Entity

Time filter

Source Type

Yerseke, Netherlands

Capet A.,National Institute of Oceanography and Applied Geophysics - OGS | Capet A.,University of Liege | Meysman F.J.R.,NIOZ | Akoumianaki I.,James Hutton Institute | And 2 more authors.
Ocean Modelling | Year: 2016

Three-dimensional (3D) ecosystem models of shelf environments should properly account for the biogeochemical cycling within the sea floor. However, a full and explicit representation of sediment biogeochemistry into 3D ocean models is computationally demanding. Here, we describe a simplified approach to include benthic processes in 3D ocean models, which includes a parameterization of the different pathways for organic matter mineralization and allows for organic matter remobilization by bottom currents and waves. This efficient approach enables decadal simulations that resolve the inertial contribution of the sea floor to the biogeochemical cycling in shelf environments. The model was implemented to analyze the benthic-pelagic coupling in the northwestern shelf of the Black Sea. Three distinct biogeochemical provinces were identified on the basis of fluxes and rates associated with benthic-pelagic coupling. Our model simulations suitably capture the seasonal variability of in situ flux data as well as their regional variation, which stresses the importance of incorporating temporally varying sediment biogeochemistry and resuspension/redeposition cycles in shelf ecosystem models. © 2016 Elsevier Ltd. Source


Prop J.,University of Groningen | Oudman T.,NIOZ | Van Spanje T.M.,Ripperdastraat 15 zwart | Wolters E.H.,Allersmaweg 56
Ornis Norvegica | Year: 2013

This study explored patterns of predation by polar bear Ursus maritimus on the nests of Pink-footed Geese Anser brachyrhynchus on the coastal tundra stretch Nordenskiöldkysten, west coast of Spitsbergen, Svalbard. Goose nests occurred in densities of up to 126 nests/km2 (mean=6.4), at an average distance of 1.5 km from the seashore, and were mainly associated with greenstone outcrops. Open, flat areas were avoided for nesting. Goose pairs nested in colonies of up to 23 nests, with 50% of the pairs nesting in colonies larger than 5. In 2011 and 2012, polar bears invaded the Pink-footed Goose nesting area to consume goose eggs, a behaviour that they had not exhibited in previous years. Polar bears selectively visited the taller outcrops and locations with the larger number of goose nests. Moreover there was a steep gradient in predation from the seashore towards the inland, with no predation at distances greater than 1.8 km from the coastline. We expect that the predation pressure by polar bears will aggravate in the coming years when more bears learn to exploit the inland goose colonies. Source


Clavier J.,Institut Universitaire de France | Chauvaud L.,Institut Universitaire de France | Carlier A.,Institut Universitaire de France | Amice E.,Institut Universitaire de France | And 4 more authors.
Aquatic Botany | Year: 2011

Community respiration and primary production were measured in a dense intertidal Zostera noltii bed on the Banc d'Arguin, Mauritania (West Africa) under aerial and submerged conditions. Metabolism was studied in situ in dark and transparent benthic chambers. CO2 fluxes in the air were measured over a series of short-term incubations (3min) using an infrared gas analyzer. Dissolved inorganic carbon fluxes were calculated from concentration changes during one-hour underwater incubations. Air and underwater irradiance levels were measured every minute throughout the experiments. Carbon respiration was lower in the air (2.2mmolm-2h-1) than underwater (5.0mmolm-2h-1); similarly, a production-irradiance model fitted to the data indicated that gross maximal photosynthetic rate was markedly lower during emergence (6.0mmolCm-2h-1) than under water (42.7mmolCm-2h-1). The δ13C values observed in shoots indicated a decrease in atmospheric CO2 contribution, compared to dissolved inorganic carbon, in Z. noltii metabolism along a depth gradient within a single location. As the seagrass bed remains under a thin layer of water at low tide at the studied site, the large difference in primary production can be mainly attributed to photosynthesis inhibition by high pH and oxygen concentration, as well as to the negative feedback of self-shading by seagrass leaves during emersion. The observed differences in respiration can be explained by the oxygen deficit at night during low tide near the sediment surface, a deficit that is consistent with the abundance of anoxia-tolerant species. © 2011 Elsevier B.V. Source


Wang Z.B.,Technical University of Delft | Hoekstra P.,University Utrecht | Burchard H.,Leibniz Institute for Baltic Sea Research | Ridderinkhof H.,NIOZ | And 2 more authors.
Ocean and Coastal Management | Year: 2012

The Wadden Sea and its associated barrier island system exhibit highly dynamic behaviour. Of major concern is the movement of water and air and the transport, erosion and deposition of sand and mud. These processes result in an ever-changing morphology (topography/bathymetry) of the islands, tidal channels, inter-tidal shoals and tidal flats. This dynamic development of the shape and nature of the Wadden area forms together with the biotic systems, the present Wadden system. The morphodynamic development of the Wadden Sea is influenced by changing environmental conditions e.g. sea-level rise as well as by human interferences. For the management and protection of the Wadden system knowledge on the morphodynamic development is essential. However, our present knowledge is not sufficient to predict the effects of human interferences under different climate change scenarios in sufficient detail and accuracy. This paper identifies the existing knowledge gaps, based on a review of the state of the art on morphodynamics of the Wadden Sea that is confronted with major requirements from a coastal zone management point of view. The identified knowledge gaps have to inspire and stimulate research in the fields of the large-scale sediment budgets, morphodynamic changes at smaller scales, processes and mechanisms of sediment transport, erosion and deposition and modelling tools. © 2012 Elsevier Ltd. Source


Hodell D.,University of Cambridge | Lourens L.,University Utrecht | Crowhurst S.,University of Cambridge | Konijnendijk T.,University Utrecht | And 4 more authors.
Global and Planetary Change | Year: 2015

We produced a composite depth scale and chronology for Site U1385 on the SW Iberian Margin. Using log(Ca/Ti) measured by core scanning XRF at 1-cm resolution in all holes, a composite section was constructed to 166.5meter composite depth (mcd) that corrects for stretching and squeezing in each core. Oxygen isotopes of benthic foraminifera were correlated to a stacked δ18O reference signal (LR04) to produce an oxygen isotope stratigraphy and age model.Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulation of these cycles provides a powerful tool for developing an orbitally-tuned age model. We tuned the U1385 record by correlating peaks in L* to the local summer insolation maxima at 37°N. The benthic δ18O record of Site U1385, when placed on the tuned age model, generally agrees with other time scales within their respective chronologic uncertainties.The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflect relative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacial and interstadial climate states and decreases during glacial and stadial periods. Much of the variance in the log(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereas the residual signal reflects suborbital climate variability. The strong correlation between suborbital log(Ca/Ti) variability and Greenland temperature over the last glacial cycle at Site U1385 suggests that this signal can be used as a proxy for millennial-scale climate variability over the past 1.5. Ma.Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5Ma, including glacial periods of the early Pleistocene ('41-kyr world') when boundary conditions differed significantly from those of the late Pleistocene ('100-kyr world'). Suborbital variability was suppressed during interglacial stages and enhanced during glacial periods, especially when benthic δ18O surpassed ~3.3-3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation was preceded by a terminal stadial event. Suborbital variability may be a symptomatic feature of glacial climate or, alternatively, may play a more active role in the inception and/or termination of glacial cycles. © 2015 The Authors. Source

Discover hidden collaborations