Paleogeographic changes have significantly shaped ocean circulation and climate dynamics throughout Earth’s history. This study integrates geological proxies with climate simulations to assess how ocean gateway evolution influenced ocean salinity near the end of the Mesozoic (~66 Ma). Our modeling results demonstrate that 1) Central American Seaway shoaling reorganizes ocean currents, and 2) Arctic marine gateway restrictions, confining Arctic–Global Ocean exchange exclusively to the Greenland–Norwegian Seaway, drive Arctic Ocean surface freshening and southward outflow of buoyant, low-salinity waters. However, only the combined effect of these two factors leads to both Arctic freshening and increased water mass stratification in the Greenland–Norwegian Seaway, proto-North Atlantic, and the Western Tethys. This scenario aligns with Maastrichtian palynological, micropaleontological, and geochemical records from high- and low-latitude sites. Our findings highlight the profound impact of these latest Cretaceous paleogeographic reconfigurations in altering global salinity patterns, underscoring their role as key drivers of global climate dynamics.

In tropical regions, seagrass meadows provide a unique habitat for benthic foraminifera, both serving as important ecosystem engineers and sensitive indicators of coastal marine ecosystems. However, their interactions remain poorly understood, particularly in the context of anthropogenic pressures and climate change. This study investigates benthic foraminiferal assemblages associated with the tropical seagrass Halophila stipulacea in the Gulf of Aqaba-Eilat (GoA) as a model system to monitor natural and anthropogenic changes. Sampling was conducted during 11 campaigns (January 2020–April 2021) at two sites: South Coast (SC), a pristine shoreline, and North Coast (NC), an urbanized area. At each site, samples were collected from three distinct environments: seagrass leaves (L), sediments within meadows (SIM), and sediments outside meadows (SOM).

Throughout all of the sampling period, we found higher abundance and diversity of benthic foraminifera in sediments within H. stipulacea meadows (SIM) compared with sediments outside meadows (SOM). These results demonstrate that H. stipulacea creates a favorable environment for benthic foraminifera compared to adjacent bare sediments. Notably, the occurrence of certain foraminiferal species in the GoA is directly linked to the presence of seagrass. The leaves also serve as nurseries for juvenile Amphistegina, a key cosmopolitan symbiont-bearing genus. Additionally, the seagrass meadows appear to mitigate anthropogenic impacts, maintaining “healthy” foraminiferal assemblages even in the urbanized northern region of the GoA (NC). These findings highlight the ecological importance of seagrass meadows for benthic foraminifera and emphasize their susceptibility to anthropogenic stressors.

Calcifying foraminifera from the orders Rotaliida and Miliolida are widely used as geochemical proxies for recording paleoceanographic conditions, while agglutinated foraminifera are often overlooked since their tests are mostly composed of foreign particles. This study investigated the geochemical properties of Textularia agglutinans, a cosmopolitan agglutinated benthic species from the order Textulariida which has an exceptional inner calcareous test and is evolutionarily basal to Rotaliida. This study confirms the evolutionary link between textulariids and rotaliids based on their geochemistry and establishes T. agglutinans as a geochemical recorder of marine environments. Specimens from the Mediterranean coast of Israel were analyzed using laser ablation ICP-MS and compared to whole-test ICP-MS measurements of rotaliid and miliolid taxa from the same location. An Mg/Ca temperature calibration was established by LA-ICP-MS analyses of cultured specimens at 15, 17, 20, and 25 °C. Results show that T. agglutinans is a mid-Mg species (~19 to ~60 mmol/mol), with an Mg/Ca temperature correlation similar to high-Mg species. Its Pb, Zn, and Mn/Ca ratios are variable, generally overlapping with rotaliids and significantly lower than miliolids. Notably, T. agglutinans exhibits significantly higher Sr/Ca ratios (3.2 to 4.7 mmol/mol) compared to most foraminifera. Raman analyses reveal that the inner wall comprises a mix of aragonite and calcite, explaining these elevated Sr/Ca ratios. Rotaliida are the most prolific group of calcifying foraminifera. Our findings suggest that rotaliid tests evolved from an agglutinated textulariid ancestor with an inner aragonitic wall, a hypothesis that is further supported by the close phylogenetic relationship of the two groups.

