Scale Of Meters Research Articles

Seagrass ecosystem conservation in Southeast Asia needs to link science to policy and practice

Seagrasses are of direct importance in sustaining the integrity and complex nature of Southeast Asian coasts. Multiple stressors, however, cause their declines at scales of square meters to square kilometers. More often, these declines are caused by human activity because the ecosystems are adjacent areas of increasing industrialization. The major driver of this activity, in turn, is the big gap or disconnect between seagrass science, policy and practice. But while the urgent need for scientific research to inform policy and practice directly is well recognized, out of the 1122 articles on seagrass published from 1973 to 2016 in the region (including China), 77% dealt with management and only 23% dealt with science. This status is, however, changing slowly in favor of more conservation oriented research and application of available science in addressing pressing issues. The need is urgent for a focused regional effort to speed up the pace and address this gap, to sustain the ecosystem services of seagrass ecosystems in the face of coastal environmental uncertainties in rapidly developing Southeast Asia. This effort should be functionally coordinated, starting with increased awareness to conserve seagrass, monitoring changes in the ecosystem, and managing their services and users.The challenge of designing effective policies for seagrass conservation in Southeast Asia is rendered even more complex by the urgent need to promote the three preconditions for a stronger science-policy-practice linkage. First, seagrass science has to be relevant. Second, that science has to be considered relevant and third, policy-making has to be open and receptive for scientific advice and public scrutiny. A new truly coordinated and functional regional program is needed aimed at: (a) establishing the principles by which seagrass ecosystems can be protected and their services maintained in the future. (b) regulating practices, which result in the destruction of seagrasses. (c) maintaining and enhancing seagrass ecosystems, and (d) establishing and promoting the interconnections of seagrass with the other coastal ecosystems as a basis of stakeholder integration and cohesion. The social and environmental ‘crisis’ coastal ecosystems face in Southeast Asia is forcing governments to increase awareness of the need for seagrass protection, adaptive management and monitoring.

Algas co-ocorrentes e morfologicamente distintas suportam uma diversa fauna associada na zona entremarés na Baía do Araçá, Brasil

Abstract Species diversity is regulated by historical, neutral and niche processes, with species tolerance, dispersal and productivity guiding diversity at larger scales, while habitat heterogeneity and biotic interactions acts in smaller scales. In rocky shores, several organisms provide secondary substrates for mobile fauna, with macroalgae being the most abundant and diverse ones. The patchiness promoted by different macroalgae hosts enhances small-scale heterogeneity and may increase and maintain the diversity of the mobile organisms, since there is a close relationship between the associated fauna and its hosts. In this study we selected three morphologically different macroalgae that coexist in the same rocky shore height in the Araçá Bay, an area under the threat of the nearby harbor expansion, and evaluated the fauna associated to each algal host. Even under similar abiotic pressure (same rocky shore height), the associated fauna of each algal host varied in number and composition, revealing a close relationship. The poorly branched foliose Ulva lactuca sustained a lower density of organisms and was dominated by isopods, while the heavily branched turf and Bostrychietum community showed a high density of organisms, with a dominance of peracarid crustaceans and annelids on the turf and more resistant groups, such as bivalves, acaris and terrestrial insects on the Bostrychietum. Previous studies in the Araçá Bay already revealed a large spatial heterogeneity in the processes and sessile organisms distribution, and here we highlight that this heterogeneity can be observed in an even smaller scale, with different algal hosts mediating the turnover of species in a scale of centimeters and meters, resulting in diversity maintenance of the associated fauna. Since the harbor expansion may prevent the occurrence of macroalgae as a result of light limitation by suspended platforms, we may expect not only a decrease in algal cover but also in the total diversity of the associated fauna in the Araçá Bay.

