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1.
Biological structures as a source of habitat heterogeneity and biodiversity on the deep ocean margins 总被引：1，自引：0，他引：1
Lene Buhl-Mortensen Ann Vanreusel rew J. Gooday Lisa A. Levin Imants G. Priede Pål Buhl-Mortensen Hendrik Gheerardyn Nicola J. King & Maarten Raes 《Marine Ecology》2010,31(1):21-50
Biological structures exert a major influence on species diversity at both local and regional scales on deep continental margins. Some organisms use other species as substrates for attachment, shelter, feeding or parasitism, but there may also be mutual benefits from the association. Here, we highlight the structural attributes and biotic effects of the habitats that corals, sea pens, sponges and xenophyophores offer other organisms. The environmental setting of the biological structures influences their species composition. The importance of benthic species as substrates seems to increase with depth as the complexity of the surrounding geological substrate and food supply decline. There are marked differences in the degree of mutualistic relationships between habitat-forming taxa. This is especially evident for scleractinian corals, which have high numbers of facultative associates (commensals) and few obligate associates (mutualists), and gorgonians, with their few commensals and many obligate associates. Size, flexibility and architectural complexity of the habitat-forming organism are positively related to species diversity for both sessile and mobile species. This is mainly evident for commensal species sharing a facultative relationship with their host. Habitat complexity is enhanced by the architecture of biological structures, as well as by biological interactions. Colony morphology has a great influence on feeding efficiency for suspension feeders. Suspension feeding, habitat-forming organisms modify the environment to optimize their food uptake. This environmental advantage is also passed on to associated filter-feeding species. These effects are poorly understood but represent key points for understanding ecosystems and biodiversity on continental margins. In this paper we explore the contributions of organisms and the biotic structures they create (rather than physical modifications) to habitat heterogeneity and diversity on the deep continental margins. 相似文献
2.
Lene Møller Madsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):87-99
The article analyses the results of the scheme for field afforestation (EU-regulation 2080/92) in Denmark. The purpose is twofold, firstly to document the afforestation on arable land taking place both within the scheme and outside the scheme for field afforestation. The former is documented in Ribe and Vejle counties whereas the latter is documented in three smaller areas: Varde, Vorbasse, and Vejle. Secondly, the article argues that in order to evaluate the afforestation not only the location within designated areas hut also the spatial parameters and configuration of new woodlands must be considered. Two methods -'forest-pictures' and ‘gradient-pictures’-are presented and applied in order to quantify the spatial configuration of new woodlands in the landscape. 相似文献
3.
Kristensen Lene Czekirda Justyna Penna Ivanna Etzelmüller Bernd Nicolet Pierrick Pullarello José Santiago Blikra Lars Harald Skrede Ingrid Oldani Simon Abellan Antonio 《Landslides》2021,18(6):1963-1980
On September 5, 2019, the Veslemannen unstable rock slope (54,000 m3) in Romsdalen, Western Norway, failed catastrophically after 5 years of continuous monitoring. During this period, the rock slope weakened while the precursor movements increased progressively, in particular from 2017. Measured displacement prior to the failure was around 19 m in the upper parts of the instability and 4–5 m in the toe area. The pre-failure movements were usually associated with precipitation events, where peak velocities occurred 2–12 h after maximum precipitation. This indicates that the pore-water pressure in the sliding zones had a large influence on the slope stability. The sensitivity to rainfall increased greatly from spring to autumn suggesting a thermal control on the pore-water pressure. Transient modelling of temperatures suggests near permafrost conditions, and deep seasonal frost was certainly present. We propose that a frozen surface layer prevented water percolation to the sliding zone during spring snowmelt and early summer rainfalls. A transition from possible permafrost to a seasonal frost setting of the landslide body after 2000 was modelled, which may have affected the slope stability. Repeated rapid accelerations during late summers and autumns caused a total of 16 events of the red (high) hazard level and evacuation of the hazard zone. Threshold values for velocity were used in the risk management when increasing or decreasing hazard levels. The inverse velocity method was initially of little value. However, in the final phase before the failure, the inverse velocity method was useful for forecasting the time of failure. Risk communication was important for maintaining public trust in early-warning systems, and especially critical is the communication of the difference between issuing the red hazard level and predicting a landslide.
相似文献4.
