Past Environments Research Articles

Solving a ‘puzzle’. The global 4.2 ka Bond Event at El Mirador cave (Sierra de Atapuerca, Burgos, Spain) and the importance of small mammal taphonomy to the interpretation of past environments and their climatic controls

The regional climatic context in which Chalcolithic (MIR5) and Bronze Age (MIR4) levels from El Mirador cave (Sierra de Atapuerca, Burgos, Spain) are framed is affected by the 4.2 ka cal. BP event, a global event defined as a cooling and aridification phase. Previous works based on palaeoenvironmental inferences indicate conflicting results regarding the possible impact of the event on vegetation and small mammals from MIR5. Pollen record illustrates a possible aridification episode that could match with the 4.2 ka cal. BP event, while the signal of this event is not clearly recorded in the small mammal assemblage, which indicates more humid environmental conditions than pollen record. Taphonomic analyses confirmed that the small mammal assemblages from MIR4 and MIR5 are the result of predation, supporting the involvement of European eagle owls ( Bubo bubo) in its formation. This avian raptor shows a marked preference for hunting animals living in the more open and wetter parts of their hunting range. Likewise, spontaneous specialisation on abundant prey species could also be observed under certain environmental conditions. This characteristic behaviour of eagle owls may have provided the contradictory results observed between the small mammal assemblage and palynological evidence. Nonetheless, taphonomic analyses also provided information about climatic conditions and fluctuations along time. The low incidence of manganese coatings and carbonate crusts deposits in small mammal bone remains from MIR5 support the presence of arid conditions during the formation of this level, which agreed with the aridification phase probably related to the 4.2 ka Bond Event inferred by palynological data from MIR5. These results provided a more robust conclusion about the paleoenvironmental contexts during the formation of Chalcolithic and Bronze Age levels at El Mirador cave.

Experimental evolution of environmental tolerance, acclimation, and physiological plasticity in a randomly fluctuating environment.

Environmental tolerance curves, representing absolute fitness against the environment, are an empirical assessment of the fundamental niche, and emerge from the phenotypic plasticity of underlying phenotypic traits. Dynamic plastic responses of these traits can lead to acclimation effects, whereby recent past environments impact current fitness. Theory predicts that higher levels of phenotypic plasticity should evolve in environments that fluctuate more predictably, but there have been few experimental tests of these predictions. Specifically, we still lackexperimental evidence for the evolution of acclimation effects in response to environmental predictability. Here, we exposed 25 genetically diverse populations of the halotolerant microalgae Dunaliella salina to different constant salinities, or to randomly fluctuating salinities, for over 200 generations. The fluctuating treatments differed in their autocorrelation, which determines the similarity of subsequent values, and thus environmental predictability. We then measured acclimated tolerance surfaces, mapping population growth rate against past (acclimation) and current (assay) environments. We found that experimental mean and variance in salinity caused the evolution of niche position (optimal salinity) and breadth, with respect to not only current but also past (acclimation) salinity. We also detected weak but significant evidence for evolutionary changes in response to environmental predictability, with higher predictability leading notably to lower optimal salinities and stronger acclimation effect of past environment on current fitness. We further showed that these responses are related to the evolution of plasticity for intracellular glycerol, the major osmoregulatory mechanism in this species. However, the direction of plasticity evolution did not match simple theoretical predictions. Our results underline the need for a more explicit consideration of the dynamics of environmental tolerance and its underlying plastic traits to reach a better understanding of ecology and evolution in fluctuating environments.

Passivity of iron surface in curing cement paste environment investigated by electrochemical impedance spectroscopy and surface characterization techniques

The curing behaviour of cement paste and formation of passive film on iron were investigated by electrochemical techniques and X-ray photoelectron spectroscopy (XPS). Open circuit potential of iron was monitored with the newly developed solid-contact-chloride reference electrode in cement paste with pH ∼13 laid at ∼0 VSHE for 56 d, indicating iron was kept in passive state. Electrochemical impedance spectroscopy results showed significant increasing trend of film and cement paste resistance with curing time. XPS elucidated formation of ferric hydroxide and ferric oxide was efficient to passivate the iron rather than ferrous products. Iron surface receded from corrosion due to high-alkaline environment of cement paste and formation of passive film.