Geophysical observations and structural models of two shallow caves in gypsum/anhydrite-bearing rocks in Germany

Abstract The development of subsurface voids and cavities in soluble rocks is controlled by the hydrological and chemical processes in the host rock. Water (enriched with carbon dioxide) percolates through fractures and bedding partings of the host rock and removes material from the rock surface. As this enlargement is a highly heterogeneous process, only some fractures and bedding partings become significantly enlarged, evolving towards larger voids and caves. The size of the enlarged voids, often reaching the metre scale, can result in mechanically unstable structures, which, when close to the surface, are prone to collapse and thus are a hazard to infrastructure. We explored two caves in the anhydrite host rock of the Permian Zechstein sequences in northern Germany using geophysical measurements: the Kalkberghöhle close to Bad Segeberg (Hamburg region) and the Jettenhöhle close to Osterode (Harz region). Based on the results of gravity and electrical measurements, we were able to identify the cave voids and to characterize the local geological setting. Using these indirect geophysical observations, we deduced a structural model for both cave sites by numerical modelling. Our structural models were successfully calibrated against the Bouguer gravity data.

Remote sensing evidence of lava–ground ice interactions associated with the Lost Jim Lava Flow, Seward Peninsula, Alaska

Thermokarst terrains develop when ice-bearing permafrost melts and causes the overlying surface to subside or collapse. This process occurs widely throughout Arctic regions due to environmental and climatological factors, but can also be induced by localized melting of ground ice by active lava flows. The Lost Jim Lava Flow (LJLF) on the Seward Peninsula of Alaska provides evidence of former lava–ground ice interactions. Associated geomorphic features, on the scale of meters to tens of meters, were identified using satellite orthoimages and stereo-derived digital terrain models. The flow exhibits positive- and mixed-relief features, including tumuli (N = 26) and shatter rings (N = 4), as well as negative-relief features, such as lava tube skylights (N = 100) and irregularly shaped topographic depressions (N = 1188) that are interpreted to include lava-rise pits and lava-induced thermokarst terrain. Along the margins of the flow, there are also clusters of small peripheral pits that may be the products of meltwater or steam escape. On Mars, we observed morphologically similar pits near lava flow margins in northeastern Elysium Planitia, which suggests a common formation mechanism. Investigating the LJLF may therefore help to elucidate processes of lava–ground ice interaction on both Earth and Mars.

Remote Sensing of Seagrass Leaf Area Index and Species: The Capability of a Model Inversion Method Assessed by Sensitivity Analysis and Hyperspectral Data of Florida Bay

The capability for mapping two species of seagrass, Thalassia testudinium and Syringodium filiforme, by remote sensing using a physics based model inversion method was investigated. The model was based on a three-dimensional canopy model combined with a model for the overlying water column. The model included uncertainty propagation based on variation in leaf reflectances, canopy structure, water column properties and the air-water interface. The uncertainty propagation enabled both a-priori predictive sensitivity analysis of potential capability and the generation of per-pixel error bars when applied to imagery. A primary aim of the work was to compare the sensitivity analysis to results achieved in a practical application using airborne hyperspectral data, to gain insight on the validity of sensitivity analyses in general. Results showed that while the sensitivity analysis predicted a weak but positive discrimination capability for species, in a practical application the relevant spectral differences were extremely small compared to discrepancies in the radiometric alignment of the model with the imagery – even though this alignment was very good. Complex interactions between spectral matching and uncertainty propagation also introduced biases. Ability to discriminate LAI was good, and comparable to previously published methods using different approaches. The main limitation in this respect was spatial alignment with the imagery with in situ data, which was heterogeneous on scales of a few meters. The results provide insight on the limitations of physics based inversion methods and seagrass mapping in general. Complex models can degrade unpredictably when radiometric alignment of the model and imagery is not perfect and incorporating uncertainties can have non-intuitive impacts on method performance. Sensitivity analyses are upper bounds to practical capability, incorporating a term for potential systematic errors in radiometric alignment may be advisable. While Thalassia testudinium and Syringodium filiforme were too spectrally similar to be discriminated purely on spectral grounds, mapping of these and other species may be achievable by exploiting co-incident factors based on ecological zonation.