Large debris-flow units commonly occur on the distal sides of subaqueous end moraines deposited by surges of Svalbard tidewater glaciers, but have rarely been described in terrestrial settings. Some researchers have argued that these kinds of debris flows reflect processes unique to the subaqueous environment, such as the extrusion of subglacial deforming layers or extensive failure of oversteepened moraine fronts. In this paper, we describe terrestrial and subaqueous parts of a single late Holocene moraine system deposited by a major surge of the tidewater glacier Paulabreen in west Spitsbergen. The ice-marginal landforms on land closely resemble the corresponding landforms on the seabed as evidenced by geomorphic mapping and geophysical profiles from both environments. Both onland and offshore, extensive areas of hummocky moraine occur on the proximal side of the maximum glacier position, and large mud aprons (interpreted as debris flows) occur on the distal side. We show that the debris-flow sediments were pushed in front of the advancing glacier as a continuously failing, mobile push moraine. We propose that the mud aprons are end members of a proglacial landforms continuum that has thrust-block moraines as the opposite end member. Two clusters of dates (~ 8000 YBP and ~ 700 YBP) have previously been interpreted to indicate two separate surges responsible for the moraine formation. New dates suggest that the early cluster indicates a local extinction of the abounded species Chlamys islandica. Other changes corresponding to the widespread 8.2 ka event within the fjord, may suggest that the extinction of the C. islandica corresponds to that time. 相似文献
5.
The OSPAR Commission has identified a set of Ecological Quality Objectives (EcoQOs) to assess eutrophication in the North Sea. In order to assess the long-term effects of different river nutrient reduction scenarios in terms of these EcoQOs, a 3-dimensional coupled physical–chemical–biological model, NORWECOM, has been used. The model results show that there is a decreasing response gradient from near-shore to offshore, where the largest effects are identified along the Dutch coast, and that the full potential of a reduction is seen after 2–3 years. The EcoQOs on winter nutrients and chlorophyll are achieved for most areas. Oxygen concentrations displace no or very low response to the modelled nutrient reductions. The study also shows that the ecological quality is controlled to a large extent by winds and ocean circulation. 相似文献
6.
Lene L. Delsett Patrick S. Druckenmiller
yvind Hammer Krzysztof Hryniewicz Espen M. Knutsen Maayke J. Koevoets Hans A. Nakrem Aubrey J. Roberts Jrn H. Hurum 《Geology Today》2019,35(1):20-25
In the Mesozoic seas, the apex predators were reptiles. From the Arctic archipelago of Svalbard, the Spitsbergen Mesozoic Research Group has excavated numerous well preserved marine reptile skeletons in order to understand the biology of these animals and the environment they lived in. The work of eleven field seasons has made this one of the largest and most productive palaeontological research projects in the high Arctic world‐wide. The initial eight seasons focused on one of the richest occurrences of Late Jurassic—earliest Cretaceous (c. 150–139 Ma) marine reptiles in the world, and nearly sixty specimens have been collected, together with a diverse assemblage of invertebrates, some of which are associated with methane seeps. The last three seasons were spent investigating events further back in time, as Spitsbergen preserves the remains from some of the first marine reptile radiations in the wake of the most devastating extinction in the history of the Earth, at the Permian–Triassic boundary (c. 252 Ma). 相似文献
7.
Adsorption of polar aromatic hydrocarbons on synthetic calcite 总被引：1，自引：0，他引：1
Lene Madsen Laila Grahl-Madsen Christian Grøn Ida Lind John Engell 《Organic Geochemistry》1996,24(12):1151-1155
The wettability of hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. A model system of synthetic calcite, cyclohexane and the three probe molecules: benzoic acid, benzyl alcohol and benzylamine, have been studied by adsorption experiments. The results clearly demonstrate the differences in the adsorption behaviour between probes with different functional groups of varying polarity and acidity. The maximum adsorption decreases in the order: benzoic acid, benzyl alcohol and benzylamine. The order of magnitude of ΔG° for the adsorption process implies the formation of a strong bond between the calcite surface and the adsorbate molecules. 相似文献
8.