Short-term microbial effects on n-alkane during the early phase degradation and consequential modification of biomarkers in a lowland subtropical rainforest in southern Taiwan: A litterbag experiment

Accurate reconstructions of past environments are critical and urgent because they can help understand how modern environments might respond to current climatic and land-use changes. However, the effect of microbial degradation and consequential modification in plant-derived-biomarkers during the early degradation phase is not yet apparent, that might bias the paleoenvironmental investigation. In this regard, a litterbag experiment was conducted to reveal the microbial effects on n-alkane-associated biomarker changes associated with three habitats (ravine, windward, and leeward) in a lowland subtropical rainforest in southern Taiwan. Freshly collected leaves of plant species Iles rotunda, Ficus benjamina, and Castanopsis carlesii were distributed in the habitat leaf litterbag experiment for 15 and 75 days incubation, respectively. The results revealed that the average leaf decomposition rate was 19.4% ± 6.4% during the first 15 days and 39% ± 11% within 75 days incubation for all leaves. The overall leaf mass degradation of I. rotunda, F. benjamina and C. carlesii in the ravine after 75 days was 58%, 51% and 41%, respectively, which were higher than those in the windward (28%, 36% and 38%) and leeward habitats (35%, 26% and 42%, respectively) indicating higher decomposition rate in the ravine habitat than the others. The predominant n-alkanes in I. rotunda were C31 and C29, whereas in F. benjamina these were C31, C29, and C33, and in C. carlesii it was C31. After 75 days, the ravine habitat showed a 60% decrease in the total n-alkane concentration compared to windward and leeward habitats, suggesting the microbial community associated with the ravine habitat has a higher efficiency of degrading n-alkanes. However, the biomarkers such as carbon preference index (CPI), average carbon length (ACL) and the C31/C29 ratio did not show statistical difference in all habitats from 15 to 75 days incubation. The next-generation sequencing revealed that microbial communities changed significantly from 15 to 75 days in all habitats. The alkB gene-containing bacteria and their family lineages increased substantially during the first 15 days incubation in all habitats. Furthermore, several bacterial genera were exclusively present in the ravine habitat, whereas some were only in the leeward and windward habitats. Despite the heterogeneity of microbial proliferation, difference in biomass and n-alkane degradation among the three habitats, most of the n-alkane-associated biomarkers remained the same. Therefore, we concluded that the microbial effects on n-alkane degradation during the early phase in plant leaves had little influence on the results of most n-alkane biomarkers.

Bed II Phytolith Palaeolandscapes (1.5-1.1 Ma) at Oldupai Gorge, Tanzania

The primary approach for reconstructing ancient plant landscapes is normally through the analysis of environmental proxy data and ultimately the application of the data from plant micro-remains to infer the vegetation patterns, distribution, and nature of past environments. Phytolith analyses serve as an important tool for identifying different micro-ecological niches in which human activities occurred. They are indicative of certain plant types and vegetation patterns, and the way in which plant landscapes respond to regional climate changes. Hence, in order to understand the ancient plant landscape of the Pleistocene Bed II sites of Oldupai Gorge 1.5 to 1.1 million years ago (Ma), a location inhabited by our early ancestors, the phytoliths research was conducted in order to reconstruct the ancient plant environments of Oldupai’s Bed II sites, namely Sam Howard Korongo (SHK), Thiongo Korongo (TK), and Bell’s Korongo (BK) because there is no enough phytolith data from these upper sections of Bed II. The preliminary results from this study indicate that TK and BK sites’ plant landscape was dominated by arboreal plants.
 Keywords: Phytolith, hominin, palaeoecology, palaeoenvironments, palaeolandscape

Microvertebrate studies in archaeological contexts: Middle Paleolithic to early Holocene past environments

Microvertebrate studies in archaeological contexts: Middle Paleolithic to early Holocene past environments

Stable isotope profiles of soil organic carbon in forested and grassland landscapes in the Lake Alaotra basin (Madagascar): insights in past vegetation changes

