Sediment Granulometry Research Articles

Two new free-living nematode species (Comesomatidae) from the continental slope of New Zealand, with keys and notes on distribution

Two new free-living marine nematode species of the family Comesomatidae are described from the continental slope of NewZealand, and their distributions at 32 sites are investigated in relation to environmental factors. Vasostoma aurata n. sp. is char-acterised by a distinctly set-off head, amphideal fovea with 4.5 turns, conspicuous chords consisting of two bands fusing atbody extremities, with outline of cell bodies usually golden-coloured, and relatively short spicules. Setosabatieria conicauda n.sp. is characterised by an amphid with 4.25–4.5 turns, the presence of only 1–3 sub-cephalic setae per file, several clusters ofintracellular inclusions, sometimes brown-coloured, in the intestinal wall, and a conical tail. Keys to all known species of Seto-sabatieria and Vasostoma are provided. Both species were mostly restricted to subsurface (1–5cm depth) sediments. The abun-dance of V. aurata n. sp. and S. conicauda n. sp. was significantly correlated with food quantity and quality, but the patternsdiffered between species. The effect of food-related factors may be directly linked to interspecific differences in food require-ments, or mediated by biogeochemical processes (i.e., tolerance of sub-surface oxygen and sulphide concentrations). No signif-icant correlations were found between sediment granulometry and abundances, despite the wide range of sediment grain-sizes (6–93% silt and clay) at the sampling sites.

Fish abundance and species richness across an estuarine–freshwater ecosystem in the Neotropics

We investigated the distributional patterns of shallow-water fish and their environmental correlates along a broad spatial scale encompassing estuarine and freshwater ecosystems. Marine-vagrant species were restricted to the sites under the influence of salinity intrusion, whereas estuarine-related and freshwater guilds were found along the entire estuarine–freshwater gradient. Primary- and secondary-freshwater fish guilds had the most widespread spatial distribution and comprised a major fraction of the total abundance and species richness. Abiotic factors correlated with fish abundance and composition along two main environmental axes, one related with variation in salinity, water transparency, and sediment granulometry and the other with the slope gradient. Species richness was significantly higher at the natural channel linking the estuarine- and freshwater-ecosystem, which probably was due to: (a) a steeper slope that favored the confluence of fish from the littoral ( 2 m) zones and (b) the sporadic inflow of saltwater that carried into this region several marine-related species. Although estuarine–freshwater ecotones are known to support few species, mainly salinity tolerant, our results suggest that habitat features and seasonal fish movement associated with salinity intrusion could lead to more diverse fish assemblages in this transitional zone.

Coastal Sedimentation Associated with the Tohoku Tsunami of 11 March 2011 in South Kuril Islands, NW Pacific Ocean

Sediment deposited by the Tohoku tsunami of March 11, 2011 in the Southern Kurils (Kunashir, Shikotan, Zeleniy, Yuri, Tanfiliev islands) was radically different from sedimentation during local strong storms and from tsunamis with larger runup at the same location. Sediments from the 2011 Tohoku tsunami were surveyed in the field, immediately and 6 months after the event, and analyzed in the laboratory for sediment granulometry, benthos Foraminifa assemblages, and diatom algae. Run-up elevation and inundation distance were calculated from the wrackline (accumulations of driftwood, woody debris, grass, and seaweed) marking the distal edge of tsunami inundation. Run-up of the tsunami was 5 m at maximum, and 3–4 m on average. Maximum distance of inundation was recorded in river mouths (up to 630 m), but was generally in the range of 50–80 m. Although similar to the local strong storms in runup height, the tsunami generally did not erode the coast, nor leave a deposit. However, deposits uncharacteristic of tsunami, described as brown aleuropelitic (silty and clayey) mud rich in organic matter, were found in closed bays facing the South Kuril Strait. These closed bays were covered with sea ice at the time of tsunami. As the tsunami waves broke the ice, the ice floes enhanced the bottom erosion on shoals and destruction of low-lying coastal peatland even at modest ranges of runup. In the muddy tsunami deposits, silt comprised up to 64 % and clay up to 41.5 %. The Foraminifera assemblages displayed features characteristic of benthic microfauna in the near-shore zone. Deep-sea diatoms recovered from tsunami deposits in two closely situated bays, namely Krabovaya and Otradnaya bays, had different requirements for environmental temperature, suggesting these different diatoms were brought to the bays by the tsunami wave entraining various water masses when skirting the island from the north and from the south.

