Dongyu Chen

Fanny Thibon

Axel Felbacq

Lucas Weppe

Marc Metian

Nathalie Vigier

Coupled survey of lithium isotopes and Li/Ca in biogenic and inorganic carbonates

Keywords: lithium isotopes, Li/Ca, marine carbonates, vital effects, synthesis

Geochemists have long considered Li isotope composition of marine carbonates as one of the most straightforward oceanic archives, tracing climate regulation by continental silicate weathering. However, despite an isotopically homogenous ocean, a large range of δ 7 Li values were reported in the literature for modern biogenic carbonates. Additionally, laboratory studies highlighted variable Li isotope fractionations during foraminifera growth and during precipitation of inorganic carbonates.

Despite an increasing interest in this topic, there is still limited understanding of Li isotopic fractionation and of Li incorporation mechanisms in carbonates. The present review aims to filling this gap by compiling and meta-analyzing the past findings from the literature. More specifically, Li/Ca and δ 7 Li data concerning the influence of mineralogy, temperature, pH, growth rate and biological processes have been exhaustively reviewed and statistically examined, including by PCA (Principal Component Analysis). For inorganic carbonate, we demonstrate that (1) the influence of mineral type is insufficiently explored (2) the effect of temperature on Li isotopes is negligible, although temperature changes can affect calcite Li/Ca ratio, and (3) calcite δ 7 Li and Li/Ca are primarily influenced by pH and growth rate.

For marine modern biogenic carbonates, our cartography highlights an uneven geographical distribution, and further studies are required in the Pacific, Indian, and Southern Oceans. Also, for both Li/Ca and δ 7 Li, there are statistically significant and systematic differences between 'bulk carbonates' and all studied marine biogenic groups (i.e. foraminifera, mollusks, brachiopods). A detailed examination of foraminifera data reveals that planktic species display δ 7 Li values statistically higher than benthic ones, and both anti-correlate with Li/Mg ratios. Overall, this review underlines the necessity of filling the identified gaps of knowledge and of attentively considering the impact of environmental parameters and biological processes for interpreting past δ 7 Li variations displayed by fossil shells.

Introduction

Lithium (Li) is the least dense of all metals and naturally occurs in the environment as a free Li + ion surrounded by water molecules [START_REF] Olsher | Coordination chemistry of lithium ion: A crystal and molecular structure review[END_REF]. During the formation of carbonates in the ocean, Li can be incorporated as a trace element in their crystallographic structure and its Li isotopic composition has been used to reconstruct the ocean Li isotope variations for inferring the relationship between climate, pCO 2 (partial pressure of carbon dioxide), and continental silicate weathering [START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF][START_REF] Kalderon-Asael | A lithium-isotope perspective on the evolution of carbon and silicon cycles[END_REF]Misra and Froelich, 2012). Indeed, Li is composed of two stable isotopes, 6 Li and 7 Li, representing 7.59% and 92.41%, respectively, with a high ability to fractionate. The Li isotopic variations observed on earth display the second largest range among non-conventional isotopes, with values exceeding 40‰ (Li isotopic composition being reported as δ 7 Li = ([( 7 Li/ 6 Li)/( 7 Li/ 6 Li) L-SVEC -1] × 1000, L-SVEC being the international standard provided by the US National Institute of Standards and Technology).

Modern oceans contain approximately 230 billion tons of Li. Their primary sources of Li are rivers and high-temperature hydrothermal fluids, which have modern fluxes of similar magnitude, of about 10×10 9 and 13×10 9 mol year -1 , respectively (Misra and Froelich, 2012).

The average δ 7 Li value of modern river waters is 23‰, with a range from 2‰ to 43‰ [START_REF] Dellinger | Riverine Li isotope fractionation in the Amazon River basin controlled by the weathering regimes[END_REF][START_REF] Huh | Lithium and its isotopes in major world rivers; implications for weathering and the oceanic budget[END_REF], which is higher than for marine hydrothermal fluids (8.3‰) [START_REF] Chan | A lithium isotope study of hot springs and metabasalts from mid-ocean ridge hydrothermal systems[END_REF][START_REF] Chan | Lithium isotope geochemistry of sediments and hydrothermal fluids of the Guaymas Basin, Gulf of California[END_REF]. Owing to the large oceanic residence time of Li (~1.5 million year) [START_REF] Huh | Lithium and its isotopes in major world rivers; implications for weathering and the oceanic budget[END_REF], Li concentration and isotopic composition of seawater are spatially homogeneously distributed ([Li] SW ~ 26 μM; δ 7 Li SW = 31±0.3‰) in the modern ocean (Millot et al., 2004), except close to hydrothermal sites [START_REF] Artigue | Tracking the Lithium and Strontium Isotope Signature of Hydrothermal Plume in the Water Column: A Case Study at the EMSO-Azores Deep-Sea Observatory[END_REF].

During weathering of silicate rocks (e.g., incongruent continental weathering, off-axis seafloor alteration, and reverse weathering in marine sediments), 6 Li is preferentially incorporated into secondary minerals, leaving residual waters enriched in 7 Li (Chan et al., 1992;[START_REF] Huh | Lithium and its isotopes in major world rivers; implications for weathering and the oceanic budget[END_REF]Pistiner and Henderson, 2003). As a result, past variations in seawater δ 7 Li have primarily been attributed to changes in global weathering regimes in response to climate or tectonic events (Crockford et al., 2020;[START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF][START_REF] Kalderon-Asael | A lithium-isotope perspective on the evolution of carbon and silicon cycles[END_REF][START_REF] Lechler | Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)[END_REF]Misra and Froelich, 2012;[START_REF] Von Strandmann | Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2[END_REF]Sun et al., 2018).

Systematically, oceanic water δ 7 Li value is frequently assumed to be similar to the carbonate record. However, determining if the formation of biogenic carbonates in the ocean is related to significant and variable Li isotope fractionations remains challenging. Low Li concentrations in these mineral phases, effects of diagenesis, and potential contamination from Li-rich authigenic minerals may bias their pristine isotopic signatures (Bastian et al., 2018;Dellinger et al., 2020;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF]. It was not until the late 20 th century that scientists first analyzed four samples of Pleistocene foraminifera Pulleniatina obliquiloculata as well as two marine carbonates by thermal ionization mass spectrometry (TIMS) (You and Chan, 1996). Their results showed that foraminifera have lighter Li isotopic composition (19.3‰, 23.0‰) during glacial times, compared to interglacial (26.6‰, 42.2‰). Then, Hoefs and Sywall. (1997) found a large fluctuation (from 7‰ to 20‰) for mixed planktic species through the Holocene, partly attributed to inadequate sample cleaning. Kosler et al. (2001) measured δ 7 Li in core-top Pulleniatina obliquiloculata by Quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and reported δ 7 Li values from 27.9‰ to 31.3‰ (modern seawater value being 31.2‰ ± 0.3‰).

In the past, the determination of Li isotope compositions in marine carbonates was constrained by instrumentation with low precision, typically exceeded 2‰. More recently, the precision was improved (Table S1), For instance, Li isotopes have been measured in low level marine carbonates using Q-ICP-MS associated to a desolvating system, within ±1.6 ‰ (2) in precision (Misra and Froelich, 2009;[START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF], Vigier et al., 2008). The use of SIMS (Secondary Ion Mass Spectrometry / ion microprobe) also enables (in situ) δ 7 Li analyses for carbonate minerals, while avoiding contamination from surface Fe-oxydes and clays, with a reproducibility of 1.5‰ -2‰ (2) (e.g. [START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF][START_REF] Rollion-Bard | Effect of environmental conditions and skeletal ultrastructure on the Li isotopic composition of scleractinian corals[END_REF]. More recently, Multicollector-Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) have allowed to achieved the measurement of Li isotopes in multiple carbonates samples, with a precision of about 0.5‰-0.8‰ (2) (e.g. Dellinger et al., 2020;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF]. As a result, numerous δ 7 Li values have been published for various groups (e.g. foraminifera (Bastian et al., 2018;[START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF]Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF][START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF], corals (Bastian et al., 2018;Dellinger et al., 2018;Marriott et al., 2004;[START_REF] Rollion-Bard | Effect of environmental conditions and skeletal ultrastructure on the Li isotopic composition of scleractinian corals[END_REF], mollusks (Dellinger et al., 2018), echinoderms (Dellinger et al., 2018), brachiopods (Dellinger et al., 2018;Gaspers et al., 2021;[START_REF] Washington | Lithium isotope composition of modern and fossilized Cenozoic brachiopods[END_REF]), as well as for marine bulk carbonate extracted by sediment leaching (e.g. Dellinger et al., 2020;[START_REF] Murphy | Reconstructing the lithium isotopic composition (δ 7 Li) of seawater from shallow marine carbonate sediments[END_REF][START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF].

