A comparison of lead and zinc sediment profiles from cores taken by diver and a gravity corer

The zinc and lead concentrations were compared in several pairs of sediment cores obtained with a modified K-B corer and by Scuba diver from Coon Lake, Canada. A slow approach to and penetration of the sediments (ca. 0.1 m s^-1) was employed for both coring devices. The modified K-B corer gave similar lead and zinc profiles to the diver cores. The divers observed that the K-B corer caused no disturbance of the surface sediment layers as it approached and entered the sediments. These results suggest that the K-B corer is suitable for use in lake studies requiring short, undisturbed cores from fine-grained sediments.     

The tom-tom corer: a new design of the Kajak corer for use in meiofauna sampling

A new corer, the tom-tom, is a modification of the basic Kajak design. New modifications increase the efficiency of the corer in soft muds and increase the stability of the corer during ascent and descent. A stepped release trigger mechanism allows the corer to trip easily in even the softest muds, and a Phleger “bomb’ weight adds stability to the device. The corer can be deployed in a slow, controlled descent from small as well as large boats to reduce bow-wave. Four cores (4.50 cm inner diameter) are taken simultaneously in a fixed spatial pattern. Limited comparative sampling revealed that the tom-tom collected more meiofauna than a Van Veen grab and attained numbers statistically indistinguishable from diver-collected cores (only small sample sizes were available however). The corer will be most efficient in sediments without an extremely well-developed, suspendable layer, and most practical for smaller vessels in environments where diver collected cores are precluded by depth, strong currents or poor visibility. Although used in meiofauna collection, the corer should be appropriate for any sampling needs requiring a relatively undisturbed core.     

Vibracoring: a new method for coring deep lakes

A major limitation facing lacustrine researchers is an inability to take long (6 to 18 m), continuous sediment cores in water depths greater than several metres at a low cost. These problems have limited the advancement of palaeolimnology and Quaternary stratigraphy. Working from a frozen lake surface, new developments make it possible to take 18 m long vibracores in water depths of at least 55 m. High-frequency low-amplitude vibrations are transferred down a series of 6 m long, 7.6 cm diameter core tubes (3 inch aluminum irrigation pipe) rigidly coupled end-to-end. Vibrations liquify sediment adjacent to the core tube walls, thus allowing penetration of the sediment. A core catcher prevents sediment from extruding out of the tube end during extraction. This cost-effective and labour efficient (two persons) coring system has been achieved by developing rigid core tube couplers, a hand-powered drum cable hoist and a set of operation procedures. The hoist cable end is attached to a clamp 1 m above the core catcher and at each coupler along the pipe string at 6 m intervals. Lifting or lowering using a drum cable hoist allows for quick coupling and decoupling of core tubes. Although vibracoring is an improvement over other systems, it still has portability limitations because of the bulk and weight of the equipment and large amount of pipe required for deep coring. Three sleds are required to transport equipment from the nearest vehicle access to the coring sites.     

Comparison of two gravity coring devices for sedimentation rate measurement by 210Pb dating techniques

Marine sediment cores were collected in Puget Sound using a 7.6 cm diameter corer and a 15 × 15 cm square cross-section corer. The cores were dated by the ²¹⁰Pb method and sedimentation rates and depth of sediment mixed layers were compared. The results show that both the sedimentation rates and the depth of sediment mixed layers obtained from small diameter corer are 2–3 times smaller than the corresponding values obtained from large cross-section corer. A cross-calibration of coring techniques seems necessary to correlate the sedimentation rates obtained using different devices.     

A corer for taking undisturbed peat samples

Summary A corer is described for sampling peats to a depth of 1 m with minimum disturbance of the sample. The instrument is simple and inexpensive to construct and is suitable for routine sampling operations.     

A multiple coring system for use with scuba

A diver-operated coring system which takes undisturbed contiguous samples has been developed. A perspex space-frame localises a number of contiguous thin-walled tubes which can be driven into the sediment and from which core samples can be extracted. The corer consists of transparent tubing and low-pressure gate valve. The system is useful for describing small-scale spatial dispersion and for sampling patchy habitats. It is light, simple, inexpensive and is flexible with respect to the size and number of contiguous cores.     