Abstract. The extent to which the central highlands of Madagascar were once covered by forests is still a matter of debate: while reconstructing past environments is inherently difficult, the debate is further hampered by the fact that the evidence documenting land cover changes and their effects on carbon and sediment dynamics in Madagascar has hitherto mainly been derived from lake coring studies. Such studies provide an integrated view over relatively large areas but do not provide information on how land-use change affects hillslopes in terms of carbon and sediment dynamics. Such information would not only be complementary to lake inventories but may also help to correctly interpret lake sediment data. Carbon stable isotope ratios (δ13C) are particularly useful tracers to study the past dynamics of soil carbon over time spans ranging from years to millennia and thus to understand the consequences of land-use change over such time spans. We analysed soil profiles down to a depth of 2 m from pristine forests and grasslands in the Lake Alaotra region in central Madagascar. Along grassland hillslopes, soil organic carbon (SOC) content was low, from 0.4 % to 1.7 % in the top layer, and decreased rapidly to ca. 0.2 % below 100 cm depth. The current vegetation predominantly consists of C4 grasses (δ13C ∼ −13 ‰), yet topsoil δ13C-OC ranges between −23.0 ‰ and −15.8 ‰, and most profiles show a decrease in δ13C-OC with depth. This contrasts with our observations in the C3-dominated forest profiles, which show a typical profile whereby δ13C values increase slightly with depth. Moreover, the SOC stock of grasslands was ∼ 55.6 % lower than along the forested hillslopes for the upper 0–30 cm layer. δ13C values in grassland and forest profiles converge to similar values (within 2.0 ± 1.8 ‰) at depths below ∼ 80 cm, suggesting that the grasslands in the Lake Alaotra region have indeed developed on soils formerly covered by a tree vegetation dominated by C3 plants. We also observed that the percent of modern carbon (pMC) of the bulk OC in the top, middle and lower middle positions of grasslands was less than 85 % near the surface. This could reflect a combination of (i) the long residence time of forest OC in the soil, (ii) the slow replacement rate of grassland-derived OC (iii) and the substantial erosion of the top positions towards the valley position of grasslands. At the valley positions under grassland, the upper 80 cm contains higher amounts of recent grass-derived OC in comparison to the hillslope positions. This is likely to be related to the higher productivity of the grassland valleys (due to higher moisture and nutrient availability), and the deposition of OC that was eroded further upslope may also have contributed. The method we applied, which is based on the large difference in δ13C values between the two major photosynthetic pathways (C3 and C4) in (sub-)tropical terrestrial environments, provides a relatively straightforward approach to quantitatively determine changing vegetation cover, and we advocate for its broader application across Madagascar to better understand the island's vegetation history.

Solving dynamic multi-objective problems using polynomial fitting-based prediction algorithm

Recently, dynamic multi-objective optimization has received growing attention due to its popularity in real-world applications. Inspired by polynomial fitting, this paper proposes a polynomial fitting-based prediction algorithm (PFPA) and incorporates it into the model-based multi-objective estimation of distribution algorithm (RM-MEDA) for solving dynamic multi-objective optimization problems. When an environment change is detected, the main mission of PFPA is to predict high-quality search populations for tracking the moving Pareto-optimal set effectively. Firstly, the non-dominated solutions obtained in past environments are utilized to predict high-quality solutions based on a multi-step movement strategy. Secondly, a polynomial fitting-based strategy is designed to fit the distribution of variables according to the obtained search populations, and capture the relationship between variables in the new search environment. Thirdly, some effective search agents are generated for improving population convergence and diversity based on characteristics of variables. To evaluate the performance of the proposed algorithm, experimental results on a set of benchmark functions, with a variety of different dynamic characteristics and difficulties, and two classical dynamic engineering design problems show that PFPA is competitive with some state-of-the-art algorithms.

On the use of body mass measures in severity assessment in laboratory passerine birds

AbstractCriteria for assessing the severity of scientific procedures in laboratory rodents include the loss of body mass. However, guidance is limited for passerine birds and application of criteria developed for mammals risks poor welfare decisions. Here, I ask whether, and how, body mass criteria could be incorporated into laboratory welfare assessment of passerines. Passerine birds strategically adjust their body mass to minimise combined mortality risk from starvation and predation. A systematic literature review found that strategic mass changes can be sizeable (sometimes > 10%) even over short timescales. Many aspects of a bird's current or past environment, including husbandry and experimental procedures, may alter perceived starvation or predation risks and thus drive strategic mass change via evolved mechanisms. Therefore, body mass criteria used for rodents may be too stringent for passerines, potentially leading to over-estimated severity. Strategic mass changes might obscure those stemming from experimental interventions yet could also offer insights into whether birds perceive an intervention or altered husbandry as a threat. Mass criteria for severity assessment should be species- and context-specific in order to balance needs for refinement and reduction. To guide the development of appropriate criteria, a future research priority is for greater data collection and sharing based on standardised routine monitoring of mass variation under a representative range of husbandry conditions and procedures.

