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The isotopic and elemental composition of the fossil shells of foraminifera are often used for reconstructing past environments and climates. These so-called proxy relations are based on the effect of environmental conditions (e.g. seawater temperature, pH) on the isotopic ratio (e.g. δ11 B or δ18 O) or partitioning of elements (commonly expressed as El/Ca or DEl ) during calcification. Whereas many studies focused on proxy-calibrations of divalent cations, incorporation of monovalent cations are less well constrained. Here we calibrate shell potassium content (K/Cacc) as a function of 1) seawater K+ concentration, 2) the ratio of potassium and calcium in seawater (K/Casw) and 3) temperature. Moreover, we analyze Na+ incorporation into the calcite as a function of seawater K+ and Ca2+ concentrations. First, we cultured specimens of the larger benthic foraminifer at four different seawater [Ca2+] and constant [K+], resulting in a range of K/Casw. Secondly, we cultured specimens of the same species at four different [Ca2+]sw and [K+]sw while keeping the ratio between these two ions constant. Finally, we tested the effect of temperature (from 18 to 28°C) on K-incorporation in this species. Measured K/Cacc values are not notably affected by [Ca2+]sw, while seawater [K+] positively influences potassium incorporation, resulting in a positive correlation between seawater K/Ca values and K/Cacc. Although the [Na+] in the culture media was constant throughout both experiments, incorporated Na responded positively to decreasing [Ca2+]sw, resulting in a positive correlation between sea water Na/Ca and Na/Cacc. The difference in the controls on K- and Na-incorporation suggests that the (biological) control on these ions differs. Part of the observed variability in element partitioning may be explained by differences in chemical speciation and crystallographic coordination in the calcite lattice. [ABSTRACT FROM AUTHOR]

Since the industrial revolution the ocean has become noisier. The global increase in shipping is one of the main contributors to this. In some regions, shipping contributed to an increase in ambient noise of several decibels, especially at low frequencies (10 to 100 Hz). Such an increase can have a substantial negative impact on fish, invertebrates, marine mammals and birds interfering with key life functions (e.g. foraging, mating, resting, etc.). Consequently, engineers are investigating ways to reduce the noise emitted by vessels when designing new ships. At the same time, since the industrial revolution (starting around 1760) greenhouse gas emissions have increased the atmospheric carbon dioxide fraction x(CO2) by more than 100 mmol mol-1. The ocean uptake of approximately one third of the emitted CO2 decreased the average global surface ocean pH from 8.21 to 8.10. This decrease is modifying sound propagation, especially sound absorption at the frequencies affected by shipping noise lower than 10 kHz, making the future ocean potentially noisier. There are also other climate change effects that may influence sound propagation. Sea surface warming might alter the depth of the deep sound speed channel, ice melting could locally decrease salinity and more frequent storms and higher wind speed alter the depth of the thermocline. In particular, modification of the sound speed profile can lead to the appearance of new ducts making specific depths noisier. In addition, ice melting and the increase in seawater temperature will open new shipping routes at the poles increasing anthropogenic noise in these regions. This review aims to discuss parameters that might change in the coming decades, focusing on the contribution of shipping, climate change and economic and technical developments to the future underwater soundscape in the ocean. Examples are given, contrasting the open ocean and the shallow seas. Apart from the changes in sound propagation, this review will also discuss the effects of water quality on ship-radiated noise with a focus on propeller cavitation noise. [ABSTRACT FROM AUTHOR]

