Dimitris Christodoulou

• PhD
• Researcher at University of Patras

Among Greece’s coastal areas, the Saronikos Gulf encounters the highest environmental challenges due to heavy metal contamination, caused by extensive urbanization and industrialization. In the present study, online databases were used to identify research articles focusing on the levels, patterns, and origins of the heavy metals on the gulf’s seaf...

This study describes the prevalent sedimentological and geochemical patterns and investigates the environmental status of the bottom of Gialova lagoon, a highly vulnerable coastal site of the EU’s Natura 2000 network. For this task, lithological, geochemical, and microfaunal analyses of sediment samples were combined with a high-resolution bathymet...

Marine litter poses a significant environmental challenge in the Saronikos Gulf, Greece. Employing an integrated approach, data from both beach and underwater sites were analyzed. The average litter density on beaches was 2.61 items / m2, with plastic being the most common material, notably small polystyrene fragments and cigarette butts. The weste...

Coastal systems have changed considerably in response to Quaternary glacial–interglacial variability. Here, we offer the first detailed assessment of geomorphic features and late Quaternary sedimentation dynamics in the Loˇsinj Channel in the Adriatic Sea. The present study attempts to resolve the complex evolution of the environments by applying h...

This study combines marine remote sensing and photogrammetry to investigate underwater cultural heritage (UCH) sites in the Gulf of Patras, Greece. The research utilized multibeam echosounders, side scan sonar, and marine magnetometers to detect potential UCH sites, followed by visual inspections using a remotely operated vehicle (ROV) equipped wit...

Advancements in remote sensing technologies and marine robotics have revolutionized the surveying of underwater cultural heritage (UCH), surpassing the limitations of conventional means. In shallow water areas, Unmanned Surface Vessels (USVs) offer advantages over research vessels, such as extended autonomous operation, maneuverability, low power c...

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...

The Patras Gulf Pockmark field is located in shallow waters offshore Patras City (Greece) and is considered one of the most spectacular and best-documented fluid seepage activities in the Ionian Sea. The field has been under investigation since 1996, though surveying was partially sparse and fragmentary. This paper provides a complete mapping of th...

Seafloor litter is the least exploited component of marine litter. The spatially variable distribution of their densities over time is a cumulative effect of sources' intensities and natural drivers like wind/wave and current conditions in interaction with seafloor morphology. Making safe interpretations about the exact spatiotemporal distribution...

Most of the eastern Adriatic rivers have cut their rocky canyons for the last time during the Last Glacial Maximum (LGM). In that period the sea level was up to 130 m lower than today and karstic rivers originated as incised valleys, with a sediment bypass to the shelf and formation of a delta at their river mouths. The Krka River mouth on the east...

Hellenic Petroleum S.A. has undertaken five Marine Seismic Surveys in the Greek territorial waters of the Ionian Sea between 2016 and 2023. Those were coupled with intensive marine noise monitoring programs, applied to 13 stations with a longitudinal span of about 300 km. Stations were mostly placed around Marine Protected Areas in coastal waters,...

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 cli...

Submerged cultural heritage provides a unique opportunity to couple paleoenvironmental and culture-historical research with the contemporary cultural heritage needs of the public where field work takes place. Greece provides an ideal locale for developing what we refer to as maritime cultural heritage asset districts (MCHAD). Here we summarize two...

In the port of Thessaloniki, Greece, benthic megalitter detection was achieved using an Unmanned Surface Vehicle (USV) equipped with a compact high resolution sidescan sonar (SSS) and a single beam echsosounder (SBES). The benthic megalitter survey was organized in two separate phases. Firstly, a systematic hydroacoustic survey using the SBES and S...

The island of Astypalea (Greece), known for its rich and pristine archeological sites, encompasses a semi-enclosed silled basin that has been very susceptible to global sea levels and regional climate changes due to its relatively modern shallow sill of 4.7 m water deep that connects the Vathy bay with the adjacent Aegean Sea. To identify the causa...

Research Highlights The Holocene paleoenvironmental evolution of a small semi-enclosed silled marine basin in the South Aegean Sea is controlled by both climatic and sea level variability. Within the general South Aegean region, the Holocene presents a general aridification trend toward the present. Background Coastal restricted basins are sensitiv...

