Continental palaeoclimate archives in subseasonal resolution remain limited in Europe, restricting insights into short-term environmental variability. This study investigates the freshwater gastropod Viviparus hellenicus as a potential high-resolution climate archive, using specimens from six habitats in Lake Trichonida, Greece, a large, deep lake in a semi-arid Mediterranean setting. Stable isotope patterns across shell ontogeny reveal sinusoidal delta 18O patterns indicative of annual cycles, with minimal seasonal bias and strong correlation to water temperature. These trends suggest that evaporation exerts limited isotopic influence in well-buffered, deep limnic systems despite semi-arid climatic conditions. In contrast, shells from a nearby shallow, transitional site show greater sensitivity to shifting water sources and evaporative enrichment of the lake water, underscoring the role of local hydrology in shaping isotopic signals. While the shells reliably record seasonal interannual temperature variability, observed delta 18O offsets and intraspecific variability complicate absolute temperature reconstructions. These uncertainties are likely to be amplified in fossil assemblages. Overall, Viviparus shells are considered promising high-resolution archives of continental climate, provided that local ecological and hydrological contexts are carefully considered.

Coral holobionts acquire energy and nutrients from heterotrophic feeding, Symbiodiniaceae symbiosis, and additional metabolic functions (e.g. nitrogen (N) fixation) from associated bacterial communities. Since symbioses often require stable environmental conditions, corals in environments with seasonal variability have likely evolved adaptation strategies by either maintaining (i.e. regulating) or shifting (i.e. conforming) key functional traits, but empirical data is needed. We investigated carbon (C) and N elemental and stable isotope ratios alongside bacterial community composition in the hydrocoral Millepora dichotoma and the scleractinian coral Stylophora pistillata every two months over one year. These data were integrated with environmental parameters to investigate potential adaptation strategies of the coral holobionts over a seasonal cycle. S. pistillata showed temporal changes in δ13C, δ15N and C:N ratios in both host and Symbiodiniaceae tissues (indicating stable host-Symbiodiniaceae C/N cycling), in combination with stable bacterial communities. M. dichotoma, did not exhibit temporal changes in elemental and stable isotope ratios, but higher δ15N and C:N variability, and 61% higher C:N ratios in Symbiodiniaceae compared to host tissue. Temporal shifts in bacterial communities resulted in significantly enriched predicted metabolic functions for C, N, and sulfur cycling in winter. Stable C/N cycling and bacterial community composition suggest a regulator-like life history strategy of S. pistillata, whereas variable C/N cycling and flexible bacterial communities indicate a conformer-like life history strategy for M. dichotoma. Both contrasting adaptation strategies enable these organisms to succeed amid current environmental change, yet to what extent this can be maintained under future climate scenarios remains to be investigated.

ABSTRACT Nutrient cycling across ecosystems is driven by complex ecological interactions, potentially impacting environmental stability. Savanna ecosystem processes are highly driven by large mammalian herbivores, so removing them likely causes significant changes in nutrient cycling in both terrestrial and aquatic habitats. Aquatic organisms in temporary savanna ponds, such as amphibian larvae (i.e., tadpoles), are good models to study this potential indirect impact. In the savanna of Comoé National Park, Ivory Coast, large mammalian herbivores declined through two civil war periods in 2002 and 2011. This led to a subsequent increase in terrestrial and aquatic vegetation density, and an altered tadpole community composition. In this study, we used stable isotope analysis to examine potential shifts in energy sources and food web positioning of savanna tadpoles. We compared tadpole samples collected before (1995 and 1996) and after the wars (2014, 2018, and 2019) from two ponds. We detected a general decrease in δ15N among tadpoles, which we interpret as a consequence of a baseline shift in δ15N values following mammalian declines. There was no overall shift in δ13C signals, suggesting that changes in primary energy resources were minimal. Observed interannual changes in isotope signals were taxon‐specific, reflecting differences in tadpoles' morphologies and respective diets, as well as site‐specific, reflecting different pond characteristics. Our findings indicate the potential importance of large mammalian herbivores in maintaining savanna ecosystem stability.

