Particulate organic matter (POM) of samples from the Lena River delta

Particulate organic matter (POM) derived from permafrost soils and transported by the Lena River represents a quantitatively important terrestrial carbon pool exported to Laptev Sea sediments (next to POM derived from coastal erosion). Its fate in a future warming Arctic, i.e., its remobilization and remineralization after permafrost thawing as well as its transport pathways to and sequestration in marine sediments, is currently under debate. We present one of the first radiocarbon (14C) data sets for surface water POM within the Lena Delta sampled in the summers of 2009 - 2010 and spring 2011 (n = 30 samples). The bulk D14C values varied from -55 to -391 per mil translating into 14C ages of 395 to 3920 years BP. We further estimated the fraction of soil-derived POM to our samples based on (1) particulate organic carbon to particulate nitrogen ratios (POC : PN) and (2) on the stable carbon isotope (d13C) composition of our samples. Assuming that this phytoplankton POM has a modern 14C concentration, we inferred the 14C concentrations of the soil-derived POM fractions. The results ranged from -322 to -884 per mil (i.e., 3060 to 17 250 14C years BP) for the POC : PN-based scenario and from -261 to -944 per mil (i.e., 2370 to 23 100 14C years BP) for the d13C-based scenario. Despite the limitations of our approach, the estimated D14C values of the soil-derived POM fractions seem to reflect the heterogeneous 14C concentrations of the Lena River catchment soils covering a range from Holocene to Pleistocene ages better than the bulk POM D14C values. We further used a dual-carbon-isotope three-end-member mixing model to distinguish between POM contributions from Holocene soils and Pleistocene Ice Complex (IC) deposits to our soil-derived POM fraction. IC contributions are comparatively low (mean of 0.14) compared to Holocene soils (mean of 0.32) and riverine phytoplankton (mean of 0.55), which could be explained with the restricted spatial distribution of IC deposits within the Lena catchment. Based on our newly calculated soil-derived POM D14C values, we propose an isotopic range for the riverine soil-derived POM end member with D14C of -495 ± 153 per mil deduced from our d13C-based binary mixing model and d13C of -26.6 ± 1 per mil deduced from our data of Lena Delta soils and literature values. These estimates can help to improve the dual-carbon-isotope simulations used to quantify contributions from riverine soil POM, Pleistocene IC POM from coastal erosion, and marine POM in Siberian shelf sediments.

Strontium-90 and tritium concentrations in surface waters of the North Pacific

Results of determinations of 90Sr and tritium polluting surface water in different parts of the North Pacific are presented. The T/90Sr ratio lies within 90-600 over the referred water area and attains 2000 near the Columbia River mouth. Tritium concentration in sea water has been noted to be affected by river runoff and terrigenous sediments.

Ostracoda in five sediment cores from the Laptev and Kara seas

Fossil ostracods were investigated in five AMS14C-dated cores from different parts of the Laptev and Kara seas. Three cores from the Laptev Sea shelf are located in river paleovalleys, and one core originates from the western continental slope. The core from the Kara Sea was obtained in the eastern shelf region. Six fossil assemblages were distinguished: estuarine (1), inner-shelf (2), middle-shelf (3), outer-shelf (4), Pre-Holocene upper continental slope (5), and Holocene upper continental slope (6). They show that during the Postglacial sea-level rise there was a transition from estuarine brackish-water environment to modern marine conditions. Assemblages 1-3 are present in the eastern Laptev Sea with the oldest ostracod-bearing samples aging back to 11.4-11.3 cal.ka. Cores from the western Laptev Sea (12.3 cal.ka, assemblages 1-4) and the Kara Sea (8.1 cal.ka, assemblages 2-4) demonstrate similar pattern in assemblage replacement, but contain a number of relatively deep-water species reflecting stronger influence of open-sea waters. Core from the continental slope, water depth 270 m (~ 17 cal.ka) encompasses assemblages 5 and 6, which are absent in the shelf cores. Assemblage 5 stands out as a specific community dominated by relatively deep-water Arctic and North Atlantic species together with euryhaline ones. The assemblages indicate inflows of Atlantic-derived waters and downslope slides due to the proximity to the paleocoastline. Assemblage (6) is similar to the modern local ostracod assemblage at this site.

(Table 1) Stratigraphic occurrence and fossil content of fossiliferous horizons in southern north Victoria Land

In contrast to the adjacent parts of the Transantarctic Mountains, the Mesozoic macrofossil record of north Victoria Land remains poorly documented. During the Ninth German Antarctic North Victoria Land Expedition (GANOVEX IX 2005/2006) twelve fossil sites in southern north Victoria Land were discovered and sampled. Fossils from the Triassic to Early Jurassic Section Peak Formation were collected from Archambault Ridge, Anderton Glacier, Skinner Ridge, Timber Peak, Vulcan Hills, Runaway Hills, Section Peak and Shafer Peak. These localities have yielded abundant fossil wood and compressions of horsetails, ferns, and seed ferns. In addition, several beetle elytra were found at Timber Peak. Fossil localities of the overlying Shafer Peak Formation and Exposure Hill-type deposits occur at Shafer Peak and in the Mount Carson area, and have yielded various trace fossils, permineralized wood, leaf compressions, and conchostracans. Two newly discovered fossil sites are associated with the late Early Jurassic Kirkpatrick lava flows. Upright-standing tree trunks have been recorded at Suture Bench, and highly fossiliferous sedimentary interbeds occur at the southwestern end of the Mesa Range. Of special interest is the exquisite fossil preservation at some of the sites. Compression fossils from Timber Peak and Shafer Peak contain well-preserved cuticles, which is very rare in the Antarctic. An Early Jurassic permineralized deposit at Mount Carson contains structurally preserved ferns. Furthermore, the arthropod fossils from sedimentary interbeds at the Mesa Range are preserved in minute detail, including antennae and limb spines of a blattid insect.