The "Guide for Marine Habitat Mapping" is the outcome of the Green Fund project entitled "Development of common methodology and techniques for marine habitat mapping". This Guide aims to provide a synopsis of the diverse array of concepts and methods used to undertake the marine habitat mapping adapted to the marine environment of the Hellenic Seas...

The aim of this study is to present the results of the first complete marine habitat mapping through marine remote sensing techniques in Gyaros Island, a remote island in the Cyclades archipelago with a great historical and ecological value. Gyaros Island is of great biological importance and, for this reason, since 2011, is part of the NATURA 2000...

Koločep bay is a 30 km elongated karst basin located between the Elafiti Islands and the mainland with a NW–SE general direction. The bay lies within the seismically active southern Dalmatia zone. Irregular grid sub-bottom profiles and two legacy reflection seismic profiles have been used to determine the overall morphology of the bay and to establ...

Monitoring of marine litter at the sea surface, the beaches and the seafloor is essential to understanding their sources, pathways and sinks and design effective clean-up programs or increase public awareness for reducing litter waste. Up until today, seafloor litter is the least exploited component of marine litter. Although the protocols for reco...

Straits are crossed by marine currents that are amplified due to constrictions. These nearshore high-velocity flows are problematic for offshore infrastructures (bridge pillars, cables, pipelines etc), but constitute an interesting carbon-free energy source. Many modern straits are dominated by tidal currents which flow axially, with reversal direc...

The evolution of the bottom water in Amvrakikos Gulf in Ionian Sea at western Greece for a 50-year timespan was assessed by benthic foraminifera assemblages. The degradation of the bottom water of Amvrakikos has been a catalyst for the surface water degradation. The east basin has shown permanent low environmental quality in bottom waters since 198...

Important evidence related to sea-level fluctuation, human evolution and dispersal that took place onshore during the Late Pleistocene and Holocene eras, are currently found underwater due to the sea-level rise. In this study, we present submarine relative paleo sea-level indicators found offshore the Lebanese coastline, at large from the prominent...

The documentation of underwater cultural heritage (UCH) is the basis for sustainable maritime development including its protection, preservation, and incorporation in coastal zone management plans. In this study, we present a multidisciplinary, non-intrusive downscale approach for the documentation of UCH implemented on the coastal area of Aegina I...

The central sewer of Athens had been discharging untreated sewage from 1950 until 1995 in the marine area between the island of Psyttalia and Keratsini. As a result, a surficial layer of organic mud was formed covering the seafloor. To assess the spatial and temporal distribution of metal contaminants in the area, six sediment cores were collected...

The spatial distribution of lithological characteristics, organic carbon and major / trace elements was studied in the surface sediments of the Gialova lagoon, a shallow water lagoon (<1.0 m) which is located at southwestern Peloponnesus (Greece). The sediment samples were collected on the basis of a detailed bathymetric map and the backscatter p r...

A series of marine remote sensing and ground-truth surveys were carried out at NW Gulf of Patras (W. Greece). The same area was surveyed in 1971 by Throckmorton, Edgerton and Yalouris, who are among the pioneers in the application of remote sensing techniques to underwater archaeology. The researchers conducted a surface reconnaissance survey to lo...

Amvrakikos Gulf is a Mediterranean landlocked, fjord-like embayment and marine protected area suffering from natural, human-induced hypoxia/anoxia and massive fish mortality events. Seasonal marine geophysical and oceanographic surveys were conducted focusing on the water-circulation patterns at the sill and the spatial-seasonal distribution of dis...

Straits are crossed by marine currents that are amplified due to the water constriction. These nearshore high-velocity flows are problematic for offshore infrastructures (bridge pillars, cables, pipelines etc), but constitute an under-estimated carbon-free kinematic energy source. Most of the straits are dominated by tidal currents which flow axial...

Amfilochia Bay (Eastern Amvrakikos Gulf, Western Greece), a complex marine area affected by tectonism, was investigated for seabed seepage manifestations and for possible inter-relationships between shallow gas accumulations and hypoxia. For this purpose, an integrated research methodology that combined geophysical, geochemical, and hydrographic su...

