Macrobenthos richness and biomass preferentially geared towards one half of asymmetrical sand waves

2020 ◽  
Author(s):  
Chiu Cheng ◽  
Bas Borsje ◽  
Sarah O'Flynn ◽  
Olivier Beauchard ◽  
Tom Ysebaert ◽  
...  
Keyword(s):  
Community Composition ◽  
North Sea ◽  
Spatial Scales ◽  
Environmental Data ◽  
Sand Wave ◽  
Small Scale ◽  
Valuable Insight ◽  
Sandy Sediment ◽  
Sediment Grain Size ◽  
Sand Waves

<p>Sand waves are dynamic, sinusoidal bedforms that have been thoroughly studied in the context of the physical and hydrodynamical processes dominating these environments. However, information about the ecological and biogeochemical characteristics within these bedform habitats have been far fewer in comparison. To address this knowledge gap, a field campaign was undertaken in the summer of 2017 to investigate the biogeomorphology of asymmetrical sand waves in the Dutch North Sea, near island Texel. The goal was specifically to address both the macrofaunal community composition and the associated biogeochemistry along the different sections of these sand waves.  Using a combination of several field sampling techniques and lab incubations on board the NIOZ RV-Pelagia, we collected a comprehensive dataset covering the macrofauna assemblage, nutrient flux, oxygen consumption, sediment grain size and permeability, as well as physical and environmental data, within a transect line (< 1 km) that covered several sand waves. Here, we show considerable variability in the species abundance, composition and biomass, which were all significantly higher on the steeper sides of the sand waves; the multivariate statistical analyses on the datasets showed a significant influence of the sand wave position on benthic composition. Correspondingly, measurements from the steep slopes also exhibited a higher concentration of chl-a and organic matter, higher O<sub>2</sub> consumption, more fine particles and lower sediment permeability. Despite the overall homogeneity (e.g., sandy sediment) of a well-developed bedform environment such as a sand wave field, it is clearly possible to find significant variations in the benthic community composition and biogeochemical activity on a small spatial scale.  Oftentimes, studies look at larger spatial scales to maximize the characterization of an entire region. However, given the diverse environmental gradients within the North Sea, our observations may not be sufficiently captured or even missed altogether when superimposed upon such large spatial scales.  Thus, a close examination of the interrelated parameters such as biology, biogeochemistry, sedimentology and morphology should also be considered, at a high resolution, over a small local scale for such seemingly uniform habitats.  We hope our results will contribute valuable insight into small-scale patterns of variability in dynamic bedform environments. </p>

scholarly journals Trophic levels of marine consumers from nitrogen stable isotope analysis: estimation and uncertainty

2015 ◽  
Vol 72 (8) ◽  
pp. 2289-2300 ◽  
Author(s):  
Simon Jennings ◽  
Johan van der Molen
Keyword(s):  
Stable Isotope ◽  
Body Mass ◽  
North Sea ◽  
Trophic Ecology ◽  
Human Impacts ◽  
Spatial Scales ◽  
Trophic Levels ◽  
Environmental Data ◽  
Irish Sea ◽  
Nitrogen Stable Isotope

Abstract Estimates of trophic levels (TLs) are used to calibrate, parameterize, and validate foodweb models and to calculate metrics and indicators of foodweb structure and human impacts. We develop a method to estimate TL from nitrogen stable isotope data (δ15N) and apply it to 5535 individuals from 62 species of marine fish and squids sampled from the Celtic Sea, English Channel, Irish Sea, and North Sea. With this method, uncertainties in δ15N at the base of the foodweb (from a marine isoscape generated with environmental data) and in trophic fractionation (from existing fixed and scaled fractionation models) are propagated through the analysis to quantify uncertainty in TL. Higher values of base and consumer δ15N lead to greater uncertainty in TL estimates for individual consumers. Base and consumer δ15N are higher in coastal regions with lower salinity, such as the Irish Sea and Channel coasts, so uncertainty in individual TL estimates is relatively high in these regions. Conversely, when base and consumer δ15N are low, as in the high salinity waters of the northern North Sea, uncertainty is relatively low. Uncertainty intervals for species' predicted TL at a reference mass (based on ≥10 individuals spanning a range of body sizes) are small compared with estimates for individual consumers, as are estimates of slope of the TL body mass relationship. For ∼50% of region and species combinations showing trends in TL with body mass, there are eight times more positive relationships than negative ones. Our approach can be applied at large spatial scales. It generates estimates of uncertainty that support more rigorous and informed comparisons of the trophic ecology of size classes, species, and species-groups. A data file that includes estimates of TL and associated uncertainty for all sampled individuals accompanies this study.