Cultures of calcifying species have been performed under controlled conditions (e.g. foraminifera (Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF] brachiopods (Gaspers et al., 2021), and mollusks (Dellinger et al., 2018)). Also, inorganic carbonate phases have been grown at the laboratory to study inorganic Li isotope fractionations (Δ 7 Li carb-sol ) and their controls, which were compared to their biogenic equivalent [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Füger et al., 2022;Gabitov et al., 2011;Marriott et al., 2004;Marriott et al., 2004;[START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF][START_REF] Taylor | Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxyan experimental approach[END_REF]. (Aragonite mussel (Dellinger et al., 2018)) to +9.7‰ (Calcite scallop (Dellinger et al., 2018)).

Theoretically, "vital effects" can be quantified when comparing the isotope signature of biogenic and inorganic phases (Dellinger et al., 2018;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF].

However, when we compile all published data from the literature, it appears that the range of Δ 7 Li carb-sol values in inorganic phases is as large as that of biogenic phases (see Fig. 1).

Consequently, it is difficult to use this method to demonstrate either the lack or the occurrence of biological Li isotope fractionations. Another key point is that the Li concentrations (or Li/Ca ratios) are rarely discussed while the environmental controls of biogenic Li concentrations may also impact Li isotopes (Thibon et al., 2021).

The present study compiles, to the best of our knowledge, all the published data on modern carbonates. Due to the low Li levels in modern marine carbonate, their Li concentration and isotopic compositions are easily influenced by silicate minerals present in the same environment (clay micrograins in particular) [START_REF] Von Strandmann | Lithium isotope evidence for enhanced weathering and erosion during the Paleocene-Eocene Thermal Maximum[END_REF]Dellinger et al., 2020;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF]Bastian et al., 2018;Dellinger et al., 2018;Misra and Froelich, 2009;[START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF][START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF]. As a consequence, our dataset does not include carbonates that have been affected by marine diagenesis. Since different authors may have inconsistent criteria for diagenetic imprint (e.g., Mn/Ca, Al/Ca, Sr/Fe, Li/(Mg+Ca), etc.), and there are significant differences in the criteria for assessing contamination in carbonate samples coming from different sites and sedimentary contexts, we strictly followed each authors' standards when selecting data to include.

Through statistical tests, we aim to clarify the potential differences in Li isotopic compositions and in Li/Ca among the various carbonate phases, and various categories, but also evaluate the role of environmental parameters when possible. This work also tentatively highlights the gaps to fill for future works in paleo-environment and paleoceanography. More detailed subset data can be found in the Sup. Mat. Table S2. Same references as in Table 1.

Multiple controls of Li/Ca and Li isotopes during inorganic carbonate growth

To date, seven studies investigated the Li isotopic composition of synthetic carbonates grown under controlled conditions [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Füger et al., 2022;Gabitov et al., 2011;Marriott et al., 2004;Marriott et al., 2004;[START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF][START_REF] Taylor | Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxyan experimental approach[END_REF]. While the study conducted by [START_REF] Taylor | Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxyan experimental approach[END_REF] focuses on carbonate formation at high temperatures (which is not discussed here), the remaining studies utilized a wide range of experimental conditions, as summarized in Table 2. Marriott et al. (2004a) were the pioneers in investigating the effect of temperature on the Li isotopic composition of inorganic carbonates. At different temperatures (5-30°C), calcite is synthesized by mixing CaCl 2 and NaHCO 3 solutions. The authors report a Li isotopic fractionation Δ 7 Li carb-sol ~ -8‰, unaffected by temperature. In contrast, calcite Li/Ca ratio decreases significantly with increasing temperature (from 7.51 to 2.47 μmol mol -1 ). Marriott et al. (2004b) further investigated the influences of minerals and salinity. Their results show that the mineral type has a decisive effect on Li isotopes. Indeed, the Li isotope fractionation during aragonite growth is relatively large (-11‰) compared to the calcite one (-3‰).

Salinity variations (from 10 to 50 psu) do not affect the Li isotopic composition for both minerals. Nevertheless, an increase in solution salinity increases the Li/Ca ratio of calcite (from 14.5 to 62.9 μmol mol -1 ), while aragonite Li/Ca remains essentially constant (19.3 μmol mol -1 ). Importantly, a comparison of the two studies (Marriott et al., 2004a and2004b) reveals a significant difference in the Li isotopic fractionation during calcite formation (of 5‰). One potential explanation might be the higher solution pH used in Marriott et al. (2004b) compared to Marriott et al. (2004a) (pH= 7.7 to 8.3 vs. 6.9 to 7.1, respectively).

Another factor could be that Marriott et al. (2004b) (2022) find that the Δ 7 Li carb-sol values range from -5.3‰ to -1.8‰, and decrease in magnitude when solution pH increases (under a growth rate of 10 -7.5 to 10 -7.9 mol m -2 s -1 ), or when the growth rate decreases (for 8.1 < pH < 8.4).

Overall, most experiments led to a lighter Li isotopic composition of the synthesized carbonates relative to the growth solution, except for a few data published by [START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF]. Additionally, all experiments led to significantly low D(Li) (< 10 -1 -10 In a seawater-like (synthetic) environment (Gabitov et al., 2011;Marriott et al., 2004), the Li isotope fractionation during calcite growth (-3.1‰ to -1.9‰) is smaller compared to one obtained during aragonite growth (-7.7‰ to -12‰). A similar phenomenon can be observed when deionized water is used; however, the extent of fractionation displayed by calcite synthesized in deionized water can be greater (-10.1‰ to +0.2‰) [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Füger et al., 2022;Marriott et al., 2004). Yet, more data are required for a reliable statistical treatment and establish the role of the solution chemical composition.

Concerning carbonate Li contents, we can compare different contexts and experiments by using Li partition coefficients (D(Li) = (Li/Ca) calcite / (Li/Ca) solution ).

For inorganic calcite, D(Li) range is wider than for inorganic aragonite (10 -5.7 -10 -2 and 10 -2.6 -10 -2.2 , respectively), but the number of data is scarce for the latter (Fig. 1).

For HMC there is currently only one data (10 -1.9 ).

Given that Li ions are incorporated differently into the calcite and the aragonite structures, a significant discrepancy between both phases would be expected for both

Li isotopes and D(Li). Indeed, Li ions substitute for the Ca ions site in aragonite, whereas in calcite, Li can be incorporated into interstitial positions in its hydrated form (Marriott et al., 2004a). This may explain why calcite D(Li) increases with increasing salinity, while aragonite D(Li) remains relatively stable when salinity varies (Marriott et al., 2004a). More data are however needed to better quantify these aspects, particularly for aragonite and HMC.

Small influence of temperature

Two studies found that the Li isotope fractionation between calcite and growth solution (Δ 7 Li carb-sol ) is negligibly affected by temperature [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Marriott et al., 2004a). [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF] experiment led to a slight but significantly negative correlation with temperature, as shown in Fig. 2A. In their experiment, other parameters such as pH and growth rate (see Fig. 2C,2E) varied as well, and among them it appears that temperature induced the smallest effect.

In contrast, D(Li) (expressed as logD(Li)) corresponding to synthetic calcites show a very consistent and negative correlation with temperature (R = -0.94, [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Marriott et al., 2004a). Thus, calcite formed at high temperatures contains less Li than at low temperatures (Fig. 2B). Both studies give consistent results and used a Ca solution enriched in Li as the growth medium, although the technique used to reach saturation was different (see Table 1). Interestingly, two other experimental studies of inorganic calcite formation (Füger et al., 2022;[START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF]

Significant influence of pH

Fig. 2C reveals a strong linear relationship between Li isotope fractionation for calcite and the solution pH. As the pH decreases, the extent of fractionation increases.

Similarly, for calcite, there is a significant linear relationship between the logD(Li)

and pH, where lower pH values correspond to higher logD(Li) values and (Fig. 2D).

The observed similarity in the behavior of Li isotope fractionation and elemental partitioning in calcite with respect to pH suggests the involvement of a common mechanism regulating both processes.

There is still controversy regarding the species in which Li is incorporated into forming carbonate, and if the solution pH may play a role. Some authors argue that there is only one type of Li incorporated into calcite, while others propose that there are more than two Li species, depending on the pH. For example, Seyedali et al.

(2021) suggested that over a large pH range (between 6.2 and 9.5), the most likely form of Li incorporation into calcite is as LiHCO 3 (rather than as Li 2 CO 3 or LiNaCO 3) .

The authors argue that in the absence of kinetic effects and with constant activity coefficients, the overall process of Li incorporation into calcite must maintain charge balance. Therefore, the equilibrium constants for the LiHCO 3 should remain unchanged as a function of pH (for a given growth rate). Fuger et al. (2019Fuger et al. ( , 2022)).

propose that the dominant reaction for Li incorporation into calcite is as follows:

Li + (aq) + H + (aq) + CaCO 3 (s) ⇋ LiHCO 3 (s) + Ca 2+ (aq) ,
which indicates that Li incorporation in calcite is not only related to the solution HCO 3 -, but also controlled by the Li + and Ca 2+ concentration of the solution. When the dissolved concentration of Ca 2+ and Li + are constant (e.g. Ca 2+ saturated solution), a decrease in pH triggers LiHCO 3 formation, and more Li can be incorporated into calcite. In contrast, when dissolved Ca concentration is not constant (the Ca 2+

concentration is usually increased at lower pH to keep an oversaturated medium), a lower pH results in less LiHCO 3 formation and, therefore, in less Li in calcite. This may explain why we observe a negative correlation between logD(Li) and pH in Fig.