Near-surface structure of a large linear dune and an associated crossing dune of the northern Namib Sand Sea from Ground Penetrating Radar: Implications for the history of large linear dunes on Earth and Titan

• Ground Penetrating Radar images obtained of a large Namib Sand Sea linear dune. • Strata up to ∼ 10 m depth show scouring and abrupt changes. • Alternating strata reveal changes in dominant wind direction. • Subsurface patterns reveal down-axis transport of sand. • Implications for wind direction and sand transport on Saturn’s moon Titan. We imaged the near-surface sedimentary structures of a large linear dune, flanking dune forms and an associated crossing linear dune never before studied in the northern Namib Sand Sea using 200-MHz Ground-Penetrating Radar (GPR). The dry, uniform sandy conditions and wavelength used allowed for highly detailed observations of sedimentary structures to depths of ∼ 12 m across a >1km lateral scan. Sedimentary features observed in the main linear dune include scouring and abrupt changes in strata such as trough cross stratification (TCS), onlap, downlap, truncation and avalanche-related bedding, all a result of complex sand transport conditions. Different phases of deposition have produced an opposed succession of strata on each side of the dune. These successions alternate 2-dimensional (2D), or bedform instability mode features with 3-dimensional (3D), or fingering mode features, separated by a clear process boundary. These alternating successions reflect a change in the dominant wind environment in the recent past. The changing winds may feed into the building and overall stability of this dune field and may be a model for conditions in other large linear/longitudinal dune fields. The subsurface structure of an oblique crossing linear dune demonstrates sand transport generally down the dune long axis in the direction predicted from modern, ERA-Interim model as well as paleoclimate model winds. This suggests relatively long-term stability of this intermediate-sized landform and the potential long-term coexistence of large dunes and secondary forms. These studies have implications for the extensive sand seas of Titan, where lack of large secondary forms may indicate a simple wind regime over long time periods.

Malebogo Mvimi: Past Environments and Plant Use in Holocene Southern Africa. A Study of Charcoal and Seed Remains from the Late Stone Age Sites of Toteng (Botswana), Leopard Cave and Geduld (Namibia)

Malebogo Mvimi: Past Environments and Plant Use in Holocene Southern Africa. A Study of Charcoal and Seed Remains from the Late Stone Age Sites of Toteng (Botswana), Leopard Cave and Geduld (Namibia)

Glaciers as microbial habitats: current knowledge and implication.

Glaciers, formed from the gradual accumulation of snow, can be continuous records representing past environments and recognized as a time capsule of our planetary evolution. Due to extremely harsh conditions, glacial ice has long been considered an uninhabitable ecosystem for microorganisms to sustain their life. However, recent developments in microbiological analysis techniques revealed the presence of unexpectedly diverse microbial strains. Glacial microorganisms could also provide valuable information, including not only biological diversity and structure but also molecular systematics, metabolic profiles, and evolutionary changes from the past climate and ecosystem. However, there are several obstacles in investigating the glacier environment, such as low regional accessibility, technical difficulties of ice coring, potential contamination during the sampling process, and low microbial biomass. This review aims to summarize recent knowledge on decontamination methods, biomass, diversity based on culture-dependent and -independent methods, application of biological proxies, greenhouse gas production and adaptive strategies in glaciers from various regions and to imply further directions for a comprehensive understanding of habitatility in an icy world including outer of our planet.

Paleoproteomics.