Coupling of fluid flow to permeability development in mid- to upper crustal environments: a tale of three pressures

Abstract Orogenic gold systems are open, flow-controlled thermodynamic systems and generally occur in mid- to upper crustal environments where there is strong coupling between fluid flow and dilatant plastic deformation. This paper considers the principles involved in such coupling, with an emphasis on the elastic and plastic volume changes and their influence on the fluid, mechanical and thermodynamic pressures. Some misconceptions regarding the magnitudes of these three distinctly different pressures and their influences on fluid flow and chemical equilibrium are addressed, with examples at both the tens of metres scale and the crustal scale. We show that the mean stress is less than twice the lithostatic stress for Mohr–Coulomb materials with cohesion and the thermodynamic pressure only has meaning under isentropic conditions and hence is less than many previously published estimates based on high mean stresses. At the crustal scale, we also include the role of critical behaviour in influencing the geometry and magnitudes of fluid pressure gradients and fluid flow velocities in open, flow-controlled systems.

Influence of geometric errors of guide rails and table on motion errors of hydrostatic guideways under quasi-static condition

Abstract Motion errors of hydrostatic guideways are mainly influenced by the geometric errors of guide rails and table which can be decomposed into harmonic waves of different frequencies based on Fourier transform. In this paper, a new approximate model is established to study the influence of geometric errors of guide rails and table on the motion errors of hydrostatic guideways using the equivalent third power of oil film thickness. It is found that, the motion errors are mainly affected by the geometric errors of guide rails rather than the geometric errors of table. The harmonic waves with wave numbers 0.5, 1.5, 2.5, 3.5, …, on the guide rails have no influence on the center displacement of table, and the harmonic waves with wave numbers 1, 2, 3, 4, …, have no influence on the yaw angle of table. The increment of land width and decrement of distance of two adjacent pads will result in enhancement of comprehensive averaging effect in consideration of center displacement and yaw angle. The approximate formulas have sufficient calculation accuracy compared with FEM when the ratio between amplitude of harmonic wave and initial film thickness is small. Using a deformed guide rail with wave numbers 0.5 and 1, the results of experiments agree well with the results calculated by approximate formulas and FEM. In the experiments, a novel method is proposed to manufacture the single harmonic wave of guide rail in the scale of micron meters, through which the amplitude and wavelength of the harmonic wave on guide rail can be controlled.

Froude supercritical flow bedforms in deepwater slope channels? Field examples in conglomerates, sandstones and fine‐grained deposits

AbstractActive margin continental slope outcrops from the Eocene Juncal Formation, the Eocene La Jolla Group and the Miocene Capistrano Formation display sedimentary structures and depositional geometries that suggest deposition from Froude supercritical flow, based on comparison to strata produced by flume experiments. These deposits range from boulder‐size soft clasts and cobble‐size hard clasts to silt and mud, and display long‐wavelength and low‐amplitude convex‐up and concave‐up geometries that range from centimetre to hundreds of metres scale, low‐angle foresets and backsets, and common internal and bounding erosion surfaces from centimetres to tens of metres in depth. In places, planar laminations, structureless beds and normally graded beds are laterally or vertically associated with such structures. In other places, consistent backsets or deep and steep‐sided scours occur. This study aimed to discuss the origin of the observed bedforms, contributed to recognition of supercritical flow deposits on continental slopes and expanded the outcrop examples of supercritical flow deposits to silt and mud. This work implies that the erosive and powerful Froude supercritical flow turbidity currents may have a substantial impact on erosional and depositional dynamics on deepwater slopes, especially on active margins due to the steep gradients and high sediment supply.

