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OceanBestPractices System: a global resource to facilitate harmonizing practices in ocean observation, data and information
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Knowledge transfer: the key to creating societal and economic benefits from marine observations
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Archaeological prospection of the nearshore and intertidal area using ultra-high resolution marine acoustic techniques: Results from a test study on the Belgian coast at Ostend-Raversijde
Get PDFThe coastal site of Ostend-Raversijde in Belgium is known for its archaeological artifacts, mainly from Roman and medieval times. In recent years, detailed geophysical and geotechnical investigations have been carried out here to test the efficiency of these techniques for geoarchaeological prospection of the subtidal and intertidal zone. Very high-resolution 2D subbottom profiling using a parametric echosounder evidenced a highly complex system of paleogullies and tidal channels, some of which can be linked to the medieval peninsula Testerep and the drowned settlement of Walraversijde. For the first time marine seismic and terrestrial electromagnetic induction (EMI) data were fully integrated in the same intertidal area. The parametric echosounder proved a highly effective tool to map the (partly excavated) peat layers and submerged landscape in high detail, even in extremely shallow water. Using a novel multitransducer parametric echosounder (SES-2000 Quattro), unique 3D imaging of the peat exploitation pattern was possible with unprecedented detail (submeter level). This sets a new standard for shallow water research and opens important new perspectives for geoarchaeological studies in nearshore areas
Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage
No full textIn future global change scenarios the surface ocean will experience continuous acidification and rising temperatures. While effects of both stressors on marine, benthic communities are fairly well studied, consequences of the interaction of both factors remain largely unknown. We performed a short-term microcosm experiment exposing a soft-bottom community from an intertidal flat in the Westerscheldt estuary to two levels of seawater pH (ambient pHT = 7.9, reduced pHT = 7.5) and temperature (10 °C ambient and 13 °C elevated temperature) in a crossed design. After 8 weeks, meiobenthic community structure and nematode staining ratios, as a proxy for mortality, were compared between treatments and structural changes were related to the prevailing abiotic conditions in the respective treatments (pore water pHT, sediment grain size, total organic matter content, total organic carbon and nitrogen content, phytopigment concentrations and carbonate concentration). Pore water pHT profiles were significantly altered by pH and temperature manipulations and the combination of elevated temperature and reduced pH intensified the already more acidic porewater below the oxic zone. Meiofauna community composition was significantly affected by the combination of reduced pH and elevated temperature resulting in increased densities of predatory Platyhelminthes, reduced densities of Copepoda and Nauplii and complete absence of Gastrotricha compared to the experimental control. Furthermore, nematode staining ratio was elevated when seawater pH was reduced pointing towards reduced degradation rates of dead nematode bodies. The observed synergistic interactions of pH and temperature on meiobenthic communities and abiotic sediment characteristics underline the importance of multistressor experiments when addressing impacts of global change on the marine environment