A new sampler for extracting undisturbed surface peat cores for growth pot experiments

The sampler extracts uncompressed cores of 13·3 cm in diameter, up to 70 cm long, from the surface layers of peat. It has two close-fitting concentric cylindrical tubes, the outer one acting as a cutter and the inner one as a collector. As the outer tube is introduced by rotation into the peat, the cut core is collected in the inner tube which is maintained in a fixed position during the rotation phase and then pushed down stepwise. This limits friction between the peat core and the wall of the corer and prevents compression or distortion of the peat. These problems are also reduced by means of three skew cutters allowing the peat to be supported during the slicing action. Air can penetrate between the tubes to the lower end of the core, suppressing any suction effect during withdrawal. The sampler has been tested and has worked satisfactorily in many different peat types.     

A comparison of 35S-SO(4)(2-) radiotracer techniques to determine sulphate reduction rates in laminated sediments

In order to find a simple and efficient method to determine sulphate reduction rates in environmental samples, we tested different 35S-SO(4)(2-) radiotracer techniques. The methods varied in the application of 35S-SO(4)(2-) and subsequent extraction of reduced 35S-sulphur species. Samples were either incubated as sediment slurries mixed with the radiotracer, or as undisturbed sediment cores after core injection of the radiotracer. Reduced 35S-sulphur species were retrieved passively by diffusion or actively by reflux distillation. The methods were applied to surface sediments derived from three aquatic habitats situated in Germany: (1) a tideless brackish water, (2) a mining lake and (3) a natural freshwater lake. The best possible method was expected to yield the highest sulphate reduction rates, which were reproducible with respect to magnitude and depth distribution. At the same time, we aimed to keep the disturbance of samples as well as the expenditure of labour and equipment to a minimum. For all three types of aquatic habitats, the combination of core injection followed by diffusion was the most reliable and efficient method. This combination is therefore recommended for determination of sulphate reduction rates in laminated sediments.     

A handy impact corer for sampling lake surface sediment

A handy impact corer for sampling of surface sediment (< 50 cm) in lakes is described. The coring apparatus consists of a sample tube, tube holder, stopper, stopper holder, shaft with wing, shaft holder, hammer, and pushing rod. The total weights are 3.8 kg (Type I: 2.3 cm inside diameter of the tube) and 6.7 kg (Type II: 5.5 cm inside diameter of the tube). The system enables confirmation of the vertical landing of the corer onto the lake bottom and effective entering of sediment into the sample tube using hammer, and prevention of falling out of the core using stopper and pushing rod.     

Shortening of surface sediment cores during sampling

Coring in recent lake sediments is most easily performed using lightweight open barrel gravity corers. The cores will in most cases have the fine lamination intact and they may thus be interpreted as representative of the sediment in situ.Parallel cores taken by means of other techniques have shown that cores taken with open barrel gravity corers become shorter than the distance of penetration in the sediment. This investigation shows that the shortening depends both on the corer diameter and on its velocity during the penetration. Experiments also show that soft layers become more reduced in thickness than stiffer ones. This may lead to misinterpretation of sedimentation rate during special periods. Seasonally occurring sediment fractions may be diluted or concentrated during the coring.     

Comparing multiple sampling platforms for measuring the behavior of humpback whales (Megaptera novaeangliae)

Multiple platform approaches for measuring the behavior of marine mammals may strengthen data quality and quantity. However, if this approach is chosen, reconciliation of behavioral measures between each platform is required. This study compared typical measures of humpback whale (Megaptera novaeangliae) behavior collected from three different sampling platforms; land‐based, boat‐based, and digital tags (Dtags), to explore similarities and/or discrepancies in data. Visual observations from land‐based platforms significantly underestimated group blow rate when compared to boat‐based platforms, whereas broad‐scale spatial movements (speed and course traveled) were measured similarly by these two platforms. Dtags were used to define dive behavior based on a time and depth criteria, where bouts of short shallow respiration dives (≤80 s and ≤10 m) were separated from longer, deeper dives (>80 s and >10 m). At a group level, land and boat platforms agreed on the number of long dives but land platforms missed bouts of short dives. At an individual level, the number of short and long dives observed by boat‐based platforms agreed with Dtag recordings. This study highlights the importance of data exploration prior to analyses in multiple platform studies to identify potential discrepancies and appropriately account for any biases.     

