Massive salt accumulations, or salt giants, have formed in highly restricted marine basins throughout geological history, but their impact on biodiversity has been only patchily studied. The salt giant in the Mediterranean Sea formed as a result of the restriction of its gateway to the Atlantic during the Messinian Salinity Crisis (MSC) 5.97 to 5.33 million years ago. Here, we quantify the biodiversity changes associated with the MSC based on a compilation of the Mediterranean fossil record. We conclude that 86 endemic species of the 2006 pre-MSC marine species survived the crisis, and that the present eastward-decreasing richness gradient in the Mediterranean was established after the MSC.

Understanding deep-time marine biodiversity change under the combined effects of climate and connectivity changes is fundamental for predicting the impacts of modern climate change in semi-enclosed seas. We quantify the Late Miocene–Early Pliocene [11.63 to 3.6 million years (Ma)] taxonomic diversity of the Mediterranean Sea for calcareous nannoplankton, dinocysts, foraminifera, ostracods, corals, molluscs, bryozoans, echinoids, fishes, and marine mammals. During this time, marine biota was affected by global climate cooling and the restriction of the Mediterranean’s connection to the Atlantic Ocean that peaked with the Messinian salinity crisis. Although the net change in species richness from the Tortonian to the Zanclean varies by group, species turnover is greater than 30% in all cases, reflecting a high degree of reorganization of the marine ecosystem after the crisis. The results show a clear perturbation already in the pre-evaporitic Messinian (7.25 to 5.97 Ma), with patterns differing among groups and subbasins.

Paleobiological and paleoecological interpretations rely on constraining the temporal resolution of the fossil record. The taphonomic clock, that is, a correlation between the alteration of skeletal material and its age, is an approach for quantifying time-averaging scales. We test the taphonomic clock hypothesis for marine demersal and pelagic fish otoliths from a 10–40 m depth transect on the Mediterranean siliciclastic Israeli shelf by radiocarbon dating and taphonomic scoring. Otolith ages span the last ~8000 yr, with considerable variation in median and range along the transect. Severely altered otoliths, contrary to pristine otoliths, are likely to be older than 1000 yr. For pelagic fish otoliths, at 30 m depth, taphonomic degradation correlates positively with postmortem age. In contrast, no correlation occurs for demersal fishes at 10 and 30 m depth, mostly because of the paucity of very young pristine (<150 yr) otoliths, possibly due to a drop in production over the last few centuries. Contrary to molluscan and brachiopod shells, young otoliths at these depths are little affected and do not show a broad spectrum of taphonomic damage, because those that derive from predation are excreted in calcium- and phosphate-rich feces forming an insoluble crystallic matrix that increases their preservation potential. At 40 m depth, all dated otoliths are very young but rather damaged because of locally chemically aggressive sediments, thus showing no correlation between taphonomic grade and postmortem age. Our results show that local conditions and the target species population dynamics must be considered when testing the taphonomic clock hypothesis.

The early Miocene mollusc faunas from the Proto-Mediterranean Sea are still poorly-known. Herein, Aquitanian gastropod assemblages from the Felli section in NW Greece are described. Two assemblages were recovered, a low-diversity coastal mudflat assemblage dominated by Granulolabium plicatum (Bruguière, 1792) and Mesohalina margaritacea (Brocchi, 1814), and a high-diversity marine assemblage dominated by Bittium larrieyense (Vignal, 1911). The marine assemblage yielded 44 species, of which three species are described as new and 23 are left in open nomenclature. A new combination is proposed for Finella perpusilla (Grateloup, 1827). The family Pyramidellidae is exceptionally represented by 15 species. 17 new occurences are reported for the Proto-Mediterranean Sea. Alvania amphitrite n. sp., Homalopoma acaste n. sp. and Pyramistomia aliakmoni n. sp. are introduced as new species.

Degradation of coastal environments is an issue that many areas in Europe are facing. In the present work, an ancient coastal lake wetland is investigated, the so-called Lake Lerna in NE Peloponnese, Greece. The area hosted early agricultural populations of modern Greece that started modifying their environment as early as the early–middle Neolithic. Two drill cores in the area of the ancient lake were analysed to establish the sedimentological succession and the depositional environments using sub-fossil assemblages (molluscs and ostracods). Three lithological and faunal units were recovered, the latter being confirmed by the statistical ordination method (non-metric multidimensional scaling). The usage of sub-fossil mollusc species for the first time in the region enriched the dataset and contributed significantly to the delimitation of the faunas. These consist of environments characterised by various levels of humidity (from stagnant waters to freshwater lake) and salinity, with ephemeral intrusions of salt water to the lake, documented by mollusc and ostracod populations. We conclude that the lake and its included fauna and flora were mostly affected by climatic fluctuations rather than human intervention in the area.

Well-preserved leaves and rhizomes of the Mediterranean endemic marine angiosperm Posidonia oceanica and the rich associated mollusc and fish fauna are contained in the early Pleistocene shallow siliciclastic sediments of the Kritika Formation of the island of Rhodes (Greece). The leaf moulds are preserved in fine-grained sands, whereas the rhizomes are found in situ within coarse-grained sediments. The associated molluscan fauna includes 79 species, 47 gastropods and 32 bivalves, most of them extant. The rhizome-associated community comprises 49 species and the leaves-associated community includes 30 species. Small gastropods grazing on microalgae (Rissoidae, Cerithiidae, Trochidae) are the most abundant elements of the fauna, however carnivorous gastropods (Nassariidae, Naticidae, Muricidae) are also diverse. Among the bivalves Lucinidae (e.g., Lucinella) numerically dominate the deeper infauna and other chemosymbiont bivalves, as Ungulinidae (Diplodonta) are also common. Although many species are not associated exclusively with this seagrass and they may occur in other environments as well, they generally thrive on P. oceanica leaves and rhizomes. The Posidonia oceanica meadows were also inhabited by several characteristic fish species which thrive in the seagrass meadows of the eastern Mediterranean until today. The studied fauna is the first reported from the early Pleistocene of Greece and shows similarities to the modern counterparts of Posidonia oceanica meadows, providing new data on the resilience of seagrass ecosystems to environmental change in general.