Variation in the components of Benthic community structure in a Coastal Lagoon as a function of Spatial Scale

1989 ◽  
Vol 40 (1) ◽  
pp. 79 ◽  
Author(s):  
A Hatcher
Keyword(s):  
Community Structure ◽  
Community Composition ◽  
Coastal Lagoon ◽  
Benthic Community ◽  
Spatial Scales ◽  
Small Scale ◽  
Benthic Community Structure ◽  
Extrinsic Factors ◽  
Sessile Invertebrates ◽  
Community Types

The perception of community structure is strongly related to the spatial resolution of data collection. To quantify variation in community structure at several spatial scales, the benthos was examined on the limestone substratum in a nearshore coastal lagoon. Community structure was described using a form of pattern analysis called correspondence analysis. Variance at three spatial scales was measured. These scales were described as: (I) between offshore and nearshore reefs (kilometres); (2) among areas on the nearshore reef-line (< 1 km); and (3) between community types on the nearshore reef-line (tens of metres and less). Organisms were classified according to higher taxa/functional classes. Parameters which varied between reef-lines included: (i) community composition determined using multivariate ordination, (ii) cover by calcareous and filamentous algae and (iii) abundance of seagrass and juvenile kelp (Ecklonia radiata). Among the areas on the nearshore reef-line, variance in community composition was due to the distribution of animals. There was a south to north gradient of increasing cover by encrusting animals and abundance of ascidians. Within the areas on the nearshore reef-line, there were two distinct community types characterized by macrophytic plants or sessile invertebrates. The major potential controls of the variation in benthic community structure were different at each of the spatial scales examined. The strong relationships between extrinsic factors and components of the communities suggested that the major potential controls were: (a) exposure to swell at the large scale (between reef-lines), (b) availability of food at the medium scale (within areas on the nearshore reef-line) and (c) biological interactions or responses to microtopography and light climate at the small scale (between and within communities on the nearshore reef-line).

Pipeline plough performance in sand waves. Part 2: kinematic calculation method

2010 ◽  
Vol 47 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Mark Fraser Bransby ◽  
Michael John Brown ◽  
Keith Lauder ◽  
Andrew Hatherley
Keyword(s):  
Calculation Method ◽  
Wave Amplitude ◽  
Scale Model ◽  
Sand Wave ◽  
Small Scale ◽  
Offshore Pipelines ◽  
Sand Waves ◽  
Calculation Methodology ◽  
Small Scale Model ◽  
Good Agreement

Offshore pipelines can be buried in the seabed by ploughing a trench, placing the pipe at its base, and then backfilling. The presence of sand waves or megaripples on the seabed surface can affect the progress of the plough and prevent the plough from generating a level trench with a uniform trench depth. A calculation method has been presented that makes assumptions about the motion of the plough to predict the kinematics of ploughs through regions of nonuniform seabeds. Results from the calculation methodology are compared with those from small-scale model tests with good agreement, and the detailed kinematics of ploughs are then examined. The calculation method suggests that as a plough moves through a sand-wave field, the oscillation of the plough about the skids results in the trench base being formed alternately by the share tip and heel. The new method allows prediction of likely offshore plough performance given known plough geometry, sand wavelength, and wave amplitude and may be used as a tool for assessing the feasibility of pipeline ploughing in zones of sand waves or megaripples.

scholarly journals Sediment Characteristics over Asymmetrical Tidal Sand Waves in the Dutch North Sea

2020 ◽  
Vol 8 (6) ◽  
pp. 409 ◽  
Author(s):  
Chiu Hwa Cheng ◽  
Karline Soetaert ◽  
Bas Wijnand Borsje
Keyword(s):  
Grain Size ◽  
North Sea ◽  
Sand Wave ◽  
Experimental Investigations ◽  
Sand Waves ◽  
Offshore Engineering ◽  
Organic Carbon Concentration ◽  
Significant Difference ◽  
Sediment Sorting ◽  
Tidal Sand