Caesium-137 and lead-210 dating of recent sediments from Mondsee (Austria)

Mean annual sedimentation rates over the last 20–30 years were determined in the pre-alpine Mondsee (Upper Austria) using Cs-137 and Pb(Po)-210 profiles for sediment core dating and two natural sediment markers. Lower sedimentation rates of about 2–3 mm yr^–1 were observed in the central part of the lake near the shore at 18–20 m and in the southern part at 30 m depth. Higher sedimentation rates of 4–7 mm yr^–1 were found in the central part of the lake at 47 and 65 m and in the northern bay at 18 and 41 m depth. At both these sites the Pb-210 profiles were strongly disturbed in the upper zone of the sediment cores, whereas the Cs-137 pattern remained intact. The higher annual sediment accumulation rates can be explained only partly by deposition of allochthonous material discharged by the streams, enhanced eutrophication in these parts of the lake, erosion and sediment focusing by turbidity currents being also probable.     

A simple vertical gill net system for variable current conditions

A new technique for suspending vertical gill nets is described. The system is designed to minimize the effects of currents, which otherwise could lift the lead line off the bottom or pull the floating line down.For more than two years, 30 m deep gill nets have been used in a Baltic Sea coastal region and have been found to work well in current, wave and wind conditions characteristic of this area. Setting a net takes about 5 minutes and retrieving it 10 minutes, even under relatively windy conditions (10–15 ms^–1). No special equipment is required to set or to haul a net, and we have used a variety of boats, from a small rowing boat to a 16 m long research vessel. The total material cost per net is about US $100.     

The extent and significance of petroleum hydrocarbon contamination in Crater Lake,Oregon

In order to evaluate hydrocarbon inputs to Crater Lake from anthropogenic and natural sources, samples of water, aerosol, surface slick and sediment were collected and analyzed by gas chromatography-mass spectrometry (GC-MS) for determination of their aliphatic and aromatic hydrocarbon concentrations and compositions. Results show that hydrocarbons originate from both natural (terrestrial plant waxes and algae) and anthropogenic (petroleum use) sources and are entering the lake through direct input and atmospheric transport. The concentrations of petroleum hydrocarbons range from low to undetectable. The distributions and abundances of n-alkanes, polycyclic aromatic hydrocarbons (PAH) and unresolved complex mixture (UCM) from petroleum are similar for all surface slick sampling sites. The estimated levels of PAH in surface slicks range from 7–9 ng/m² which are low. Transport of petroleum-derived hydrocarbons from the lake surface has resulted in their presence in some sediments, particularly near the boat operations mooring (total petroleum HC = 1440 μg/kg, dry wt. compared to naturally derived n-alkanes, 240 μg/kg, dry wt.). The presence of biomarkers such as the tricyclic terpanes, hopanes and steranes in shallow sediments further confirms petroleum input from boat traffic. In the deep lake sediments, petroleum hydrocarbon concentrations were very low (16 μg/kg, dry wt.). Very low concentrations of PAH were detected in shallow sediments (17–40 μg/kg at 5 m depth near the boat operations) and deep sediments (3–15 μg/kg at 580 m depth). The individual PAH concentrations in sediments (μg/kg or ppb range) are at least three orders of magnitude less than reported threshold effects levels (mg/kg or ppm range, test amphipod Hyalella azteca). Therefore, no adverse effects are expected to occur in benthic biota exposed to these sediments. Boating activities are leaving a detectable level of petroleum in surface waters and lake sediments but these concentrations are very low.     

Evaluation of a standpipe corer for sampling aquatic interstitial biotopes

The relative efficiencies of two sizes of a standpipe corer were evaluated. The size composition of the gravel sampled by the corer was very similar to that (below the opening size of the core chamber) of the streambed. The small corer (25 cm³ sample size) produced a mean overestimate of total numbers of only 19% even in highly heterogeneous gravels. Most of the taxa commonly in the substrates sampled did not escape from the corer. A few rare taxa were consistently over- or under-estimated and possible reasons for this are discussed.     