Pedogenic carbonates can provide important information regarding paleoclimatic conditions. Compared with East Africa, Pleistocene pedogenic carbonates in Sudan, particularly calcretes, have received very little attention, particularly with regard to local paleoclimatic reconstructions. Pleistocene alluvial sediments aged from similar to 230 to <17 ka were deposited along the middle Atbara River in eastern Sudan. Intercalated in these alluvial deposits are paleosols in which different types of pedogenic carbonates occur. Petrographic, mineralogical and isotopic analyses were performed to reconstruct the regional paleoenvironmental conditions. The investigated pedogenic carbonates are appropriate for paleoclimatic reconstruction because they are free of inherited carbonate and diagenetic modification. The paleosols identified in a previous study as Aridisols/Calcisols contain calcrete horizons that consist of an orthic nodular horizon, sometimes overlain by a laminar horizon. Paleosols identified as Vertisols contain slickensides, and disorthic and septaric nodules. The paleosols show stable carbon and oxygen isotope values ranging between -9.12 and -5.12 parts per thousand, and between -7.25 and -4.09 parts per thousand, respectively. Supporting the previous study, the inferred climatic conditions were arid to semi-arid, with a mixture of C-3 and C-4 vegetation cover, and paleoprecipitation greater than 350 mm/yr, similar to that of the present-day, with likely higher rainfall during the formation of Vertisols than Aridisols/Calcisols. The thickness and morphology of Pleistocene calcretes in eastern Sudan are similar to those in East Africa, suggesting similar climatic conditions during their formation. Well-and weakly-developed calcretes in Aridisols formed in distal and proximal floodplains, respectively, whereas well-developed vertic horizon in Vertisols formed in distal floodplains.

The Mediterranean Sea is warming at a rate exceeding the global average. Long-term, high-resolution data are essential for contextualizing changes within broader temporal scales, and coral skeletons provide valuable environmental archives, especially in data-sparse regions or as supplements to existing records. While coral-based reconstructions are well established in tropical settings, they remain limited in temperate areas. As the only reef-building zooxanthellate coral in the Mediterranean, Cladocora caespitosa is particularly important for expanding coral-based environmental archives in these understudied regions. Here, we present records of delta 18O and delta 13C in the skeletons of C. caespitosa from a global change sentinel site in NW Mediterranean. This study provides the most accurate temperature-delta 18O calibration equations for C. caespitosa, including a traditional linear model and a novel exponential model that better accounts for the region's wide seasonal temperature range. Both calibrations rely on long-term in situ water temperature data and a multi-corallite composite approach to reduce non-climatic variability. Seasonal trends in delta 13C reveal, for the first time, variation in the coral's autotrophy-heterotrophy balance, while geochemical anomalies in the skeletons signal thermal stress effects on biomineralization. Our findings establish C. caespitosa skeletons as critical archives for reconstructing anthropogenic warming and its ecological effects in the Mediterranean.

The present study aims to understand the impact of submarine groundwater discharge (SGD) on a coastal area with different lithology and degrees of SGD. Sampling campaigns took place in Puck Bay and the Gulf of Gdańsk, southern Baltic Sea encompassing years between 2009 and 2021. The methodological approach combined geophysical characterization of the surface sediments with detailed spatial and temporal (isotope) biogeochemical investigations of pore and surface waters, and was supported by nearshore groundwater and river surveys. Acoustic investigations identified areas of disturbance that may indicate zones of preferential SGD release. The composition of porewater and the differences in the bay's surface waters disclosed SGD as common phenomenon in the study area. Regional SGD was estimated through a radium mass balance. Local estimation of SGD, based on porewater profiles, revealed highest SGD fluxes at the sandy shoreline, but relatively low elemental fluxes. Though SGD was low at the muddy sites corresponding elemental fluxes of nutrients and dissolved carbon exceeded those determined at the sandy sites due to intense diagenesis in the top sediments. SGD appears to be sourced from different freshwater endmembers; however, diagenesis in surface sediments substantially modified the composition of the mixed solutions that are finally discharged to coastal waters. Overall, this study provides a better understanding of the SGD dynamics in the region by a multi-approach and emphasizes the need to understand the processes occurring at the sediment-water interface when estimating SGD.

