Unusual Total Organic Carbon (TOC) Distribution and Possible Hot Spot in the Central Mediterranean Sea Available to Purchase

Offshore Environmental Baseline Surveys are pillars for each offshore activity (drilling, pipe/Cable laying, platform installation, etc.). In Spring 2020 a water and sediment offshore environmental baseline study has been carried out in the Central Mediterranean Basin for an O&G development project (sealines and platforms). Despite the Mediterranean Sea is generally considered poor in terms of dissolved nutrients, results of water and sediment Total Organic Carbon (TOC) concentration suggest an unusual distribution in part of the study area, with hot spots located in bottom waters. Hot spots consist in peaks of TOC (average concentrations of 12.03 mg/L and 8.07 mg/L in area with concentrations around 1.5-2.0 mg/L) which spreads in upper water layers and in surrounding waters in all directions, with an area of influence of dozen kms. In addition, TOC hot spots in sediments were observed in 10 to 30 km radius. Average TOC content in sediments was 2.59%, twice higher than the average value of the whole data set (1.11%) and similar to values measured in nearshore stations. Since the sampling in this area was performed over multiple days, organic carbon hot spots could potentially be continuous over time. Furthermore, the vertical distribution of TOC along the water column is opposite to what resulted in the other stations of the area with higher values measured close to the bottom and decreasing when reducing depth. Two hypotheses have been formulated about hot spots origin: 1) an accumulation of TOC in deeper water layers, as a result of oceanic circulation or 2) an underwater source of organic carbon. Results of microbial data analyses on sediment, and presence of a rich and abundant benthic community in the area close to the stations with higher values for TOC in water, indicates the second hypothesis as the most adherent to field data. Further focused studies are needed.