Patterns of beta diversity in riparian ground beetle assemblages (Coleoptera Carabidae): A case study in the River Aniene (Central Italy)

We investigated riparian ground beetle communities to: (1) identify the main environmental factors determining species composition; (2) determine whether sites with similar ecological characteristics have similar species composition as a result of local selection; and (3) provide some indications for conservation of these insects. For 45 sampling sites in the River Aniene we measured: elevation, river bank morphology, percentage of shaded area, habitat heterogeneity, sediment depth, sediment granulometry and geographic position. We then used Canonical Correspondence Analysis (CCA) to investigate the importance of these variables in structuring beetle communities and cluster analysis (CA) to identify groups of sites with similar species composition. Granulometry and elevation were the most important parameters influencing species composition. Position of assemblages in CCA space was partially similar to their groupings in CA. In particular, silty sediments hosted a homogeneous group of species (with several highly specialized elements), well separated from all other clusters, suggesting that this type of substrate exerts a strong local selection pressure on ground beetle species. Communities characterized by species associated with coarse sediments were typically found in isolated localities. Further isolation of these populations by impoundments would have a serious impact on their persistence.

Adjustment coefficients for planimetric analysis of the granulometry of coarse-grained sediments

Adjustment coefficients for planimetric analysis of the granulometry of coarse-grained sedimentsThe relationship between results from granulometric analyses of by sieving and by planimetry was investigated by numerical simulation of cubes filled with boulders, cobbles and pebbles. Cross-sections through the sediment were simulated and compared with photos of an actual outcrop wall. Volumes estimated on the basis of planimetric analysis using the cross-sections were compared with sieve analyses, thus allowing to determine adjustment coefficients. The coefficients for pebbles and cobbles have a small standard error, but are larger for boulders, which might be a consequence of too small areas formed by the cross-sections.

In situ production and respiration of the benthic community during emersion on subtropical intertidal sandflats

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 441:33-47 (2011) - DOI: https://doi.org/10.3354/meps09362 In situ production and respiration of the benthic community during emersion on subtropical intertidal sandflats Li-Hua Lee1,2, Li-Yung Hsieh1,2, Hsing-Juh Lin2,3,* 1Endemic Species Research Institute, Jiji, Nantou 552, Taiwan 2Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan 3Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan *Email: hjlin@dragon.nchu.edu.tw ABSTRACT: In situ benthic community production and respiration during emersion were measured monthly in the course of a 19 mo survey from June 2008 to December 2009 by monitoring CO2 fluxes in benthic chambers on intertidal sandflats of a subtropical coastal wetland. Maximum gross community production (GCPm) and community respiration (CR) all exhibited higher values in summer and fall and lower values in spring and winter. GCPm and CR were positively correlated with air temperature. Temperature coefficients (Q10) showed that a rise of 10°C would increase the GCPm and CR by factors of 3.72 and 4.80, respectively. GCPm was also positively correlated with sediment grain size and negatively correlated with the silt/clay content. CR exhibited a strong positive correlation with sediment chlorophyll a concentration and macrofaunal biomass. To provide an accurate annual budget of benthic production during emersion, corrections were considered for cloudiness and the time lag between emersion and maximum production due to vertical migration of benthic diatoms and variations in CR during nighttime emersion periods. Annual net community production (NCP) during emersion on sandflats was estimated to be 2.87 g C m−2 yr−1, indicating an autotrophic system. However, taking into account the variation in benthic metabolism during immersion, the subtropical intertidal sandflats shifted to a heterotrophic system, and annual NCP was calculated to be −91.47 g C m−2 yr−1. KEY WORDS: Carbon sink · Gross community production · Community respiration · Net community production · Sediment granulometry · Kaomei Wetland · Taiwan Full text in pdf format PreviousNextCite this article as: Lee LH, Hsieh LY, Lin HJ (2011) In situ production and respiration of the benthic community during emersion on subtropical intertidal sandflats. Mar Ecol Prog Ser 441:33-47. https://doi.org/10.3354/meps09362 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 441. Online publication date: November 15, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Further evidence for the effect of particle-size diversity on deep-sea benthic biodiversity