2D

. Fuger et al. ( 2022) therefore suggest that LiHCO 3 is dominant within a specific pH range, rather than the entire range of 6.3 to 9.5.

Concerning Li isotopes, early precipitation experiments (Marriott et al., 2004a;Marriott et al., 2004b) did not consider pH as a potential variable because Li + in seawater mainly remains surrounded by four water molecules, in contrast with other biogeochemical tracers such as boron, for which speciation in seawater is known to be pH dependent (e.g. [START_REF] Foster | Reconstructing Ocean pH with Boron Isotopes in Foraminifera[END_REF]. Nevertheless, a positive correlation was recently found for inorganic calcite between Δ 7 Li carb-sol and solution pH [START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF][START_REF] Füger | Effect of growth rate and pH on lithium incorporation in calcite[END_REF]Marriott et al., 2004a;Marriott et al., 2004b). As the pH of the solution increases, the extent of fractionation of the calcite Li isotope decreases.

As shown in Fig. 2C, this pH effect may reconcile the isotopic discrepancy observed between the two Marriott et al. studies (2004a;2004b). In contrast, the stalactite experiments performed by [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF] exhibit a small (negative) correlation between Δ 7 Li carb-sol and solution pH, but the range of tested pH was narrow (from 7.4 to 8.3 Fig. 2C), and the calcite growth rate significantly higher. It cannot be excluded that variations in the Li aqueous speciation caused by changes in solution chemistry may induce changes in the equilibrium isotopic fractionation factor. Indeed, under a given growth rate and at isotopic equilibrium, if dissolved Li occurs under as a single specie only, the isotopic fractionation should remain constant.

Another parameter of importance is the Saturation Index (SI), which is often related to the solution pH. In our Fig. S2 (Supplementary Material), we can see that at a single SI, a large variation of isotopic fractionations can be found. Also, when SI increases significantly, relatively small  7 Li carb-sol variations are observed. This preliminary observation suggests a weak influence of the SI on Li isotopic fractionation. However, as experimental conditions among the various studies are very distinct in salinity, in solution chemical composition and in calcium concentrations, it is difficult to directly compare their SI values. More experimental work will need to be undertaken under natural seawater conditions to better evaluate the role of this parameter. Finally, it cannot be excluded that the trends as a function of pH (Fig. 2C and Fig. 2D) may also beat least partly -driven by growth rates.

Strong influence of growth rate

Currently, there are two articles investigating the influence of the growth rate of inorganic calcite on Li isotope fractionation [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Füger et al., 2022).

However, their measurement methods for growth rate differ. Füger et al. (2022) used mass balance equations. [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF] applied image analysis to estimate the surface area of calcite and conducted eight experiments to establish a relationship between surface area and growth mass. Despite these differences, the two studies display a consistent trend, as displayed in Fig. 2E and 2F and consequently we consider in the following that their comparison appears overall reasonable. Füger et al. (2022) show that logD(Li) values of inorganic calcite increase with the calcite growth rate (usually expressed in mol m -2 s -1 ) (Fig. 2F). As growth rates increase from 10 -8.1 to 10 -7.1 mol m -2 s -1 , D(Li) values rise strongly from 10 -4.8 to 10 -2.9 , indicating that at a higher growth rate it is easier for Li to enter calcite grains. This was previously reported for divalent ions in calcite, i.e., Ba 2+ , Sr 2+ , Mg 2+ [START_REF] Gabitov | Partitioning of strontium between calcite and fluid[END_REF][START_REF] Mavromatis | Barium partitioning in calcite and aragonite as a function of growth rate[END_REF][START_REF] Mavromatis | Kinetics of Mg partition and Mg stable isotope fractionation during its incorporation in calcite[END_REF]. A growth entrapment model (GEM) was developed to explain this process [START_REF] Watson | A conceptual model for near-surface kinetic controls on the trace-element and stable isotope composition of abiogenic calcite crystals[END_REF]. The GEM suggests that the surface composition of a crystal in equilibrium with a solution is usually different from that of a bulk crystal (as divalent ions are enriched at the crystal surface). If the crystal grows excessively fast, this equilibrium is broken, and the slower diffusing divalent ions become trapped and eventually form a solid by direct substitution of Ca ions.

However, Li + ions do not usually directly replace Ca 2+ , due to a large difference in ionic radii, and to charge imbalance [START_REF] Füger | Effect of growth rate and pH on lithium incorporation in calcite[END_REF]. This behavior is expected to be close to that of Na and other alkali elements. Notably, it has been shown that Na + concentration of calcite depends on the number of calcite defects [START_REF] Busenberg | Kinetic and thermodynamic factors controlling the distribution of SO 3 2and Na + in calcites and selected aragonites[END_REF]. These crystal defects are controlled by the growth rate, i.e., the faster the growth rate, the more defects are observed at the surface of the newly formed crystals, and the more Na + ions can enter the crystals. Okumura and Kitano.

(1986) reached the same conclusion for other alkali elements (K + and Rb + ). A recent study further supported that D(Li) and D(Na) display a similar linear relationship with growth rate [START_REF] Füger | Effect of growth rate and pH on lithium incorporation in calcite[END_REF]. Overall, these studies indicate that growth rate plays an essential role in the Li -and other alkali -content of calcite.

It is however noteworthy that no correlation between growth rate and logD(Li) was observed in the slowly growing calcite from a doubly concentrated seawater solution [START_REF] Gabitov | Elemental uptake by calcite slowly grown from seawater solution: An in-situ study via depth profiling[END_REF]. It may be explained by the fact that natural seawater contains a large amount of Mg 2+ and SO 4 2-

, which can readily incorporate the calcite and potentially change its crystal structure. This discrepancy suggests that a direct comparison of synthetic calcite with marine authigenic calcite is not always appropriate, at least for D(Li).

Considering Li isotopes, the recent study of (Füger et al., 2022) revealed that calcite Δ 7 Li carb-sol value remains essentially constant (Δ 7 Li carb-sol =-2.76±0.22‰) when the calcite growth rate remains at a low level (< 10 -7.7 mol m -2 s -1 ). However, as the growth rate increases (>10 -7.7 mol m -2 s -1 ), the Δ 7 Li carb-sol increases rapidly in magnitude. This indicates that more 6 Li is incorporated into calcite at higher growth rates (Fig. 2E). [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF] also observed a negative correlation between Δ 7 Li carb-sol and growth rate (Fig. 2E). By comparing the data from Marriott et al. (2004a) and Marriott et al., (2004b), although the surface area is not specified we note that calcite with faster growth rates (0.2 g h -1 vs 0.09 g h -1 ) leads to a larger isotopic fractionation (-8‰ versus -3‰), , as initially suggested by [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF], and this is fully consistent with the above findings Füger et al. (2022) suggested that, when the growth rate is slow, isotopic fractionation operates near equilibrium, the net reaction rates of precipitation and dissolution are essentially equal, Δ 7 Li carb-sol is small and constant. When the growth rate increases and gradually separates from equilibrium conditions, desolvation of the inner hydration sphere of aqueous Li + ion increases the kinetic isotopic fractionation.

Note that the relationship between isotopes of divalent cations and growth rate can be expressed by the transition state theory (TST), assuming the generation of a Ca 1-x Me x CO 3 -composed diluted solid solution, whose rate of precipitation under steady-state chemical conditions is equivalent to that of the CaCO 3 phase. In fact, as shown in Fig. 2E, Fuger et al. ( 2022) managed to fit both published datasets using an adapted TST model, with specific backward calcite dissolution rate, distinguishing it from the one classically used for divalent ions. However, assuming that Li is a priori not present in calcite under a solid solution form, the same authors still consider desolvation as the most reasonable process explaining the observed negative trend.

Principal component analysis (PCA) of the combined effects

Overall, previous studies have shown that the inorganic calcite-solution Li isotopic fractionation appears little affected by temperature, salinity, and Li concentration of the growth solution, and display a higher influence of solution pH and kinetic effects related to the growth rate (see Fig. 2).

As the synergy of several parameters may control Li isotope fractionation and D(Li), we applied a principal component analysis (PCA) to the published inorganic calcite data in order to further identify the most influent parameters. In Fig. 3A, our principal component analysis was applied to the two experiments reporting growth rate data [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF]Füger et al., 2022) 2). On the other hand, the disparities within the [START_REF] Day | Lithium isotopes and partition coefficients in inorganic carbonates: Proxy calibration for weathering reconstruction[END_REF] and the Fuger et al. ( 2022) datasets are mostly related to principal component 2, and can be associated to differences in aqueous Ca 2+ concentrations and pH. To some extent, this may also be related to growth rates, at least for the Fuger et al. study, which used Ca-based mass balance equations to determine them (see section 2.4).

