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As part of the HIPPO (HIgh-resolution Primary Production multi-prOxy archives) project, environmental monitoring was carried out between March and October 2021 in the Bay of Brest. The aim of this survey was to better understand the processes which drive the incorporation of chemical elements into scallop shells and their links with phytoplankton dynamics. For this purpose, biological samples (scallops and phytoplankton) as well as water samples were collected in order to analyze various environmental parameters (element chemical properties, nutrients, chlorophyll a, etc.). Given the large number of parameters that were measured, only the major results are presented and discussed here. However, the whole dataset, which has been made available, is much larger and can potentially be very useful for other scientists performing sclerochronological investigations, studying biogeochemical cycles or conducting various ecological research projects. The dataset is available at https://doi.org/10.17882/92043 (Siebert et al., 2023).

Ba/Cashell, Mo/Cashell, and Li/Cashell chronologies of Pecten maximus can provide information on past phytoplankton dynamics. Distinct Ba, Mo, and Li peaks in the shells are associated with algal blooms. This study evaluated the underlying hypothesis that respective element profiles reliably record variations in phytoplankton dynamics occurring within the water column. Therefore, the chemical content of scallops from the Bay of Brest, France, that lived on the sediment surface was compared to conspecific specimens living in a cage above the seafloor and compared with the phytoplankton abundance and the physicochemical properties of the water column. As demonstrated, Ba/Cashell and Mo/Cashell peaks occurred contemporaneously in specimens within the cage and on the sediment, but were higher in the latter. Furthermore, element/Ca peaks agreed with the timing of particulate Ba and Mo enrichments in the seawater. These data support the assumption of a dietary uptake of both elements. Differences in peak heights between shells living in a cage and on the seafloor were controlled by rates of filtration and biomineralization. While the timing and magnitude of Ba/Cashell peaks were linked to Ba-containing diatoms, Mo/Cashell peaks were related to blooms of Mo-enriched dinoflagellate and diatom aggregation events. Two episodes of slight Li enrichment occurred synchronously in cage and sediment shells. Although the exact mechanism causing such Li increases remains unresolved, the findings suggest a link to large diatom blooms or the presence of a specific diatom taxon. This study refines previously hypothesized relationships between trace element enrichments in scallop shells and phytoplankton dynamics.

Shells of the fast-growing bivalve Pecten maximus serve as a geochemical archive for the reconstruction of past phytoplankton dynamics. Specifically, high-resolution, temporally accurately aligned molar barium-to-calcium (Ba/Cashell), molybdenum-to-calcium (Mo/Cashell) and lithium-to-calcium ratios (Li/Cashell) of the shell calcite revealed distinct peaks which are closely linked to phytoplankton dynamics. Yet, the development and applicability of these geochemical proxies is still at an early stage and needs further calibration. In this study, we examined the relationship between the timing and magnitude of Ba/Cashell, Mo/Cashell and Li/Cashell peaks of P. maximus and the occurrence of various phytoplankton species (diatoms and dinoflagellates) from a statistical perspective. Studied shell samples (three specimens per calendar year) as well as detailed phytoplankton observation data were derived from the well-studied costal ecosystem of the Bay of Brest (France) over three years (2011, 2012 and 2019). An algorithm-based pseudo-random sampling simulation technique was established that analyzed the complex phytoplankton datasets with respect to the profiles of Ba/Cashell, Mo/Cashell and Li/Cashell to identify potential patterns between phytoplankton and trace element time-series. The simulation results indicate that the timing and magnitude of Ba/Cashell, Mo/Cashell and Li/Cashell peaks agreed best with the occurrence of specific phytoplankton blooms that developed ca. one to two weeks earlier. The data suggest that the formation of transient Ba/Cashell peaks had a plurispecific origin, i.e., potentially linked to blooms of ingestible diatom, dinoflagellate and flagellate species enriched in Ba that occurred 8 to 12 days earlier. Observed peaks in Mo/Cashell profiles demonstrably followed the timing and intensity of blooms of the dominant dinoflagellate genus Gymnodinium spp. after a short time lag of around 8 days, potentially linked to an enhanced enzyme activity o