The positive correlation between sediment particle-size diversity (a measure of habitat heterogeneity) and deep-sea macrofaunal diversity was first demonstrated two decades ago. The causality of this relationship was not elucidated because of the potential influence of macrofauna on sediment granulometry. Here we test the generality of this correlation using smaller organisms with limited mobility and limited ability to change the physical structure of sediments. Results of partial regressions accounting for the effect of water depth and food availability showed that nematode species and genus diversity were positively correlated with sediment particle-size diversity on the continental slope of New Zealand. Trophic diversity was not correlated with sediment particle-size diversity, however, which could suggest that the relationship between habitat heterogeneity and diversity was not the result of food partitioning between species/genera. Our findings provide support for the importance of small-scale habitat heterogeneity in the maintenance of local diversity in the deep sea, one of the few known environmental factors that may directly influence species co-existence in this biome.

Impacts of maintenance dredged material disposal on macrobenthic structure and secondary productivity

The results of a monitoring programme to assess the spatial impacts associated with ongoing dredged material disposal activity at a dispersive, coastal disposal site (southwest UK) are described. Benthic impacts were assessed using benthic community structure and secondary productivity estimates.Analyses of univariate indices (including secondary production) and multivariate community structure revealed differences between stations inside and those outside the disposal site were minimal. Generally, stations within and outside the disposal site were characterised by the same species. Regression models indicated that the variability in biological structure and secondary production was predominantly accounted for by natural variables (e.g., depth, sediment granulometry) with only a small amount of residual variability being due to contaminant variables. Thus, the elevated levels of certain contaminants in the vicinity of the disposal area were not sufficient to result in significant ecological or ecotoxicological changes. We ascribe such findings partly to the dispersive nature of the disposal site.

High Variability in Sediment Characteristics of a Neotropical Stream Impacted by Surface Mining and Gully Erosion

This study examined patterns of stream sediment granulometry, organic matter (OM) and metal concentration, and surface water characteristics in a catchment in the Brazilian Iron Quadrangle that is highly impacted by surface iron mining and gully erosion. Sediment granulometry indicated fine sediment deposition at impacted stream sites, i.e., tendencies towards bimodal particle size distributions with an additional peak in the sand fraction at impacted stream sites that did not occur at pristine reference sites, as well as towards smaller mean sediment particle sizes at impacted sites than at reference sites. Impacted sites also had significantly lower sediment OM contents than reference sites. Sediment heavy metal and arsenic concentrations did not differ between impacted and reference sites and were generally below published target or threshold effect concentrations. Impacts on surface water characteristics occurred only locally at a site that received tailings pond effluent from an iron mine and had very low pH and conductivity values. Sediment characteristics exhibited substantial spatial variability in the studied tropical catchment, showing that land use impacts can hardly be detected in routine monitoring and impact assessment studies that adopt a before–after control-impact approach and do not consider pristine reference streams. These results underline the importance of high-resolution and long-term sediment monitoring as well as integrated basin-scale sediment management programs.

