Past Environments Research Articles

Contribution of archaeobotany to understand taphonomic phenomena. The case of a Preboreal palaeochannel of Autrecourt-et-Pourron (Ardennes, France)

Palaeoecology, through the analysis of the interactions between environmental factors and ecosystems, refines the knowledge of the structuring process of plant communities and helps to understand the complexity of past environments. However, it is necessary to analyse the taphonomic phenomena (deposition, conservation, degradation) affecting plant macrofossil assemblages in order to perform relevant palaeoecological analyses. Indeed, plant macrofossils may be under or over-represented in carpological assemblages, depending on the resistance of their cell membranes and the sedimentary condition deposits. For this reason, it is necessary to estimate the representative quality of the conserved part as a source of information. Like all archaeological documents, the plant archives are distorted by the processes of formation of the sedimentary levels and, ignore the diagenetic history of the sedimentary layers could lead to wrong palaeoecological interpretations. To this aim, we analysed plant macrofossils contained in the wet sediments of a Meuse palaeochannel (Autrecourt-et-Pourron, Ardennes, France). This archaeobotanical study of an oxbow lake dated to the Preboreal (11.7–10.7 ka cal. BP), provides a reference of a taphonomic referential according to a hierarchy of organic remain preservations. This framework successfully helped the palaeoecological interpretations of the Autrecourt-et-Pourron off-site, and it has brought robustness to environmental history reconstruction of the early Holocene in the Ardennes Meuse.

Palynofacies analysis – principles and application for paleoenvironmental studies: implications from Bulgaria

The use of palynofacies analysis has been steadily increasing during the last decades. This stems from both commercial interests (i.e., hydrocarbon exploration) and academic research of past environments and studies of the global climate changes that took place during the Phanerozoic. In both commercial and academic contexts, there is a need for a better understanding of palaeoenvironmental changes in order to correctly date and interpret the depositional facies recorded in boreholes and outcrops. The present paper introduces this important analysis in the Bulgarian literature with characteristic examples of different palynofacies types documented by the author in Cretaceous sections in Bulgaria and their interpretation. These examples highlight the value of using palynofacies and palynomorph associations in an integrated approach for paleoenvironmental reconstructions in Bulgaria.

Footprints of global change in marine life: Inferring past environment based on DNA methylation and gene expression marks

Ocean global warming affects the distribution, life history and physiology of marine life. Extreme events, like marine heatwaves, are increasing in frequency and intensity. During sensitive stages of early fish development, the consequences may be long-lasting and mediated by epigenetic mechanisms. Here, we used European sea bass as a model to study the possible long-lasting effects of a marine heatwave during early development. We measured DNA methylation and gene expression in four tissues (brain, muscle, liver and testis) and detected differentially methylated regions (DMRs). Six genes were differentially expressed and contained DMRs three years after exposure to increased temperature, indicating direct phenotypic consequences and representing persistent changes. Interestingly, nine genes contained DMRs around the same genomic regions across tissues, therefore consisting of common footprints of developmental temperature in environmentally responsive loci. These loci are, to our knowledge, the first metastable epialleles (MEs) described in fish. MEs may serve as biomarkers to infer past life history events linked with persistent consequences. These results highlight the importance of subtle phenotypic changes mediated by epigenetics to extreme weather events during sensitive life stages. Also, to our knowledge, it is the first time the molecular effects of a marine heatwave during the lifetime of individuals are assessed. MEs could be used in surveillance programs aimed at determining the footprints of climate change on marine life. Our study paves the way for the identification of conserved MEs that respond equally to environmental perturbations across species. Conserved MEs would constitute a tool of assessment of global change effects in marine life at a large scale.

Identifying physiological and environmental influences on otolith chemistry in a coastal fishery species

Otolith (ear stone) chemistry provides powerful insights into the lives of fish. Although frequently used to reconstruct past environments, the influence of physiology remains unsettled. As such, we investigated the relationships between otolith chemistry, physiological factors and environmental factors in an iconic fishery species, snapper (Chrysophrys auratus). Lifetime otolith profiles were analysed of carbon (δ13C) and oxygen (δ18O) isotopes, and elemental concentrations of lithium (Li:Ca), magnesium (Mg:Ca), manganese (Mn:Ca), strontium (Sr:Ca), and barium (Ba:Ca). Mixed-effects modelling alongside a detailed literature review was used to investigate physiological (age, otolith growth rate, fish size, sex) and environmental influences (sea-surface temperature and chlorophyll-a) on otolith chemistry. Carbon isotopes and magnesium related to physiological factors, suggesting their potential as physiological proxies. Physiology also weakly related to strontium and lithium. By contrast, oxygen isotopes, barium, and manganese (except for natal signatures) were suggested to provide insights into past environments. Our study stresses the importance of consistency in biological characteristics for study designs, and highlights the potential of physiological proxies for distinguishing between populations in uniform water bodies. This study has not only reinforced our confidence in field applications of otolith chemistry, but has furthered our understanding of the influence of physiology.

