Konstantinos Topouzelis

University of the Aegean · Department of Marine Sciences

Anthropogenic litter, such as plastic, is investigated by the global scientific community from various fields employing diverse techniques. The goal is to assess and finally mitigate the pollutants' impacts on the natural environment. Plastic litter can accumulate in different matrices of aquatic and terrestrial ecosystems, impacting both biota and...

There is a growing international interest in addressing marine litter, including plastics, and discussions are underway at the Intergovernmental Negotiating Committee (INC) on the creation of an international legally binding instrument to end plastic pollution. Under these circumstances, the need for monitoring is emphasized as a means of establish...

Anthropogenic impacts on the marine environment, coupled with the increasing sea surface temperature in the Mediterranean Sea, can lead to an increase in the frequency of marine mucilage formations.

In the aftermath of the devastating Storm Daniel that hit the eastern Mediterranean in September 2023, this study leveraged Sentinel-2 satellite imagery to assess runoff-carried floating marine debris and natural debris in the Aegean Sea. Two key regions, the Pagasetic Gulf and the Pineios River delta, were investigated, revealing possible differen...

Multirotor drones have been shown to be operationally suitable to survey macro-litter in different environments. The potential standardization of drone-based litter survey framework would allow an homogenization of data collection and assessment from different works.

Multirotor drones can be efficiently used to monitor macro-litter in coastal and riverine environments. Litter on beaches, dunes and riverbanks, along with floating litter on coastal and river waters, can be spotted and mapped from aerial drone images. Items detection and classification are prone to image resolution, which is expressed in terms of...

The Northern Thermaikos Gulf is a semi-enclosed coastal region of the Aegean Sea, characterized by anthropogenic and natural stresses such as intense industrial and agricultural activities, urban outflows, and several river discharges facing severe pollution events. The main motivation of this study is to investigate the prevailing oceanographic co...

Marine aquaculture has been expanding rapidly in recent years, driven by the growing demand for marine products. However, this expansion has led to increased competition for space and resources with other coastal zone activities, which has resulted in the need for larger facilities and the relocation of operations to offshore areas. Moreover, the c...

Fish population spatial distribution data provide essential information for fleet monitoring and fishery spatial planning. Modern high resolution ocean color remote sensing sensors with daily temporal coverage can enable consistent monitoring of highly productive areas, giving insight in seasonal and yearly variations. Here is presented the methodo...

Among the emerging applications of remote sensing technologies, the remote detection of plastic litter has observed successful applications in recent years. However, while the number of studies and datasets for spectral characterization of plastic is growing, few studies address plastic litter while being submerged in natural seawater in an outdoor...

Large-area, artificial floating marine litter (FML) targets were deployed during a controlled field experiment and data acquisition campaign: the Plastic Litter Project 2021. A set of 22 Sentinel-2 images, along with UAS data and ancillary measurements were acquired. Spectral analysis of the FML and natural debris (wooden planks) targets was perfor...

Dissolved oxygen (DO) is one of the most critical parameters for aquaculture, as it is vital for all living organisms. The survival, growth and food intake of fish is directly affected by changes in DO concentration. Therefore, the systematic and continuous monitoring of DO is of crucial importance for proper production management. DO does not chan...

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...

Sentinel-2 (S2) images have been used in several projects to detect large accumulations of marine litter and plastic targets. Their limited spatial resolution though hinders the detection of relatively small floating accumulations of marine debris. Thus, this study aims at overcoming this limit through the exploration of fusion with very high-resol...

Plastic is the third world’s most produced material by industry (after concrete and steel), but people recycle only 9% of plastic that they have used. The other parts are either burned or accumulated in landfills and in the environment, the latter being the cause of many serious consequences, in particular when considering a long-term scenario. A s...

Unmanned Aerial Systems (UAS) have been recently used as a close-range remote sensing tool, providing high spatial and temporal resolutions compared to other remote sensing methods. Their abilities have constantly increased their use in many environmental studies with very satisfactory results. However, the acquisition of reliable information for a...

One of the most significant environmental problems of Thermaikos Gulf is the occasional formation of extended eutrophication phenomena (red tides, mucilaginous aggregates). Herein, we investigate the contribution of hydrodynamic processes on the formation of such events, under the effects of different meteorological and river discharge conditions....

Scientists in the marine domain process satellite images in order to extract information that can be used for monitoring, understanding, and forecasting of marine phenomena, such as turbidity, algal blooms and oil spills. The growing need for effective retrieval of related information has motivated the adoption of semantically aware strategies on s...

Unmanned aerial systems (UAS) are widely used in the acquisition of high-resolution information in the marine environment. Although the potential applications of UAS in marine habitat mapping are constantly increasing, many limitations need to be overcome—most of which are related to the prevalent environmental conditions—to reach efficient UAS sur...

Unmanned aerial systems (UAS, aka drones) are being used to map macro-litter on the environment. Sixteen qualified researchers (operators), with different expertise and nationalities, were invited to identify, mark and categorize the litter items (manual image screening, MS) on three UAS images collected at two beaches. The coefficient of concordan...