Li/Ca and Li isotopes in biogenic carbonates

Several studies have been conducted to determine the role of environmental parameters on Li/Ca ratios measured in biogenic carbonates. Field samples and laboratory cultures demonstrate that the incorporation of Li is affected by a variety of factors such as temperature, dissolved inorganic carbon (DIC), pH and biology ("vital effects") (Dellinger et al., 2018;[START_REF] Hall | Li/Ca in multiple species of benthic and planktic foraminifera: Thermocline, latitudinal, and glacialinterglacial variation[END_REF][START_REF] Hathorne | Lithium in the aragonite skeletons of massivePorites corals: A new tool to reconstruct tropical sea surface temperatures[END_REF][START_REF] Lear | Benthic foraminiferal Li/Ca; insights into Cenozoic seawater carbonate saturation state[END_REF]Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]. According to [START_REF] Delaney | Lithium-to-calcium ratios in modern, Cenozoic, and Paleozoic articulate brachiopod shells[END_REF], temperature initially appeared to significantly influence the Li/Ca ratio of brachiopod shells, similar to that observed in synthetic calcite (Marriott et al., 2004).

However, no systematic relationship between Li/Ca and temperature has been found

for other types of biogenic carbonates. Instead, culture experiments and core top studies have shown that the Li/Ca ratio of foraminifera is mostly influenced by growth rate, solution Li/Ca ratio and DIC [START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF][START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF][START_REF] Lear | Benthic foraminiferal Li/Ca; insights into Cenozoic seawater carbonate saturation state[END_REF][START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]. Also for mollusks, Li/Ca ratios have recently been inferred to result from a combination of biological processes, growth rate, and planktic productivity (Dellinger et al., 2020;[START_REF] Thébault | Li/Ca enrichments in great scallop shells (Pecten maximus) and their relationship with phytoplankton blooms[END_REF][START_REF] Thébault | Investigation of Li/Ca variations in aragonitic shells of the ocean quahog Arctica islandica, northeast Iceland[END_REF].

Concerning Li isotopes, it has been first considered that inorganic carbonate precipitation experiments could provide a theoretical basis for the study of Li isotopic fractionation mechanism during carbonates growth. However, natural processes related to the organism biology may cause additional isotopic effects (Roberts et al., 2018;Dellinger et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF], Thibon et al., 2021). In particular, Li isotopes may be, at the cellular level, strongly fractionated during transmembrane active and passive transport (Poet, Vigier, Bouret et al., 2023). Some of these transporters (Na-H Exchangers: NHE) are ubiquistpresent in all living species -and involved in intracellular pH regulation at play during the growth of calcifying species.

In addition, different carbonate-producing organisms may form shells or skeletons with entirely different structures, growth rates, and mineralogy (Dellinger et al., 2018;[START_REF] Rollion-Bard | Effect of environmental conditions and skeletal ultrastructure on the Li isotopic composition of scleractinian corals[END_REF]. Besides, the calcifying fluid may be chemically and isotopically distinct from the seawater in which the organisms live. Another complication is that the environment in which organisms live may change over time (e.g., seawater pH, saturation state, nutrients). Finally, after the organism's death, sedimentary processes may bias the original carbonate isotopic signature, such as contamination by silicate minerals or Fe-Mn oxides, structure modification, isotope exchange, and fluid circulations during early diagenesis. In the following, we review the literature data (1) separating results from laboratory cultures and modern carbonates collected in the ocean and (2) providing a detailed focus on foraminifera data, since this group represents most of the published data, allowing statistical treatments. For this analysis, we took into account only the values validated by the authors as free from diagenetic effects, based on various geochemical tracers and/or optical observations. Note that several methods have recently been developed for ensuring reliable and precise Li isotopic analyses of natural -low level -carbonate phases (e.g. Bastian et al., 2018;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF][START_REF] Van Hoecke | Single-step chromatographic isolation of lithium from whole-rock carbonate and clay for isotopic analysis with multi-collector ICP-mass spectrometry[END_REF].

Laboratory cultures of calcifying organisms: a means to study fractionating mechanisms

Several studies investigated "vital effects" on Li/Ca and Li isotopes through aquarium cultures of calcifying organisms, i.e. foraminifera (Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF], mollusks (Dellinger et al., 2018) and brachiopods (Gaspers et al., 2021). So far, all foraminifera cultured at the laboratory are calcitic and epi-benthic species (Amphistegina lessonii and A. lobifera), meaning that they operate photosynthesis and can thus be studied as a biological analogue to planktic species [START_REF] Erez | Vital effect on stable-isotope composition seen in foraminifera and coral skeletons[END_REF].

While inorganic carbonates Δ 7 Li carb-sol exhibit a positive correlation with pH (see Fig. 2C), this trend is not observed in foraminifera calcite grown in laboratory [START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]) (A. lobifera). However, measurements were performed in situ by ion probe and the 0.7‰ variation expected for the studied pH range is challenging to reach with this method [START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF]). Roberts et al. (2018) cultivated A. lessonni and highlighted an opposite trend compared to the inorganic calcite, as for a pH increase from 7.9 to 8.6, a slight decrease in foraminifera  7 Li was observed from 31.6‰ to 30.8‰ (measured using MC-ICP-MS, with a precision of ±0.4‰). Roberts et al.

(2018) suggested that a pH change induces the formation of another Li hydration sphere (LiOH) in solution, which may increase the rates of 6 Li desolvation. However, ion desolvation is usually related to the first hydration sphere and the formation of

LiOH is unlikely at this pH (Füger et al., 2022). The pH effect on calcifying organisms and their Li isotopic composition therefore requires additional investigations. [START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF] showed that the δ 7 Li values of cultured A. lessonii strongly depend upon the seawater DIC concentrations, with foraminifera δ 7 Li value ranging from 21.6‰ to 41.9‰ (measured by SIMS with a 2σ precision of ±2‰) for a DIC range of 1.0 to 3.0 mmol/kg. They suggested that Li + , entering the cytoplasm through Na + /H + exchanger (NHE), may fractionate Li isotopes in favor of the light 6 Li, as expected by kinetic isotopic fractionation. A recent experimental study confirms the potential of NHEs to strongly fractionate Li isotopes (Poet, Vigier, Bouret et al., 2023). Thus, a low seawater DIC may lead to an increase in NHE activity in order to increase the pH and the alkalinity of the calcifying fluid, promoting carbonate precipitation. This process favours preferential 6 Li transfer. Unfortunately, Roberts et al. (2018) and [START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF] did not report foraminifera growth rates, which is likely an important factor influencing Li isotope composition (Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]. For instance, an increase in seawater DIC may decrease the pH at the foraminiferal surface [START_REF] Glas | The O 2 , pH and Ca 2+ microenvironment of benthic foraminifera in a high CO 2 world[END_REF], which may slow down the shell growth.

At high DIC (> 2 mmol kg -1 ), [START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF] reported strong isotopic fractionations in favor of the heavy 7 Li in A. lessonni tests (δ 7 Li as high as 41.9‰).

Bivalve cultures also show positive biological Li isotopic fractionation in both their shells and their soft tissues (see Dellinger et al., 2018;Thibon et al., 2021). A key role of Li homeostasis has been inferred. When the internal balance of Li input and output is disturbed by external conditions (e.g. high pH, high DIC, high Li contents), it is expected that the isotope composition varies, because of NHE activity in particular.

The net internal Li budget can therefore be affected and may favor either the light or the heavy isotope, depending on the ratio of input versus output fluxes (Thibon et al., 2021).

The 3D graph shown in Fig. 4, may reconcile all foraminifera cultures data published thus far. Indeed, there is a relationship between foraminifera δ 7 Li and DIC when foraminifera are cultured at a given and constant pH (red plane). At variable pH, when the DIC is maintained constant, the foraminifera δ 7 Li values remain constant (blue plane, [START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]. In contrast, when both pH and DIC vary (Roberts et al., 2018), Li isotopes follow a trend that cuts the previous datasets, indicating a combination of both effects with a dominance of the pH effect (yellow line). Perhaps compensating effects, related to intracellular H + and DIC homeostasis, may play a major role in the Li transfer and resulting isotope compositions. Additional experiments with variable pH at a much higher DIC could be useful to better understand the Li isotope fractionation mechanisms at play in foraminifera cells. weakly related to the temperature (Dellinger et al., 2018). A significant amount of δ 7 Li data for calcitic shells (Mytilus edulis and Pecten maximus) lie above the seawater isotopic composition, i.e. enriched in the heavy 7 Li (Dellinger et al., 2018), and cannot be explained by the sole effect of the growth rate. Dellinger et al. (2018) suggested that Li is actively removed from the calcification site, with an isotope fractionation in favour of the preferential removal of 6 Li. This hypothesis is supported by the negative correlation between δ 7 Li and Li/Ca, as well as between δ 7 Li and Mg/Ca, and are consistent with the key role of Li cell transporters (NHE) recently highlighted at the cellular level (Poet, Vigier, Bouret et al., 2023).