Molar barium-to‑calcium ratios in bivalve shells (Ba/Cashell) have been proposed in a variety of studies to serve as a potential proxy for the reconstruction of phytoplankton dynamics. However, the link between phytoplankton and Ba/Cashell profiles remains unclear and needs to be deciphered more accurately. In this study, we analyzed the relationship between Ba/Cashell peaks and specific phytoplankton species, and assessed the applicability of Ba/Cashell ratios as a species-specific phytoplankton proxy. The timing of peaks in highly resolved Ba/Cashell time-series in Pecten maximus shells (Bay of Brest, France) from two years (2011,2012) were compared to the chlorophyll a concentration and the occurrence of individual diatom and dinoflagellate species. In addition, Monte Carlo simulations were used to approximate a species-specific contribution to the measured Ba/Cashell peaks. The results clearly demonstrated that the Ba/Cashell profiles cannot be explained either by the chlorophyll a concentration nor by the total diatom or dinoflagellate abundance. Instead, time-series of specific phytoplankton, especially diatoms, revealed a high degree of synchronicity with Ba/Cashell peaks when temporally lagged by 8 to 13 days (depending on species). The Monte Carlo simulations suggested that the Ba/Cashell peak heights cannot be fully explained by the observed phytoplankton cell concentration, but rather by individually weighted phytoplankton time-series, most likely caused by inter-species differences such as cell size and chemical ability to adsorb Ba. Moreover, the approximated species-specific weighting factors agreed well between the studied years. According to our findings, Ba/Cashell peaks are likely associated with blooms of specific phytoplankton taxa, with a time lag of ca. one to two weeks, and the amount of cell-associated Ba varies between phytoplankton species. These conclusions provide further insights into the formation of Ba enrichments in bivalve shells and

Phytoplankton dynamics in coastal ecosystems is increasingly altered by land-based human activities. Yet, this global vision conceals major disparities, among sites and through time. As conventional monitoring time series are quite sparse and relatively short, biological records of environmental variability appear as relevant tools to gain insights into phytoplankton dynamics over larger temporal and spatial scales. Here, we present results of an interdisciplinary project dealing with chemical information archived in shells of Pecten maximus (Bivalvia; Pectinidae), known to form daily growth striae on its shell surface. Several individuals were collected in the Bay of Brest (France) in 2011 and 2012, and analyzed for the molybdenum and lithium concentrations in their soft tissues and the element-to-calcium ratios (Mo : Ca and Li : Ca) in their calcitic striae. All shells revealed high synchrony and reproducibility in their Mo : Ca and Li : Ca profiles, characterized with a major peak at the end of May and in mid-June 2011, respectively. Detailed analysis of physical, chemical, and biological variables measured in seawater during an extensive 9-month environmental survey enabled a meticulous description of phytoplankton dynamics in 2011 and its impact on shell geochemistry. Main findings strongly suggest that (1) the timing of Mo : Ca peaks reflects the occurrence of silicon limitation and diatom aggregation periods, (2) the height of these peaks relates to the amplitude of the first spring diatom bloom, and (3) Li : Ca serves as a proxy for the temporal dynamics of diatom biovolume and of biogenic silica recycling at the sediment–water interface.

X-ray microspectroscopy is a powerful analytical method in geoscientific and environmental research as it provides a unique combination of nanoscale imaging with high spectroscopic sensitivity at relatively low beam-related sample damage. In this study, “classical” scanning transmission soft X-ray microscopy (STXM) with X-ray absorption spectroscopy and the recently established soft X-ray ptychography are applied to the analysis of selected rock varnish samples from urban and arid desert environments. X-ray ptychography enhances the spatial resolution relative to STXM by up to 1 order of magnitude. With its high chemical sensitivity, it can resolve nanoscale differences in valence states of the key varnish elements manganese (Mn) and iron. Our results emphasize the complex nanoarchitecture of rock varnish as well as the diverse mineralogy of the Mn oxy–hydroxide matrix and its embedded dust grains. In contrast to the fast-growing urban varnish, the slow-growing arid desert varnish revealed a remarkable nanoscale stratification of alternating Mn valence states, providing hints on the layer-wise and still enigmatic growth process., Version of record

Oxygen depletion threatens an increasing number of shallow water environments, specifically habitats below the seasonal halocline in coastal settings of the Baltic Sea. To understand the natural variations of dissolved oxygen levels on seasonal and inter-annual time-scales prior to the instrumental era, high-resolution archives are urgently required. The present study evaluates the potential use of Mn/Ca values in shells of the bivalve, Arctica islandica to infer concentrations of past dissolved oxygen concentrations. This study is based on laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) data of six contemporaneous specimens and demonstrates that background variations of shell Mn/Ca are inversely linked to dissolved oxygen concentrations in the water column (r = −0.68; R2 = 0.46, p < 0.0001), which in turn are coupled to the amount of dissolved Mn. The regular seasonal changes were superimposed by sharp Mn/Ca peaks, most likely resulting from the ingestion of a large amount of Mn-rich organic particles. The availability of such particles can increase due to the resuspension of food particles by strong bottom currents or alternatively, result from increased particle flux from surface waters after major river discharges and subsequent phytoplankton blooms. Besides sharp Mn/Ca peaks, often accompanied by sharp Ba/Ca peaks and increased shell growth rate. In addition, after exceptional major barotropic inflows from the North Sea, the biogeochemical steady-state conditions remained disturbed for up to ca. two years, because the redox-sensitive elements were removed from the water column by oxygenated waters, and it took time for them to build up again in the water column. Therefore, subsequent to such Major Baltic Inflows (MBIs), dissolved Mn levels and shell Mn/Ca values were strongly reduced despite summertime low-oxygen conditions. As demonstrated here, Mn/Ca data of A. islandica shells can potentially serve as a proxy for dissolved oxygen