Underwater cultural heritage (UCH) sites constitute an important part of the overall cultural heritage both nationally and globally as they carry cultural, environmental, scientific, technological, political, economic and social viewpoints. UCH includes not only submerged sites and buildings, but also vessels and aircrafts. The Inner Ionian Sea in...

Detailed multi-beam bathymetry, sub-bottom acoustic, and side-scan sonar observations of submerged canyons with tufa barriers were used to characterize the Zrmanja River karst estuary on the eastern Adriatic coast, Croatia. This unique karst environment consists of two submerged karst basins (Novigrad Sea and Karin Sea) that are connected with rive...

The marine environment is the final recipient and digester of litter. Floating and benthic litter constitute the majority of litter items in the marine environment while both remain quite unexploited due to their demand in high-cost and time-consuming surveys. In this paper we propose an integrated approach for assessing in detail the spatial distr...

Gialova lagoon is located in the northwest of Pylos city (Prefecture of Messinia, SW Peloponnesus) and is part of the Ecological Network "Natura 2000". The aim of the current research is the assessment of the ecological quality of the lagoon using hydroacoustic technique and the monitoring of abiotic and biotic parameters on seasonal basis. Side sc...

The ‘Evolved GE.N.ESIS Project’ highlights the underwater cultural heritage resources off the coast of Methoni, Greece that could locally drive sustainable socioeconomic growth. An integrated marine geophysical survey, a hydrographic survey, and a GNSS survey were conducted off Methoni, recording six historic wreck sites, artefacts, the ruins of a...

Impacts of man-made acoustic noise on the marine environment are associated to the frequency and timing of any activity as well as the distribution and abundance of marine life. Offshore commercial operations, shipping activities, energy exploration and pile driving add noise to the already established ambient noise levels. Attention has been raise...

Amvrakikos Gulf is a hypoxic ecosystem prone to both physical and anthropogenic pressure. However, it is experiencing a series of anthropogenic interventions on-and offshore , at the Preveza straits, where the oxygenation mechanism of the Gulf is taking place. Dredging, marine structures and other interventions, added further stress to the ecosyste...

In this work, multibeam echosounder (MBES) and dual frequency sidescan sonar (SSS) data are combined to map the shallow (5–100 m) benthic habitats of the National Marine Park of Zakynthos (NMPZ), Greece, a Marine Protected Area (MPA). NMPZ hosts extensive prairies of the protected Mediterranean phanerogams Posidonia oceanica and Cymodocea nodosa, a...

This work presents the materials, methods and results of the West Patraikos Gulf ambient and seismic noise monitoring project, realized during the marine 3D seismic survey that was conducted by the Hellenic Petroleum S.A., in 2015. Dense acoustic noise monitoring data were acquired and processed close to the seismic source to as far as away from it...

The palaeogeographical reconstruction of the coastline as well as the detection of potential off-shore submerged archaeological objectives, constitute the objective of the marine survey in the Vathi bay.

Geometry and kinematics of the active submarine faults over the North Aegean Trough, a complex and highly deforming boundary zone between the Eurasian and the Anatolian/Aegean micro-plates, were examined to investigate how a strike slip motion propagates through an extensional domain. The bathymetric and seismic reflection data analysis show, that...

The interconnection between cultural heritage found in terrestrial and marine environments is beginning to garner international more scholarly attention as researchers investigate the linkages between human adaptation to changing coastal environments. In terms of world cultural heritage, land and sea should be considered as an integrated system. As...

The preferred procedure nowadays for benthic habitat mapping is combining marine acoustic and ground truthing methods, with the former ones tending to be the swath sonars, such as the Multi Beam Echo Sounders (MBES) and the Side-Scan Sonars (SSS). Both above acoustic systems, in conjunction with an extensive underwater video footage, were employed...

Modern underwater remote sensing technology introduces many advantages that extend the range of conventional diving work providing the means to survey in a detailed and systematic fashion large seafloor area. There are two general approaches regarding the application of these techniques in underwater archaeology; they are being increasingly used to...