Geochemistry and mineralogy of contrasting supergene gold alteration zones, southern New Zealand

Supergene alteration of gold deposits has had important geochemical effects that changed the mineralogy and textures of near-surface exposures and can affect the economics of gold mines by enhancing gold liberation and increasing gold grades. This study links observed mineralogy with 655 water analyses from environments relevant to supergene processes in the Otago Schist goldfield of southern New Zealand, and these analyses are used as proxies for past supergene processes. There are two contrasting supergene alteration styles in otherwise identical host rocks and mineralisation zones in this area. Long-term groundwater alteration of sediments and underlying basement near to a regional unconformity developed progressively since the Cretaceous. This alteration has affected orogenic gold deposits exposed at the unconformity, and has resulted in supergene enrichment of gold with localised formation of centimetre scale gold nuggets. Alteration processes occurred under circumneutral pH conditions (pH 6–8.5), and was accompanied by extensive oxidation and clay alteration of basement rocks and sediments. Gold was mobilised as thiosulphate and bisulphide complexes and was reprecipitated by redox changes near the unconformity. The chemical processes of supergene enrichment were primarily abiotic, with minor bacterial facilitation of late stage gold mobility at the micron scale. In contrast, supergene alteration of eroding freshly-exposed mountain outcrops has occurred in the late Cenozoic without Au enrichment apart from liberation and minor particle size enhancement. The ambient pH of the associated waters was also circumneutral, but localised and temporary acidification (to pH ∼3) has occured on the metre scale or less in sulphidic outcrops. This supergene alteration was dominated by oxidation but some low redox minerals, senarmontite and secondary stibnite, have formed during the early stages of oxidation or subsequent reduction. Sulphide decomposition, with associated localised acidification and gold remobilisation was probably enhanced by bacterial processes in these exposed outcrops.

Climatic instability before the Miocene Climatic Optimum reflected in a Central European lacustrine record from the Most Basin in the Czech Republic

The work investigates the extensive freshwater lacustrine deposits of the Most Formation, which formed in the period between 17.7Ma and ca. 15.9Ma, in order to describe climate changes just before the Miocene Climatic Optimum (MCO). The Most Basin, an incipient rift within the European Cenozoic Rift System, exhibited a sedimentary environment that was sufficiently stable to preserve orbital signatures of environmental changes. Changes in the mineral composition of the sediments were characterised in terms of variations in their elemental composition, particularly their Al/Si and K/Ti element ratios and Fe, Sr, and Zr elemental abundances, which were efficiently obtained using X-ray fluorescence spectroscopy with a density of 3–4 samples per metre of core (approximately 15–20 samples per precession cycle). The sediments are distinguished by the presence of distinct and correlated horizons (1–10cm thick) containing Sr, Ba-rich crandallite, a mineral from the aluminium-phosphate-sulphate (APS) group. Chemo-, magneto-, and cyclostratigraphy were used to correlate eight cores with lengths up to 240m and to date the sediment; discrepancies at scales of up to two precession cycles (each ca. 20kyr, typically ~4m per cycle) were observed. The primary age model was based on magnetic polarity analysis (5 reversals) and later refined at the metre scale using cyclostratigraphy. We interpret the onset of the basin-wide lacustrine phase in the Most Basin as being a consequence of the enhanced input of fluvial clastic sediment to the former peat swamps during the high-eccentricity period at 17.7–17.55Ma, i.e., immediately after the initial decay of the East Antarctic ice sheet according to Levy et al. (2016). The most important environmental change recorded by the lacustrine interval in the Most Basin occurred at 16.44Ma during an eccentricity maximum and is nearly coeval with further shrinkage of the East Antarctic ice sheet. The second stage of monotonous lacustrine deposition, which exhibited enhanced precession-controlled compositional variability in 16.1–16.0Ma witnessed the onset of the MCO. Sediments younger than 15.9Ma are missing due to erosional removal after subsequent basin inversion. The sediments of the Most Formation represent an archive of environmental change in central Europe during the early stages of the MCO and have a temporal resolution ca. 5kyr.

