Soft Sediment Samples Research Articles

Spatial response of hard- and mixed-bottom benthic epifauna to organic enrichment from salmon aquaculture in northern Norway

Norwegian Atlantic salmon aquaculture is continuing to expand in northern regions dominated by hard- and mixed-bottom substrates. Such habitats contain rich benthic epifaunal communities, including sponges and other sessile invertebrates susceptible to the impacts of particulate material released from finfish farms. Here, conventional soft-sediment sampling techniques are unable to discern the impacts of farm waste, and new monitoring methods and indicator taxa must be identified. This study improves understanding of the impacts of particulate waste released from salmon farms on the density and structure of benthic epifaunal communities on mixed- and hard-bottom substrates. The diversity, density, and composition of epifaunal communities and visually conspicuous benthic infauna were recorded in towed camera transects along the enrichment gradient (~50-800 m) of 3 salmon farms in northern Norway. Elevated fluxes of particulate material in the vicinity of all farms significantly affected epifaunal community composition, as did the coverage of some key substrate types. The defecated mounds of lugworms and the seastar Asterias rubens were notably more abundant near the farms where fluxes were elevated. The sponges Polymastia spp. and Phakellia spp. and the soft coral Duva florida showed significant declines in density with increasing sedimentation and were principal taxa in communities at natural sedimentation levels. Results identify taxa with both positive and negative spatial associations to particulate waste released from finfish farms and the potential for the development of an epifauna indicator-based index for monitoring the environmental impacts of aquaculture in hard- and mixed-bottom dominated substrates.

Biological traits of benthic macrofauna show sizebased differences in response to bottom trawling intensity

Bottom trawling results in widespread impacts to the structure and composition of benthic communities. Although an ecosystem approach to fisheries management aims to conserve marine biodiversity and ecosystem function, there remains a lack of empirical evidence regarding the effects of trawling on benthic functional properties. Here, we examined the sensitivity of benthic macrofauna communities to trawling using their biological traits, and compared trait responses across size-categories and survey types. We collected 84 benthic soft-sediment samples by Van Veen grab (0.1 m2) in the Kattegat in 2016, and complemented with 827 Haps cores (0.0143 m2) gathered over a long-term monitoring programme between 2006 and 2013. By analysing trait response in 3 size categories (small: 1-4 mm fraction; large: ≥4 mm fraction; full community: all individuals combined), we demonstrate a size-dependent effect of trawling on benthic trait composition, where the traits of large-bodied fauna (≥4 mm) were more sensitive. Specifically, larger sessile, deep-living, suspension-feeding, tube-dwelling, subsurface deposit-feeding, burrow-dwelling, and long-lived (≥10 yr) individuals were among the most affected. Our results based on large fauna were largely in agreement with trait responses observed in the multi-year monitoring data, suggesting that trait data gathered from a targeted one-time sampling event can convey information on both acute (short-term) and chronic (long-term) trawling impacts. Given that most trawling impact assessments do not consider size-based effects, we outline how size-separating the community can be used to improve the detectability of trawling impacts, and provide new insights into the functional impacts of fishing on the seabed.

The influence of coring method on the preservation of sedimentary and biogeochemical features when sampling soft-bottom, shallow coastal environments

It is frequently assumed that taking samples of soft marine sediments using surface-based gravity coring equipment causes minimal disruption to their sedimentological, biogeochemical, and biological condition. This assumption was evaluated by examining the potential disturbances caused when obtaining soft-sediment samples either by SCUBA or Craib-coring, comparing sediment oxygen microprofiles, benthic oxygen flux rates and sediment solid phase analyses (chlorophyll a (Chl a), organic carbon, and porosity) between both methods and against reference values measured in situ by benthic lander. The two sampling methodologies were tested in shallow coastal environments on the west coast of Scotland and generally the results obtained from cores collected using SCUBA exhibited values closest to those observed in situ. Oxygen penetration depth was significantly shallower in cores obtained by Craib-corer compared with the SCUBA cores. Craib cores also produced higher oxygen uptake rates which could be caused by greater levels of sediment disturbance during sampling. In addition, more homogenous levels of Chl a in the top 1 cm of the Craib cores, compared with the SCUBA samples, may indicate either resuspension or compression during gravity coring. Using SCUBA for shallow-water soft-sediment sampling permits steady and controlled core-tube insertion and extraction, and more measured retrieval of the cores to the surface; this probably accounts for the observed differences. Whereas benthic lander-based in situ measurement would be the preferred method for analyzing sediment parameters in detail in this type of environment, SCUBA-based sampling offers a more accurate alternative to surface-based gravity coring.