Characterization of the seafloor at the SYSTCO stations based on video observations and ground truthing sedimentology

An underwater camcorder mounted on a lander frame was used to image the sedimentary conditions and the epibenthic fauna at the seafloor along the SYSTCO transect. Four stations were monitored; on the lower shelf (600 m), continental slope (2000 m), abyssal plain (5300 m), and on top of a seamount (2100 m). The sediment surface was filmed for different time lengths between 3 and 19 min, while the camera was towed over distances ranging from 11 to 187 m, resulting in areas filmed between 4 and 71 m 2 per station. From the gathered images, epifauna was counted and identified to the lowest possible taxonomic level. For ground truthing, two to three replicate multicorer samples per station were vertically sectioned per centimeter down to 5 cm depth and analyzed for sediment granulometry. Differences in the sedimentary characteristics could be related to both water depth and topography according to the multicorer samples. The video footage from each station showed a range of different sediment surface types and widely varying epifaunal abundance, the lowest number of readily identifiable organisms being present on the abyssal plain and the highest on the lower shelf.

Context dependence of marine ecosystem engineer invasion impacts on benthic ecosystem functioning

Introduced ecosystem engineers can severely modify the functioning on invaded systems. Species-level effects on ecosystem functioning (EF) are context dependent, but the effects of introduced ecosystem engineers are frequently assessed through single-location studies. The present work aimed to identify sources of context-dependence that can regulate the impacts of invasive ecosystem engineers on ecosystem functioning. As model systems, four locations where the bivalve Ruditapes philippinarum (Adams and Reeve) has been introduced were investigated, providing variability in habitat characteristics and community composition. As a measure of ecosystem engineering, the relative contribution of this species to community bioturbation potential was quantified at each site. The relevance of bioturbation to the local establishment of the mixing depth of marine sediments (used as a proxy for EF) was quantified in order to determine the potential for impact of the introduced species at each site. We found that R. philippinarum is one of the most important bioturbators within analysed communities, but the relative importance of this contribution at the community level depended on local species composition. The net contribution of bioturbation to the establishment of sediment mixing depths varied across sites depending on the presence of structuring vegetation, sediment granulometry and compaction. The effects of vegetation on sediment mixing were previously unreported. These findings indicate that the species composition of invaded communities, and the habitat characteristics of invaded systems, are important modulators of the impacts of introduced species on ecosystem functioning. A framework that encompasses these aspects for the prediction of the functional impacts of invasive ecosystem engineers is suggested, supporting a multi-site approach to invasive ecology studies concerned with ecosystem functioning.

What is the relative importance of sediment granulometry and vertical gradients to nematode morphometrics?

Nematode morphometrics were compared at 11 fine-sand and three muddy-sediment sites on the Louisiana, USA continental shelf to explore nematode–sediment relationships. Over 1800 nematodes were measured, and morphometric profiles through 4 cm were examined. The mean length of nematodes did not differ between muds and sands, although nematode diameter was greater in muds below 2 cm in sediment depth. Sand-dwelling nematodes, which slide through interstitial pore spaces, were longer relative to their diameter compared to nematodes that burrow through muddy sediments lacking interstices. Nematode diameter increased with both increasing particle size and particle heterogeneity among sandy stations. In muds, nematode length, diameter and biovolume increased with sediment depth, although length:width ratio did not vary with depth in the sediment. In sands, nematode length and length:width ratio increased with increasing sediment depth, but neither diameter nor biovolume varied with depth in the sediment. These results suggest that nematode body size and shape are related both to variation in sediment pore spaces and to vertical gradients within sediments. Within sands, body size variation attributable to granulometry was greater than variation associated with vertical gradients, while within muds variation in body size with sediment depth was greater than variation associated with particle size. Variation in body shape was similar along the vertical sediment profile and with variation in particle size in both sands and muds. We conclude that nematodes are excellent test organisms with which to test hypotheses regarding the confounded effects of sediment granulometry and chemical gradients in benthic ecosystems.

