Marine remote sensing and visual census techniques for the detection and mapping of benthic litter
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Date
2024-10-24
Authors
Κοντός, Αλκιβιάδης
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Abstract
This thesis, entitled « Marine Remote Sensing and Visual Census Techniques for the Detection and Mapping of Benthic Litter » by geologist Alkiviadis Kontos, was conducted as part of the interdisciplinary postgraduate program of the University of Patras, titled "Oceanography - Exploration, Mapping, and Management of the Marine Environment," under the supervision of Professor Maria Geraga.
The aim of this study was to document and evaluate benthic litter in specific locations in the Aegean Sea. To achieve this goal, acoustic data (side-scan sonar data) provided by Oceanus Lab were processed, along with related data collected during port cleanup missions by the environmental organization "S.A.V.E." (Santorini's Active Volcanic Environment) in collaboration with the Oceanus Lab in ports of the Southern Aegean during the period 2022-2023.
The introductory section of the thesis provides a brief overview of the issue of marine litter, with emphasis in macro and megalitter, its environmental impact, and the importance of its removal from the seabed. The study's objective is also outlined, which is to assess the utility of 400 kHz side-scan sonar (SSS) in detecting macro and megalitter by comparing the results with those from a typical seabed cleanup conducted by divers. A literature review is then presented, covering geophysical methods and their effectiveness in mapping the seabed, sources of marine macro-litter, the methodology for seabed cleanups by divers, and the limitations/challenges involved in these efforts.
The research methodology is subsequently described, beginning with the description of the study area and its seabed, the equipment used for the collection of geophysical data, and the procedure of data processing. The second part of this section details the data collection process from the cleanup operations, how the findings were categorized, and how they were analyzed.
Finally, the results of the methods are presented: (a) the mosaic mapping of the seabed in the port of Thessaloniki and the locations of the identified targets, along with their geometric characteristics, and (b) the distribution of the collected debris and its characteristics from the cleanups, along with a factorial analysis aimed at identifying trends in their dispersion. The thesis concludes with a summary, interpretation, comparison, and discussion of the findings.
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Keywords
Marine litter, Mapping, Side scan sonars