Floating Marine Litter (FML) are mainly plastics or synthetic polymers that float on the sea surface after being deliberately discarded or unintentionally lost along beaches, rivers or marine environments. In recent years, much focus has been placed on locating, tracking and removing plastic items in both coastal areas and in the open ocean. The us...

Biogenic films are very thin surface oils, frequently observed near aquaculture farms, that affect the roughness and the optical properties of the sea surface, making them visible in SAR and multispectral images. The purpose of this study is to investigate the potential of satellite SAR and multispectral sensors in the detection of biogenic oil fil...

Hyperspectral PRISMA images are new and have not yet been evaluated for their ability to detect marine plastic litter. The hyperspectral PRISMA images have a fine spectral resolution, however, their spatial resolution is not high enough to enable the discrimination of small plastic objects in the ocean. Pansharpening with the panchromatic data enha...

Thermaikos Gulf is a typical, river-fed, microtidal, semi-enclosed, coastal inlet of the east-central Mediterranean Sea. It is an important coastal ecosystem susceptible to several anthropogenic pressures, strong river discharges and variable meteorological and ocean (met-ocean) conditions. One of the most significant environmental problems of the...

Windrow is a long-established term for the aggregations of seafoam, seaweeds, plankton and natural debris that appear on the ocean surface. Here, we define a “litter windrow” as any aggregation of floating litter at the submesoscale domain (<10 km horizontally), regardless of the force inducing the surface convergence, be it wind or other forces su...

The objective of this study is to evaluate the efficiency of two well-known algorithms (Ocean Colour 4 for MERIS [OC4Me] and neural net [NN]) used in the calculation of chlorophyll-a (Chl-a) from the Sentinel-3 Ocean and Land Colour Instrument (OLCI) compared to in situ measurements covering the Mediterranean Sea. In situ data set, obtained from th...

Whilst both plastic production and inputs at sea have increased since the 1950s, several modelling studies predict a further increase in the coming years in these respective quantities. We compiled scientific literature on trends in marine litter, consisting largely of plastic and microplastics in the ocean, understanding that monitoring programs o...

Marine litter (ML) accumulation in the coastal zone has been recognized as a major problem in our time, as it can dramatically affect the environment, marine ecosystems, and coastal communities. Existing monitoring methods fail to respond to the spatiotemporal changes and dynamics of ML concentrations. Recent works showed that unmanned aerial syste...

Marine conservation and management require detailed and accurate habitat mapping, which is usually produced by collecting data using remote sensing methods. In recent years, unmanned aerial systems (UAS) are used for marine data acquisition, as they provide detailed and reliable information through very high-resolution orthophoto-maps. However, as...

In the present integrated monitoring study, the quality of the marine environment of the Thermaic Gulf was appraised by measuring physical, chemical and biological parameters of the seawater and seabed. Water and sediment samples were seasonally collected during sampling campaigns from selected stations located at the inner part of Thermaic Gulf. T...

The identification of oceanographic circulation related features is a valuable tool for environmental and fishery management authorities, commercial use and institutional research. Remote sensing techniques are suitable for detection, as in situ measurements are prohibitively costly, spatially sparse and infrequent. Still, these imagery application...

Marine habitat mapping is essential for updating existing information, preserving, and protecting the marine environment. Unmanned Aerial Systems (UAS) are an important tool for monitoring and mapping coastal and marine environment because of their ability to provide very high-resolution aerial imagery.Environmental conditions have a critical role...

Remote sensing is a promising tool for the detection of floating marine plastics offering extensive area coverage and frequent observations. While floating plastics are reported in high concentrations in many places around the globe, no referencing dataset exists either for understanding the spectral behavior of floating plastics in a real environm...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Satellites collecting optical data offer a unique perspective from which to observe the problem of plastic litter in the marine environment, but few studies have successfully demonstrated their use for this purpose. For the first time, we show that patches of floating macroplastics are detectable in optical data acquired by the European Space Agenc...

Coastal areas are remarkable regions with high spatiotemporal variability. Many domains are affected by their physical and biological processes, from tourism to biodiversity and productivity. Coastal ecosystems perform several critical ecosystem services and functions such as water oxygenation and nutrient provision, seafloor and beach stabilizatio...

The use of unmanned aerial systems (UAS) over the past years has exploded due to their agility and ability to image an area with high-end products. UAS are a low-cost method for close remote sensing, giving scientists high-resolution data with limited deployment time, accessing even the most inaccessible areas. This study aims to produce marine hab...

Coastline change and human activities in shoreline zones are two factors indicating the vulnerability and the quality of a coastal environment. In this article, coastline evolution and spatiotemporal differences on coastal touristic infrastructure are presented as two case studies. Both case studies have increasing interest among scientists monitor...

Sustained observations are required to determine the marine plastic debris mass balance and to support effective policy for planning remedial action. However, observations currently remain scarce at the global scale. A satellite remote sensing system could make a substantial contribution to tackling this problem. Here, we make initial steps towards...

Aerial surveys in coastal areas using Unmanned Aerial Vehicles (UAVs) present many limitations. However, the need for detailed and accurate information in a marine environment has made UAVs very popular. The aim of this paper is to present a protocol which summarizes the parameters that affect the reliability of the data acquisition process over th...