The causes of early metazoan diversification during the Ediacaran-Cambrian transition interval are controversial, partly because the global correlation of the Ediacaran-Cambrian boundary remains problematic due to a lack of unambiguous stratigraphic markers. Here we report geochemical data from two fossiliferous sections (Majada de Andaluz and Vía Verde) that straddle the Ediacaran-Cambrian interval in the Central Iberian Zone, Spain. Carbon isotope chemostratigraphy reveals a rise to a low positive δ13Ccarb plateau at the base of the Majada section, which is associated with the first appearance of Cloudina and a pristine Sr isotope value of 0.708512, suggesting that the lower Villarta Formation correlates with the terminal Ediacaran strata in China and Namibia. A prominent negative δ13Ccarb excursion is also revealed from the lower member of the Villarta Formation at Majada, likely corresponding to the global basal Cambrian carbon isotope excursion (BACE). Nitrogen isotope data from the correlative Vía Verde section reveal a similar trend to that found in coeval strata of South China, and indicate a change from predominantly anaerobic to aerobic nitrogen cycling in Central Iberia. By correlating sections in which both the BACE excursion and Treptichnus pedum are recognized, it appears that T. pedum is exclusively found above the BACE, which postdates the last appearance of Cloudina and a negative δ13Ccarb plateau. Further studies of sections with both fossil and isotopic control will help to constrain the timing and causation of Ediacaran-Cambrian bioradiations as well as their relationship to global carbon cycle perturbations.

The hyperarid Atacama Desert is one of the driest and oldest deserts on Earth, rendering it a valuable climate archive. However, unraveling its past climate is particularly challenging and the few studied paleoclimate records of the region reveal strong temporal and spatial variabilities. To enhance our understanding of these dynamics we investigated a sedimentary record in the Yungay valley located in the southern hyperarid Atacama Desert. We employed paleomagnetic and radiocarbon dating, and for the first time for Atacama Desert sediments, a meteoric Be-10/Be-9 based method for determining the depositional age. The respective 4.20 m deep profile comprises a lower alluvial fan deposit with a maximum age of 3.8 +/- 0.8 Ma, and an upper 1.84 m thick clay pan deposit that has accumulated over the last 19 ka. Different proxies including grain size, salt concentration, and elemental composition indicate an aridity increase around 2.3 Ma ago and repeated dry and wet phases during the late Pleistocene and the Holocene. The latter climatic shifts can be assigned to variabilities of the South American Summer Monsoon and El Ni & ntilde;o Southern Oscillation with moisture sources from the Atlantic and the Pacific Ocean, respectively. This study provides deeper insights into the heterogeneous climate of the hyperarid Atacama Desert and underlines the importance of interdisciplinary investigations to decipher climate systems and their effect on potential habitable regions in such an extreme environment.

The Eocene–Oligocene transition (EOT, ca. 40–33 Ma) marks a transformation from a largely ice-free to an icehouse climate mode that is well recorded by oxygen-stable isotopes and sea surface temperature proxies. Opening of the Southern Ocean gateways and decline in atmospheric carbon dioxide levels have been considered as factors in this global environmental transformation and the growth of ice sheets in Antarctica during the Cenozoic. A more comprehensive understanding is still needed of the interplay between forcing versus response, the correlation among environmental changes, and the involved feedback mechanisms. In this study, we investigate the spatio-temporal variation in export productivity using biogenic Ba (bio-Ba) from Ocean Drilling Program (ODP) sites in the Southern Ocean, focusing on possible mechanisms that controlled them as well as the correlation of export productivity changes to changes in the global carbon cycle. We document two high export productivity events in the Southern Ocean during the late Eocene (ca. 37 and 33.5 Ma) that correlate to proposed gateway-driven changes in regional circulation and to changes in global atmospheric pCO2 levels. Our findings suggest that paleoceanographic changes following Southern Ocean gateway openings, along with more variable increases in circulation driven by episodic Antarctic ice sheet expansion, enhanced export production in the Southern Ocean from the late Eocene through early Oligocene. These factors may have played a role in episodic atmospheric carbon dioxide reduction, contributing to Antarctic glaciation during the Eocene–Oligocene transition.

Franz et al. (2023) report a diverse and three-dimensionally preserved suite of mid-Proterozoic microfossils from miarolitic cavities within the granitic Volyn pegmatite field, a major granitic plutonic complex in NW Ukraine. The biota is dated at between ∼ 1.76 and ∼ 1.5 Ga and includes fungus-like objects. This biota is reported as evidence of organisms living within the continental lithosphere, illuminating part of a ∼ 1.8–0.8-billion-year interval of the Proterozoic Eon characterised by relatively low climatic variability and slow biological evolution. We show that at least some of this putative diversity represents modern contamination including plant hairs, a distinctive pollen grain assignable to the extant conifer genus Pinus, and likely later fungal growth. Comparable diversity is shown to exist in modern museum dust, presented as an example of potential airborne contamination and calling into question whether any part of the Volyn “biota” is biological in origin. We emphasise the need for scrupulous care in collecting, analysing, and identifying Precambrian microfossils.