A field incubation approach to evaluate the depth dependence of soil biogeochemical responses to climate change

Soil biogeochemical processes may present depth-dependent responses to climate change, due to vertical environmental gradients (e.g., thermal and moisture regimes, and the quantity and quality of soil organic matter) along soil profile. However, it is a grand challenge to distinguish such depth dependence under field conditions. Here we present an innovative, cost-effective and simple approach of field incubation of intact soil cores to explore such depth dependence. The approach adopts field incubation of two sets of intact soil cores: one incubated right-side up (i.e., non-inverted), and another upside down (i.e., inverted). This inversion keeps soil intact but changes the depth of the soil layer of same depth origin. Combining reciprocal translocation experiments to generate natural climate shift, we applied this incubation approach along a 2200 m elevational mountainous transect in southeast Tibetan Plateau. We measured soil respiration (Rs) from non-inverted and inverted cores of 1 m deep, respectively, which were exchanged among and incubated at different elevations. The results indicated that Rs responds significantly (p < .05) to translocation-induced climate shifts, but this response is depth-independent. As the incubation proceeds, Rs from both non-inverted and inverted cores become more sensitive to climate shifts, indicating higher vulnerability of persistent soil organic matter (SOM) to climate change than labile components, if labile substrates are assumed to be depleted with the proceeding of incubation. These results show in situ evidence that whole-profile SOM mineralization is sensitive to climate change regardless of the depth location. Together with measurements of vertical physiochemical conditions, the inversion experiment can serve as an experimental platform to elucidate the depth dependence of the response of soil biogeochemical processes to climate change.     

藏北高原各听石器初步观察

各听石器采自藏北高原色林错东南岸古湖滨基岩岗丘上,由硅质岩打制的边刮器、凹缺刮器、端刮器、石核和石片组成,时代可能为旧石器时代晚期或新石器时代。     

Caractéristiques du microphytobenthos d'un lac volcanique. Characterization of the Microphytobenthos in a Volcanic Meromictic Lake (Lake Pavin,France). II. Productivity and Relationships

The collection of microphytobenthos for primary production studies in Lake Pavin was performed with a Jenkin sampler. This corer permits sampling at different levels below the surface of the lake. Five levels (10, 20, 30, 40, and 60 m below the surface) were regularly investigated for more than one year. Each was inhabited by a characteristic population of dominant diatoms. The primary production, which was very large during the summer, decreases with depth. During the winter, the ¹⁴C assimilation occurs at a very low rate in clear incubators, but in dark incubators, the rate is high. Therefore, the ¹⁴C fixation in darkness is greater than the photosynthetic assimilation. This phenomenon together with the very important data recorded for photosynthetic efficiency (especially at the lowest levels, 40 and 60 m deep) suggest that microphytes on the bottom of the lake assimilate organic compounds during much of the year.     

Community structure and spatial distribution of benthic fauna in the Bellingshausen Sea (West Antarctica)

The structure and spatial distribution of the macrofauna community of the Bellingshausen Sea in the western sector of Antarctica was studied during the ‘BENTART–06’ oceanographic expedition. This is one of the least explored Antarctic seas. A total of 20 box cores were sampled at 11 stations ranging from 157 to 3,304 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 25 higher taxa of invertebrates were collected. Deeper sampling sites were less rich in taxa (4–7 taxa), whereas the figures were higher at shallower sites (up to 17 taxa). Faunal density on the sea bottom revealed a horizontal spatial gradient from the western sites with extremely low figures (90 indiv./m²) towards the eastern ones with the highest figures (1,360 indiv./m²) close to the Antarctic Peninsula. Several abiotic factors (depth, redox, organic matter, carbonates and particle size of surficial sediments) were measured simultaneously on the sea floor to characterise the substrate preferences of the fauna. Positive correlations were found between the faunal distribution and a combination of depth, redox values, and organic matter content of sediments. This indicates decreasing availability of food in the deeper bottoms of the Bellingshausen Sea with a prevalence of depauperated bottoms dominated almost exclusively by a foraminiferans community.     

Fish distribution and benthic invertebrate biomass relative to depth in an Ontario lake

Synopsis A survey of fish distribution relative to depth in Lake Opinicon, Ontario, using the strip count method showed 80–90% of the biomass to be concentrated along the lake margins at a depth of up to 2.5 m. This figure applied throughout the summer, and to both day and night. Invertebrate diversity and biomass was also biassed towards the margins but slightly less so (mean summer figure 68% of biomass at depth of 2.5 m or less) for the segment of the lake studied. The central parts of the lake have good populations of 1–2 cm Chironomus spp. not predated by fish.There is a close link between the distribution of the specific prey organisms of fish species and the fish themselves. In their predominantly marginal distribution both are concentrated into the area of maximum productivity.