Due to ongoing ocean warming, subtropical environments are becoming accessible to tropical species. Among these environments are the vermetid reefs of the Southeastern Mediterranean (SEM). In the last decades, these valuable coastal habitats witnessed the proliferation of numerous alien species of tropical origin. Among the meiofauna thriving on these reefs are benthic foraminifera, single cell marine organisms that make a significant contribution to global carbonate production. It has been widely recognized that benthic foraminifera, among other invasive species, thrive in the macroalgal cover, and it has been suggested that their populations are becoming a significant new source of sediment substrate. Here, we report on the first systematic assessment of the population size of the benthic foraminifera, allowing a comparison with data from the native tropical habitat of these species. Our study is based on a seasonal sampling of benthic foraminifera from confined sampling areas at four sites along the vermetid reef platforms of the Israeli SEM coast. Our survey reveals a patchy distribution of each species with peak population densities exceeding 100,000 specimens per m², making the SEM a hotspot of benthic foraminifera, with population densities comparable to tropical coral reef environments. The assemblages of the SEM hotspot are dominated by cosmopolitan foraminiferal taxa and tropical invaders from the Indo-Pacific (e.g., Amphistegina lobifera, Pararotalia calcariformata, soritids, and Hauerina diversa). In contrast to foraminiferal hotspots in the tropics, which are completely dominated by larger symbiont-bearing taxa, the SEM hotspot stands out due to high abundances of non-symbiont-bearing species Textularia agglutinans and small miliolids. An intriguing observation is the significant heterogeneity in composition and density of foraminiferal assemblages between the vermetid reefs' southern and northern areas (Israel), indicating that the productivity of the dominant species are also modulated by local yet unknown environmental factors.

In sub/tropical waters, benthic foraminifera are among the most abundant epiphytic organisms inhabiting seagrass meadows. This study explored the nature of the association between foraminifera and the tropical seagrass species H. stipulacea, aiming to determine whether these interactions are facilitative or random. For this, we performed a "choice" experiment, where foraminifera could colonize H. stipulacea plants or plastic "seagrasses" plants. At the end of the experiment, a microbiome analysis was performed to identify possible variances in the microbial community and diversity of the substrates. Results show that foraminifera prefer to colonize H. stipulacea, which had a higher abundance and diversity of foraminifera than plastic seagrass plants, which increased over time and with shoot age. Moreover, H. stipulacea leaves have higher epiphytic microbial community abundance and diversity. These results demonstrate that seagrass meadows are important hosts of the foraminifera community and suggest the potential facilitative effect of H. stipulacea on epiphytic foraminifera, which might be attributed to a greater diversity of the microbial community inhabiting H. stipulacea.

In this study we revisited the Cretaceous of the Eratosthenes Seamount (ESM) from IODP LEG 160 Hole 967E, updating the chronology, depositional environment, and paleobathymetry of the ESM. Our goal was also to address the spatio-temporal distribution of organic matter and, by comparison with the eastern margins of the Levant Basin, discuss basin-wide controls on its deposition and preservation.

The investigated core has a relatively continuous Cretaceous succession from the Aptian to the Danian. By identifying the Pα Zone we conclude that the base of the Paleocene is included in the 967E section. A total of 17 ages were identified, with low sedimentation rates of 0.04–

2.37 cm/kyr. Petrographic analysis revealed pronounced differences, from micritic pellets, benthic foraminifera, algae, and mollusks in the bottom part of the core, to deep water facies in the uppermost Cretaceous. Paleobathymetry ranged between 0.5 and 5 m in the Aptian to 300–600 m in the Maastrichtian.

Both high productivity and OMZ conditions prevailed during the Cenomanian–Turonian, as well as elsewhere in the eastern Mediterranean. While the low core recovery might affect reliable interpretation, we present two alternative explanations for the high vs. low organic content of the Campanian–Maastrichtian in the eastern Levant Basin vs. the ESM: (1) Location relative to upwelling cells; (2) Relative bathymetry, with the ESM representing a paleohigh for much of the Cretaceous, similar to the organic-poor anticline deposits in the eastern Levant, where the massive intervals of organic-rich carbonates accumulated only in the synclines of the Syrian Arc deformational belt.