Physical oceanography and current meter measurements on the Gulf of Lion continental margin between June 1993 and July 1996

Nine hydrographic cruises were performed on the Gulf of Lion continental margin between June 1993 and July 1996. These observations are analysed to quantify the fluxes of particulate matter and organic carbon transported along the slope by the Northern Current and to characterise their seasonal variability. Concentration of particulate matter and organic carbon are derived from light-transmission data and water sample analyses. The circulation is estimated from the geostrophic current field. The uncertainty on the transport estimate, related to the error on the prediction of particle concentrations from light-transmission data and the error on velocities, is assessed. The particulate matter inflow entering the Gulf of Lion off Marseille is comparable to the Rhône River input and varies seasonally with a maximum transport between autumn and spring. These modifications result from variations of the water flux rather than variations of the particulate matter concentration. Residual transports of particulate matter and organic carbon across the entire Gulf of Lion are calculated for two cruises enclosing the domain that were performed in February 1995 and July 1996. The particulate matter budgets indicate a larger export from the shelf to deep ocean in February 1995 (110 ± 20 kg/s) than in July 1996 (25 ± 18 kg/s). Likewise, the mean particulate organic carbon export is 12.8 ± 0.5 kg/s in February 1995 and 0.8 ± 0.2 kg/s in July 1996. This winter increase is due to larger allochthonous and autochthonous inputs and also to enhanced shelf-slope exchange processes, in particular the cascading of cold water from the shelf. The export of particulate matter by the horizontal currents is moreover two orders of magnitude larger than the vertical particulate fluxes measured at the same time with sediment traps on the continental slope.

(Table 2) Vertical distribution of particulate matter and its organic and mineral components in waters of the Tropical Atlantic in November 1984

Results of multiyear investigation of distribution and composition of suspended matter in waters off the northwest coast of Africa are presented. Large-scale circulation, upwelling, river runoff, and aeolian deposition affect distribution and evolution of biochemical composition of particulate matter. Concentrations of organic carbon, nitrogen, chlorophyll, phytoplankton and trace metals in the particulate matter are determined. Ratios of these components exhibit seasonal variations.

Bacterioplankton and bacteriobenthos in surface layer waters and sediments between the Sakhalin Island and the Eastern Asia in June 2006

This work presents results of a study of plankton and benthic microbiocenoses of the Amur River estuary. It is shown that distribution of total abundance and indicator groups of bacteriobenthos are characterized by stronger heterogeneity compared with bacterioplankton and that it depends on the Amur River runoff and bottom type. The river runoff helps by increasing overall bacterioplankton abundance in the near-mouth part of the estuary. Microorganisms utilizing low concentrations of organic matter (OM) play major role in processes of OM utilization in water and bottom sediments. Saprophytic bacteria play a significant role in OM utilization only in water at certain sampling sites in the Tatarsky Strait and Sakhalin Bay and in bottom sediments sampled in the mouth part of the estuary. Some parts of the estuary subjected to organic contamination are found according to microbiological characteristics. It is shown that fluctuation of salinity leads to change of the role of bacteria with different food demands in the microbial community.

2012-2014 sedimentation data for the Congaree River floodplain, SC, USA

This dataset contains sedimentation data that was collected for the Congaree River floodplain, SC, USA. The study sites were located at floodplain positions with varying flood frequencies and geomorphic positions. Flood frequency was determined using hydrological statistics based on data acquired from USGS gage #02169500 for the Congaree River; sites are classified as having high, intermediate, or low flood frequency. The geomorphic position classification was determined using field observations; sites are classified as abandoned channel, ridge, river margin, and swale positions. Sediment deposition was measured in centimeters and reflects the amount of sediment that was deposited on a feldspar clay pad that was installed at each of the sampling sites. The feldspar pads were installed in the summer of 2012 and cored and measured for deposition amounts in the summer of 2014. In the summer of 2012, soil samples were collected at each of the sampling sites. Each soil sample was analyzed for soil texture (percent sand, silt, and clay), major and micro-nutrients (parts per million), percent organic matter, and pH.

Species name, classification (WORMS), abundance and biomass of the megabenthic communities of the Algarve

The present study analysed the megabenthic diversity in subtidal soft bottoms and assessed the main environmental drivers of megabenthic community organisation along the Algarve coast (southern Portugal). We tested the hypothesis that megabenthic communities respond to the same environmental drivers than macrofauna. We found that similar to macrofauna, megafaunal communities were organised in relation to the depth of closure, light reaching the bottom, and the hydrodynamic conditions related with exposure within the shallower areas. The influence of the main river outflow prevailed over other drivers, but only up to 9 m depth. We found that seven different spatial units should be considered, each characterised by different indicator species. Additionally, among a total of 412 taxa collected between 4 and 50 m depth, we provide the characteristics of the 64 commonest species in terms of occurrence, frequency, distribution, abundance, bathymetric and sedimentary preferences, which constitutes most valuable information for ecosystem modelling. Megabenthic alpha diversity decreased with depth, contrary to evenness and was higher in the proximity of the river Guadiana and in highly exposed shores. We conclude that the megafauna, which is significantly quicker to collect and analyse, can provide an accurate alternative to macrofauna sampling, as their communities are shaped by the same drivers.