info:eu-repo/semantics/published

Stable carbon and nitrogen isotope ratios of collagen from bone and dentin have frequently been used for dietary reconstruction, but this method is limited by protein preservation. Isotopes of the trace element zinc (Zn) in bioapatite constitute a promising proxy to infer dietary information from extant and extinct vertebrates. The Zn-66/Zn-64 ratio (expressed as delta Zn-66 value) shows an enrichment of the heavy isotope in mammals along each trophic step. However, preservation of diet-related delta Zn-66 values in fossil teeth has not been assessed yet. Here, we analyzed enamel of fossil teeth from the Late Pleistocene (38.4-13.5 ka) mammalian assemblage of the Tam Hay Marklot (THM) cave in northeastern Laos, to reconstruct the food web and assess the preservation of original delta Zn-66 values. Distinct enamel delta Zn-66 values of the fossil taxa (delta Zn-66(carnivore) < delta Zn-66(omnivore) < delta Zn-66(herbivore)) according to their expected feeding habits were observed, with a trophic carnivore-herbivore spacing of +0.60% and omnivores having intermediate values. Zn and trace element concentration profiles similar to those of modern teeth also indicate minimal impact of diagenesis on the enamel. While further work is needed to explore preservation for settings with different taphonomic conditions, the diet-related delta Zn-66 values in fossil enamel from THM cave suggest an excellent long-term preservation potential, even under tropical conditions that are well known to be adverse for collagen preservation. Zinc isotopes could thus provide a new tool to assess the diet of fossil hominins and associated fauna, as well as trophic relationships in past food webs.

The North Atlantic Oscillation is the dominant atmospheric pressure mode in the North Atlantic region and affects winter temperature and precipitation in the Mediterranean, northwest Europe, Greenland, and Asia1. The index1 that describes the sea-level pressure difference between Iceland and the Azores is correlated with a dipole precipitation pattern over northwest Europe and northwest Africa. How the North Atlantic Oscillation will develop as the Greenland ice sheet melts is unclear2. A potential past analogue is the early Holocene, during which melting ice sheets around the North Atlantic3, 4 freshened surface waters, affecting the strength of the meridional overturning circulation5. Here we present a Holocene rainfall record from northwest Africa based on speleothem δ18O and compare it against a speleothem-based rainfall record from Europe6. The two records are positively correlated during the early Holocene, followed by a shift to an anti-correlation, similar to the modern record, during the mid-Holocene. On the basis of our simulations with an Earth system model, we suggest the shift to the anti-correlation reflects a large-scale atmospheric and oceanic reorganization in response to the demise of the Laurentide ice sheet and a strong reduction of meltwater flux to the North Atlantic, pointing to a potential sensitivity of the North Atlantic Oscillation to the melting of ice sheets.

We applied three different LA systems (213 nm nanosecond solid state, 193 nm nanosecond excimer, and 200 nm femtosecond laser) coupled to a quadrupole ICP-MS or a sector field ICP-MS, respectively, for the analysis of different sulfide minerals (pyrrhotite, chalcopyrite, and sphalerite). Ablation craters were investigated via back-scattered electron (BSE) images to compare the amounts of melt produced, and fractionation factors were calculated to determine the degree of down-hole fractionation. Our results show significant differences in melting between the three LA systems. While samples show massive melting when using the ns systems, no melting has been observed utilizing the fs laser. Fractionation factors for a variety of elemental pairs indicate the absence of down-hole fractionation even at the highest melt production. The extent of melting of different sulfide specimens is independent of melting temperatures of these materials. Although no down-hole fractionation has been observed, Fe/S fractionation as calculated from sensitivities deviate among pyrrhotite and chalcopyrite when applying the 193 nm ns and 200 nm fs systems. Analyses of synthetic pyrrhotite with known PGE concentrations using the 200 nm fs LA system yielded moderately precise and accurate concentration data (3–4%; 4–14% 2SD) utilizing sulfide as the external reference material. Application of NIST610 as the reference material improved the precision to 1.4–2.4% 2SD and the deviation from reference values to 5–7%.