Wooden Well at the First Farmers’ Settlement Area in Uničov, Czech Republic

Some of the most extraordinary finds from the Early Neolithic period are wooden wells. These constructions permit unusual insights into Neolithic settlements, their subsistence and environment, as well as into the surrounding landscape. A recent excavation of a Neo lithic settlement at Uničov in central Moravia, Czech Republic, yielded the discovery of a wooden well with a sediment infill from the beginning of the Neolithic period and allowed to study an array of topics by a multi-proxy approach using a set of complementary methods. Our study of the wooden lining demonstrates the carpeting skills of the first farmers, required also for building so-called ‘longhouses’. By comparing dendrochronological and radiocarbon dating, we estimated the time span of the well’s existence. The construction was used repeatedly over a longer time and was finally filled in intentionally. Studies of the well’s infill shed light on its usage and decline, providing a great proxy for the study of living dynamics and handling of waste in a Neolithic village. The environmental record extracted from botanical residues indicates that the immediate surroundings of the settlement were covered by an open-canopy woodland with a dominance of oak and hazel, and a large proportion of open habitats, whereas the surrounding landscape was not noticeably affected by humans. Key Words: Wooden well, past environment, subsistence strategy, Linearbandkeramik, Uničov, eastern Central Europe

Paleoenvironmental implications of Sr and Nd isotopes variability over the past 48 ka from the southern Sea of Japan

Millennial scale variations of terrigenous provenance in marine realm are closely related to regional environment and climate changes. Therefore, a wealth of information of past environment and climate can be constrained via fingerprinting sediment provenance. The Sea of Japan is a unique marginal sea in the North Pacific due to its high sill and distinct thermohaline circulation. The modern hydrography in the Sea of Japan is mainly affected by the East Asian Monsoon and Tsushima Warm Current, one branch of the Kuroshio Current. The Sea of Japan communicates with neighboring seas through four shallow and narrow straits, indicating great effects of global eustatic sea level change on its environment over glacial-interglacial cycles. Here we examine the terrigenous provenance in fine-grained fraction (<63 μm) of core KCES1, located near one end of the Tsushima Strait of the Sea of Japan over the last 48 ka, using radiogenic isotopes of strontium (Sr) and neodymium (Nd). Our data suggest that the terrigenous provenance in core KCES1 was mainly derived from the Yangtze River after 7 ka and a mixture of Yangtze and Yellow Rivers during the last glacial and deglacial periods. Notably, pronounced negative excursions of εNd values at HS1 were attributed to minor additions of unradiogenic Nd contribution from China-Korea cratonic hinterland. A binary mixing model further reveals that >85% terrigenous material is derived from the Yangtze and Yellow Rivers over the last 48 ka. Moreover, abrupt variations in sediment provenance occurred at ~18 ka and ~ 7 ka, which coincide with variations in oceanic surface circulation and deep ventilation recorded in the Sea of Japan. We suggest that paleo-Tsushima Warm Current invaded into the Sea of Japan with reopening of the Tsushima Strait at HS1 and the Tsushima Warm Current substantially entered the Sea of Japan after 7 ka due to intensified Kuroshio Current and rising eustatic sea level. The inflow of Tsushima Warm Current gives rise to a range of changes in surface hydrography, deep ventilation, ecological communities and productivity and sediment texture. The combination of fluxes of paleo-rivers and the intensity of Kuroshio Current, which are closely tied to the eustatic sea level and the East Asian Monsoon, plays a key role in controlling the variations in sediment provenance in the Ulleung Basin. Our study provides unique insight into the tight coupling between changes in sediment provenance and oceanic environment over the last 48 ka in the Sea of Japan.