In the last year, the Greek islands of the eastern Aegean Sea were the main entrance points used by refugees arriving in the EU. The crossing between Turkey and the eastern Aegean islands is carried out using mostly small inflatable boats. Additionally, wooden and plastic vessels of various sizes are abandoned at the beaches upon arrival together w...

Marine domain awareness is important for crisis management in case of accidents but also as a surveillance tool against illicit discharge activities. Copernicus Sentinel-1 data are used for the detection of spills as they are provided free and in near real time. The availability of data and the recently developed cloud infrastructures give the oppo...

Dynamic processes in coastal zones and human activities in the coastal environment produce pressure on cultural heritage, especially in touristic places. Unmanned aerial systems (UAS) are used as an additional tool for monitoring cultural heritage sites in sensitive coastal areas. UASs provide low-cost accurate spatial data and high-resolution imag...

A rapidly rising amount of plastic litter on land and at sea is becoming a global wicked environmental problem. Here, we present an innovative exploratory application of unmanned aerial systems (UAS) and open-access satellite imagery in remote detection of floating plastics in natural seawater, through a dedicated aquatic environment experiment. We...

An open-source approach for oil spill detection using Sentinel-1 SAR images

In the epoch of anthropogenic climate change that nature is traversing, the vastly biodiverse coastal ecosystems in Mediterranean suffer from significant impacts. The silent, overlooked and degraded, yet remarkable ecosystem service providers, Mediterranean seagrasses can mitigate the resulting impacts by relentlessly sequestering the so-called ‘bl...

Coastline change and human activities in shoreline zones are two factors indicating the vulnerability and the quality of a coastal environment. In this article, coastline evolution and spatiotemporal differences on coastal touristic infrastructure are presented as two case studies. Both case studies have increasing interest among scientists monitor...

MARINE-EO is a Research and Development project using a Pre-Commercial Procurement (PCP) mechanism with the scope to develop innovative beyond the state-of-the-art downstream applications which meet the demand of maritime authorities and stakeholders, leveraging on the existing services and other products from the Copernicus portfolio. More specifi...

MARINE-EO is a Research and Development project using a Pre-Commercial Procurement (PCP) mechanism with the scope to develop innovative beyond the state-of-the-art downstream applications which meet the demand of maritime authorities and stakeholders, leveraging on the existing services and other products from the Copernicus portfolio. More specifi...

Last years the role of Unmanned Aerial Systems becoming more and more crucial in a wide variety of scientific aspects that need fast and reliable geodata to monitor coastal cultural heritage areas. The dynamic processes in the coastal zone and human activities on the coastal environment produce pressure in cultural heritage especially in touristic...

An important population of the endemic Mediterranean fan mussel Pinna nobilis thrives in the marine protected area of the Gera Gulf (Lesvos island, northeastern Aegean Sea, Greece), and was assessed for the first time. To estimate the abundance, spatial distribution and habitat use of fan mussels in the Gera Gulf, a distance sampling underwater sur...

The collection of detailed and accurate information about marine habitats and flora species is crucial for mapping, monitoring and management of marine and coastal environments. Remote sensing is widely used to collect information at marine environments, while in recent years the potential use of UAS for mapping is examined. The aim of this paper i...

Abstract Last years the role of Unmanned Aerial Systems becoming more and more crucial in a wide variety of scientific aspects that need fast and reliable geodata. Nowadays UAS have a prominent role in post-earthquake damage assessment as they are capable of collecting high in resolution data for mapping the results of a catastrophic event. The imp...

Seagrass meadows play a vital role in coastal ecosystems health as constitute an important pillar of the coastal environment. So far, regional scale habitat mapping was implemented with the use of freely available medium scale satellite images (Sentinel-2 or Landsat-8). The Unmanned Aerial Systems (UAS) have increase the spatial resolution of the o...

Seagrasses are traversing the epoch of intense anthropogenic impacts that significantly decrease their coverage and invaluable ecosystem services, necessitating accurate and adaptable, global-scale mapping and monitoring solutions. Here, we combine the cloud computing power of Google Earth Engine with the freely available Copernicus Sentinel-2 mult...

Seagrass meadows are one of the most important coastal habitats across the globe. These are mainly constituted by the marine plants of the genus Posidonia and Thalassia. In the Mediterranean Sea, Posidonia oceanica is the dominant endemic plant that affects physical, biogeochemical and biological processes. The decline in the spatial distribution h...

This study presents the methodology followed for the evaluation of buildings damage after the earthquake of 12 th of June in Vryssa, Lesvos island. For this purpose, VHR multispectral images from a flight from a UAS were acquired. The methodology consisted of two main steps. Firstly, through the orthorectification and radiometric calibration proced...

The aim of this paper is to present the methodology followed and the results obtained by the synergistic exploitation of geo-information methods towards 3D mapping of the impact of the catastrophic earthquake of June 12th 2017 on the traditional settlement of Vrisa on the island of Lesvos, Greece. A campaign took place for collecting: a) more than...