An evaluation of terrain‐based downscaling of fractional snow covered area data sets based on LiDAR‐derived snow data and orthoimagery

AbstractReliable maps of snow‐covered areas at scales of meters to tens of meters, with daily temporal resolution, are essential to understanding snow heterogeneity, melt runoff, energy exchange, and ecological processes. Here we develop a parsimonious downscaling routine that can be applied to fractional snow covered area (fSCA) products from satellite platforms such as the Moderate Resolution Imaging Spectroradiometer (MODIS) that provide daily ∼500 m data, to derive higher‐resolution snow presence/absence grids. The method uses a composite index combining both the topographic position index (TPI) to represent accumulation effects and the diurnal anisotropic heat (DAH, sun exposure) index to represent ablation effects. The procedure is evaluated and calibrated using airborne‐derived high‐resolution data sets across the Tuolumne watershed, CA using 11 scenes in 2014 to downscale to 30 m resolution. The average matching F score was 0.83. We then tested our method's transferability in time and space by comparing against the Tuolumne watershed in water years 2013 and 2015, and over an entirely different site, Mt. Rainier, WA in 2009 and 2011, to assess applicability to other topographic and climatic conditions. For application to sites without validation data, we recommend equal weights for the TPI and DAH indices and close TPI neighborhoods (60 and 27 m for downscaling to 30 and 3 m, respectively), which worked well in both our study areas. The method is less effective in forested areas, which still requires site‐specific treatment. We demonstrate that the procedure can even be applied to downscale to 3 m resolution, a very fine scale relevant to alpine ecohydrology research.

Cutting through the smoke: the diversity of microorganisms in deep-sea hydrothermal plumes.

There are still notable gaps regarding the detailed distribution of microorganisms between and within insular habitats such as deep-sea hydrothermal vents. This study investigates the community composition of black smoker vent microorganisms in the Southern Hemisphere, and changes thereof along a spatial and chemical gradient ranging from the vent plume to surrounding waters. We sampled two hydrothermal vent fields, one at the South West Indian Ridge (SWIR), the other at the East Scotia Ridge (ESR). Samples were collected across vent fields at varying vertical distances from the origin of the plumes. The microbial data were sequenced on an Illumina MiSeq platform for the 16SrRNA gene. A substantial amount of vent-specific putative chemosynthetic microorganisms were found, particularly in samples from focused hydrothermal venting. Common vent-specific organisms from both vent fields were the genera Arcobacter, Caminibacter and Sulfurimonas from the Epsilonproteobacteria and the SUP05 group from the Gammaproteobacteria. There were no major differences in microbial composition between SWIR and ESR for focused plume samples. However, within the ESR the diffuse flow and focused samples differed significantly in microbial community composition and relative abundance. For Epsilonproteobacteria, we found evidence of niche-specificity to hydrothermal vent environments. This taxon decreased in abundance by three orders of magnitude from the vent orifice to background water. Epsilonproteobacteria distribution followed a distance–decay relationship as vent-effluents mixed with the surrounding seawater. This study demonstrates strong habitat affinity of vent microorganisms on a metre scale with distinct environmental selection.

Global permittivity mapping of the Martian surface from SHARAD

SHARAD is a subsurface sounding radar aboard NASA's Mars Reconnaissance Orbiter, capable of detecting dielectric discontinuities in the subsurface caused by compositional and/or structural changes. Echoes coming from the surface contain information on geometric properties at metre scale and on the permittivity of the upper layers of the Martian crust. A model has been developed to estimate the effect of surface roughness on echo power, depending on statistical parameters such as RMS height and topothesy. Such model is based on the assumption that topography can be characterized as a self-affine fractal, and its use allows the estimation of the dielectric properties of the first few metres of the Martian soil. A permittivity map of the surface of Mars is obtained, covering several large regions across the planet surface. The most significant correspondence with geology is observed at the dichotomy boundary, with high dielectric constant on the highlands side (7 to over 10) and lower on the lowlands side (3 to 7). Other geological correlations are discussed.