Unseating “State” and “Archive”: Mobility and Manipulation in Past Environments and Present Praxis

AbstractThese concluding reflections assess how the contributors to this special issue intervene in key assumptions that shape the current field of archival studies. As the “archival turn” gains ground, forms of Euro- and state-centrism reappear in scholarship otherwise innovative in its attention to the textual remnants of the past. Here, instead, we explore the methodological stakes involved in defining both the “archive” and the historical power brokers who created and preserved a documentary record in pursuit of their varied social, cultural, economic, and political projects. The essay points to the resurgence of culturalist and civilisational indices for comparative archivistics, and follows the arguments collected in this issue to assert by contrast the often uneven and uneasy regional, administrative, and procedural definitions at work within preserved records. Identifying “mobility” as both a methodological tactic and a historical process, this conclusion presents a fluid rather than fixed textual landscape and presents an alternative frame for investigating preservationist practices.

Reviewing the Paleo- Biological Remains of Rajagala Mahalena Cave in The Eastern Province of Sri Lanka

The Rajagala is the dry lowland of the island, which lies at or below 900m asl, is confined to the north-central and southeastern parts of Sri Lanka. The zone comprises a plain rarely rising above c.40 m asl, but which contains isolated eroded remnants or monadnocks. The site of Rajagala is spread over 1025 acres consisting of more than 700 archaeological remains of prehistoric and historic periods. Preliminary investigations revealed that prehistoric human activity took place in the natural cave of the area before the third century BC. Accordingly, from 2016 to 2019, a selected cave called Maha Lena (ML) was excavated for further investigation. This cave was excavated jointly by Deccan College and the University of Sri Jayawardanepura. Excavations in 2018 and 2019 revealed a large number of prehistoric evidences. Among them are stone tools, bone tools, animal bones, and botanical remains. The main focus of this research paper is to analyze the biological remains found during the excavation of the ML Cave and to assess what the past environment was like through it. We have very limited knowledge of prehistoric research and information in the Eastern Province compared to the Low land Wet Zone of Sri Lanka. Accordingly, the focus was on research questions on the subsistence of prehistoric humans living in the caves of the Eastern Province and how environmental conditions have changed concerning the wet zone. Faunal and botanical remains have been recorded from ML, denoting the prevalence of climatic conditions similar to those of the present.

Engineering Education and Bourdieu: using Field, Capital and Habitus to Enhance Responsiveness

This paper takes a close look at the relevance of Bourdieu’s concepts of habitus, field and capital in enhancing learning in engineering education andproposes that effective engineering education can be achieved through the adoption of appropriate measures related to Bourdieu’s theories.it further shows the link between the concepts of field, capital and habitus and explores how engineering institutions can restructureteaching methods and curriculum content in a way that students can relate and respond to. This paper also highlights environmental and foundational changes that need to be imbibed from the elementary stages of education to help mould a potential teacher to be effective in the field and build capital that further impacts his effectiveness as a teacher. Again, through the review of related literature, this study explores how academia’s habitus affects their teaching methods within the field and the effect of institutional systems and environment on the pedagogy of engineering educators. The study further outlines some of the challenges limiting the field of engineering education stemming from deficiencies from an individuals past and current environment, followed by a description of key initiatives and recommendations aimed at better pedagogy and learning techniques for productive ngineering education.

Reconstructing the heterogeneity of past woodlands in anthracology using the spatial distribution of charcoals in archaeological layers: Applied to the postglacial occupation of the Abeurador cave (Hérault) in the South of France

Previous methodological developments in the field of anthracology have led to the definition of rigorous sampling methods in archaeological contexts, which provide highly accurate and reliable taxonomic frequency spectra as a basis for understanding past woodland vegetation. However, the fuelwood taxon frequency spectra represent a synthetic picture of forest composition in the environs of an archaeological site. Our aim in this paper is to describe the heterogeneity of woodland distribution. The Abeurador cave (Hérault) in the south of France, has previously provided an exceptionally rich palaeoecological study. We further explore the spatial frequency distributions of the charcoal taxa found in charcoal scatters from two layers dated to the Mesolithic (Preboreal). The frequencies of abundant taxa have a unimodal distribution in the sampled grid squares, close to the normal distribution. The ratio s2/m (variance/mean) termed the ‘distribution index’, estimates the regularity of distribution of each taxon in the grid squares. We hypothesized that the frequency distribution of a taxon in a layer could be considered to be its statistical sampling distribution (i.e. probability distribution) in the firewood collection catchment at a given time, since the quantity of this taxon fluctuates in each firewood assemblage according to its probability of collection, relating to its distribution heterogeneity (or accessibility) in the past environment. The distribution index was then used to estimate the heterogeneity of the palaeoenvironmental distribution of each taxon and thus its random, uniform or clustered distribution. On this basis, we propose a mapped restitution of the evolution of the main woodland species in the surroundings of the Abeurador during the Early Holocene, integrated with the whole sequence dynamics.