Paleoproteomics, the study of ancient proteins, is a rapidly growing field at the intersection of molecular biology, paleontology, archaeology, paleoecology, and history. Paleoproteomics research leverages the longevity and diversity of proteins to explore fundamental questions about the past. While its origins predate the characterization of DNA, it was only with the advent of soft ionization mass spectrometry that the study of ancient proteins became truly feasible. Technological gains over the past 20 years have allowed increasing opportunities to better understand preservation, degradation, and recovery of the rich bioarchive of ancient proteins found in the archaeological and paleontological records. Growing from a handful of studies in the 1990s on individual highly abundant ancient proteins, paleoproteomics today is an expanding field with diverse applications ranging from the taxonomic identification of highly fragmented bones and shells and the phylogenetic resolution of extinct species to the exploration of past cuisines from dental calculus and pottery food crusts and the characterization of past diseases. More broadly, these studies have opened new doors in understanding past human–animal interactions, the reconstruction of past environments and environmental changes, the expansion of the hominin fossil record through large scale screening of nondiagnostic bone fragments, and the phylogenetic resolution of the vertebrate fossil record. Even with these advances, much of the ancient proteomic record still remains unexplored. Here we provide an overview of the history of the field, a summary of the major methods and applications currently in use, and a critical evaluation of current challenges. We conclude by looking to the future, for which innovative solutions and emerging technology will play an important role in enabling us to access the still unexplored “dark” proteome, allowing for a fuller understanding of the role ancient proteins can play in the interpretation of the past.

Global tephra studies: role and importance of the international tephra research group “Commission on Tephrochronology” in its first 60 years

Abstract. Tephrochronology is a correlational and age-equivalent dating method whereby practitioners characterize, map, and date tephra (or volcanic ash) layers and use them stratigraphically as connecting and dating tools in the geosciences (including volcanology) and in studies of past environments and archaeology. Modern tephra studies per se began around 100 years ago (in the 1920s), but the first collective of tephrochronologists with a common purpose and nascent global outlook was not formed until 7 September 1961 in Warsaw, Poland. On that date, the inaugural “Commission on Tephrochronology” (COT) was ratified under the aegis of the International Union for Quaternary Research (INQUA). The formation of COT is attributable largely to the leadership of Kunio Kobayashi of Japan, the commission's president for its first 12 years. We were motivated to record and evaluate the function and importance of COT because tephrochronology continues to grow globally and its heritage needs to be understood, appreciated, and preserved. In addition, studies on cryptotephras, which are fine-grained glass-shard and/or crystal concentrations preserved in sediments or soils but insufficiently numerous to be visible as a layer to the naked eye, have also expanded dramatically in recent times. Therefore, in this article, we review the role and impacts of COT under the umbrella of INQUA for 53 of the last 60 years or under IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior) for 7 of the last 60 years, including since 2019. The commission also functioned under other names (abbreviated as COTS, CEV, ICCT, COTAV, SCOTAV, and INTAV; see Table 2 for definitions). As well as identifying key persons of influence, we describe the development of the commission, its leaders, and its activities, which include organizing nine specialist tephra field meetings in seven different countries. Members of the commission have participated in numerous other conferences (including specialist tephra sessions) or workshops of regional to international scale, and they have played leading roles in international projects such as INTIMATE (INTegrating Ice-core, MArine and TErrestrial records) and SMART (Synchronising Marine And ice-core Records using Tephrochronology). As well as strongly supporting early-career researchers including graduate students, the commission has generated 10 tephra-themed journal volumes and two books. It has published numerous other articles including field guidebooks, reports, and specialist internet documents/sites. Although its fortunes have ebbed as well as flowed, the commission began to prosper after 1987 when key changes in leadership occurred. COT has blossomed further, especially in the past decade or so, as an entire new cohort of specialists, including many engaged in cryptotephra studies, has emerged alongside new geoanalytical and dating techniques or protocols to become a vibrant global group today. We name 29 elected officers who have been involved with COT since 1961 as well as 15 honorary life members. After reviewing the aims of the commission, we conclude by evaluating its legacies and by documenting current and future work.

