Sediment rejection by recent scleractinian corals: a key to palaeo-environmental reconstruction

26 of the 59 living species of scleractinian corals found in Western Atlantic and Caribbean waters, less than 68 metres deep, and two fungiid genera from the Pacific are analysed in terms of their behaviour, sediment rejecting properties, functional morphology and distribution patterns.The contrasting behaviour and skeletal structure of the two solitary fungiids provides evidence for the construction of a theoretical mechanical model which is applied to the subsequent interpretation of the more complex colonial reef corals from the Atlantic province.Regional distribution patterns, growth forms and calical orientations of the Atlantic species and their associated sediment types were noted in dives across transects in extreme environments in the Caribbean. Representative samples were then selected from the five functional ecological niches in the Florida keys, and subjected to inundations of sized and painted carbonate sand particles in the laboratory. The coral was filmed before the sedimentary influx, on impact and during rejection. The skeletons were then extracted and dissected to construct a mechanical model compatible with their behavioural functions.There are four means of sediment rejection: distension by the stomodeal up-take of water, tentacular action, ciliary beat, and mucus entanglement. Differences in sediment rejection are ascribed to two factors (1) variations in the polyps' distensional capacity, and (2) the geometry of the calice.A theoretical model of characteristic scleractinian distribution patterns on an Atlantic patch reef mirrors regional distribution patterns. The sediment rejecting experiments are used as additional evidence for interpreting other behavioural activities of greater consequence e.g. food gathering and the removal of excrement.Theoretical models are described for the relationship of calical form to polypal function and calcical orientation to distribution patterns on the corallum; and also variations in growth form. Ecological distributions, in local patch reef and regional occurrences, are outlined in terms of the recent scleractinian corals of the Atlantic province. These models are tested against some rugose and tabulate coral distributions in the Irish Carboniferous.

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Zusammenfassung 26 der 59 Korallenarten (Scleractinia), die im westlichen Atlantik und der Karibischen See in weniger als 68 m Wassertiefe leben, und 2 Fungia-Gattungen des Pazifiks werden auf Verhalten, Fähigkeit Sediment abzuschütteln und funktioneller Morphologie untersucht. Aufgrund der Gegensätze in Verhalten und Skelettstruktur der beiden Fungia-Einzelkorallen wird ein theoretisches Modell erarbeitet, das dann auf die komplizierteren koloniebildenden Korallen angewandt wird.Regionale Verteilung, Wuchsformen und Kelchorientierung der atlantischen Korallen und die dazugehörigen Sedimente wurden in Tauchgängen in extremen Bereichen der Karibischen See erfaßt. Repräsentative Korallen-Exemplare wurden dann von fünf ökologisch definierten Bereichen der Florida Keys gesammelt und im Labor mit sortierten und gefärbten Karbonatsandkörnern überschüttet. Die Korallen wurden vor dem Experiment, während des Schüttens und des Abschüttelns gefilmt. Danach wurden die Skelette herauspräpariert und ein mechanisches Modell entwickelt, das die verhaltensbedingten Funktionen berücksichtigt.Das Sediment wird mit Hilfe von vier Mechanismen abgeschütteln: Ausdehnung der Weichteile durch Aufnahme von Wasser, Tentakelbewegungen, Ziliarbewegungen und Schleimumwicklung. Unterschiede in der Fähigkeit, Sediment abzuschütteln, wurden auf 1. Unterschiede in der Fähigkeit des Polypen, sich auszudehnen, und 2. Unterschiede in der Kelchform zurückgeführt.Ein theoretisches Modell der Korallenverteilung auf einem isolierten Riff spiegelt die Grundzüge regionaler Verteilung wider. Die Sedimentabschüttel-Experimente ergeben zusätzliche Anhaltspunkte für die Interpretation anderer Verrichtungen von größerer Bedeutung, z. B. Nahrungsaufnahme und Entfernung von Exkrementen. Theoretische Modelle für das Verhältnis von Kelchform zu Polypenfunktion und von Kelchorientierung zur Position auf dem Korallenstock und zu Wuchformunterschieden werden beschrieben.Ökologische Verteilungen, lokal und regional, werden anhand der rezenten Korallen des Atlantiks aufgezeigt. Diese Modelle werden dann am Beispiel der Verteilung rugosen und tabulaten Korallen im Karbon Irlands getestet.