Crustacean assemblages along the Guadiana River estuary (south-western Iberian Peninsula)

The spatial distribution of the subtidal crustacean assemblages of the Guadiana River estuary was studied previous to the building of the Alqueva Dam (the biggest dam in Europe). The differences between an estuarine and marine environment seem to be the main reason responsible for the composition and distribution of the crustaceans along the study zone. The Guadiana estuary has shown high number of species in comparison with other nearby estuaries and this richness seems justified by the scarce influence of pollutants (most of them have shown low or moderate values) and their hydrodynamic and granulometric characteristics (76 species were found, 39 in the estuarine area). A gradient of enrichment and structuring of the assemblages was shown from the upstream to the marine zones and a spatial segregation of species was found along this estuarine environmental gradient, e.g. the amphipod Corophium multisetosum and the isopod Cyathura carinata in the upper estuary; the amphipod Bathyporeia cf. pilosa and the isopods Lekanesphera levii and Saduriella losadoi in the middle estuary; the amphipod Melita hergensis in the mouth; and a high number of species in the marine area. Since the Alqueva Dam will reduce the river discharges and may cause changes in the abiotic characteristics such as granulometry of sediments or salinity, this study establishes a baseline against which a monitoring programme or follow-up studies could measure any significant effects of the dam or related impacts.

The distribution of meiofauna on back-reef sandy platforms in the Maldives (Indian Ocean)

The Maldivian archipelago comprises some of the most characteristic and significant world atoll systems, but the meiobenthic assemblages of these islands continue to be largely unknown. To investigate variations in meiofaunal spatial distribution and biodiversity in back-reef platforms, three transects were studied, two at Felidhoo (the north and east sides) and one at South Male. The sedimentological features of the samples obtained were also analyzed to further current knowledge on the relationships that exist between sediments and meiofauna. Our results reveal that the meiofaunal assemblage at these locations is well diversified and includes 20 major taxa. Nematodes and copepods are dominant, together forming 68% of the total meiofauna, followed by platyhelminthes, polychaetes and ostracods. The nematode assemblage is very rich and composed of 34 families and 123 genera – 96 of which (78%) set new records for the Maldives. The structures of the meiofaunal and nematode assemblages are relatively similar on the ‘large-scale’ level (i.e. when the different platforms are compared) and reveal a low β-diversity. However, significant dissimilarities were detected within each platform, emphasizing that such ‘small-scale’ differences are the main factors determining the structure of the meiofauna and, in particular, the nematode assemblages. Although significant differences were not detected between the transects, greater levels of dissimilarity were recognized at North Felidhoo. Here, the building of inclined deposit layers plays a significant role in increasing the heterogeneity of the platform habitats and sediments, confirming the great importance of sediment granulometry as an environmental variable. Indeed, a close relationship is observed between meiofauna (especially for the nematodes) and grain size, which appears to control the structure, diversity and trophic composition of the Maldivian meiofauna assemblages, thus highlighting the high biodiversity existing in the medium-coarse sands.

Macro benthic community assemblage before and after the 2007 tsunami and earthquake at Paracas Bay, Peru

Macrobenthic soft bottom community assemblages were studied from December 2006 to December 2007 at Paracas Bay (Atenas Beach, 13°45' S, 76°17' W, Peru), including the period of the tsunami of 15 August 2007, providing a unique opportunity to assess the effects of this type of natural disturbance in soft bottom marine ecosystems. The results show that the tsunami affected the soft bottom community assemblage by changing the sediment granulometry, the biomass and abundance of epifaunal species, and by increasing the silt proportion. The event affected all functional groups, resulting in an increased numbers and biomass of filter feeder and grazers that were followed soon after by predators during the post-tsunami period. A similar pattern was observed for biomass and the abundance of infaunal species without changing the functional groups. The slow recovery observed after four months was likely related to the loss of sediment stability. In summary, there were differences in the structure and composition of soft bottom macrofaunal assemblages before and after the earthquake and posterior tsunami disturbance, forcing benthic communities to initiate re-colonisation processes.