The behavior of asymmetrical bedforms, which include many tidal sand waves, is challenging to understand. They are of particular interest since they are mostly located within areas prone to offshore engineering activities. Most experimental investigations regarding asymmetrical bedforms consider the riverine environment, are limited to a single sand wave or a few scattered ones, and focus only on differences between crest and trough. Hardly any information is available on sediment compositional changes along asymmetrical tidal sand waves, despite their abundance offshore. An asymmetrical sand wave field located off the coast of Texel Island in the North Sea was studied in June and October 2017. A total of 102 sediment samples were collected over two seasons along a single transect that covered five complete sand waves to measure the grain size composition, organic carbon concentration, chlorophyll-a (chl-a) concentration, and sediment permeability. We found significant variations in these sediment parameters between the sand wave trough, crest, and gentle and steep slopes, including a difference in permeability of more than 2-fold, as well as a difference in median grain size exceeding 65 µm. Based on these characteristics, a sand wave can be divided into two discrete halves: gentle slope + crest and steep slope + trough. Our results indicate a distinct sediment-sorting process along the Texel sand waves, with a significant difference between the two halves of each sand wave. These data could serve as input for process-based modeling of the link between sediment-sorting processes and seabed morphodynamics, necessary to design offshore engineering projects.

Sediment sorting in tidal sand waves fields: the internal structure revealed?

2020 ◽  
Author(s):  
Johan Damveld ◽  
Bas Borsje ◽  
Pieter Roos ◽  
Suzanne Hulscher
Keyword(s):  
Grain Size ◽  
Internal Structure ◽  
Nonlinear Effects ◽  
Wave Formation ◽  
Sand Wave ◽  
Small Scale ◽  
Suspended Sediment Transport ◽  
Geophysical Research ◽  
Sand Waves ◽  
Tidal Sand

&lt;p&gt;Tidal sand waves are rhythmic bed forms found on coastal shelves all around the world. An important property of sand waves is their mobility, as they display migration rates of several meters per year. Insight in these dynamics is of practical relevance, as this behaviour may interfere with offshore engineering activities. State-of-the-art morphodynamic models are used to predict sand wave dynamics, but they still overestimate dimensions such as their height (Van Gerwen et al, 2018). Moreover, these models often assume a uniform grain size distribution, whereas field observations indicate a clear sorting of sediments along sand waves. Previous modelling studies found that a combination of sediment mobility effects and tidal current strength may explain these sorting patterns (e.g. van Oyen and Blondeaux, 2009). However, as these models were limited to the early stage of sand wave formation, they did not account for the nonlinear effects of increasing sand wave amplitudes. Our goal is to include these nonlinear effects in order to further unravel sorting processes, in particular the internal sand wave structure.&lt;/p&gt;&lt;p&gt;Hereto we extend the work by van Gerwen et al (2018), allowing for an arbitrary number of sediment fractions, and we adopt the active layer approach of Hirano (1971) to account for bed stratigraphy. To investigate the role of asymmetry in hydrodynamic forcing, we include a residual current superimposed on the dominant tidal component.&lt;/p&gt;&lt;p&gt;Results show that in general the crests of sand waves are coarser than the troughs. In the case of an asymmetrical forcing, larger sediments are found on the upper lee slope, whereas the smaller grains are deposited on the lower lee slope. Due to migration, also the internal structure of the sand wave is revealed over time, showing the same pattern as found on the lee slope surface. Many field studies have shown that these model results qualitatively agree with observations on surficial sorting patterns (e.g. Cheng et al, 2018). However, as field data on the internal sediment structure is scarce, it is difficult to validate this model output.&lt;/p&gt;&lt;p&gt;Hence, the question remains whether the results on the internal sorting are a true representation of the substrate of sand waves. Nonetheless, the model results give insight in the processes governing grain size sorting over and in sand waves, which could be a valuable element in developing future coastal management strategies, such as sand extraction.&lt;/p&gt;&lt;p&gt;&lt;em&gt;Cheng, C.H., Soetaert, K., &amp; Borsje, B.W. (2018). Small-scale variations in sediment characteristics over the different morphological units of tidal sand waves offshore of Texel. NCK Days 2018.&lt;br&gt;&lt;/em&gt;&lt;em&gt;Hirano, M. (1971). River bed degradation with armouring. Trans. Jpn. Soc. Civ. Eng, 3, 194-195.&lt;br&gt;&lt;/em&gt;&lt;em&gt;Van Gerwen, W., Borsje, B.W., Damveld, J.H., &amp; Hulscher, S.J.M.H. (2018). Modelling the effect of suspended load transport and tidal asymmetry on the equilibrium tidal sand wave height. Coastal Engineering, 136, 56-64.&lt;br&gt;&lt;/em&gt;&lt;em&gt;Van Oyen, T., &amp; Blondeaux, P. (2009). Tidal sand wave formation: Influence of graded suspended sediment transport. Journal of Geophysical Research: Oceans, 114(C7).&lt;/em&gt;&lt;/p&gt;