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Résumé 26 espèces vivantes de coraux scléractiniens sur 59, furent découvertes dans l'Atlantique-Ouest et les eaux des Caraïbes, à moins de 68 m de fond; 2 genera fungiid du Pacifique sont analysés en fonction de leur comportement, des propriétés de rejet des sédiments dont ils font preuve, de leur morphologie fonctionelle et de leurs reséaux de distribution.Le contraste dans le compartement et dans la structure squelettique des deux fungiids solitaires, justifie la construction d'un modèle théorique mécanique qui est appliqué à l'interprétation suivante des coraux de récif coloniaux et plus complexes que l'on trouve dans la région atlantique.Les réseaux de distribution régionale, les formes de croissances d'orientations calicales de l'espèce atlantique et les types de sédiments qui leur sont associés, ont été remarqués lors de plongées aux environs extrêmes de la mer Caraïbe. Des échantillons représentatifs ont ensuite été sélectionnés dans les cinq niches écologiques fonctionelles des cayes de Floride. Puis ont été soumis, en laboratoire à des inondations de particules de sable carbonaté taillées et teintes. Le corail a été filmé avant l'entrée des sédiments, pendant l'opération et pendant le rejet. Les squelettes, ont ensuite été extraits et disséqués pour construire un modèle mécanique compatible avec leurs fonctions de compartement.Il existe quatre modes de rejet des sédiments: dilatation par absorbsion stomodéal d'eau, action tentaculaire, action ciliaire et enveloppement de mucus.Les différences dans le rejet de sédiments sont imputables a deux facteurs (1) les variations de la capacité dimensionelle du polype et (2) la géométrie du calice. Un modèle théorique des réseaux le distribution scléractiniènne, charactéristique sur un petit récif atlantique, réflecte des sébeaux de distribution régionale. Les expériences sur le rejet de sédiments, sont utilisées comme preuve supplémentaire à l'interprétation d'autres activités de comportement, comme par exemple, la recherche de nourriture ou l'émission d'éxcréments.Les modèles théoriques sont décrits pour permettre le rapport entre la forme calicale et la fonction polypale, plus entre l'orientation calicale et les résaux de distribution sur le corallum, ainsi que pour étudier les variations dans les formes de croissance. L'étude des coraux scléractiniens récents de la province atlantique, permet d'établir une ébauche de leur répartition écologique, aussi bien sur les petits récifs locaux qu'au niveau des incidences régionales. Les modèles sont également testés grace à des répartitions de coraux rugueux et tabulates dans le Carbonifière Irlandais.

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Multiple exposures and dynamic vulnerability: Evidence from the grape industry in the Okanagan Valley, Canada

This paper assesses the vulnerability of grape growers and winery operators in the Okanagan Valley, British Columbia to climate variability and change, in the context of other sources of risk. Through interviews and focus groups, producers identified the climatic and non-climatic risks relevant to them and the strategies employed to manage these risks. The results show that the presence of multiple exposures affects the way in which producers are vulnerable to climate change. Producers are vulnerable to conditions that not only affect crop yield, but also affect their ability to compete in or sell to the market. Their sensitivity to these conditions is influenced in part by institutional factors such as trade liberalization and a “markup-free delivery” policy. Producers’ ability to adapt or cope with these risks varies depending on such factors as the availability of resources and technology, and access to government programmes. Producers will likely face challenges associated with the supply of water for irrigation due to a combination of climatic changes and changing demographics in the Okanagan Valley, which in turn affect their ability to adapt to climatic conditions. Finally, adaptations made by producers can change the nature of the operation and its vulnerability, demonstrating the dynamic nature of vulnerability.     