Granulometry, mineralogy and trace elements of marine sediments from the Gulf of Milazzo (NE Sicily): evaluation of anthropogenic impact

Granulometry, mineralogy, and trace element concentrations are determined in marine sediments from thirty-six sampling sites in the littoral environment of the Gulf of Milazzo (NE Sicily). Sediment samples were collected in August 2008, along 18 seaward transects, at water depths of ‐10, ‐20 and ‐30 m, by using a Van Veen grab. Grain-size analysis shows predominance of sand (56%) and silt (35%) fractions with respect to clay (7%) and gravel (2%) fractions. Bulk mineralogical analysis documents the presence of quartz, micas, feldspars, calcite, and chlorite, which reflect erosion processes affecting the Kabilian-Calabrian Units. Concentrations of most trace elements in the deeper sediments were notably higher than shallower ones, due to the gradual increase of the fine fraction (<63 mm). Concentrations of Cr, Ni, Pb and, at lesser extent, Zn and Cu in the <63 mm fraction appear to be potentially hazardous, exceeding national and international regulatory guidelines, both close to the Milazzo industrial area and at Capo Rasocolmo. Trace element mean values from the Gulf of Milazzo are comparable with those measured in polluted sediments collected in the Gulf of Palermo and Augusta Bay with a moderate enrichment in Zn. Differ ent sources of trace elements and different geochemical mechanisms are probably responsible of this distribution. Among these sources and mechanisms, local anthropogenic inputs, different contents of organic matter, and surface water circulation may be invoked.

Magnetic granulometry of recent sediments from the Huguang Maar and its implication for provenience

To understand the origin and its climatic implications of the Huguang Maar sediments, we conducted laser grain size analysis and rock mangtic measurement for the recent deposits from the Huguang Maar and for the volcanic rocks of the caldera for comparison. The grain size distributions are dominated by clayey silts for both the bulk sediments and magnetic separates. Acquisition of isothermal remanent magnetization (IRM) and thermal demagnetization of IRM suggest (titano) magnetite as the dominating magnetic mineral in the sediments; high coercivity minerals are not detected. Therefore, the ratio of the susceptibility of anhysteretic remanent magnetization (k ARM) to the weak field magnetic susceptibility (k), k ARM/k can be used to estimate the grain size of magnetite. The sediments and volcanic rocks yield values of 13.7 and 11.8 for the k ARM/k, respectively, corresponding to grain size values of ∼0.03 µm and ∼0.05 µm. The magnetic granulometry of lake sediments is distinctive from one of the Chinese loess, in which published data suggest a value of 6.0 for k ARM/k, and grain size of ∼0.1 µm, but is akin to the nearby volcanic rocks. Although a Loess Plateau source of the lake sediments cannot be fully ruled out, the catchment is most probably the main source. We explain the slightly finer magnetite grain size in sediments than in the volcanic rocks as being disintegrated of particles during erosion and transportation. We conclude that there is no evidence for aeolian input of the Loess Plateau dusts into the Huguang Maar, and the relationship between magnetic parameters of the lake sediments and winter monsoon intensity is probably more complicated than previously thought.

Effects of experimental small‐scale cockle (Cerastoderma eduleL.) fishing on ecosystem function

AbstractThe cockleCerastoderma eduleL. occurs at commercially exploited densities within both species‐poor and species‐rich assemblages, dominating the faunal biomass and potentially acting as a key contributor to a number of ecological functions. The questions considered were: Is the delivery of ecological functions affected by the removal ofC. edule? Does the biodiversity of the affected assemblage affect the extent to which it is altered? To explore these questions, adult cockles were removed from experimental plots at two shores in the North‐West of England: a species‐poor shore at Warton Sands, Morecambe Bay, and a more diverse shore at Thurstaston, Dee estuary. Impacts on the functioning of the systems were determined during a 4‐month study in summer 2007 by direct measurements of benthic primary production, organic matter content and sediment granulometry, and by indirect analyses using Biological Traits Analysis. Removal of adult cockles led to significant changes in faunal assemblage composition and in the distribution of biological traits, with increased biodiversity and an increased prevalence of traits relating to opportunistic taxa observed following the removal ofC. edule. These changes occurred at both study sites and hence were independent of the initial biodiversity of the assemblages. Sediment granulometry was significantly affected; however, surface chlorophyll and organic matter were not affected. This implies a minimal impact on these functions and a high degree of functional redundancy within the macrofauna. The implications of these findings and future areas of research are discussed.