Brachiopod culture experiments revealed that the Li concentration of calcitic brachiopods (Magellania venosa) ranges from 2.3 to 3.5 ppm and their δ 7 Li values range from 27.5‰ to 28.1‰, with no significant effect of temperature (Gaspers et al., 2021). In contrast, when pH decreases (from 7.6 to 7.35), there is a slight increase of the Li isotopic fractionation, from -2.7‰ to -3.4‰, consistent with the trend displayed by inorganic calcite. A higher solution CaCl 2 concentration (lower Mg/Ca or Li/Ca ratios) also leads to a small increase in the Li isotope fractionation (from -2.7‰

to -4.6‰).

Overall, all laboratory cultures published thus far reveal that "vital effects" may impact both Li concentrations and Li isotopic compositions of soft and calcified tissues of foraminifera and mollusks.

Modern carbonates collected in the ocean

The environment of marine carbonates is more complex than that of in-lab synthesis and aquarium cultures because it is more susceptible to disturbances by other materials, such as contamination by marine particles (e.g., clays or Fe-Mn oxides), or by processes occurring during early diagenesis or in the water column. However, the study of modern marine shells is interesting because the Li isotopic composition of the modern ocean is homogeneous, as well as its Li/Ca ratio, so the study of contrasted isotopic signatures given by modern marine samples can give essential clues. This however requires a good representative nature of the considered dataset.

According to the characteristics of the samples, published Li data can be divided into two major categories. Several publications have sampled by picking various organisms from the same species or from the same trophic group. This was performed for foraminifera [START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF][START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF]Marriott et al., 2004;Misra and Froelich, 2012;Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF], corals (Bastian et al., 2018;Dellinger et al., 2020;Marriott et al., 2004;Misra and Froelich, 2009), mollusks (Bastian et al., 2018;Dellinger et al., 2018), brachiopods [START_REF] Washington | Lithium isotope composition of modern and fossilized Cenozoic brachiopods[END_REF]Gaspers et al., 2021), and echinoderms (Dellinger et al., 2018). In most of these studies, shells and tests are pre-cleaned in order to remove potential contamination from oxides, silicate minerals or organic matter. In the second category of publications, the whole carbonate fraction of a marine sediment sample was extracted using a preferential dissolution by a weak acid generally (for modern carbonates: Dellinger et al., 2020;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF] for past reconstructions: [START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF][START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF][START_REF] Kalderon-Asael | A lithium-isotope perspective on the evolution of carbon and silicon cycles[END_REF][START_REF] Lechler | Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)[END_REF]Misra and Froelich, 2012;[START_REF] Murphy | Reconstructing the lithium isotopic composition (δ 7 Li) of seawater from shallow marine carbonate sediments[END_REF][START_REF] Von Strandmann | Global climate stabilisation by chemical weathering during the Hirnantian glaciation[END_REF][START_REF] Von Strandmann | Lithium isotope evidence for enhanced weathering and erosion during the Paleocene-Eocene Thermal Maximum[END_REF][START_REF] Von Strandmann | Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2[END_REF][START_REF] Washington | Lithium isotope composition of modern and fossilized Cenozoic brachiopods[END_REF]. In the following, the present study will refer to the corresponding data as "bulk carbonates" (bulk). A couple of studies have compared both methods (Bastian et al., 2018;Misra and Froelich, 2012;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF].

The current geographical distribution of all  7 Li data published for marine carbonates is shown in Fig. 5. This compilation includes biogenic carbonate samples primarily from marine surface sediments (burial depths less than 2 cm), and for a small number, these data concern living organisms from the water column (e.g., foraminifera).

First of all, Fig 5 highlights significant gaps. Indeed, most studies (viz. 44% of the data) focus on the Atlantic Ocean, with a relatively small amount of data available for the Pacific Ocean, and only a few foraminifera data for the Indian Ocean. Another observation is that most studies concern the middle and low latitudes, and littoral environments. In the objective to use modern species as equivalent to reconstruct past variations of the open ocean Li isotopic composition -and its links with climatethese gaps appear essential to fill. (Bastian et al., 2018;Dellinger et al., 2020;Marriott et al., 2004;Misra and Froelich, 2009), foraminifera [START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF][START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF]Marriott et al., 2004;Misra and Froelich, 2012;Roberts et al., 2018;[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF] mollusks (Bastian et al., 2018;Dellinger et al., 2018) brachiopods [START_REF] Washington | Lithium isotope composition of modern and fossilized Cenozoic brachiopods[END_REF], echinoderms (Dellinger et al., 2018) and "bulk" carbonates (obtained by preferential dissolution, see text) (Bastian et al., 2018;Dellinger et al., 2020;[START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF][START_REF] Murphy | Reconstructing the lithium isotopic composition (δ 7 Li) of seawater from shallow marine carbonate sediments[END_REF].

It is possible to compare data among the different studied biological groups, keeping in mind that all environmental conditions have not been explored similarly. This allows us to highlight where the knowledge is the strongest and to evaluate the representative nature of the average value that can be calculated for each one. As shown in Fig. 6 and in Fig. S3, modern marine carbonates display a wide range of < 0.01).

Among calcitic organisms, there are also significant differences (Wilcoxon test: p-val.

< 0.0001) between foraminifera (28.3 ± 5.9‰ n = 84), mollusks (30.9± 10.7‰ n = 33), and brachiopods (26.8 ± 1.8‰, n = 75), and they are all statistically higher than bulk carbonates (i.e. extracted by preferential dissolution) (23.9 ± 2.1‰, n = 31). This suggests that vitalbiological -effects are able to influence the Li isotopic composition of carbonates and that the Li isotopic fractionation can vary between species and between individuals. Also, bulk -calcite -carbonate  7 Li values are lower than the data displayed by picked foraminifera, mollusks or brachiopods, indicating that there are still calcitic phases of importance (Foram ooze, Sponge spicules etc.), which have not been investigated yet, despite playing key role in the bulk fractions  7 Li values.

Fig. 6: Compilation of all existing data for δ 7 Li and Li/Ca (in μmol mol-1) for modern (core top as circles, living as triangles) biogenic carbonates [START_REF] Delaney | Lithium-to-calcium ratios in modern, Cenozoic, and Paleozoic articulate brachiopod shells[END_REF][START_REF] Hall | Li/Ca in multiple species of benthic and planktic foraminifera: Thermocline, latitudinal, and glacialinterglacial variation[END_REF]Marriott et al., 2004a;Marriott et al., 2004b;[START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF][START_REF] Bryan | [END_REF][START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF][START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF][START_REF] Bryan | [END_REF][START_REF] Hendry | [END_REF][START_REF] Rollion-Bard | Effect of environmental conditions and skeletal ultrastructure on the Li isotopic composition of scleractinian corals[END_REF]Misra and Froelich, 2012;Bastian et al., 2018;Roberts et al., 2018;[START_REF] Dellinger | [END_REF][START_REF] Von Strandmann | Assessing bulk carbonates as archives for seawater Li isotope ratios[END_REF]Delinger et al., 2020;[START_REF] Washington | Lithium isotope composition of modern and fossilized Cenozoic brachiopods[END_REF]Gaspers et al., 2021;Dellinger et al., 2018). "HMC" denotes high magnesium calcite. "Mixed" denotes a mixture of calcite and aragonite. "Bulk" denotes sedimentary carbonate fraction extracted by preferential leaching (see text). The vertical solid and dashed line is for the seawater δ 7 Li value (31 ± 0.3‰) (Millot et al., 2004). The seawater Li/Ca ratio is 2505 μmol mol -1 . Each data point represents a value for a carbonate sample. The grey numbers on the right denote the number of published data. Asterisks show the significance of the difference inferred through a Mann-Whitney-Wilcoxon tests: ns (not significant) for p > 0.05, * for p < 0.05, ** for p < 0.01, *** for p < 0.001, **** for p < 0.0001 (highly significant difference).

Among the aragonitic species, there is no significant difference in δ 7 Li between corals (19.4 ± 3.6‰, n = 91) and mollusks (18.2 ± 5.9‰, n = 12) (p > 0.05), but they are both statistically different (p < 0.0001) from bulk carbonates (21.6 ± 1.3‰, n = 27).

In contrast with calcitic environments, the aragonitic bulk carbonate fractions display higher  7 Li values than all other groups studied thus far.

Most of the modern biogenic carbonates display lower δ 7 Li values than seawater, such as all brachiopods, echinodermata, and all aragonitic carbonates. However, some δ 7 Li values are higher than seawater, such as the calcitic shells of mollusks, and a small fraction of foraminifera data. This indicates that they can be enriched in the heavier Li isotope 7 Li relative to seawater, as observed in culture experiments [START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]. More recently, Thibon et al. (2021) showed that it is possible to have an enrichment in 7 Li in marine soft tissues, depending on the Li input/output (excretion) flux and of the magnitude of kinetic isotope fractionation related to the Li transport.