Hydrodynamics and sediment dynamics of North Sea sand waves and sand banks

1993 ◽  
Vol 343 (1669) ◽  
pp. 461-474 ◽  
Keyword(s):  
Drag Coefficient ◽  
Turbulent Flows ◽  
North Sea ◽  
Surface Effect ◽  
Numerical Models ◽  
Pressure Sensors ◽  
Bedload Transport ◽  
Sand Wave ◽  
Sand Waves ◽  
A Site

Seabed drag coefficients have been measured at a site within the Norfolk Banks and at a site within the sand wave field in the southern North Sea, using pressure sensors and moored current meters. At the sand banks site a seabed tripod measuring turbulent flows within 1 m of the bed was also used. The results are generally in agreement with values used in numerical models. At the sand banks site, the drag coefficient increases with wind conditions, but at the sand waves site there is a reduction during the highest wave conditions, attributed to the drag reduction caused by sand resuspension from the bed. This result suggests that sediment effects must be considered if wave/current interaction is included in numerical models of the region. The drag coefficient for reversing tidal flows over the asymmetric sand waves is found to be larger for flow towards the steeper face, suggesting a small form drag component. Studies of sand movement used bedform mapping, fluorescent sand tracing and photography of migrating ripples. There is evidence for the early stages of formation of a new bank between Broken Bank and Well Bank. At the sand waves site, ripple migration is found to be a useful estimator of bedload transport under conditions of negligible suspension. Over the sand banks, a definite correlation of surface water properties, notably the turbidity, with the topography of the banks was observed. The mechanism for this surface effect is not known but it is consistent with the observation of features, seen in satellite visible light images, which outline the shapes of the banks.

scholarly journals Commercial fish abundance estimation in the Belgian part of the North Sea through eDNA ddPCR analyses

2021 ◽  
Vol 4 ◽  
Author(s):  
Sam Desmet ◽  
Rein Brys ◽  
Sabrina Neyrinck ◽  
Kris Hostens ◽  
Sofie Derycke
Keyword(s):  
Community Composition ◽  
North Sea ◽  
Water Samples ◽  
Fish Abundance ◽  
Small Scale ◽  
Target Species ◽  
Important Species ◽  
The North ◽  
Marine Diversity ◽  
The North Sea

Monitoring of fish assemblages in the Belgian part of the North Sea (BPNS) mainly happens through trawling. While effective, this method is invasive and destructive as it disturbs bottom communities, catches non-target species and removes organisms from the environment. A more sustainable alternative for monitoring marine diversity is the use of environmental DNA (eDNA) which comprises intra- and extracellular genetic material that comes from the shedding of organic material, like scales and mucus in the case of fish. When applying metabarcoding on eDNA, community composition can be inferred simply by analysing a small volume of water. Therefore the technique does not disturb the environment, and the high sensitivity of eDNA allows the detection of rare and transient species that are frequently missed by traditional sampling methods. Next to determining community composition, the amount of eDNA copies in the water could potentially be used to quantify target fish species in the marine environment. Here, we investigate whether eDNA concentrations from marine water samples correlate with local fish abundance estimates obtained via traditional beam trawling. Species specific Droplet Digital Polymerase Chain Reaction (ddPCR) assays were designed and tested for three economically important species: common sole (Solea solea), plaice (Pleuronectes platessa) and whiting (Merlangius merlangus). In march 2020, 12 sites in the BPNS were selected based on absence, low and high abundances of the three target species as observed in epibenthos monitoring data from previous years. In each site, 2L of seawater was collected with a niskin bottle from ca 1m above the sea floor. Subsequently, beam trawl transects of 1 km were conducted and all epibenthos species caught in the trawling net were morphologically identified, counted and weighted. Our results indicate promising correlations between eDNA concentrations obtained with the ddPCR assays and the number of specimens in the net for all three species. Some “false” positive results were obtained with the ddPCR, but these may actually be “true” positive detections because the fish might be present in the area but were not caught in the trawling transects. This warrants further investigation to see how far eDNA signals can be detected in the North Sea system. Next, 50 water samples were collected in Autumn 2020, involving more locations with or without the three fishes. This time samples were taken at the beginning, middle and end of the 1 km transects to investigate small scale horizontal variation in eDNA concentrations. The autumn samples are currently being processed. In March 2021, samples will be taken at different depths (surface, middle of the water column and ca 1m above the seafloor) to investigate whether there are any vertical patterns in eDNA distribution in a very well mixed system such as the BPNS. A DNA shedding experiment will be performed as well to estimate the rate at which the three fishes shed DNA. This will provide important information on how quickly fishes can be detected when they swim by. The information obtained with the field sampling and experimental setting will help to strengthen the correlation to a point that reliable abundance estimations of our target species become possible and will allow us to evaluate the potential of eDNA as a sustainable alternative/addition to traditional monitoring methods.

