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Patras Gulf pockmark field (Western Greece) is a tectonically controlled field that has been activated at least twice by strong earthquakes (M5.4, 14 July 1993 and M6.4, 8 June 2008), and episodic gas seepages have been recorded in the past using geophysical means. A distributed temperature sensor (DTS) system was deployed inside a shallow pockmark and along an active fault at the northern end of the field. This ongoing experiment represents the first long-term monitoring ever conducted on gas-bearing pockmarks and active faults by the DTS system. For now, we have acquired and analyzed data regarding about 1.56 years. One of the primary objectives of this study is to establish methodological queues for data processing and analysis, including spectral analysis and incomplete data treatment techniques, to be standardized for use in further stages of the experiment. Spectral analysis was proven capable of separating the temperature footprint of background environmental components, such as sea-atmosphere heat flux, tides, and winds/waves, from high-frequency temperature residuals. Those residuals represent unusual events that might be correlated to seismicity. Monitoring the causal relationship between seismic activity and seabed water temperature changes in the field was thus attempted. No significant local earthquakes occurred during the monitoring period. Although the relation between seismicity and irregular seabed water temperature events was not systematic, we postulate that four thermal events have a causative link with the local seismicity. The DTS system constitutes a low-cost monitoring system, and the promising preliminary results of this experiment suggest that it is worth testing for a longer period. [ABSTRACT FROM AUTHOR]

The primary objective of this research is to demonstrate advanced surveying methods and techniques for coastal erosion identification and monitoring in a densely human-populated coastline, the southern coastline of the Gulf of Patras (Greece), which diachronically suffers erosion problems expected to become worse in the forthcoming years due to climate change and human intervention. Its importance lies in the fact that it presents a robust methodology on how all modern scientific knowledge and techniques should be used in coastal erosion problems. The presented methods include the use of satellite and aerial photo imaging, shallow seabed bathymetry and morphology, sediment sampling, geotechnical investigations, as well as hydrodynamic modelling. The results are extensively analyzed in terms of their importance in coastal erosion studies and are cross-validated to define those areas most vulnerable to erosion. Towards this scope, the seabed erosion rate produced by hydrodynamic modelling is compared with the coastal vulnerability index (CVI) calculations performed in the examined area to identify which coastal zones are under a regime of intensive erosion. The results between the CVI and the seabed erosion rate appear to coincide in terms of the erosion potential, especially in zones where the vulnerability regime has been calculated as being high or very high, with the P. oceanica meadows playing an important role in reducing erosion. [ABSTRACT FROM AUTHOR]

Abstract: Oceanographic research in the Amvrakikos Gulf in Western Greece, a semi-enclosed embayment isolated from the Ionian Sea by a narrow, shallow sill, has shown that it is characterised by a fjord-like oceanographic regime. The Gulf is characterised by a well-stratified two layer structure in the water column made up of a surface layer and a bottom layer that are separated by a strong pycnocline. At the entrance over the sill, there is a brackish water outflow in the surface water and a saline water inflow in the near-bed region. This morphology and water circulation pattern makes the Amvrakikos Gulf the only Mediterranean Sea fjord. The investigations have also shown that the surface layer is well oxygenated, whereas in the pycnocline, the dissolved oxygen (DO) declines sharply and finally attains a value of zero, thus dividing the water column into oxic, dysoxic and anoxic environments. At the dysoxic/anoxic interface, at a depth of approximately 35 m, a sharp redox cline develops with Eh values between 0 and 120 mV occurring above and values between 0 and −250 mV occurring below, where oxic and anoxic biochemical processes prevail, respectively. On the seafloor underneath the anoxic waters, a black silt layer and a white mat cover resembling Beggiatoa-like cells are formed. The dysoxic/anoxic conditions appeared during the last 20 to 30 years and have been caused by the excessive use of fertilisers, the increase in animal stocks, intensive fish farming and domestic effluents. The inflicted dysoxia/anoxia has resulted in habitat loss on the seafloor over an area that makes up just over 50% of the total Gulf area and approximately 28% of the total water volume. Furthermore, anoxia is also considered to have been responsible for the sudden fish mortality which occurred in aquaculture rafts in the Gulf in February 2008. Therefore, anoxic conditions can be considered to be a potential hazard to the ecosystem and to the present thriving fishing and mariculture industry in the Gulf. [Copyright &y& Elsevier]