Application of surface analytical methods for hazardous situation in the Adriatic Sea: monitoring of organic matter dynamics and oil pollution

Abstract. Surface analytical methods are applied to examine the environmental status of seawaters. The present overview emphasizes advantages of combining surface analytical methods, applied to a hazardous situation in the Adriatic Sea, such as monitoring of the first aggregation phases of dissolved organic matter in order to potentially predict the massive mucilage formation and testing of oil spill cleanup. Such an approach, based on fast and direct characterization of organic matter and its high-resolution visualization, sets a continuous-scale description of organic matter from micro- to nanometre scales. Electrochemical method of chronoamperometry at the dropping mercury electrode meets the requirements for monitoring purposes due to the simple and fast analysis of a large number of natural seawater samples enabling simultaneous differentiation of organic constituents. In contrast, atomic force microscopy allows direct visualization of biotic and abiotic particles and provides an insight into structural organization of marine organic matter at micro- and nanometre scales. In the future, merging data at different spatial scales, taking into account experimental input on micrometre scale, observations on metre scale and modelling on kilometre scale, will be important for developing sophisticated technological platforms for knowledge transfer, reports and maps applicable for the marine environmental protection and management of the coastal area, especially for tourism, fishery and cruiser trafficking.

Re-sedimented deposits in the rift section of the Campos Basin

An integrated petrologic-sedimentologic-stratigraphic-seismic study of the Lagoa Feia Group, rift section of the Campos Basin, has shown that rift sedimentation was dominantly intrabasinal (carbonate and stevensitic deposits), with siliciclastic deposits restricted to the proximity of graben border faults. The bivalve bioclastic rudstones (“coquinas”) that constitute the rift reservoirs show commonly limited abrasion of the bioclasts, and were deposited both on basement highs and lows throughout the rift section. Although in situ deposits of stevensite ooids and peloids occur dominantly at the base of the succession, these particles are ubiquitous to the entire rift section, mixed in variable proportion with siliciclastic and carbonate sediments. The environmental conditions required for the formation of stevensite and the growth of bivalves are mutually exclusive, as stevensite forms only at pH greater than 10, while bivalves cannot tolerate pH greater than 9. The common mixture of well-rounded basaltic rock fragments with angular, granitic-gneissic rock fragments and feldspars in the sandstones and conglomerates indicates recycling of epiclastic deposits from the early rift section, combined with first-cycle contribution from the plutonic basement. The studied cores show no evidence of subaerial exposure, and there is a lack of bioturbation, suggesting harsh environmental conditions. The rift deposits are dominantly massive or faintly-laminated, with diffuse facies boundaries. Structures indicative of unidirectional or oscillatory flow are subordinate. Integration of seismic, sedimentologic and petrographic evidence indicates that the Campos Basin rift section is formed mostly by re-sedimented gravitational deposits. The onset of the rift sedimentation occurred in synformal depressions, where bivalve banks or stevensite ooids were formed in shallow lacustrine environments under variable alkalinity conditions. With the development of half-grabens and concentration of the tectonic activity along the border faults, recurrent tectonic events promoted the mixing and gravitational re-deposition of stevensitic, clastic and bioclastic sediments in deeper, fault-bounded troughs. Large-scale units, hundreds of meters thick, were generated by major tectonic events, whereas compositional variations in the scale of meters were possibly a product of lake-level climatic fluctuations. Thus, due to syn-rift and mainly to post-rift erosion (the Neo-Aptian unconformity), the preserved rift section of the Lagoa Feia Group comprises mostly sediments deposited in the central troughs of the half-graben structures. Marginal sediments were extensively eroded and re-sedimented as gravity-driven mixed deposits. This new model, constructed form the integration of seismic, stratigraphic, sedimentologic and petrologic data, diverges substantially from the presently accepted model for the sedimentation of the rift section, opening new possibilities for the exploration of Campos Basin, as well as of similar settings, as in the adjacent Santos Basin.