Structural characteristics of the halite fabric type ‘Kristallbrocken’ from the Zechstein Basin with regard to its development

The Kristallbrocken are a characteristic centimetre- to decimetre-sized, laminated halite fabric type occurring in the Stassfurt Formation in the Zechstein Basin. Up to now, the nature of the Kristallbrocken, i.e. if they are relics of fine-grained, polycrystalline halite beds or clasts of ‘single crystal-layers’, as well as the deformation mechanisms of this halite type, were not clear from the literature. Drill core material from the salt deposit Teutschenthal at the southern rim of the Zechstein Basin now allowed investigating less intensely deformed samples for the first time. The deformational behaviour of these Kristallbrocken ranges from brittle to ductile, which is evidenced by fractured Kristallbrocken on the one hand and weakly bent or even folded Kristallbrocken on the other hand. Local X-ray texture measurements demonstrated that the Kristallbrocken are definitely single crystals and that they can be regarded as relics of formerly larger ‘single crystal-layers’ of up to several dm² in size. The folded Kristallbrocken clearly display by their single grain texture characteristics that their crystal lattice is bent, which was most likely enabled by a kind of flexural-shear folding, and did not develop after deformation from a fine-grained aggregate by recrystallisation. Due to their monocrystallinity, their originally large size, and the solid inclusions forming the internal lamination, the Kristallbrocken have clearly stronger rheological properties than the surrounding fine- to coarse-grained polycrystalline rock salt, and thus also deform by fracturing.     

Patterns of Irrigated Agricultural Land Conversion in a Western U.S. Watershed: Implications for Landscape-Level Water Management and Land-Use Planning

In irrigated agricultural landscapes, land-use conversion may have landscape-level social, hydrological, and ecological effects. We used geographic information systems (GIS) and interviews to analyze development effects on irrigation in the Henry's Fork Watershed, Idaho. Farmers developed irrigation there in the 19th century, and incidental recharge from canal seepage and flood irrigation raised groundwater levels and expanded wetlands. Cohesive culture in agricultural communities sustained irrigation systems until amenity-driven demographic shifts beginning in the 1970s led to development approved by local governments with land-use planning but no water-management authority. Although only 5% of irrigated land has been converted, development has fragmented irrigated landscapes and made canal-system operation more difficult, potentially reducing groundwater levels, wetland extent, and return flows critical to downstream irrigators and fish and wildlife. We discuss future scenarios, highlighting the need for increased communication among local and state governments regarding land use and water management in irrigated landscapes across the West.     

THE IMPACT-FLOOD CONNECTION: DOES IT EXIST?*

In a recent article in Terra Nova, Kristan-Tollmann and Tollmann (1994) suggested that the Biblical Flood can be explained by seven fragments of a comet that impacted the ocean at seven locations on Earth at 03.00h (C.E.T.) on 23 September, 9545 yr BP. We demonstrate that all the ‘geological proofs’ that allegedly support their conclusions are not supported by the available data on impact cratering. Their hypothesis is based on insufficient and ambiguous data, selective citation, and incomplete comprehension of previous research.     

Equations for the Estimation of Strong Ground Motions from Shallow Crustal Earthquakes Using Data from Europe and the Middle East: Horizontal Peak Ground Acceleration and Spectral Acceleration

This article presents equations for the estimation of horizontal strong ground motions caused by shallow crustal earthquakes with magnitudes M_w 5 and distance to the surface projection of the fault less than 100km. These equations were derived by weighted regression analysis, used to remove observed magnitude-dependent variance, on a set of 595 strong-motion records recorded in Europe and the Middle East. Coefficients are included to model the effect of local site effects and faulting mechanism on the observed ground motions. The equations include coefficients to model the observed magnitude-dependent decay rate. The main findings of this study are that: short-period ground motions from small and moderate magnitude earthquakes decay faster than the commonly assumed 1/r, the average effect of differing faulting mechanisms is not large and corresponds to factors between 0.8 (normal and odd) and 1.3 (thrust) with respect to strike-slip motions and that the average long-period amplification caused by soft soil deposits is about 2.6 over those on rock sites. Disappointingly the standard deviations associated with the derived equations are not significantly lower than those found in previous studies.     