Sedimentary bulk organic matter and various molecular organic components exhibit strong CO 2 -dependent carbon isotope fractionation relative to dissolved inorganic carbon sources. This fractionation (εp) has been employed as a proxy for paleo- p CO 2. Yet, culture experiments indicate that CO 2 -dependent εp is highly specific at genus and even species level, potentially hampering the use of bulk organic matter and non-species-specific organic compounds. In recent years, significant progress has been made towards a CO 2 proxy using controlled growth experiments with dinoflagellate species, also showing highly species-specific εp values. These values were, however, based on motile specimens, and it remains unknown whether these relations also hold for the organic-walled resting cysts (dinocysts) produced by these dinoflagellate species in their natural environment. We here analyze dinocysts isolated from core tops from the Atlantic Ocean and Mediterranean Sea, representing several species (Spiniferites elongatus, S. (cf.) ramosus, S. mirabilis, Operculodinium centrocarpum sensu Wall and Dale (1966) (hereafter referred to as O. centrocarpum) and Impagidinium aculeatum) using laser ablation–nano-combustion–gas-chromatography–isotope ratio mass spectrometry (LA/nC/GC-IRMS). We find that the dinocysts produced in the natural environment are all appreciably more 13 C-depleted compared to the cultured motile dinoflagellate cells, implying higher overall εp values, and, moreover, exhibit large isotope variability. Where several species could be analyzed from a single location, we often record significant differences in isotopic variance and offsets in mean δ13 C values between species, highlighting the importance of single-species carbon isotope analyses. The most geographically expanded dataset, based on O. centrocarpum, shows that εp correlates significantly with various environmental parameters. Importantly, O. centrocarpum shows a CO 2 -dependent εp above ∼ 240 µ atm p CO 2. Similar to other marine autotrophs, relative insensitivity at low p CO 2 is in line with active carbon-concentrating mechanisms at low p CO 2 , although we here cannot fully exclude that we partly underestimated εp sensitivity at low p CO 2 values due to the relatively sparse sampling in that range. Finally, we use the relation between εp and p CO 2 in O. centrocarpum to propose a first p CO 2 proxy based on a single dinocyst species. [ABSTRACT FROM AUTHOR]

The chemical composition of foraminiferal shells is a well-known tool in paleoceanography to reconstruct past environments and climate. Their application is based on the relation between environmental variables and the concentration of elements incorporated or stable isotope fractionation during calcification. The vast majority of these so-called proxy relationships are based on the foraminiferal order of the Rotaliida, which, for example, encompasses all living planktonic species. However, there are more orders of foraminifera with calcifying members, some of which have fundamentally different biomineralization pathways, such as the Nodosariida, the Polymorphinida and the Vaginulinida. All these belong to the class of the Nodosariata and produce calcite shells, which may serve as carriers of paleoenvironmental and climate signals. The microstructures of these shells and overall morphology of these foraminifera strongly deviate from the Rotaliida, suggesting that their elemental and stable isotopic composition do not necessarily respond similarly to environmental parameters. A potential advantage of the Nodosariata is that they appear considerably earlier in the fossil record (Carboniferous) than the Rotaliida (Jurassic), thereby possibly extending the range of foraminifer-based paleoceanographic reconstructions considerably. To test the potential application of Nodosariata foraminifera as paleoproxies, we investigated incorporation of 5 elements in 11 species as a function of environmental parameters from a transect sampled in the Gulf of Mexico. Their element composition (B / Ca, Na / Ca, Mg / Ca, Sr / Ca and Ba / Ca) shows a distinct geochemical signature for these foraminifera, different to that of members of other foraminiferal orders. Results also show an increase in Mg / Ca values with increasing temperature, similar to that known for the Rotaliida, which suggest that Nodosariata shells might be useful for paleotemperature reconstructions. The difference in Mg / Ca–temperature calibration in Nodosariata compared to Rotaliida, with the large differences in their morphology, shell microstructures and overall geochemical composition, suggests that the Mg / Ca-to-temperature relationship is partly independent of the exact calcification mechanism. We compare Mg / Ca–temperature sensitivities across foraminiferal orders and describe a relationship between the average Mg / Ca and the sensitivity of the Mg / Ca–temperature calibration. For other elements, the variability across orders is smaller compared to that in Mg / Ca, which results in more similar El / Ca–environmental calibrations. [ABSTRACT FROM AUTHOR]