Global earth mineral inventory: A data legacy.

Minerals contain important clues to understanding the complex geologic history of Earth and other planetary bodies. Therefore, geologists have been collecting mineral samples and compiling data about these samples for centuries. These data have been used to better understand the movement of continental plates, the oxidation of Earth's atmosphere and the water regime of ancient martian landscapes. Datasets found at ‘RRUFF.info/Evolution’ and ‘mindat.org’ have documented a wealth of mineral occurrences around the world. One of the main goals in geoinformatics has been to facilitate discovery by creating and merging datasets from various scientific fields and using statistical methods and visualization tools to inspire and test hypotheses applicable to modelling Earth's past environments. To help achieve this goal, we have compiled physical, chemical and geological properties of minerals and linked them to the above-mentioned mineral occurrence datasets. As a part of the Deep Time Data Infrastructure, funded by the W.M. Keck Foundation, with significant support from the Deep Carbon Observatory (DCO) and the A.P. Sloan Foundation, GEMI (‘Global Earth Mineral Inventory’) was developed from the need of researchers to have all of the required mineral data visible in a single portal, connected by a robust, yet easy to understand schema. Our data legacy integrates these resources into a digestible format for exploration and analysis and has allowed researchers to gain valuable insights from mineralogical data. GEMI can be considered a network, with every node representing some feature of the datasets, for example, a node can represent geological parameters like colour, hardness or lustre. Exploring subnetworks gives the researcher a specific view of the data required for the task at hand. GEMI is accessible through the DCO Data Portal (https://dx.deepcarbon.net/11121/6200-6954-6634-8243-CC). We describe our efforts in compiling GEMI, the Data Policies for usage and sharing, and the evaluation metrics for this data legacy.

Rock varnish in La Proveedora/Sonora in the context of desert geobiological processes and landscape evolution

Desert varnish is a dark microlayer that forms on rocky surfaces that is usually associated with arid and desert environments. It consists mainly of clay minerals (60%), while the rest are Fe and Mn oxides. Growth rates are very slow and vary from <1 to 40 μm/ky. Although different proposals exist to explain their formation mechanisms, these processes are still unknown. Around the world, various groups and human communities have created petroglyphs with different meanings in desert varnish. In the Sonoran Desert, the archaeological site La Proveedora is known for having many petroglyphs made in granite rock varnishes. It is believed that people groups occupied the area during the mid-Holocene (ca 5000-3000 BC). The research was carried out by analyzing and looking for possible signals and contributions from past environments and current processes that are preserved in the varnish layers. The X-ray diffraction, laser breakdown spectra and scanning electron microscopy with energy dispersive spectroscopy analyses in varnish samples, showed that the distribution and concentrations of Fe and Mn exhibit an alternating behavior on a depth scale from the surface until contact with granite. The DNA analysis showed a major presence of the Proteobacteria and Actinobacteria groups. Notably, some of these microorganisms can incorporate Fe and Mn into their metabolic processes and mobilize them through the varnish for its formation. The 14C radiocarbon dating (370 ± 54 cal BP) indicates a very young age associated primarily with recent microorganisms. However, a first approximation was obtained for the minimum age (5000-1000 yr BP). The comparison between the areas of varnish and the surfaces within the petroglyphs suggests that the varnish formation occurred under conditions in the past when the humidity was higher, and that it is probably a very slow, intermittent or uncoated formation mechanism today.

Investigating Plant Micro-Remains Embedded in Dental Calculus of the Phoenician Inhabitants of Motya (Sicily, Italy).

Plant records reveal remarkable evidence about past environments and human cultures. Exploiting dental calculus analysis and using a combined approach of microscopy and gas chromatography mass spectrometry, our research outlines dietary ecology and phytomedicinal practices of the ancient community of Motya (Sicily, eight to sixth century BC), one of the most important Phoenician settlements in the Mediterranean basin. Micro-remains suggest use or consumption of Triticeae cereals, and animal-derived sources (e.g., milk and aquatic birds). Markers of grape (or wine), herbs, and rhizomes, endemic of Mediterranean latitudes and the East, provide insight into the subsistence of this colony, in terms of foodstuffs and phytotherapeutic products. The application of resins and wood of Gymnosperms for social and cultural purposes is hypothesized through the identification of Pinaceae secondary metabolites and pollen grains. The information hidden in dental calculus discloses the strong human-plant interaction in Motya’s Phoenician community, in terms of cultural traditions and land use.

