling. This study uses surface sediments and sediment cores to infer spatial characteristics and temporal changes at the MELMARINA primary sites, Merja Zerga in Morocco, Ghar El Melh in Tunisia and Lake Manzala in Egypt. In addition, surface sediment sampling was undertaken at Egyptian Lake Bardawil and sediment cores were collected from the Lagune de Nador (Morocco). Sediment distribution patterns are investigated using GIS with georeferenced sample locations to facilitate display and resurvey. Major variations in sedimentary organic matter and, particularly, carbonate content, occur within and between sites. Local landscapes combined with hydrological and biogeochemical processes influence the distributions of sediment bulk components (carbonates, organic material and clastic matter) and molluscan shells and shell debris are an important source of sedimentary carbonate at all three primary sites. Sediment cores were dated using natural (²¹⁰Pb) and artificial (¹³⁷Cs) radionuclides, and sediment accumulation rate changes indicate that sources of sediment supply varied markedly through the twentieth century but have generally diminished after the mid-1960s. Sedimentary siliceous microfossils (diatoms) were generally poorly preserved, but mollusc shell remains were well represented. Sediment chronologies and sediment bulk composition allow discussion of some recent changes in bulk, minerogenic and biogenic sediment accumulation patterns in the SMR lagoons. Sediment accumulation rates also varied between sites and multiple cores from Lake Manzala indicated that rates showed considerable spatial variability. Low-level sediment contamination by fossil fuel combustion particulates and trace metals was demonstrated for Ghar El Melh and Lagune de Nador where Pb and Zn accumulation rates were highest in twentieth century sediment. It is emphasized that sediment quality and quantity have strong influences on lagoon ecosystem function and sedimentation is relevant to hydromorphology and to concepts of ecological quality. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: J. R. Thompson & R. J. Flower Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons     

Recent stratigraphy and accumulation of sediment in the deep,oligotrophic Lake Pääjärvi in South Finland

Laminated sediment is deposited in the deep areas (> 30 m) of Lake Pääjärvi. In the diatom microstratigraphy a regular alteration of planktonic and littoral floras, which goes in pace with the visual structure, reflects the yearly cycle of sedimentation. Considerable variation in sedimentation was found to have occurred during the past two decades. A sequence, dated to the early 1960's, in which the organic content was exceptionally high, could be identified in the sediment at 6–14 cm depth even in shallower areas where laminations are not formed. This level was used as a marker horizon when determining the recent distribution of sediment by means of 19 cores taken from different parts of the lake. The average annual sediment accumulation in the profundal zone of the lake is 340 g m^?2a^?1 dry weight, of which 25 g m^?2 a^?1 (1100 kJ m^?2 a^?1) is organic carbon.     

Abundance of macroalgal organic matter in biofilms: evidence from n-alkane biomarkers

Biofilm development on titanium panels immersed in the surface waters of Dona Paula Bay was investigated using molecular biomarkers such as n-alkanes and other chemical and biological parameters. Biofilm biomass measured as organic carbon (OC), organic nitrogen (ON), chlorophyll a, diatoms and bacterial numbers on the titanium panels generally increased over the period of immersion. Total lipids and n-alkane concentration also showed similar trends. n-alkanes from C(12) to C(30) were detected in the biofilm samples, which showed a bimodal distribution. The first mode consisted of n-alkanes > C(23) with a strong even over odd predominance. In the second mode, the n-alkanes < C(23) were more abundant with odd carbon number maxima at C(15), C(17) and C(19) and a strong odd over even carbon number predominance (Carbon Preference Index > 2). The predominance of these odd-chain n-alkanes strongly indicates that the organic matter derived from macroalgal sources was the major contributor to the biofilm organic matter developed on the titanium panels over the 15 d period of study. The data suggest that molecular characterization is a useful tool in understanding the sources of biofilm organic matter. The observed abundance of macroalgal organic matter during the 15 d period of biofilm development may play an important role in subsequent fouling by micro- and macrofouling organisms.