Tropical environmental change in North Sumatra at the Last Glacial Maximum: Evidence from the stable isotope composition of cave guano

Insular Southeast Asia is of critical importance to global biodiversity, climate, and socioeconomics. Past environmental histories are a crucial factor influencing contemporary patterns and, in this region, fluctuating sea-level and climate change during the Last Glacial Period (LGP) resulted in drastic changes in both land extent and vegetation cover. However, understanding the past environments of this tropical region is hampered by its sheer size and relative lack of traditional continental proxy records, such as lake sediments. To provide further insight into the response of vegetation to the changing environmental conditions, we use the stable carbon isotope composition (δ13C) of a bat guano sequence from Liang Mbelen Cave in North Sumatra, to determine whether tropical grass (C4 vegetation) or forest (C3 vegetation) was present in the area from c. 30 to 10 cal kyr BP. Our results confirm the presence of C4 vegetation during the LGP; however, we find that the timing of grass expansion was just prior to the Last Glacial Maximum (LGM; 23–19 kyr BP). Comparing Liang Mbelen with the other evidence from across the region, we find a generally consistent pattern of peak tropical grasses often occurring prior to the LGM in Sundaland, with the timing of forest encroachment variable, although beginning at c. 25 cal kyr BP. We find that the timing of the shift from savanna to forest systems in Sundaland is similar to changes in obliquity, likely resulting in a decrease or elimination of the dry season that favoured forest expansion. Understanding past vegetation history will help the management and protection of the fragile and ecologically valuable ecosystems of SE Asia.

A global synthesis of ecosystem services provided and disrupted by freshwater bivalve molluscs.

ABSTRACTIdentification of ecosystem services, i.e. the contributions that ecosystems make to human well‐being, has proven instrumental in galvanising public and political support for safeguarding biodiversity and its benefits to people. Here we synthesise the global evidence on ecosystem services provided and disrupted by freshwater bivalves, a heterogenous group of >1200 species, including some of the most threatened (in Unionida) and invasive (e.g. Dreissena polymorpha) taxa globally. Our systematic literature review resulted in a data set of 904 records from 69 countries relating to 24 classes of provisioning (N = 189), cultural (N = 491) and regulating (N = 224) services following the Common International Classification of Ecosystem Services (CICES). Prominent ecosystem services included (i) the provisioning of food, materials and medicinal products, (ii) knowledge acquisition (e.g. on water quality, past environments and historical societies), ornamental and other cultural contributions, and (iii) the filtration, sequestration, storage and/or transformation of biological and physico‐chemical water properties. About 9% of records provided evidence for the disruption rather than provision of ecosystem services. Synergies and trade‐offs of ecosystem services were observed. For instance, water filtration by freshwater bivalves can be beneficial for the cultural service ‘biomonitoring’, while negatively or positively affecting food consumption or human recreation. Our evidence base spanned a total of 91 genera and 191 species, dominated by Unionida (55% of records, 76% of species), Veneroida (21 and 9%, respectively; mainly Corbicula spp.) and Myoida (20 and 4%, respectively; mainly Dreissena spp.). About one third of records, predominantly from Europe and the Americas, related to species that were non‐native to the country of study. The majority of records originated from Asia (35%), with available evidence for 23 CICES classes, as well as Europe (29%) and North America (23%), where research was largely focused on ‘biomonitoring’. Whilst the earliest record (from 1949) originated from North America, since 2000, annual output of records has increased rapidly in Asia and Europe. Future research should focus on filling gaps in knowledge in lesser‐studied regions, including Africa and South America, and should look to provide a quantitative valuation of the socio‐economic costs and benefits of ecosystem services shaped by freshwater bivalves.

Diagenetic nutrient supplies to the Proterozoic biosphere archived in divergent nitrogen isotopic ratios between kerogen and silicate minerals.

Nitrogen isotopes and abundances in sedimentary rocks have become an important tool for reconstructing biogeochemical cycles in ancient ecosystems. There are two archives of nitrogen in the rock record, namely kerogen‐bound amines and silicate‐bound ammonium, and it is well documented that the isotopic ratios of these two archives can be offset from one another. This offset has been observed to increase with metamorphic grade, suggesting that it may be related to the bonding environment in differing nitrogen host phases and associated equilibrium isotope fractionation. However, theoretical bounds for this effect have not been established, and it remains possible that some isotopic offsets predate metamorphism. In support of this hypothesis, we report an unexpectedly large isotopic offset of 4–5‰ in siltstones of very low metamorphic grade from the late Mesoproterozoic Diabaig Formation in NW Scotland (1.0 Ga). Carbon to nitrogen ratios of bulk rocks are 2–3 times lower than in other Mesoproterozoic sections. The rocks also contain early‐formed phosphate concretions and display wrinkled surfaces on bedding planes, indicative of fossilised microbial mats. Collectively, these data are most parsimoniously interpreted as evidence of diagenetic ammonium release from microbial mats into porewaters, followed by partial oxidation to nitrite or nitrate at the sediment–water interface. This process would render residual ammonium in clays isotopically heavy, while the resulting nitrite or nitrate would be relatively lighter and captured in new biomass, leading to the observed isotopic divergence. The same diagenetic degradation pathway likely also liberated phosphate that was trapped within concretions. Diagenetic release of nutrients is known to occur in modern settings, and our data suggest that nitrogen isotopes may be a way to track this local sedimentary nutrient source in past environments. Lastly, we speculate that diagenetic nutrient recycling within Proterozoic microbial mats may have created a favourable niche for eukaryotic organisms in shallow waters.