Abstract. Head et al. (2023) emphasize the importance of the Volyn biota for the evolution, especially in the so-called ‘boring billion’, in a detailed outline about the biological and geological context. However, they question that the Volyn biota represent Precambrian fossils and instead argue that they are young contaminants of ‘museum dust’. In addition, they postulate that they are of abiotic origin. We present here a detailed discussion of their points of concern based on presented data, including some additional information. Their points of concern were: One object, shown by Franz et al. (2023) is similar to a pollen grain, another object is similar to trichomes; we show indications for fossilization and summarize our arguments against ‘museum dust’. They question the fossil character of the biota and argue for a biomineralization; we show that the biomineralization in trichomes is distinct from the mineralization of the biota. They missed information about the internal structure; we repeat the presented information about the internal structure in more detail, which is also indicative of fossil material and inconsistent with trichomes. They argue that we did not compare via infrared spectroscopy the biota with recent fungi; since the biota experienced temperatures near 300 °C, we think that a comparison with thermally degraded chitosan is more appropriate. They question the use of strongly negative δ13C as an argument for biotic origin, but we show that in combination with positive δ15N values and the geological situation, a biotic origin is more likely than abiotic synthesis. In addition, Popov (2023) questioned the age of the Volyn biota, which we postulated as between approximately 1.5 and 1.7 Ga. He argues that the fossils could be Phanerozoic. We will also outline our arguments for the minimum age of 1.5 Ga.

The Volyn biota, fossilized organisms with a minimum age of 1.5 Ga, were found in cavities in granitic pegmatites from the Korosten Pluton, NW Ukrainian shield. Fossilization was due to an influx of hydrothermal fluorine-rich waters, which silicified the outermost part of the organisms, thus preserving the 3D morphology. Details of the morphology (investigated by scanning electron microscopy) show that the majority of the specimens are filamentous, of a large variety with diameters ranging from similar to 10 to similar to 200 mu m, thin filaments with typical branching and thick filaments with ball-shaped outgrowths and dented surface. Filaments can be straight or conical, curvilinear, or strongly curved, up to millimeters in length, some with a central channel. Some filaments show indications of segmentation and are grown as sessile organisms onto substrate; others show both intact ends, indicating a non-sessile, free-living lifestyle. Objects with flaky morphology and agglutinating filaments are interpreted as fossil biofilms. Other objects are hollow and show a large variety of forms; spherical objects are scarce. Infrared spectroscopy indicates the presence of chitosan in one filament type, electron microprobe analysis of nanometer-sized inclusions in filaments identified the presence of Bi(Te,S) minerals, and both observations are compatible with the interpretation as fungi-like organisms. Stable C- and N-isotope data of bulk samples are in the range of -31 parts per thousand to -47 parts per thousand delta C-13 and of +3 parts per thousand to +10 parts per thousand delta N-15, indicating possible methanogens as part of the subsurface microecosystem. The Volyn biota indicate that at 1.5 Ga complex forms of life existed in the continental deep biosphere, well above the microscopic level, including fungi-like organisms resembling eukaryotes.

Abstract Increasing urbanisation and intensified agriculture lead to rapid transitions of ecosystems. Species that persist throughout rapid transitions may respond to environmental changes across space and/or time, for instance by altering morphological and/or biochemical traits. We used natural history museum specimens, covering the Anthropocene epoch, to obtain long‐term data combined with recent samples. We tested whether rural and urban populations of two ground beetle species, Harpalus affinis and H. rufipes, exhibit spatio‐temporal intraspecific differences in body size. On a spatial scale, we tested signatures of nitrogen and carbon stable isotopes enrichments in different tissues and body components in recent populations of both species from urban and agricultural habitats. For body size examinations, we used beetles, collected from the early 20th century until 2017 in the Berlin‐Brandenburg region, Germany, where urbanisation and agriculture have intensified throughout the last century. For stable isotope examinations, we used recent beetles from urban and agricultural habitats. Our results revealed no spatio‐temporal changes in body size in both species' females. Body size of H. rufipes males decreased in the city but remained constant in rural areas over time. We discuss our findings with respect to habitat quality, urban heat and interspecific differences in activity pattern. Although nitrogen isotope ratios were mostly higher in specimens from agricultural habitats, some urban beetles reached equal enrichments. Carbon signatures of both species did not differ between habitats, detecting no differences in energy sources. Our results indicate that increasing urbanisation and intensified agriculture are influencing species' morphology and/or biochemistry. However, changes may be species‐ and sex‐specific.

