Are the foraminiferal assemblages useful proxy for detecting methane emissions in shallow water environments? the case of Scoglio d’Africa (Tuscan Archipelago, Northern Tyrrhenian Sea)

In this research benthic foraminiferal response to shallow water methane (CH4) emissions located in the area around Scoglio d’Africa (Tuscan Archipelago, Northern Tyrrhenian Sea were used as proxy for the individuation of) was investigated. The site is located in the southernmost part of the Elba-Pianosa Ridge, a mainly submarine, north-south elongated morpho-structural high separating the Tuscany Shelf to the east from the Corsica Basin to the west. In the study area, submarine methane emissions have been studied since the 1960s and they are linked to the combined action of two processes: biogenic (microbial process called methanogenesis) and thermogenic origin. The aim of the study is to verify the use of foraminifera as a proxy for detecting the presence of methane emissions and elaborate a microfaunal pattern distribution to apply in recent, future and fossil record. Methane (CH4) is an important greenhouse gas, with a global warming potential about 20 times as large as carbon dioxide (CO2) on a 100-year horizon. In the marine environment, coastal areas represent methane hotspots highly exceeding emissions from the open ocean. In this view, Scoglio d’Africa provides a much-promising study site for multidisciplinary marine research like carbon capture and storage, geochemistry of hydrothermal fluids and ocean acidification vs. benthic and pelagic organisms. The microfaunal analyses were carried out from sediment samples coming from 11-16 m depth are shown. The samples were collected by grab and scuba during two sampling surveys in 2021 and 2022. The preliminary results of this research highlighted a very patch distribution and variability in density and biodiversity probably linked to the irregular distribution of the venting activity on the ground floor. The complexity of the interaction of the ecological factors characterizing extreme environments such as shallow hydrothermal vents did not allow us to carry out a real pattern of biota responses in situ. However, some significant considerations can be highlighted. Firstly, a strong loss of biodiversity and collapse in faunal density are recorded due to the combined effect by the CH4 emissions and the mud flow setting. Secondarily, the rare living specimens are represented by agglutinated species like Lepidodeuterammina ochracea and Ammodiscus sp., miliolid taxa like Quinqueloculina stelligera and Siphonaperta agglutinans, and among hyaline species, Rosalinids and H. depressula resulted the more resilient taxa. Moreover, the research provides new constrains on the ecological behaviour of some foraminiferal species in response to extreme conditions due to methane release.