A model for thin layer formation by delayed particle settling at sharp density gradients

Thin layers – regions where plankton or particles accumulate vertically on scales of a few meters or less – are common in coastal waters, and have important implications for both trophic dynamics and carbon cycling. These features can form by a variety of biological and physical mechanisms, including localized growth, shear-thinning, and directed swimming. An additional mechanism may result in the formation of thin layers of marine aggregates, which have been shown to decrease their settling velocity when passing through sharp density gradients, a behavior termed delayed settling. Here, we apply a simple vertical advection-diffusion model to predict the properties of aggregate thin layers formed by this process. We assume a constant vertical flux of particles from the surface, which is parameterized by observations from laboratory experiments with marine aggregates. The formation, maintenance, and shape of the layers are described in relation to non-dimensional numbers that depend on environmental conditions and particle settling properties. In particular, model results demonstrate layer intensity and sharpness both increase with higher Péclet number (Pe), that is, under conditions with weaker mixing relative to layer formation. Similarly, more intense and sharper layers are found when the delayed settling behavior of aggregates is characterized by a lower velocity minimum. The model also predicts layers that are vertically asymmetric and highly “peaky” when compared with a Gaussian distribution, features often seen in thin layers in natural environments. Lastly, by comparing model predictions with observations of thin layers in the field, we are able to gain some insight into the applicability of delayed settling as a thin layer formation mechanism in different environmental conditions.

Small-scale removal of seagrass (Zostera marina L.): effects on the infaunal community

ABSTRACTEelgrass meadows are a common feature in shallow waters along the Norwegian coast, where they provide a habitat for a diverse infaunal community. Recreational boat anchoring and moorings physically scour seagrass and may affect the ecosystem functioning and resilience of the system to natural and anthropogenic disturbances. A small-scale eelgrass (Zostera marina) removal experiment was conducted to study the effects on macro- and meiofauna. Entire plants, including the rhizomes, were removed from 4 m2 patches in three eelgrass meadows in the inner Oslofjord in October 2010. Core samples were taken after a recovery period of 10 months, from the removed patches as well as from the surrounding meadow. Macrofauna (>500 μm) and meiofauna (63–500 μm) in the sediment were investigated for possible effects of the eelgrass removal. Macrofauna and meiofauna composition were site specific and therefore location was identified as the main determinant for the infaunal community. The eelgrass did not regrow within the recovery period and bare sediment patches with only single eelgrass shoots were present during the sampling. Our analyses support an influence of the removal on individual species, but not the complete community. In particular one species, the gastropod Peringia ulvae, was encountered in higher numbers in samples from the removed patches than in control samples. From a management perspective, such minor removal of eelgrass, on the scale of square metres, appears to have no long-lasting detrimental effect to the infaunal community in sheltered meadows with muddy sediments.

The biogeography of kin discrimination across microbial neighbourhoods.

The spatial distribution of potential interactants is critical to social evolution in all cooperative organisms. Yet the biogeography of microbial kin discrimination at the scales most relevant to social interactions is poorly understood. Here we resolve the microbiogeography of social identity and genetic relatedness in local populations of the model cooperative bacterium Myxococcus xanthus at small spatial scales, across which the potential for dispersal is high. Using two criteria of relatedness—colony‐merger compatibility during cooperative motility and DNA‐sequence similarity at highly polymorphic loci—we find that relatedness decreases greatly with spatial distance even across the smallest scale transition. Both social relatedness and genetic relatedness are maximal within individual fruiting bodies at the micrometre scale but are much lower already across adjacent fruiting bodies at the millimetre scale. Genetic relatedness was found to be yet lower among centimetre‐scale samples, whereas social allotype relatedness decreased further only at the metre scale, at and beyond which the probability of social or genetic identity among randomly sampled isolates is effectively zero. Thus, in M. xanthus, high‐relatedness patches form a rich mosaic of diverse social allotypes across fruiting body neighbourhoods at the millimetre scale and beyond. Individuals that migrate even short distances across adjacent groups will frequently encounter allotypic conspecifics and territorial kin discrimination may profoundly influence the spatial dynamics of local migration. Finally, we also found that the phylogenetic scope of intraspecific biogeographic analysis can affect the detection of spatial structure, as some patterns evident in clade‐specific analysis were masked by simultaneous analysis of all strains.