Concerning our compilation of Li/Ca ratios, it is striking that all modern marine biogenic carbonates are significantly (by several orders of magnitude) depleted in Li (<90 mol mol -1 ) compared to the present-day seawater value (2505 mol mol -1 ). On average, calcite groups contain more Li than aragonite ones. By calculating the LogD(Li) for these groups, we can compare their data to the ones found experimentally for inorganic equivalents. In biogenic carbonates, LogD(Li) range from -3.17 to -1.68, while they cover a wider range in inorganic phases, between -5.70 and -1.99. Interestingly, for Li isotopes, the opposite is observed: the  7 Li carb-sol distribution range for biogenic carbonates is larger than that for inorganic phases, independently of mineral types (see Fig. 1).

In biogenic calcite, Li/Ca ratios for mollusks, foraminifera, brachiopods, and bulk range from 9.9 to 52.5 mol mol -1 , from 2.69 to 24.33 mol mol -1 , from 5.7 to 49.2 mol mol -1 and from 20.4 to 57.5 mol mol -1 , respectively. Except for mollusks, there is a reverse trend between the average  7 Li and the average Li/Ca ratio. In particular, foraminifera display the highest average isotopic composition and also the lowest Li/Ca ratio (12.48 ± 7.9 mol mol -1 , n=305) (Fig. 6). Their range in Li/Ca ratios also appears restricted compared to the variations observed within each of the other groups.

This may be due to the fact that Li/Ca ratios have been mostly measured in similar samples for which Li isotopes could be measured too. When no isotopic measurements were performed due to low Li levels, no Li concentration was measured neither and this limitation may induce a significant bias.

In contrast to biogenic calcite, biogenic aragonite appears to display a positive relationship between  7 Li and Li/Ca, when comparing average values for mollusks, cnidarian, and bulk carbonates. Aragonitic mollusks are particularly depleted in Li compared to calcitic mollusks, although the number of data is small (Li/Ca = 5.02 ± 7.2 μmol mol -1 , n = 5). Cnidarians display relatively low Li/Ca ratios (7.33 ± 6.3 μmol mol -1 , n = 168), while bulk aragonite extracted from sedimentary fractions display the highest average Li/Ca ratio.

Finally, high-Mg calcite echinoderm specimens display the highest Li/Ca values of the whole carbonate dataset, although only 3 data are reported in the literature (70.27 ± 21.08 μmol mol -1 , n = 3) (Dellinger et al., 2018).

Focus on foraminifera species

Foraminifera are single-celled eukaryotic organisms belonging to the Phylum Granuloreticulosa [START_REF] Pearson | Oxygen Isotopes in Foraminifera: Overview and Historical Review[END_REF], and many secrete a test (or shell) made of calcium carbonate, generally low-Mg calcite, but possibly high-Mg calcite in porcelaneous species, and aragonite in some groups. Some species may include sedimentary particles [START_REF] Pearson | Oxygen Isotopes in Foraminifera: Overview and Historical Review[END_REF][START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF]. "Benthic" marine foraminifera majority live on or within the seafloor sediment, while a number float in the water column at various depths (known as "planktic") (Hemleben et al., 2012). Currently, studies of Li isotopes in modern marine foraminifera are mainly focused on planktic species, while relatively few studies have been conducted on natural benthic foraminifera species (Table 3).

Planktic and benthic foraminifera do not exhibit significant differences in Li/Ca ratios, except for the Antarctic Ocean where the Li/Ca ratio of planktic foraminifera is statistically higher than that of benthic species (Table 3). In contrast, differences can be observed for Li isotopes. At first, the Li isotopic compositions of living foraminifera from the Pacific Ocean water column appear consistent with that of foraminifera picked from surface sediments. This suggests that the Li isotopic signal is not rapidly affected by early diagenesis (although specific chemical treatment targeted the removal of contaminant phases and only data validated by authors as free from diagenetic effects were considered). In contrast, we detect no significant difference between the different oceans for either planktic or benthic foraminifera, but the number of data is small and the test power would deserve to be reinforced with additional data for Pacific and Indian oceans. in the vertical direction, planktic and benthic habitats play a more decisive role in the foraminifera Li isotopic composition. The higher δ 7 Li values measured systematically in planktic species (compared to the benthic ones collected in the same ocean) are consistent with a pH control. Indeed, in modern oceans, the pH of surface seawater (up to 8.33 ± 0.1) is usually higher than that of the bottom seawater (down to 7.52 ± 0.05) [START_REF] Lauvset | Processes Driving Global Interior Ocean pH Distribution[END_REF], except close to hydrothermal sites. Indeed, there is a positive correlation between pH and Δ 7 Li carb-sol observed in inorganic calcite (Fig. 2C) (Füger et al., 2022;[START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF], i.e. with no influence of biology. However, the large difference observed between the two marine habitats (benthic and planktic) cannot be explained by the slope shown in Fig. 2C. Indeed, the published sampling depth of benthic foraminifera is considerable, ranging from 96 to 3729 m (Marriott et al., 2004;Roberts et al., 2018), which corresponds to a pH range as large as for the whole seawater one. Thus, substituting the highest (8.33) and lowest (7.52) seawater pH into the equation in Fig. 2C, yields isotopic fractionations (Δ 7 Li carb-sol ) of -3.2‰ and -4.2‰, respectively, so the theoretical maximum isotopic difference that can be produced between planktic and benthic (using the regression shown in Fig. 2C) is 1‰.

In contrast, benthic foraminifera δ 7 Li values are lower by -6 or -7‰ from the seawater value while planktic δ 7 Li are lower by -1 to -3‰. Consequently, other factors such as biological processes, growth rates and temperature would deserve to be investigated in the future. Interestingly, we found a negative linear correlation between the δ 7 Li and Li/Mg ratio for benthic and planktic foraminifera (Fig. 9). Li/Mg ratio of corals and foraminifera is more strongly related to temperature than Li/Ca, and has been recently proposed as a proxy for reconstructing global ocean temperature (Rollion- [START_REF] Rollion-Bard | Possible controls on Li, Na, and Mg incorporation into aragonite coral skeletons[END_REF][START_REF] Stewart | Refining trace metal temperature proxies in cold-water scleractinian and stylasterid corals[END_REF][START_REF] Zhu | Magnesium partitioning into vaterite and its potential role as a precursor phase in foraminiferal Mg/Ca thermometer[END_REF]. Although this temperature indicator is mostly applied to aragonitic carbonates and high-Mg calcite thus far, a similar correlation can be observed for the calcitic foraminifera dataset (Fig. 9). Therefore, we cannot completely rule out that differences in seawater surface and bottom temperatures may lead to the formation of different Li/Mg ratios in planktic and benthic foraminifera, which in turn result in differences in their Li isotopic compositions.

The growth rate may also be an additional factor affecting the Li isotopic composition of calcite, as shown in Fig. 2E for inorganic phases, where low growth rate corresponds to higher calcite δ 7 Li (within the range of ocean pH). However, it is more complicated for foraminifera, as their growth rate may also be a function of metabolism, nutrient availability and environmental conditions. Due to the lack of published data of foraminifera growth rates coupled with Li measurements, we cannot further explore the influence of this factor to explain the observed difference between planktic and benthic species. foraminifera. The blue solid lines report previous aragonitic phases data regression [START_REF] Stewart | Refining trace metal temperature proxies in cold-water scleractinian and stylasterid corals[END_REF], and bright green solid lines reports HMC data regression [START_REF] Stewart | Refining trace metal temperature proxies in cold-water scleractinian and stylasterid corals[END_REF].

Shadings show 95% confidence intervals.

Due to the lack of published data of foraminifera growth rates coupled with Li measurements, we cannot further explore the influence of this factor to explain the observed difference between planktic and benthic species.

Based on our compilation (Table 3), it is however possible to evaluate the "species effect", by quantifying the significance of isotopic differences between various genera of planktic foraminifera (Fig. 9). The δ 7 Li values of Globigerinoides (28.8 ± 1.9‰, n = 9) are statistically lower (p < 0.001) than those of Globigerina (30.2 ± 1.1‰ n = 8)

and Orbulina (30.5 ± 1.6‰ n = 25). Statistical differences (p < 0.01) are also observed between Orbulina (30.5 ± 1.6‰ n = 25) and Neogloboquadrina (28.2 ± 2.9‰ n=5). It should be noted that the number of Globigerinoides (9),Globigerina (8) and Neogloboquadrina (5) samples is relatively small. No significant difference are revealed between living Orbulina universa (30.6 ± 0.62‰ n=6) and core-top

Orbulina universa (30.5 ± 1.8‰,n=19), confirming the lack of impact of rapid diagenesis, at least for this species (or correct pre-cleaning conditions as inferred previously).

Concerning Li/Ca ratio, Fig. 9 shows no "species effect" for planktic foraminifera, while this ratio is much more variable among benthic species. However, as described in section 2, this observation may be biased by the lack of Li concentrations measurements made in foraminifera tests not providing enough material for Li isotope measurements. This may concern low Li level species, low density (e.g. porous, thin) tests, or species with a weak abundancy in the sediment.