The boundary between the Devonian and the Carboniferous has been drawn using ammonoids, conodonts and miospores, while geochemical data have only rarely been used. The sampling of eight sections (Aprath, Apricke, Effenberg, Wocklum, Stockum, Drewer WJ, Drewer WA, Marsberg) at the northern margin of the Rhenish Mountains demonstrates the potential of the isotope ratio of organic carbon to regionally correlate sections in different facies areas. With the help of the carbon isotopes, a distinct stratigraphic succession is documented, which is characterised by several positive and negative excursions; this succession was recorded in all examined sections. The carbon isotopes can therefore make a significant contribution to the stratigraphic subdivision of sections and complement the biostratigraphic methods.

The Miocene mica‐clay deposits of Groß Pampau (northern Germany) are well known for their diverse assemblages of marine mammals. Despite numerous systematic and biostratigraphic studies, an in‐depth palaeoecological analysis of its molluscan assemblages and a comprehensive palaeoenvironmental reconstruction are lacking. Here, we integrate new faunal, sedimentological and geochemical data to reconstruct the marine palaeoecosystem of the Upper Miocene sedimentary succession of Groß Pampau, and to identify the drivers controlling the composition, ecological structure and temporal dynamics of its macrobenthic molluscan assemblages. Fossil evidence, coupled with analyses of clay mineral composition, grain size distribution and geochemical data (total organic carbon, total nitrogen, δ 13 C, δ 18 O, δ 15 N of sediment and shells), suggests a warm–temperate, mesotrophic, low‐energy, offshore marine setting mostly below storm wave base and a pronounced surface‐to‐bottom water temperature gradient. Low variability in sedimentological and geochemical signals indicates generally stable physicochemical conditions, whereas the occurrence of the opportunistic species Varicorbula gibba suggests occasionally unfavourable bottom conditions, possibly related to transient hypoxia. Canonical correspondence analysis indicates that the distribution of molluscan assemblages correlates with total organic carbon and nitrogen content, suggesting organic matter availability at the sea floor as a controlling factor. A pattern of repetitive punctuated stasis of molluscan assemblages is defined by the temporal persistence in taxonomic and ecological composition, occasionally interrupted by shifts to a different faunal configuration. We suggest that both stable environmental conditions and biotic interactions (i.e. the top‐down control exerted by carnivorous gastropods and environmental modification by ubiquitous burrowing deposit feeders) probably contributed to the observed temporal stability.

Abstract. Agglutinated foraminiferal assemblages of the Turonian–Coniacian from the GSSP (Global Boundary Stratotype Section and Point) of Salzgitter–Salder (Subhercynian Cretaceous Basin, Germany) and other sections, including Bielefeld–Ostwestfalendamm (Münsterland Cretaceous Basin, Germany) and the Dover–Langdon Stairs (Anglo-Paris Basin, England), from the temperate European shelf realm were studied in order to collect additional stratigraphic and paleoenvironmental information. Stable carbon isotopes were measured for the Bielefeld–Ostwestfalendamm section to establish a reliable stratigraphic correlation with other sections. Highly diverse agglutinated foraminiferal assemblages were obtained from sections in the German basins, whereas the fauna from Dover is less rich in taxa and less abundant. In the German basinal sections, a morphogroup analysis of agglutinated foraminifera and the calculated diversities imply normal marine settings and oligotrophic to mesotrophic bottom-water conditions. Furthermore, acmes of agglutinated foraminifera correlate between different sections and can be used for paleoenvironmental analysis. Three acmes of the species Ammolagena contorta are recorded for the Turonian–Coniacian (perplexus to lower striatoconcentricus zones, lower scupini Zone, and hannovrensis Zone) and likely imply a shift to more oligotrophic bottom-water conditions. In the upper scupini Zone below the Turonian–Coniacian boundary, an acme of Bulbobaculites problematicus likely indicates enhanced nutrient availability. In general, agglutinated foraminiferal morphogroups display a gradual shift from Turonian oligotrophic environments towards more mesotrophic conditions in the latest Turonian and Coniacian.