Hans-Christian Teien Brit Salbu Frode Kroglund Lene Sørlie Heier Bjørn Olav Rosseland 《Applied Geochemistry》2007
Cationic Al species (Ali) cause toxic effects towards fish in acidified water. As several factors can influence the Ali-speciation, acid neutralising capacity (ANC) has been applied as an alternative indicator for acidification and effects towards fish. However, the critical range of ANC for biological stress has been shown to be dependent upon the concentration of organic material (DOC). Using in situ size fractionation techniques the influence of particulate and colloidal DOC (0–400 μM) on Ali-speciation and ANC-values was investigated in Norwegian streams. During high flow events with high river transport of DOC the Ali concentration increased by a factor of 2 due to retention of colloidal Al species (>10 kDa), probably organic, in the chromatography column. Ultrafiltration (?10 kDa) of water prior to chromatography reduced the influence of non-toxic organic Al-species, on Ali-speciation. The charge balanced ANC-values (ANCcb) were also significantly lower (on average 34 μeq L−1) in ultrafiltered water compared to unfiltered water samples, as base cations were associated with colloidal DOC (>10 kDa to 0.45 μm) and organic acids were not incorporated in the ANCcb estimate. Thus, ANCcb will underestimate the acidification effects towards fish in organic waters increasing with concentration of colloidal DOC present. Alkalinity based ANC-values (ANCalk), which include a fraction of organic acids, were similar in unfiltered and ultrafiltered waters, but higher than ANCcb-values of ultrafiltered samples. Thus, ANCalk-values also underestimate the acidification effects on fish in organic waters. Based on ultrafiltered samples, however, ANCcb-values was negatively correlated with Ali independent of the DOC present and thus a more correct indicator for toxic Al-species. 相似文献
9.
Bryozoan–stromatolite associations (bryostromatolites) formed conspicuous reef structures throughout the Sheinwoodian (Wenlock) to Ludfordian (Ludlow) stratigraphy on Gotland but have not been described so far. They are mainly composed of encrusting bryozoans forming a complex intergrowth with porostromate and spongiostromate microbes and are different from the abundant stromatoporoid–coral–algal reefs with respect to their composition. In the bryostromatolite different growth stages can be identified. The observed succession can be taken as evidence for cyclic environmental changes during reef formation. Stenohaline reef-dwelling organisms, such as echinoderms, sponges, corals and trilobites, indicate fully marine salinities. Ten localities exposing bryostromatolites were discovered. Individual bryostromatolites are small with few decimetres up to one metre in size, and occur solely in shallow marine areas. Common features of these reefs on Gotland are cauliflower-like growth, a high bryozoan diversity, a high abundance of phosphatic fossils and components such as bryozoan pearls and inarticulate phosphatic brachiopods, enhanced bioerosion, Palaeomicrocodium crusts, vadose silt and gypsum pseudomorphs. The high abundance of Palaeomicrocodium, as well as the alternation with other crust-forming contributors, suggest that it could have been formed directly at the palaeo-sea surface, probably in times of minor but high-frequency sea-level fluctuations. Vadose silt and pseudomorphs after gypsum in reef cavities indicate subaerial exposure shortly after reef growth. The high amount of phosphatic components indicates a high nutrient input, probably by dust. All bryostromatolites were formed in times of strongly elevated δ13C values. The unusual combination of sedimentological and palaeoecological features, as well as their occurrence exclusively during strong positive δ13C excursions, are evidence that the bryostromatolite development responded to climatic/oceanographic changes, which may have played an important role in reef control. 相似文献
10.
Lene Møller Madsen Thomas Theis Nielsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):157-161
In many higher education curricula, pre-structured step-by-step laboratory exercises in introductory courses in geographical information systems (GIS) are an important part of the training of future geographers. The reasons for this approach to teaching GIS are manifold, such as large numbers of students, off-the-shelf desktop software that is often complex, technical challenges, and scarce faculty resources. Often the reasons are well agreed upon by members of a university faculty and among the students. Research in other fields has shown that the use of a controlled manual for laboratory work often provides low learning potentials. However, not much empirical research has dealt with this issue within a GIS learning environment. Inspired by research on the value of student-generated questions within science education, the authors take a closer look at the type of student-generated questions and their relation to students' self-image of their learning approach in two pre-structured GIS laboratory settings at two Danish universities. They conclude that the vast majority of student-generated questions are of a basic information type and independent of the students' self-image of their learning approach. Further, it is found that wonderment questions, i.e. questions that are reflective in nature and show students the process towards acquiring extended geographical knowledge and software proficiency, are rarely asked. 相似文献