Rising sea surface temperatures and extreme heat waves are affecting symbiont-bearing tropical calcifiers such as corals and Large Benthic Foraminifera (LBF). In many ecosystems, parallel to warming, global change unleashes a host of additional changes to the marine environment, and the combined effect of such multiple stressors may be far greater than those of temperature alone. One such additional stressor, positively correlated to temperature in evaporation-dominated shallow-water settings is rising salinity. Here we used laboratory culture experiments to evaluate the combined thermohaline tolerance of one of the most common LBF species and carbonate producer, Amphistegina lobifera. The experiments were done under ambient (39 psu) and modified (30, 45, 50 psu) salinities and at optimum (25 °C) and warm temperatures (32 °C). Calcification of the A. lobifera holobiont was evaluated by measuring alkalinity loss in the culturing seawater, as an indication of carbonate ion uptake. The vitality of the symbionts was determined by monitoring pigment loss of the holobiont and their photosynthetic performances by measuring dissolved oxygen. We further evaluated the growth of Peneroplis (P. pertusus and P. planatus), a Rhodophyta bearing LBF, which is known to tolerate high temperatures, under elevated salinities. The results show that the A. lobifera holobiont exhibits optimal performance at 39 psu and 25 °C, and its growth is significantly reduced upon exposure to 30, 45, 50 psu and under all 32 °C treatments. Salinity and temperature exhibit a significant interaction, with synergic effects observed in most treatments. Our results confirm that Peneroplis has a higher tolerance to elevated temperature and salinity compared to A. lobifera, implying that a further increase of salinity and temperatures may result in a regime shift from Amphistegina- to Peneroplis-dominated assemblages.

Global warming permits range expansions of tropical marine species into mid-latitude habitats, where they are, however, faced with cold winter temperatures. Therefore, tolerance to cold temperatures may be the key adaptation controlling zonal range expansion in tropical marine species. Here we investigated the molecular and physiological response to cold and heat stress in a tropical symbiont-bearing foraminifera that has successfully invaded the Eastern Mediterranean. Our physiological measurements indicate thermal tolerance of the diatom symbionts but a decrease in growth for the foraminifera host under both cold and warm stress. The combined (‘holobiont’) transcriptome revealed an asymmetric response in short-term gene expression under cold versus warm stress. Cold stress induced major reorganization of metabolic processes, including regulation of genes involved in photosynthesis. Analyses limited to genes that are inferred to belong to the symbionts confirm that the observed pattern is due to changes in the regulation of photosynthesis-related genes and not due to changes in the abundance of the symbionts. In contrast to cold stress, far fewer genes change expression under heat stress and those that do are primarily related to movement and cytoskeleton. This implies that under cold stress, cellular resources are allocated to the maintenance of photosynthesis, and the key to zonal range shifts of tropical species could be the cold tolerance of the symbiosis.

The recent growing interest in Late Cretaceous biserial planktonic foraminifera (heterohelicids) has greatly enhanced their use as paleoceanographic and biostratigraphic markers. Pseudotextularia nuttalli, one of the most common cosmopolitan planktonic foraminifera, has an exceptionally long evolutionary range (Turonian-Maastrichtian). The image processing procedure we developed in this study enabled us to document changes in the growth pattern of Ps. nuttalli over time and between different oceanic provinces, and to identify possible speciation events within this lineage. The analysis was complemented by morphometric measurements of the penultimate chamber and test.

The morphometric analyses do not indicate an early speciation event within this lineage, and thus, do not support splitting to Planoheterohelix praenuttalli (Turonian-Coniacian) and Pseudotextularia nuttalli (Coniacian-Maastrichtian). Our results indicate a gradual phyletic increase in mean test size from the Santonian through the Maastrichtian, along with increasing morphological diversification. This trend seems to coincide with the global cooling that culminated in the Late Cretaceous.

Comparing between Ps. nuttalli from different oceanic provinces reveals that the Southern Tethys specimens are significantly less developed than their counterparts from the two tropical oceanic localities. This adaptive responsiveness suggests a negative correlation between test size and high productivity conditions in the upper water column.

The case of Ps. nuttalli lineage exemplifies how extraordinary long-range species (>30 My) can evolutionarily change over time from “primitive” to “developed” forms, without showing a morphological gap. Such species may also show adaptive morphological diversification in response to different environments and, thus, are valuable for palaeoceanographic and paleoecologic reconstructions.

The recovery time of marine productivity following the Cretaceous-Paleogene (KPg) mass extinction varies tremendously with location (hundreds to millions of years), with possible delays in the tropics as compared to higher latitudes. This heterogeneity is based on prevalent oligo- to mesotrophic marine environments. While highly productive eutrophic environments are less prevalent, they play a greater role in the carbon cycle. Here we present data from a eutrophic region within the tropical southern Tethys. Records of both organic matter and calcite production in this locality exhibit stability across the KPg boundary. In addition, our study points to a remarkably rapid recovery (<11 kyr), even possibly continuous high productivity across the KPg boundary, despite the tropical location. Moreover, the characteristic KPg δ¹³C negative excursion is observed in our locality, but is independent of high productivity, possibly indicating a reduction in the δ¹³C of the DIC of the ocean due to the input of light carbon from the atmosphere. Thus, this study provides new insight into the functioning of eutrophic ecosystems during environmental stress imposed by the ecological crisis.