Geochemical and Geophysical Monitoring of Hydrocarbon Seepage in the Adriatic Sea

Abstract

Hydrocarbon seepage is overlooked in the marine environment, mostly due to the lack of high-resolution exploration data. This contribution is about the set-up of a relocatable and cost-effective monitoring system, which was tested on two seepages in the Central Adriatic Sea. The two case studies are an oil spill at a water depth of 10 m and scattered biogenic methane seeps at a water depth of 84 m. Gas plumes in the water column were detected with a multibeam system, tightened to sub-seafloor seismic reflection data. Dissolved benthic fluxes of nutrients, metals and Dissolved Inorganic Carbon (DIC) were measured by in situ deployment of a benthic chamber, which was used also for the first time to collect water samples for hydrocarbons characterization. In addition, the concentration of polycyclic aromatic hydrocarbons, as well as major and trace elements were analyzed to provide an estimate of hydrocarbon contamination in the surrounding sediment and to make further inferences on the petroleum system.

Semi-Automated Data Processing and Semi-Supervised Machine Learning for the Detection and Classification of Water-Column Fish Schools and Gas Seeps with a Multibeam Echosounder

“…In light of the above, ongoing research aims to enrich the feature space with bathymetryderived features (e.g., slope, curvature, bathymetric position index [50]). These may give more or better information on hydrocarbons whose efflux through the seafloor causes positive or negative seafloor geomorphological features, such as pockmarks [16].…”

“…In the south-eastern corner of site A were numerous depressions (pockmarks) in the sediment caused by methane seeps. These seeps are of particular interest because they work counter to ocean carbon capture and sequestration (CCS) schemes by releasing carbon back to the ocean [ 16 ]. There were no such depressions at site B.…”

“…Confusion matrix of the ensemble model. Results of the classification are reported in Figures 13-16, using latitude-depth views (panels A) and Kernel Density Estimation (KDE) top views (panels B).Depth profiles (A panels) in Figures[13][14][15][16] show that the platform was always correctly identified as expected at the center of the unseen scenes, especially in the upper depth layers. The bottom part of the structure was, on the contrary, often masked by the presence of fish aggregations, gas and/or noise.…”

“…Indeed, the wide area insonified with a single swath (typically covering about 120°) differentiates MBESs from SBES whose main beam widens less than 20° and therefore requires far more survey time to achieve equivalent coverage. Novel and compelling applications of WCI from MBES range from qualitative descriptions of fish school behavior and morphological characteristics [ 11 , 12 , 13 , 14 ], oil and gas leakage detection [ 15 , 16 , 17 , 18 ], kelp ecosystem mapping [ 19 , 20 ] and aquaculture monitoring [ 21 ], to assessing the mean abundance of marine macro-litter [ 22 , 23 ] and providing other valuable insights to marine systems [ 24 , 25 , 26 , 27 ].…”

Use of UIoT for Offshore Surveys Through Autonomous Vehicles

“…Underwater observation systems like ENDURUNS meet the growing demand for technological improvement in ocean exploration and monitoring aimed at increasing our understanding of the ocean interior for a valuable number of scientific, industrial and political reasons [6,7]. Deep water exploration and new data collection in this domain are of special interest to provide new insights into a variety of geological and ecological processes [8,9], such as underwater hydrocarbons exploration, offshore carbon capture and storage, exploitation of deep-sea mineral resources, as well as for seafloor observatories [10][11][12][13]. At the same time, political drivers push toward the implementation of new coordinated marine monitoring programmes for establishing, preserving and restoring relevant Marine Protected Areas, as stated in the EU Marine Strategy Framework Directive (2008/56/EC).…”