We investigated the role of the size fractions in the isotopic and chemical differences observed between foraminifera species or habitats. However, in many publications, the precise determination of this parameter is not provided, with access often limited to either a broad range of sizes or only the minimum size. As depicted in Fig. S4 and Fig. S5, no significant relationship with size can be observed at this stage. It is noteworthy that the 2D size fraction of foraminifera may not be directly linked to the growth rate, as it is influenced by factors such as the carbonate structure and density, lifespan, and other biological processes involved in the biomineralization process. The recently inferred explanation is that there is a Li speciation effect at the mineral surface.

 A similar situation arises for growth rate: an increase in calcite growth rate leads to an increase in D(Li) values and in the Li isotope fractionation. The interpretation is still debated.

For biogenic carbonates:

 Marine biogenic carbonate studies mainly concern the Atlantic Ocean (44% of the data), so more effort should be put into other oceanic conditions in order to cover a broader range of environmental conditions.

 δ 7 Li values are statistically different between foraminifera, mollusks, and brachiopods, and they are all statistically higher than the values measured in bulk carbonates. This strongly suggests that vital -biological -effects can influence the Li isotopic composition of biogenic carbonates and that the isotopic fractionation of Li isotopes can vary between species and between individuals.

 The δ 7 Li values of planktic foraminifera are statistically higher than those of benthic foraminifera. Statistical differences are also evidenced between different species of planktic foraminifera. This supports a key role of genetics and metabolic effects that may be explored for future paleo reconstructions. In particular, the relationship between foraminiferal Li/Mg ratio and temperature suggests a new potential for reconstructing paleo-temperature that would deserve to be reinforced.

Fig. 1 :

 1 Fig. 1: Range of A) carbonate -water Li isotope fractionations ( 7 Li carb-sol ) and B) Li partition coefficients (D(Li) in μmol mol -1 = (Li/Ca) carb /(Li/Ca) sol ) published for inorganic calcite (light green), inorganic aragonite (light blue), modern biogenic calcite (dark green) and modern biogenic aragonite (dark blue). Modern biogenic phases include core-top data and a few living organisms.

  , show that, at constant temperature, the variations in both Li isotope values and D(Li) values are much larger than those caused by varying the temperature alone. It strongly suggests that temperature is not the dominant control factor and that other parameters play a crucial role in Li incorporation by calcite. Finally, Day et al. (2021) and Marriott et al. (2004a) evaluate the effect of temperature for aragonite and high magnesium calcite. Their Li data are roughly consistent with the results obtained for calcite. Nevertheless, additional experiments, covering a larger temperature range, are required to precisely confirm these statements (see Fig. 2A and 2B).

Fig. 2 :

 2 Fig. 2: Compilation of Li isotopic fractionations and Li partition coefficients between precipitated inorganic carbonate and growth solution. Each data point represents a value measured for one carbonate aliquot (A and B) Effect of temperature. The black dashed lines indicate linear regressions for calcite, gray shading represents confidence intervals. Data are from Marriott et al. (2004a) and Day et al. (2021); (C and D) Effect of the solution (final) pH. Black dashed lines indicate linear regressions for calcite. Data are from Seyedali et al. (2021) and Füger et al. (2022); (E and F) Effect of the growth rate (in log10). The trend shown in Fig. 2E is reported from Fuger et al. (2022) and represents a TST model using specific modifications (e.g. backward calcite dissolution rate), distinguishing it from the TST model classically used for divalent ions (see text for more details).

  . It indicates that the Δ 7 Li carb-sol and Log (Growth rate) anti-vary with each other on the principal component 1 (Dim 1), representing 69.4% of the whole dataset variability (other graphs and details on all Dimensions can be seen in the Supplementary Material). It overall shows that the variability between the two studies is discriminated primarily by Δ 7 Li carb-sol and Log(Growth rate), which is also consistent with Fig.2E. Fig. 3A also highlights a strong relationship between D(Li) and Log(Growth rate) on Dim1. However, Day et al. data are grouped on this Dimension and therefore the growth rate does not participate much to their variance. On the other hand, the larger "intragroup" variability of the Fuger et al. data is mainly associated to pH variations following the principal component 2 (Dim 2), in agreement with Fig. 2D. Thus, this analysis shows that -based on the currently available data -the growth rate of calcite appears to be a major parameter for calcite Li isotope compositions.Due the lack of growth rate data in[START_REF] Seyedali | The effect of solution chemistry on elemental and isotopic fractionation of lithium during inorganic precipitation of calcite[END_REF], we conducted another PCA, including other potentially relevant parameters that are available and also variable for the three considered experiments (e.g. bicarbonate ion concentration (ion concentration (Ca 2+ ), solution pH, and the Saturation Index (SI)). Similarly, all details on all Dimensions are given in the Sup. Mat. Even if there does not seem to be a dominant parameter in Dim1 explaining most of the variance, Fig.3Bshows that both Δ 7 Li carb-sol and D(Li) variability are mostly related to changes in solution pH and in dissolved Ca 2+ concentrations. Since both parameters may influence the calcite growth rate, this result appears consistent with Fig.2CDEF.

Fig. 3 :-

 3 Fig. 3: Principal component analysis (PCA) for inorganically precipitated calcite. Dim 1 and Dim 2 are principal components 1 and 2. Arrow length is proportional to the percentage contribution of these first three principal components to the observed variation of each variable. A), the relationship between D(Li), Δ 7 Li carb-sol , pH, and the Log(Growth rate) is depicted. Dim 1, Dim 2 and Dim 3 represent 98.9% of the variability in the dataset. B) illustrates the relationship between △ 7 Li carb-sol , solution ions (Ca 2+ , CO 3 2-, HCO 3 -), SI, and pH. Dim1, Dim2, and Dim3 explain 83.2% of the variability in the dataset. See Sup Mat for complementary PCA results (Fig. S1-1; S1-2).

Fig. 4 :

 4 Fig. 4: Three-dimensional scatter plots of δ 7 Li versus DIC and pH for cultured epi-benthic foraminifera. Blue plane indicates groups experiments performed at constant DIC. Red plane is for constant pH experiments[START_REF] Vigier | Lithium isotopes in foraminifera shells as a novel proxy for the ocean dissolved inorganic carbon (DIC)[END_REF]. The yellow dots show results obtained byRoberts et al. (2018) during an experiment where both DIC and pH varied.

Fig. 5 :

 5 Fig. 5: Worldwide distribution of modern marine carbonates with published Li isotopic compositions.  7 Li values concern corals(Bastian et al., 2018; Dellinger et al., 2020; Marriott

δ 7

 7 Li values, from 14.9‰ (aragonitic mollusks,Dellinger et al. (2018)) to 40.7‰ (calcitic mollusks fromDellinger et al. (2018)). Marine calcite δ 7 Li range from 19.5 ‰ to 40.7‰, high Mg calcite from 24.1‰ to 24.4‰ and aragonite from 14.9‰ to 23.8‰. There is a significant difference (Wilcoxon test: p-val. < 0.0001) between aragonite (19.27 ± 3.7‰ n = 103) and calcite (28.14 ±6.5‰ n = 192) or high Mg calcite (24.2 ± 0.3‰ n = 3). In contrast with laboratory precipitated inorganic carbonates, which result in contrasting results, biogenic minerals highlight a more systematic distinction between calcite and aragonite. Of note that there is a relatively small statistical difference between calcite and high Mg calcite (Wilcoxon test: p-val.

Fig. 7 :

 7 Fig. 7: The Li isotopic composition of modern oceanic foraminifera of different habitats distinguished by oceans, except epi-benthic foraminifera, coming from laboratory-cultured (in pink). The horizontal bars represent the seawater line. Asterisks show the significance of the Mann-Whitney-Wilcoxon tests used to observe differences between pairs of groups: ns (not significant) for p > 0.05, * for p < 0.05, ** for p < 0.01, *** for p < 0.001, **** for p < 0.0001 (highly significant difference).