Geometry and kinematics of the active submarine faults over the North Aegean Trough

A marine geoarcheological survey was conducted at the southwestern end of the Argosaronic gulf in Greece, an area of archaeological importance. The survey was initiated by the discovery of a Late Bronze Age (LBA) shipwreck off Modi Islet. The survey which employed echo-sounding, sub-bottom profiling, side scan sonar systems and sediment coring exte...

The southwestern flank of the Hellenic Fold and Thrust Belt, situated along the southern edge of the Dinarides-Albanides-Hellenides continental convergent zone, was examined for reconstructing the tectonic deformation. This investigation presents an integrated study of onshore sedimentologic and structural analyses, as well as offshore seismic line...

The Corinth Rift, central Greece, enables analysis of early rift development as it is young (<5Ma) and highly active and its full history is recorded at high resolution by sedimentary systems. A complete compilation of marine geophysical data, complemented by onshore data, is used to develop a high-resolution chronostratigraphy and detailed fault h...

The Corinth Rift, central Greece, enables analysis of early rift development as it is young (<5 Ma) and highly active and its full history is recorded at high resolution by sedimentary systems. A complete compilation of marine geophysical data, complemented by onshore data, is used to develop a high-resolution chronostratigraphy and detailed fault...

The Corinth Rift, central Greece, enables analysis of early rift development as it is young (<5 Ma), highly active and its full history is recorded at high-resolution by sedimentary systems. A complete compilation of marine geophysical data, complemented by onshore data, is used to develop a high-resolution chronostratigraphy and detailed fault his...

The southwestern flank of the Hellenic fold and thrust belt, situated along the southern edge of the Dinarides–Albanides–Hellenides continental convergent zone, was examined for reconstructing the tectonic deformation. This investigation presents an integrated study of onshore sedimentological and structural analyses, as well as offshore seismic li...

The LoLADRIA project represents a multidisciplinary effort to recover, for the first time, long paleoenvironmental and paleoclimate records from existing coastal karst lakes and submerged karstic lakes of the eastern Adriatic shelf in Croatia. At glacial low sea levels large areas of the continental shelf were exposed, making them available to earl...

The marine area around Gyaros Isl. was extensively studied using geoacoustical systems (sub bottom profiler, side-scan sonar, single beam echosounder) and underwater imaging and sediment sampling methods, towards mapping priority habitat types, emphasizing on Posidonia oceanica and calcareous red algae (coralligenous) formations. The seabed around...

Helike, the Achaean Dodecapolis capital, in the Corinth Gulf, Greece, was, according to historical sources, devastated and disappeared from sight during an earthquake followed by sea invasion on to land in 373/372 B.C. A marine remote sensing survey, which was carried out to examine a landslide following a 6.2 R earthquake in 1995, that affected th...

In the present paper we present the marine remote surveying conducted aiming to investigate an ancient shipwreck offshore Kefalonia island, in Ionian Sea, Greece. Within the framework of the survey efforts were given to examine the site formation of the wreck and to define the best practices for the detection and mapping of similar potential archae...

The study area, Aetoliko Lagoon is a unique coastal Mediterranean landlocked ecosystem, controlled by tectonic activity and is characterized by permanent oxygen-depletion conditions (hypoxia/anoxia). The geological conditions, the geomorphology and the bathymetry of the lagoon, make the Aetoliko Lagoon an area of special interest for the research o...

In the present study, the spatial distribution pattern of the surficial sediments and Posidonia oceanica meadows in prodeltaic area of River Acheloos is presented.

The present study presents the results of the preliminary marine geophysical survey conducted in 2006 at the gulf of Sounion, southern Attica, Greece. The site is of great archaeological importance since cape Sounion served as a navigational landmark and a naval fortress protecting the sea-lanes towards the metropolis of Athens and the silver mines...

Mapping of natural and cultural marine heritage sites is substantial to national and regional inventories aiming to conservation and protection and the management of coastal and offshore resources. Within this concept this study presents the results of a marine geophysical survey in conjunction with visual inspection, conducted at Leros Island, Gre...