Combining Nitrogen Isotopes and Redox Proxies Strengthens Paleoenvironmental Interpretations: Examples From Neoproterozoic Snowball Earth Sediments

The history of the nitrogen cycle on Earth is linked to the redox evolution of the surface environment. Many nitrogen cycle fluxes are microbially mediated, and the particular fluxes operating at any given time in an ecosystem depend on the presence, absence or abundance of oxygen. However, interpreting this relationship is complicated as several isotopic fractionations associated with N-cycling are not diagnostic of a particular redox state. Thus, linking nitrogen isotopic analyses with redox-sensitive proxies is essential when interpretating past environments. Specifically, we use concentrations of U, V and Mo, along with Fe-speciation, to augment and contextualize nitrogen isotopic measurements. As an example, we consider samples from the Neoproterozoic Cryogenian period to suggest that there was oxygenated water, with associated aerobic N cycle fluxes. This interpretation is based on positive δ15N values between 4 to 80/00, Fe-speciation data consistent with anoxic bottom water during the Snowball ocean and oxygenated after, and redox-sensitive trace metals indicative of oxic weathering and surface water. Typically, high δ15N values are interpreted to reflect enhanced denitrification. We propose potential causes including a post-Snowball freshwater melt lid that suppressed deep water ventilation and that denitrification occurred more rapidly at high temperatures after the Snowball. These interpretations are buttressed by combined N isotope and redox analyses. This approach is especially useful during times of dynamic redox in the ocean-atmosphere system to interpret biologic isotopic signals.

Case Study: Bilbo – Aggression and Escape Behaviours in a Horse

A case study of how past trauma and inadequate current environment can interact to create and maintain problematic behaviors. Bilbo, a young mare with a significant history of aggression and causing injury is sold with the advice that she be euthanized for her behavior. Six weeks later, her new owner called Certified Horse Behavior Consultant Abigail Allen for a consultation, because she is no longer able to be handled at her owner’s facility. Through providing outlets for foraging, opportunities to learn with target training, a proper diet, and the right kind of environmental enrichment, Abigail and her client were able to help Bilbo become more relaxed and significantly less aggressive.

Identifying environmental drivers of shell shape and size variation in a widely distributed marine bivalve along the Atlantic Patagonian coast

Since the impacts of climate change on marine benthic organisms are already detectable in many aspects, it is crucial to address the potential responses of marine organisms and their interactions with the environment. In particular, the study of phenotype traits along latitudinal gradients is a powerful tool for exploring species responses in a changing environment. This work aims to: i) Quantify the variation in shell shape and size of the stripped clam Ameghinomya antiqua (King, 1832) along a 1600 km latitudinal gradient in the Atlantic Patagonian coast using geometric morphometric (GM) methods; ii) Identify environmental effects on shell shape and size change, using generalized additive mixed models GAMMs; iii) Estimate the effect size of different factors influencing shell shape and size variation. The combination of GM and GAMM allowed the quantification and identification of previously unknown relationship between morphological axes of variation and environmental variables. Results suggest that salinity is the most important factor determining shell shape, mainly affecting the outline while temperature has a substantial but weaker effect. More elongated shells and longer ligaments are observed under (less favorable) conditions of low salinity and temperature. GAMM showed that chlorophyll-a concentration, used as a proxy for food supply, has the most significant effect on shell size, and shell growth does not match the somatic soft-tissue growth. These results may help to predict the effects of climate change on the size and shape of marine benthic species and bivalves in particular. Furthermore, they provide new insights for using shell size and shape as proxies for the reconstruction of past environments and climates.