Tide-induced variability in beach surface moisture: Observations and modelling

The moisture content w_s of a beach surface strongly controls the availability of sand for aeolian transport. Our predictive capability of the spatiotemporal variability in w_s, which depends to a large extent on water table depth, is, however, limited. Here we show that water table fluctuations and surface moisture content observed during a 10-day period on a medium-grained (365μm) planar (1:30) beach can be predicted well with the nonlinear Boussinesq equation extended to include run-up infiltration and a soil–water retention curve under the assumption of hydrostatic equilibrium. On the intertidal part of the beach the water table is observed and predicted to continuously fall from the moment the beach surface emerges from the falling tide to just before it is submerged by the incoming tide. We find that on the lower 30% of the intertidal beach the water table remains within 0.1–0.2 m from the surface and that the sand is always saturated (w_s≈20%, by mass). Higher up on the intertidal beach, the surface can dry to about 5% when the water table has fallen to 0.4–0.5 m beneath the surface. Above the high-tide level the water table is always too deep (>0.5 m) to affect surface moisture and, without precipitation, the sand is dry (w_s < 5 − 8%). Because the water table depth on the emerged part of the intertidal beach increases with time irrespective of whether the (ocean) tide falls or rises, we find no need to include hysteresis (wetting and drying) effects in the surface-moisture modelling. Model simulations suggest that at the present planar beach only the part well above mean sea level can dry sufficiently (w_s < 10%) for sand to become available for aeolian transport. ©2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Along-shelf hydrographic anomalies in the Nordic Seas (1960–2011): locally generated or advective signals?

The northward flow of warm and saline Atlantic Water through the eastern Nordic Seas sustains a spring-bloom ecosystem that hosts some of the world’s largest commercial fish stocks. Abrupt climatic changes, or changes beyond species-specific thresholds, may have severe effects on species abundance and distribution. Here, we utilize a numerical ocean model hindcast to explore the similarities and differences between large-scale anomalies, such as great salinity anomalies, and along-shelf hydrographic anomalies of regional origin, which represent abrupt changes at subannual time scales. The large-scale anomalies enter the Nordic Seas to the south and propagate northward at a speed one order of magnitude less than the Atlantic Water current speed. On the contrary, wind-generated along-shelf anomalies appear simultaneously along the Norwegian continental shelf and propagate northward at speeds associated with topographically trapped Kelvin waves. This process involves changes in the vertical extent of the Atlantic Water along the continental slope. Such a dynamic oceanic response both affects thermal habitats and has the potential to ventilate shelf waters by modifying the cross-shelf transport of nutrients and key prey items for early stages of fish.     

Fluvial seed dispersal of riparian trees: transport and depositional processes

Fluvial seed dispersal considers both the transport and deposition of seeds where channel geomorphic structures, hydrology and seed dispersal traits contribute to transport times and depositional locations. This study examines the influence of stream flow patterns on fluvial seed dispersal of buoyant white alder (Alnus rhombifolia) seeds by applying a one‐dimensional transport model. Conceptually, the model separates the stream into two components: (i) the main channel where the seeds are transported downstream; and (ii) the transient storage zone where seeds are temporarily detained or deposited on the river bank. Transport processes are characterized by an advection–dispersion equation which is coupled to a transient storage model using an exponential decay term. The model parameters: longitudinal dispersion (D_L), exchange coefficient (α), main channel area (A) and storage zone (A_s) are estimated based on field experiments conducted in a confined, bedrock‐gravel bed river with pool‐riffle morphology located in coastal northern California. The riparian zone is inhabited by Alnus rhombifolia that disperse buoyant seeds in mid‐spring coinciding with the end of the wet, Mediterranean season. Artificial seeds, with similar traits of buoyancy and density to alder seeds, were used to quantify transport times and depositional locations. Preferential deposition resulted in stream reaches with larger A_s, high A_s/A ratios, and faster exchange coefficients corresponding to divergent stream flow (back‐eddies, re‐circulating flow, flow expansions) caused by geomorphic structures such as the ends of bar/riffle features and bends in the stream. The results demonstrate the importance of transient storage for seed transport and depositional processes. Morphological features that increase a channel's complexity create complex flow structures that detain seeds and provide a greater opportunity for deposition to occur. The model provides a simplification of river hydraulics to represent dispersal dynamics and lends itself to further understanding of hydrochory processes and associated population structure. Copyright © 2015 John Wiley & Sons, Ltd.