The resistance of hard corals to warming can be negatively affected by nitrate eutrophication, but related knowledge for soft corals is scarce. We thus investigated the ecophysiological response of the pulsating soft coral Xenia umbellata to different levels of nitrate eutrophication (control = 0.6, medium = 6, high = 37 μM nitrate) in a laboratory experiment, with additional warming (27.7 to 32.8 °C) from days 17 to 37. High nitrate eutrophication enhanced cellular chlorophyll a content of Symbiodiniaceae by 168%, while it reduced gross photosynthesis by 56%. After additional warming, polyp pulsation rate was reduced by 100% in both nitrate eutrophication treatments, and additional polyp loss of 7% d −1 and total fragment mortality of 26% was observed in the high nitrate eutrophication treatment. Warming alone did not affect any of the investigated response parameters. These results suggest that X. umbellata exhibits resistance to warming, which may facilitate ecological dominance over some hard corals as ocean temperatures warm, though a clear negative physiological response occurs when combined with nitrate eutrophication. This study thus confirms the importance of investigating combinations of global and local factors to understand and manage changing coral reefs.

Abstract. The Volyn biota, fossilized organisms with a minimum age of 1.5 Ga, were found in cavities in granitic pegmatites from the Korosten pluton, NW Ukrainian shield. Fossilization was due to influx of hydrothermal fluorine-rich waters, which silicified the outermost part of the organisms, thus preserving the 3D morphology. Details of the morphology (investigated by scanning electron microscopy) show that the majority of the specimens is filamentous, of a large variety with diameters ranging from ~10 µm to ~200 µm, thin filaments with typical branching, thick filaments with ball-shaped outgrowths and dented surface. Filaments can be straight or conical, curvilinear or strongly curved, up to mm in length, some with a central channel. Some filaments show indications for segmentation, are grown as sessile organisms onto substrate; others show both intact ends, indicating growth in soft medium or floating in water. Objects with flaky morphology and agglutinating filaments are interpreted as fossil biofilms. Other objects are hollow and show a large variety of forms; spherical objects are scarce. Infrared spectroscopy indicates the presence of chitosan in one filament, electron microprobe analysis of nm-sized inclusions in filaments identified the presence of Bi(Te,S) minerals, and both observations are compatible with the interpretation of filaments as fungi-like organisms. Stable C- and N-isotope data of bulk samples are in the range of -31 to -47 ‰ δ13C/12C, and of +3 to +10 ‰ δ15N/14N, indicating possible methanogenic bacteria as part of the subsurface micro-ecosystem. The Volyn biota show that at 1.5 Ga fungi-like organisms lived in the continental deep biosphere, where complex forms of life existed, well above the microscopic level.

Extraordinary innovation of metazoans and their morphological diversity have been linked to a major step in the oxygenation of the Earth surface system in the late Ediacaran–early Cambrian. However, the role of oxygen in driving animal evolution has been an intense debate, as emerging geochemical evidence has implied a static state or unidirectional change in marine redox landscape. Nitrogen is an essential nutrient for living organisms, and has the great potential to establish linkages between nutrient cycle, marine redox, and biological evolution. In this study, we conducted a high-resolution analysis of nitrogen isotopes for the early Cambrian succession within a deep basinal drill-core section (Huitong) from Hunan Province, South China. Combining new and published nitrogen isotope data from the Nanhua Basin, we propose two phases of δ15N variations alongside a long-term decrease in δ15N baseline during the late Ediacaran–Cambrian Age 4. The first one was characterized by temporal δ15N swings in the late Ediacaran–Cambrian Age 2, and the second one was marked by the rise in spatial δ15N heterogeneity in the Cambrian Age 3–Age 4. This spatiotemporal pattern of δ15N variations indicates a shift from temporal redox fluctuations to spatial redox heterogeneity, along with deoxygenation in the continental basin from the late Ediacaran to Cambrian Age 4. Correspondingly, the nitrogen sources for primary producers have changed from dominantly single speciation in the late Ediacaran–Cambrian Age 2 to multiple speciation during the Cambrian Age 3–Age 4. We propose that the spatial heterogeneities in oxygen levels and nitrogen speciation along the continental shelf was probably the main controlling factor for the rapid proliferation of metazoans in the Cambrian Epoch 2.