Fig. 8 :

 8 Fig. 8: A) Li isotopic composition of modern foraminifera versus Li/Mg ratio measured in their shells; and B) Li/Mg versus seawater temperature. Each data point represents a carbonate sample. The black line with pink shade is the regression of compilation data for

Fig. 9 :

 9 Fig. 9: Box plots exhibiting Li/Ca ratios and Li isotope compositions of modern foraminifera, organized by phylum. Seawater δ 7 Li are added as a grey bar for comparison. The numbers at the right of each box indicate the number of samples. Asterisks show the significance of the Mann-Whitney-Wilcoxon tests used to observe differences between pairs of groups: ns (not significant) for p > 0.05, * for p < 0.05, ** for p < 0.01, *** for p < 0.001, **** for p < 0.0001 (highly significant difference). For a representation with size fractions included, see

Table 1 :

 1 Summary of the Li isotopic composition of biogenic and abiogenic carbonates.

		Δ 7 Li carb-sol Minimum	Δ 7 Li carb-sol Maximum	Mean	2sd	N
	Biogenic calcite	-11.5‰	+9.7‰	-2.83‰	6.5 192
	Synthetic calcite	-10.1‰	+3.8‰	-5.11‰	6.1	73
	Biogenic aragonite	-16.2‰	-5.7‰	-11.7‰	4.2 168
	Synthetic aragonite	-12.0‰	-7.7‰	-10.9‰	2.9	8

Table 2 :

 2 Summary of the characteristics of all published experiments of inorganic carbonate precipitation. *HMC indicates high magnesium calcite. 219

	-5 ), essentially

218

.1 Debated mineralogical control

	Synthetic inorganic carbonates include three types: calcite, aragonite, and
	high-magnesium calcite (HMC). As illustrated in Fig. 1, most published Li/Ca and
	 7 Li values concern calcite minerals (n = 85 and 73 respectively), while there are only
	few experimental data for inorganic aragonite (n = 6 and 8 respectively). Therefore, it
	remains difficult to compare both datasets statistically. For inorganic calcite, every
	additional published experiment has enlarged the range of values for Δ 7 Li carb-sol and
	D(Li), and we can suspect that it will be the same for experimental aragonite in the
	future.
	Another concern arises from the lack of synthesis experiments conducted under
	natural seawater conditions. Although Gabitov et al. (2011) initially employed
	seawater, they diminished its volume by half through evaporation. Consequently, the
	concentrations of all dissolved elements were twice as high as those found in typical
	natural seawater. Other published experiments used simplified artificial seawater or
	deionized water.

  [START_REF] Hall | Determination of the lithium isotopic composition of planktic foraminifera and its application as a paleo-seawater proxy[END_REF][START_REF] Hathorne | Temporal record of lithium in seawater: A tracer for silicate weathering?[END_REF][START_REF] Vigier | In situ measurements of Li isotopes in foraminifera[END_REF] Misra and Froelich, 2012

	Species	Source	Habits	n	δ 7 Li (‰)	n	Li/Ca (μmol mol -1 ) Reference
	Orbulina universa	Living	Planktic 5	30.5 ± 0.3 5	11.32 ± 0.75	Misra and Froelich, 2012
	Globigerina ruber	Coretop Planktic 2	30.6 ± 0.1 2	13.51 ± 0.78	Misra and Froelich, 2012
	Globigerina triloba	Coretop Planktic 6	30.1 ± 0.6 6	12.88 ± 1.32	Misra and Froelich, 2012
	Globigerinoides conglobatus	Coretop Planktic 3	29.1 ± 0.8 3	10.92 ± 0.69	Misra and Froelich, 2012; Hathorne et al., 2006
	Globigerinoides sacculifer	Coretop Planktic 5	29.0 ± 0.6 14 12.34 ± 0.54	Hall et al., 2005; Misra and Froelich, 2012; Hathorne et al., 2006; Hall and Chan, 2004
	Globorotalia cultrata	Coretop Planktic 2	29.7 ± 0.2 2	11.90 ± 0.28	Hathorne et al., 2006
	Globorotalia menardiib	Coretop Planktic 1	29.1	1	12.50	Hall et al., 2005
	Globorotalia merdii	Coretop Planktic 4	30.2 ± 0.2 4	10.94 ± 1.14	Misra and Froelich, 2012
	Globorotalia truncatulinoides	Coretop Planktic 5	28.7 ± 1.5 3	12.97 ± 0.9
	Globorotalia tumida	Coretop Planktic 3	28.1 ± 1.5 3	11.56 ± 0.46	Hathorne et al., 2006 Misra and Froelich, 2012
	Neogloboquadrina dutertrei	Coretop Planktic 4	29.1 ± 0.8 4	12.73 ± 0.6	Hathorne et al., 2006 Misra and Froelich, 2012
	Neogloboquadrina pachyderma Coretop Planktic			13 18.28 ± 0.70	Hendry et al., 2009
	Orbulina universa	Coretop Planktic 17 30.4 ± 0.8 32 11.9 ± 1.43	Hall et al., 2005; Hathorne et al., 2006 Misra and Froelich, 2012; Hall and Chan, 2004
	Cibicidoides cicatricosus	Coretop Benthic			5	15.36 ± 0.86	Hall and Chan, 2004
	Cibicidoides incrassatus	Coretop Benthic			7	14.47 ± 0.53	Hall and Chan, 2004
	Cibicidoides mundulus	Coretop Benthic 11 23.9 ± 1.8 11 13.08 ± 0.88	Roberts et al., 2018
	Cibicidoides pachyderma	Coretop Benthic			56 12.76 ± 1.44	Hall and Chan, 2004 ; Bryan and Marchitto, 2008
	Cibicidoides robertsonianus	Coretop Benthic			5	13.63 ± 0.81	Hall and Chan, 2004
	Cibicidoides wuellerstorfi	Coretop Benthic 7	23.6 ± 2.4 14 14.96 ± 2.23	Roberts et al., 2018; Hall and Chan, 2004 2005 Yun
	Cibicidoides rugosus	Coretop Benthic			5	14.22 ± 0.49	Hall and Chan, 2004
	Euuvigerina sp.	Coretop Benthic 1	21.1	1	14.4	Marriott et al., 2004a
	Hoeglundina elegans	Coretop Benthic			37 3.78 ± 0.50	Bryan and Marchitto, 2008
	Planulina ariminensis	Coretop Benthic			17 13.76 ± 1.45	Bryan and Marchitto, 2008
	Planulina foveolata	Coretop Benthic			13 12.31 ± 1.41	Bryan and Marchitto, 2008
	Uvigerina peregrina	Coretop Benthic			36 16.70 ±1 .90	Bryan and Marchitto, 2008

Table 4 .

 4 Average δ 7 Li and Li/Ca values for modern foraminifera from different oceans and habitats

	(uncertainties are standard deviation (SD))
		n	δ 7 Li (‰)	n	Li/Ca (μmol mol -1 )
	Living	5	30.5 ± 0.3	5	11.32 ± 0.75
	Planktic	5	30.5 ± 0.3	5	11.32 ± 0.75
	Pacific ocean	5	30.5 ± 0.3	5	11.32 ± 0.75
	Coretop	78	28.1 ± 3.0	299	12.48 ± 3.98
	Planktic	56	29.7 ± 1.1	89	12.86 ± 2.57
	Antarctic			13	18.28 ± 0.70
	Atlantic	44	29.6 ± 1.2	75	11.94 ± 1.30
	Indian ocean	7	29.8 ± 0.8
	Pacific ocean	5	30.1 ± 1.2	1	11.50
	Benthic	22	24.0 ± 2.0	210	12.32 ± 4.44
	Atlantic	14	23.4 ± 1.9	203	12.24 ± 4.46
	Indian ocean	4	24.6 ± 2.4	4	16.75 ± 1.91
	Pacific ocean	4	25.3 ± 1.7	3	12.07 ± 0.90
	If representative, the published dataset would indicate that foraminifera  7 Li values do
	not differ significantly among the different oceans, in the horizontal direction, while

Table3Compilation of δ 7 Li and Li/Ca ratios measured for modern foraminifera (uncertainties are given at the standard deviation  level)

Acknowledgements

Consequently, we included both living and sediments top-layer foraminifera in our compilation. δ 7 Li values vary from 24.9‰ to 32.5‰ for planktic foraminifera, and from 19.4‰ to 27.3‰ for benthic ones (Fig. 7). There are significant differences between planktic (29.7 ± 2.9‰ n=70) and benthic foraminifera (24 ± 4.1‰ n=23) (see Table 4 and also Fig. S3).

Conclusions

This review compiled and investigated major studies of Li/Ca and Li isotopes in inorganic and biogenic carbonates, providing an overview of the actual state of knowledge in the field. It primarily shows that it is extremely difficult to highlight "vital effects" -or the lack of "vital effects"simply by using a direct comparison between biogenic and inorganic carbonates. Indeed, both types of carbonates vary significantly -and generally differently -as a function of specific parameters. Another point of attention is the various gaps in the knowledge concerning the influence of mineral types, growth rates, environmental conditions outside the Atlantic Ocean, and calcifying species with low Li/Ca ratios. Finally, we highlighted that the combination of Li/Ca and Li isotopes appear to be useful for interpreting the influence of environmental or biological parameters. In more detail, we observed the following main points:

For inorganic carbonates:

 Current experimental studies mainly focused on calcite, while relatively little data are available for aragonite and high-Mg calcite. It is therefore too early to determine the role of the carbonate structure and mineralogy on Li isotopes.

 The temperature has little to no effect on the Li isotopic composition of inorganic calcite, but changes in temperature can affect calcite Li/Ca ratios. (//anr.fr/Projet-ANR-18-CE34-514 0002; www.iso2met-project.fr/). On behalf of M.M., the IAEA is grateful to the Government of the Principality of Monaco for the support provided to its Marine Environment Laboratories. Finally, we greatly thank the three reviewers and the editor for their fruitful and detailed comments that helped improving the manuscript.

 The extent of Li isotope fractionation between calcite and solution can be