Präzisions-Forstwirtschaft – was ist das? | Precision forestry – what's that?

2007 ◽  
Vol 158 (8) ◽  
pp. 235-242 ◽  
Author(s):  
Hans Rudolf Heinimann
Keyword(s):  
Business Processes ◽  
Spatial Scales ◽  
Supply Chain Coordination ◽  
Sensor Technology ◽  
Small Scale ◽  
Soil Physics ◽  
Coordination Problem ◽  
Precision Engineering ◽  
Precision Forestry ◽  
And Control

The term «precision forestry» was first introduced and discussed at a conference in 2001. The aims of this paper are to explore the scientific roots of the precision concept, define «precision forestry», and sketch the challenges that the implementation of this new concept may present to practitioners, educators, and researchers. The term «precision» does not mean accuracy on a small scale, but instead refers to the concurrent coordination and control of processes at spatial scales between 1 m and 100 km. Precision strives for an automatic control of processes. Precision land use differs from precision engineering by the requirements of gathering,storing and managing spatio-temporal variability of site and vegetation parameters. Practitioners will be facing the challenge of designing holistic, standardized business processes that are valid for whole networks of firms,and that follow available standards (e.g., SCOR, WoodX). There is a need to educate and train forestry professionals in the areas of business process re-engineering, computer supported management of business transactions,methods of remote sensing, sensor technology and control theory. Researchers will face the challenge of integrating plant physiology, soil physics and production sciences and solving the supply chain coordination problem (SCCP).

scholarly journals Artificial neural network analysis of microbial diversity in the central and southern Adriatic Sea

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Danijela Šantić ◽  
Kasia Piwosz ◽  
Frano Matić ◽  
Ana Vrdoljak Tomaš ◽  
Jasna Arapov ◽  
...  
Keyword(s):  
Neural Network ◽  
Network Analysis ◽  
Bacterial Community ◽  
Microbial Diversity ◽  
Community Composition ◽  
Adriatic Sea ◽  
Bacterial Community Composition ◽  
Environmental Data ◽  
Large Contribution ◽  
Neural Network Analysis

AbstractBacteria are an active and diverse component of pelagic communities. The identification of main factors governing microbial diversity and spatial distribution requires advanced mathematical analyses. Here, the bacterial community composition was analysed, along with a depth profile, in the open Adriatic Sea using amplicon sequencing of bacterial 16S rRNA and the Neural gas algorithm. The performed analysis classified the sample into four best matching units representing heterogenic patterns of the bacterial community composition. The observed parameters were more differentiated by depth than by area, with temperature and identified salinity as important environmental variables. The highest diversity was observed at the deep chlorophyll maximum, while bacterial abundance and production peaked in the upper layers. The most of the identified genera belonged to Proteobacteria, with uncultured AEGEAN-169 and SAR116 lineages being dominant Alphaproteobacteria, and OM60 (NOR5) and SAR86 being dominant Gammaproteobacteria. Marine Synechococcus and Cyanobium-related species were predominant in the shallow layer, while Prochlorococcus MIT 9313 formed a higher portion below 50 m depth. Bacteroidota were represented mostly by uncultured lineages (NS4, NS5 and NS9 marine lineages). In contrast, Actinobacteriota were dominated by a candidatus genus Ca. Actinomarina. A large contribution of Nitrospinae was evident at the deepest investigated layer. Our results document that neural network analysis of environmental data may provide a novel insight into factors affecting picoplankton in the open sea environment.

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