Estimation of the advection effects induced by surface heterogeneities in the surface energy budget

Abstract. The effect of terrain heterogeneities in one-point measurements is a continuous subject of discussion. Here we focus on the order of magnitude of the advection term in the equation of the evolution of temperature as generated by documented terrain heterogeneities and we estimate its importance as a term in the surface energy budget (SEB), for which the turbulent fluxes are computed using the eddy-correlation method. The heterogeneities are estimated from satellite and model fields for scales near 1 km or broader, while the smaller scales are estimated through direct measurements with remotely piloted aircraft and thermal cameras and also by high-resolution modelling. The variability of the surface temperature fields is not found to decrease clearly with increasing resolution, and consequently the advection term becomes more important as the scales become finer. The advection term provides non-significant values to the SEB at scales larger than a few kilometres. In contrast, surface heterogeneities at the metre scale yield large values of the advection, which are probably only significant in the first centimetres above the ground. The motions that seem to contribute significantly to the advection term in the SEB equation in our case are roughly those around the hectometre scales.

Small-scale spatial heterogeneity of stable isotopes signatures (δ15N, δ13C) in Sphagnum sp. transfers to all trophic levels in oribatid mites

Small-scale heterogeneity is important for understanding soil animal diversity since it may explain their local coexistence. We investigated the heterogeneity within and between three Sphagnum microhabitats (Sphagnum lawn: apical green part, decomposing brown part; submerged Sphagnum) and the heterogeneity of potential consumers (oribatid mites) in two German peatlands (Dubringer Moor, Klockenbruch) using stable isotopes (15N, 13C). Small-scale heterogeneity of the potential food resource (Sphagnum sp.) in 15N and 13C was high. The heterogeneity of 15N signatures of Sphagnum sp. was transferred to oribatid mite taxa indicating that Sphagnum sp. is their basal food resource. The close relationship between stable isotopes ratios in Sphagnum sp. and oribatid mites on the scale of a few meters furthermore points to the low mobility of mites. When oribatid mites where aggregated into trophic levels, the strongest correlation occurred between 15N in Sphagnum sp. and oribatid mites of the first trophic level. Oribatid mites spanned 9.1 δ15N and 4.4 δ13C units in the Dubringer Moor and 9.5 δ15N and 4.7 δ13C units in the Klockenbruch indicating that they span over about three trophic levels. Three oribatid mite species (Rhysotritia ardua, Hydrozetes lacustris, Pergalumna nervosa) were trophic generalists whereas eleven other species (e.g. Hoplophthiracarus illinoisensis, Hypochthonius rufulus) had rather narrow trophic ranges as indicated by variance in 15N and 13C signatures. Isotopic signatures of similar oribatid mites collected in the green and brown parts of the Sphagnum lawn were rather close together suggesting that they use the same food sources. In the Sphagnum lawn, oribatid mites low in the food web were primary decomposers such as Platynothrus peltifer and Nothrus pratensis, whereas Oppiella spp. had high δ15N signatures pointing to fungal feeding or predation/scavenging. Limnozetes rugosus and Hydrozetes lacustris had the highest 15N signatures indicating that these taxa are high in the food web possibly feeding on protozoans and nematodes living in the biofilm on the stems and branches of Sphagnum sp.