Native biodiversity collapse in the eastern Mediterranean

Abstract

Global warming causes the poleward shift of the trailing edges of marine ectotherm species distributions. In the semi-enclosed Mediterranean Sea, continental masses and oceanographic barriers do not allow natural connectivity with thermophilic species pools: as trailing edges retreat, a net diversity loss occurs. We quantify this loss on the Israeli shelf, among the warmest areas in the Mediterranean, by comparing current native molluscan richness with the historical one obtained from surficial death assemblages. We recorded only 12% and 5% of historically present native species on shallow subtidal soft and hard substrates, respectively. This is the largest climate-driven regional-scale diversity loss in the oceans documented to date. By contrast, assemblages in the intertidal, more tolerant to climatic extremes, and in the cooler mesophotic zone show approximately 50% of the historical native richness. Importantly, approximately 60% of the recorded shallow subtidal native species do not reach reproductive size, making the shallow shelf a demographic sink. We predict that, as climate warms, this native biodiversity collapse will intensify and expand geographically, counteracted only by Indo-Pacific species entering from the Suez Canal. These assemblages, shaped by climate warming and biological invasions, give rise to a ‘novel ecosystem’ whose restoration to historical baselines is not achievable.

Natural experiments and long-term monitoring are critical to understand and predict marine host–microbe ecology and evolution

“…The gradual increase in salinity caused by the expansion of the Panama Canal, along with predicted increased runoff and evaporation, will likely result in greater movement of marine species between the tropical Western Atlantic and the TEP [ 84 ] ( Fig 4 ). Construction of the Suez Canal in 1869 caused an influx of saline water into the Mediterranean that was followed by the intrusion of invasive species from the subtropical Red Sea [ 85 ]. Rats introduced to islands of the Chagos Archipelago precipitated a decline in bird density, thereby reducing the nitrogen input on land and in the sea with downstream effects on coral reef productivity [ 86 ].…”

At the crossroads: early Miocene marine fishes of the proto-Mediterranean Sea

“…In the area of the Western Tethys, the late Eocene-middle Miocene MHB (Fig. 5) constituted a marine corridor at the border between the proto-Mediterranean and the Paratethys (Rögl, 1998); the proto-Mediterranean Sea developed due to the closure of the western part of the Tethys Ocean (Bialik et al, 2019;Torfstein and Steinberg, 2020). At this time, the proto-Mediterranean Sea, including the MHB, transited from a global biodiversity hotspot to a subtropical marine sea (Renema et al, 2008).…”

“…Connectivity between marine realms largely controls the fate of fish populations and biodiversity (Worm and Tittensor, 2018). Early Miocene proto-Mediterranean biodiversity is particularly interesting because, at that time, the basin's connection with the Indo-Pacific realm ceased to exist (Rögl, 1998;Bialik et al, 2019;Torfstein and Steinberg, 2020;Sun et al, 2021), while the marine biodiversity hotspot was shifting toward the southeast (Renema et al, 2008) and the climate was cooling (Cornacchia et al, 2018), marking the onset of a subtropical gradually oligotrophic regime in the proto-Mediterranean Sea. However, the early Miocene fossil fish record from the Mediterranean area is particularly sparse.…”

Low Pufferfish and Lionfish Predation in Their Native and Invaded Ranges Suggests Human Control Mechanisms May Be Necessary to Control Their Mediterranean Abundances

“…For example, around the island of Rhodes (Greece), 11 out of 88 fish species recorded were found to be non-native species (Kalogirou et al, 2010). Lessepsian migrants make up 85% of total teleost abundance in southeastern Turkey in 2015 (Mavruk et al, 2017), and are likely the cause of a native mollusk population collapse in Israel (Albano et al, 2021). Knowledge of a system's predators for an invasive species can help understand the potential direct and indirect impacts of the new species in the food web and evaluate the potential resiliency of the native community to this disturbance (Grüss et al, 2017;Chagaris et al, 2020).…”