Tidal notches in Mediterranean Sea: a comprehensive analysis

Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology. Our results suggest that, considering \u2018the development of tidal notches the consequence of midlittoral bioerosion\u2019 (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development. Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them

Preservation of modern and MIS 5.5 erosional landforms and biological structures as sea level markers : a matter of luck?

The Mediterranean Basin is characterized by a significant variability in tectonic behaviour, ranging from subsidence to uplifting. However, those coastal areas considered to be tectonically stable show coastal landforms at elevations consistent with eustatic and isostatic sea level change models. In particular, geomorphological indicators—such as tidal notches or shore platforms—are often used to define the tectonic stability of the Mediterranean coasts. We present the results of swim surveys in nine rocky coastal sectors in the central Mediterranean Sea using the Geoswim approach. The entire route was covered in 22 days for a total distance of 158.5 km. All surveyed sites are considered to have been tectonically stable since the last interglacial (Marine Isotope Stage 5.5 [MIS 5.5]), because related sea level markers fit well with sea level rise models. The analysis of visual observations and punctual measurements highlighted that, with respect to the total length of surveyed coast, the occurrence of tidal notches, shore platforms, and other indicators accounts for 85% of the modern coastline, and only 1% of the MIS 5.5 equivalent. Therefore, only 1% of the surveyed coast showed the presence of fossil markers of paleo sea levels above the datum. This significant difference is mainly attributable to erosion processes that did not allow the preservation of the geomorphic evidence of past sea level stands. In the end, our research method showed that the feasibility of applying such markers to define long-term tectonic behaviour is much higher in areas where pre-modern indicators have not been erased, such as at sites with hard bedrock previously covered by post-MIS 5.5 continental deposits, e.g., Sardinia, the Egadi Islands, Ansedonia, Gaeta, and Circeo. In general, the chances of finding such preserved indicators are very low.peer-reviewe

MedFever : An expanding network of citizen-run observatories monitoring shallow coastal underwater temperatures in Italy

MedFever – An expanding network of 12 small observatories was established in the Tyrrhenian Sea in 2021 by MedSharks and ENEA, building on the experience of an observation point established in 2016 in the Gulf of Naples. Very high frequency measurements (15 minutes) at some standard depths (5-15-35m; occasionally at 10-20-25-30-50-60m) were obtained by voluntary diving centers using calibrated HOBO sensors (after calibration accuracy is about ±0.1 °C) in 12 stations evenly covering the Tyrrhenian sea. Due to various technical problems, some records are missing. The dataset proposed here will be upgraded annually

Spatiotemporal distribution of great white shark (Carcharodon carcharias, Linnaeus 1758) along Italian coasts: Records from international Medlem program and other contributions

The Great white shark (Carcharodon carcharias Linnaeus 1758), is an apex predator living in almost all the seas of the world, preferring cold-temperate and temperate waters among the 8 and the 25° C (Compagno et al., 2005). It is nevertheless present with important populations in only 8 areas of the globe: California and Baja California, Mexico, central Chile, New England, Mediterranean Sea, Western South Africa, southern Australia, New Zealand and Japan (Compagno et al., 2005). Recently it was added to IUCN redlist as vulnerable species (IUCN 2001). It is one of the 72 species that have been observed in Italian waters (Vacchi & Serena, 2010), the biology and ecology of this shark is still quite misunderstood. Despite being aware of the importance of this species in the marine ecosystem (Carey et al., 1982; Casey & Pratt, 1985; Klimley et al., 1992) and in spite attention paid to it by the public, much remains to be discovered about the Mediterranean Great White Shark. The aim of the present work was to organize and analyze data concerning the spatiotemporal pattern of distribution of white sharks along Italian coasts, collected by international LEM programme database and by other contributions

DNA from historical and trophy samples provides insights into white shark population origins and genetic diversity

This work was supported by Aberdeen University, the Marine Biological Association and Save Our Seas Foundation (SOSF). We thank Mr Oliver Crimmen, Dr Colin MacLeod, Dr Sharon Mitchell and Patricia Crombie for their support, Dr Takashi Sawada for valuable comments on elasmobranch tooth formation and Professor Richard Aspden for use of the freezer mill for grinding osteodentine. Thanks to Steffano Vanni, Giuseppe Guarrasi, Enrico Bellia, Helmut Wellendorf, Radek Šanda, Peter Adamik and Georges Lenglet for allowing access to material from museum and private collections.Peer reviewedPublisher PD

A comprehensive analysis of tidal notches in the Mediterranean Sea

Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology. Our results suggest that, considering 'the development of tidal notches the consequence of midlittoral bioerosion' (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development. Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them

Reply to comment by Evelpidu N., and Pirazzoli P. on "Tidal notches in the Mediterranean sea: A comprehensive analysis"

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