On Some New Recorded Syllidae (Polychaeta: Phyllodocida) for Mediterranean Waters

Aims: This paper gives an account of the syllid species from different stations Rasheed, Domiatte, El Borrulus, Bardweel, El Aresh, also provides some information on the morphology, distribution an d habitat of those species. Study Design: Descriptive study and distribution. Place and Duration of Study:Syllidae species were collected from the Eastern Mediterranean coast of Egypt by A cruise (El �Yarmook) in May-June 2013. Methodology: Soft-sediment samples were collected byVan Veen grab indifferent depths (10, 20, 50,100, 200 m) and different habitats. Results: A total of 47syllid species from 221 taxa

Three Potential Sources of Microfungi in a Treated Municipal Water Supply System in Sub-Tropical Australia

Some microfungi are known to be opportunistic human pathogens, and there is a body of scientific opinion that one of their routes of infection may be water aerosols. Others have been implicated as causative agents of odours and off-tastes in drinking water. This study was undertaken to investigate three potential sources of microfungi in a treated, oligotrophic municipal water supply system in sub-tropical Australia. Formation of the microfungal component of developing biofilm on hard surfaces in water storage reservoirs was also assessed. Inside and outside air samples were collected from two reservoirs using two types of Burkard air samplers. Biofilm and soft sediment samples were collected from the inner surfaces of asbestos cement water pipes and from pipe dead ends respectively. These were analysed for microfungal growth and sporulation using Calcofluor White stain and epifluorescent microscopy. Artificial coupons of glass, PVC and concrete were immersed in two reservoirs to assess microfungal biofilm formation. This was analysed periodically using Calcofluor White stain and epifluorescent microscopy, cultures of coupon swabs and scanning electron microscopy. Fungal spores were recovered from all air samples. The number of colonies and the genera were similar for both inside and outside air. Microfungal filaments and sporulating structures were recovered from most of the pipe inner surface biofilm and dead end sediment samples, but were sparser in the biofilm than in the sediment samples. No recognisable, vegetative filamentous fungi were found in the slowly developing biofilm on coupons. This study indicates that airborne spores are an important potential source of microfungi found in water storage reservoirs. It has also demonstrated conclusively that filamentous microfungi grow and sporulate on water pipe inner surfaces and in soft sediments within the water distribution system.

New series of corers for taking undisturbed vertical samples of soft bottom sediments

A new series of sediment corers - a Single Tube Gravity Corer and a Multiple Tube Gravity Corer has been developed for taking undisturbed vertical soft sediment samples, and a Hydraulic Pressure Multiple Tube Corer has been preliminarily designed. The Single Tube Gravity Corer can be operated by hand easily without using a winch, and it might be the simplest and the cheapest core sampler available. The Multiple Tube Gravity Corer was developed based on the Single Corer, which normally consists of three coring tubes, however, it is possible to install up to six tubes. The Hydraulic Pressure Multiple Tube Corer has been designed based on the Multiple Corer, which would take undisturbed sediment samples, and would be controlled by a computer and monitored by an underwater video camera. The pore water collection and the sediment Eh measurement-subsampling process through the transparent plastic tube wall is straightforward. Compared to other types of coring devices, such as the famous KC Kajak sediment core sampler made in Denmark; these corers have greater reliability, being simple in structure, relatively light weight, easy and efficient to operate, highly adaptable, and relatively inexpensive to produce.