Altering intertidal sediment topography: effects on biodiversity and ecosystem functioning

AbstractSedimentary marine systems are often highly productive and perform important nutrient regeneration functions as they efficiently decompose organic material. In recent years the role of habitat effects and of species composition in ecosystem functioning has become of interest. Estuarine environments are frequently subject to considerable anthropogenic pressures whilst supporting a variety of habitats ranging from well sorted soft muds through biogenically stable sediments to highly mobile coarse sands. There is therefore considerable spatial complexity in habitat type and faunal composition. This study set out to observe the effects of altering the topographical habitat features of an estuarine mudflat on a range of porewater nutrient concentrations (NH4+, NO3−, NO2−, PO43− and SiO) collected from four depths (3, 5, 9, and 12 cm) and on faunal composition. Two treatments (Shelled Nets and Net Controls) were used to alter the topography from simple mud to a mussel shell crumble and were compared to un‐manipulated Control areas. Sediment granulometry and organic matter content analyses alongside biological traits analysis of the fauna were also conducted.Differences were observed in porewater nutrient concentrations between the Control and both netted treatments at 5 cm depth only; the species diversity and abundance were also different in the netted treatments compared to the Controls, although no difference between the two manipulated treatments were observed. The changes in faunal composition were attributed solely to the altered topography and the observed nutrient changes were attributed to the faunal alteration rather than the topographical manipulation.

Boundary conditions of morphodynamic processes in the Mura River in Slovenia

Many alpine gravel-bed rivers have been altered in the past due to human interventions. A typical transboundary alpine river in Central Europe flowing over Austria, Slovenia, Croatia and Hungary is the Mura River (length: 465 km, catchment area: 14,304 km 2 ). The main problem of the river before leaving Austria is bed degradation (average 0.5 m from 1970 to 2000) as a combined consequence of river regulation works and the reduced sediment supply from the upstream reaches due to the construction of hydro power plants. River restoration measures for the river reach on the border between Austria and Slovenia (SLO–A Mura reach) were proposed in 2000 to support both ecological and flood protection purposes that apply the concept “of self-restoration”. In order to apply similar process-oriented restoration strategies in the Mura River downstream in Slovenia, we consider the potentials for self-forming river processes. We have analysed the sediment granulometry and morphology of the Mura River in Slovenia, and discussed morphodynamic processes to detect potential for the Mura River recovery into a more diverse morphological structure. The cross section area increased by 8% between 1979 and 2005 on average, mainly due to riverbed degradation. On average, the thalweg of the Mura riverbed in Slovenia had degraded by 0.28 m in the 1979–2007 period, with the highest degradation of 2.28 m in one cross section and some cross sections being stable. The high river degradation trend from the SLO–A Mura reach is slowly shifting to the downstream direction into the Mura River in Slovenia. Nevertheless, the clear downstream coarsening of river sediments turns into the normal trend of sediment fining in the Mura River reach in Slovenia. The “self-restoration” potential in the Mura River reach in Slovenia is larger than on the SLO–A Mura reach due to still active morphological fluvial processes. These processes can be enhanced by the inflow of fresh coarse sediments from the SLO–A Mura reach, where active measures for re-establishing sediment transport are under way. In the long term, this will not work as proposed, if no sediment inflow is re-established from the Mura headwaters in Austria.