The occurrence and origin of methane (CH4) generated by serpentinization of ultramafic rocks is of current timely interest in planetary geology, astrobiology and energy resource exploration, as it may contribute, in particular, to decipher the source of methane on Mars, the origin of life and the potential of abiotic hydrocarbon synthesis. Methane...

The Gulf of Corinth is a classic young active continental rift initiating <5 Ma and with current extension rates up to 15 mm/yr. The modern rift (ca. 1-2 Myr old) has been studied extensively both onshore and offshore. In this paper we bring together the results of study of the offshore rift with existing onshore data to generate a model for how th...

The distribution of the natural radionuclides ((238)U, (232)Th, (226)Ra, (40)K) and the artificial (137)Cs was studied in sediment cores collected from Amvrakikos Gulf, a seasonal anoxic marine basin, using γ-ray spectrometry. The activity of radionuclides, along with the concentrations of Fe and Mn, were also studied in relation to the total organ...

Considerable seepage of natural gas occurs throughout the Katakolo Bay, both at sea and on land, along the Ionian coast of Peloponnesus (Western Greece). Explosive levels of CH 4 and toxic concentrations of H 2 S accu-mulating in the ground, pose a severe hazard for humans and tourist infrastructures. A wide offshore and on-shore gas survey, includ...

Acoustic classification systems and the Sediment Trend Analysis method were used to identify and map the bed diversity in a very shallow (<3.0m), coastal lagoon, Pappas lagoon, Western Greece. Analogue acoustic data, collected by means of a 100 kHz side scan sonar system, were digitized and classified into six acoustic classes using recently develo...

Twenty marine sediment samples, selected downcore from six sediment cores, which were retrieved from the Patras Harbour, were studied for their elemental composition using three analytical techniques: INAA, ICP-MS and AAS. Standard reference materials were used to verify the accuracy of the analysis techniques. In total, the concentrations of 30 ma...

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 lay...

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 lay...

The combined interpretation of the detailed bathymetric, sub-bottom profiling and side scan sonar data acquired offshore the Eastern Harbour of Alexandria, revealed evidences for the reconstruction of the coastal geomorphology of Alexandria at the Hellenistic-Roman periods. A series of scarps obtained at sub-bottom profiles at a water depth of 8 m...

A new seafloor observatory, the Gas Monitoring Module (GMM), has been developed for continuous and long-term measurements of methane concentration in seawater at the benthic boundary layer, as a result of marine environmental geology and technology synergy. The module is designed to host a series of sensors controlled and managed by a data acquisit...

Surficial and subsurficial sediment samples derived from gravity cores, selected from the harbour of Patras, Greece, were analyzed for grain size, water content, bulk density, specific gravity, organic carbon content and specific activities of natural radionuclides and (137)Cs. The specific activities of (232)Th, (226)Ra, (40)K and (137)Cs were mea...

Recent studies have speculated that the prophetic powers of Pythia, the woman of the Delphic Oracle, at the Temple of Apollo in Greece, were induced by hydrocarbon vapors, specifically ethylene, rising from bedrock fissures at the intersection of the E-W Delphi fault with the NNW-SSE Kerna fault, and producing neurotoxic effects, including trance a...

A new seafloor observatory, the gas monitoring module (GMM), has been developed for continuous and long-term measurements of methane and hydrogen sulphide concentrations in seawater, integrated with temperature (T), pressure (P) and conductivity data at the seafloor. GMM was deployed in April 2004 within an active gas-bearing pockmark in the Gulf o...

Gas seepages along the Ionian coast of the northwestern Pelopon- nesus (Greece), at Killini, Katakolo, and Kaiafas reflect deep hydrocarbon-generation processes and represent a real hazard for humans and buildings. Methane microseepage, gas concentration in offshore and onshore vents, and gas dissolved in water springs, including the isotopic analy...

Gas seeps along the Ionian coast of the northwestern Peloponnesus (Greece) constitute a severe hazard for humans and buildings. Methane, migrating from deep carbonatic hydrocarbon reservoirs, is seeping in amounts potentially explosive and hydrogen sulfide is beyond the levels that induce toxicological diseases and lethal effects. The seeps are rel...