Magnetic fabrics indicating Late Quaternary seismicity in the Himalayan foothills

The anisotropy of magnetic susceptibility (AMS) study was performed on soft sediment samples from a trenched fault zone across the Himalayan frontal thrust (HFT), western Himalaya. AMS orientation of K min axes in the trench sediments is consistent with lateral shortening revealed by geometry of deformed regional structures and recent earthquakes. Well-defined vertical magnetic foliation parallel to the flexure cleavage in which a vertical magnetic lineation is developed, high anisotropy, and triaxial ellipsoids suggest large overprinting of earthquake-related fabrics. The AMS data suggest a gradual variation from layer parallel shortening (LPS) at a distance from the fault trace to a simple shear fabric close to the fault trace. An abrupt change in the shortening direction (K min) from NE–SW to E–W suggests a juxtaposition of pre-existing layer parallel shortening fabric, and bending-related flexure associated with an earthquake. Hence the orientation pattern of magnetic susceptibility axes helps in identifying co-seismic structures in Late Holocene surface sediments.

Freeze corer No. 3 for lake sediments

Freezing of sediment in situ at the lake bottom using a freeze corer has become an important method for taking samples of soft sediments aimed for detailed stratigraphic analyses. Over the past decades a variety of freeze corers have been designed, from very simple metal tubes filled with dry ice that are dropped into the sediment to high-tech samplers using electric pumps, hydraulics and liquid nitrogen. The freeze corer described here is a compromise of getting good samples without a too complicated technique. It is designed for coring from lake ice, using a steel wire with a stopper on the ice to keep the corer in fixed position during freezing. It consists of a thermos connected to a thin freeze wedge (width 15 cm, length 100 cm, max thickness 6 cm). The dry ice is kept in the thermos until the freeze wedge has been lowered into the sediment to avoid water freezing on the wedge during descent through the water column; a wet steel-wedge surface disturbs the sediment stratigraphy less than a wedge on which rapid freezing occurs. The dry ice is kept in the thermos by a trapdoor that is opened by a messenger. When the trapdoor is opened the dry ice begins to drop into the wedge, which is filled with ethanol. This process continues concurrently with the consumption of ice in the wedge until the thermos is empty. Using 6–8 kg of dry ice and 4 l of ethanol (95%), a 3-cm-thick and up to 80-cm-long crust of frozen sediment is obtained in 20–25 min on each side of the wedge. The crust is easily detached intact from the wedge using a small volume of hot water, poured inside the wedge.

Meiofauna communities along an abyssal depth gradient in the Drake Passage

Abstract Meiofauna standing stocks and community structure are reported for the first time for abyssal soft-sediment samples in Antarctic waters. At seven stations within a depth range of 2274–5194 m a total of 128 sediment cores were retrieved with a multiple corer (MUC) on board of the R.V. Polarstern during the ANDEEP-1 cruise (ANT XIX/3). The metazoan meiofauna (defined by a lower size limit of 40 μm) was identified and counted, and one core per station was preserved for CPE, C/N, TOM and grain size analyses. Meiofauna densities are in the range of 2731 Ind./10 cm2 at 2290 m depth and 75 Ind./10 cm2 at 3597 m depth, with nematodes being the dominant group at all stations. Nematodes account for 84–94% followed by copepods with 2–8% of the total meiofauna. Other frequent taxa found at each station are kinorhynchs, loriciferans, tantulocarids, ostracods and tardigrades. There is a general tendency of decreasing abundances of metazoan meiofauna with increasing depth, but not all higher level taxa displayed this pattern. In addition, a tendency of decreasing higher taxon density with increasing depth was observed. Standing stocks are higher than the average found at similar depths in other oceans.

A new method for the quantitative separation of diatom frustules from lake sediments

Achieving a purified fraction of diatom frustules from soft sediment samples is an essential requirement for using their biogenic silica as a carrier of paleolimnological and paleoenvironmental information. Because diatom frustules behave hydrodynamically unlike most mineral grains, these types of particles can theoretically be separated in liquids. Based on this principle, a new method has been developed, which employs split‐flow thin fractionation (SPLITT) as a tool for separating diatom frustules from other sedimentary particles. The SPLITT channel selected for this study had a length of 20 cm, a breadth of 4 cm, and a height of 371 µm. For optimum results, samples were pretreated, e.g., suspended and wet‐sieved prior to any processing with the SPLITT cell. The sample concentrations used in the fractionation process were below 0.1% (w/v) to minimize particle‐particle interaction, which affects the quality of the separation. The advantages of SPLITT fractionation over other tested methods are good reproducibility, high throughput by continuous flow, minimum losses of frustules, and minimum contamination of the diatom fraction by minerals or sponge spicules. Separation results from representative sediment samples of different origin, age, and compaction as well as various organic (0.5% to 10% total organic carbon) and biogenic opal contents (1% to 20% biogenic silica) are presented and discussed. They demonstrate that the developed separation technique yields highly purified and, within the processing tolerances, quantitative samples of diatom frustules from bulk lacustrine sediments.

Estimation of the available phosphate for phytoplankton stored in the soft sediments of the river Lot

Bioassays have been carried out with the green algae Scenedesmus crassus on samples of soft sediments collected along the river Lot (about fifty samples distributed over a 300 km length) in order to evaluate the phosphate bioavailability. From an other study, it was possible to know the percent of bottom surface covered by soft sediments. The link between the distribution of soft sediment and phosphate bioavailability leads to a longitudinal representation of the storage in the whole river. The results point out the parts of the river where bioavailable phosphate is stored and have implications for possible role of the stored phosphate in the eutrophication process in some areas of the river Lot.

Modifications of the Ekman Sampler

AbstractMany types of sediment samplers have been designed for specific purposes and for sampling in different aquatic environments. The objective of this technical note has been to introduce two specific improvements of the traditional Ekman grab sampler, which is a well‐known apparatus for sampling of soft sediments, especially in bottom faunistic contexts. The two new modifications concern the automatic closing mechanism. The jointed quadrant and the jointed, hooked axis, both made of brass, provide a much handier and more reliable operation than, e.g., the traditional automatic mechanism.

Lightweight corer for undisturbed sampling of soft sediments : Pedersen, T F; Malcolm, S J; Sholkovitz, E R Can J Earth Sci V22, N1, Jan 1985, P133–135

Lightweight corer for undisturbed sampling of soft sediments : Pedersen, T F; Malcolm, S J; Sholkovitz, E R Can J Earth Sci V22, N1, Jan 1985, P133–135

A lightweight gravity corer for undisturbed sampling of soft sediments : Pedersen, T.F., S.J. Malcolm and E.R. Sholkovitz, 1985. Can. J. Earth Sci., 22(1):133–135

A lightweight gravity corer for undisturbed sampling of soft sediments : Pedersen, T.F., S.J. Malcolm and E.R. Sholkovitz, 1985. Can. J. Earth Sci., 22(1):133–135

A lightweight gravity corer for undisturbed sampling of soft sediments

A lightweight, portable gravity corer is described that collects up to 3 m long, 10 cm diameter undisturbed cores from sediments of exceptionally high porosity. The corer employs a triple O-ring seal to hold sediments in an unsupported, catcher-free plastic barrel simply by suction.

Errors in the anisotropy of magnetic susceptibility and magnetic remanence of unconsolidated sediments produced by sampling methods

Samples from glacial varves were obtained by cutting cubes and by pushing plastic cubical containers into the sediment. The anisotropy of magnetic susceptibility results show that the mean angular difference in the kmax direction can be altered by 32° by pushing in the sample containers in a north to south versus an east to west direction. The values of lineation and Q are raised or lowered dependent upon the direction of push and the original fabric direction.Mean remanence directions can deviate by as much as 43° in a single clay layer dependent upon the direction in which the sample containers are inserted into the sediment. Corresponding changes in mean intensity of the remanence also demonstrate that the remanence has been affected by pushing in sample containers. The overall results underline the need to adopt trustworthy procedures for the sampling of soft sediments deposited by settling and traction.