Evidence for signatures of ancient microbial life in paleosols

Loess-paleosol sequences are terrestrial archives of past climate change. They may host traces of ancient microbial life, but little information is available on the recovery of microbial biomarkers from such deposits. We hypothesized that microbial communities in soil horizons up to an age of 127 kyr carry information related to past environments. We extracted DNA from a loess-paleosol sequence near Toshan, Northern Iran, with 26 m thick deposits showing different degrees of soil development, performed quantitative PCR and 16S rRNA gene amplicon sequencing. Periods of soil formation archived within the loess sediment led to higher diversity and bacterial abundance in the paleosol horizons. Community composition fluctuated over the loess-paleosol sequence and was mainly correlated with age and depth, (ADONIS R2 < 0.14, P ≤ 0.002), while responses to paleosol soil traits were weaker. Phyla like Bacteriodetes, Proteobacteria or Acidobacteria were more prevalent in paleosol horizons characterized by intense soil formation, while weakly developed paleosols or loess horizons hosted a higher percentage and diversity of Actinobacteria. Taken together, our findings indicate that the microbial community in loess-paleosol sequences carries signatures of earlier environmental conditions that are preserved until today.

Microbial biomarkers reveal a hydrothermally active landscape at Olduvai Gorge at the dawn of the Acheulean, 1.7 Ma

Landscape-scale reconstructions of ancient environments within the cradle of humanity may reveal insights into the relationship between early hominins and the changing resources around them. Many studies of Olduvai Gorge during Pliocene-Pleistocene times have revealed the presence of precession-driven wet-dry cycles atop a general aridification trend, though may underestimate the impact of local-scale conditions on early hominins, who likely experienced a varied and more dynamic landscape. Fossil lipid biomarkers from ancient plants and microbes encode information about their surroundings via their molecular structures and composition, and thus can shed light on past environments. Here, we employ fossil lipid biomarkers to study the paleolandscape at Olduvai Gorge at the emergence of the Acheulean technology, 1.7 Ma, through the Lower Augitic Sandstones layer. In the context of the expansion of savanna grasslands, our results represent a resource-rich mosaic ecosystem populated by groundwater-fed rivers, aquatic plants, angiosperm shrublands, and edible plants. Evidence of a geothermally active landscape is reported via an unusual biomarker distribution consistent with the presence of hydrothermal features seen today at Yellowstone National Park. The study of hydrothermalism in ancient settings and its impact on hominin evolution has not been addressed before, although the association of thermal springs in the proximity of archaeological sites documented here can also be found at other localities. The hydrothermal features and resources present at Olduvai Gorge may have allowed early hominins to thermally process edible plants and meat, supporting the possibility of a prefire stage of human evolution.

Simultaneous δ2 H and δ18 O analyses of water inclusions in halite with off-axis integrated cavity output spectroscopy.

Stable isotope compositions of ancient halite fluid inclusions have been recognized to be valuable tools for reconstructing past environments. Nevertheless, in order to better understand the genesis of halite deposits, it could be of great interest to combine both δ2 H and δ18 O measurements of the water trapped as inclusions in the defects of the mineral lattice. We developed a method combining off-axis integrated cavity output spectroscopy (OA-ICOS) connected on line with a modified elemental analyzer (EA-OA-ICOS) to perform those measurements. The first step was to test the method with synthetic halite crystals precipitated in the laboratory from isotopically calibrated waters. Water isotopic signatures have been measured with conventional techniques, equilibration for δ18 O and chromium reduction for δ2 H. Then, we modified and optimized a conventional EA to connect it online with an OA-ICOS instrument for H2 O measurements. The technique is first evaluated for calibrated free water samples. The technique is also evaluated for salt matrix effect, accuracy, and linearity for both isotopic signatures. Then, the technique is used to measure simultaneously δ2 H and δ18 O values of halite water inclusions precipitated from the evaporation experiments. Data generated with this new technique appeared to be comparable with those inferred from prior off-line technique studies. The advantages offered by the OA-ICOS technique are the simultaneous acquisition of both isotopic ratios and the substantial reduction of data acquisition time and sample aliquot size. Natural halite samples have been analyzed with this method. Natural halite samples as old as Precambrian have also been analyzed with this method.

Optimizing extraction and targeted capture of ancient environmental DNA for reconstructing past environments using the PalaeoChip Arctic-1.0 bait-set

AbstractSedimentary ancient DNA (sedaDNA) has been established as a viable biomolecular proxy for tracking taxon presence through time in a local environment, even in the total absence of surviving tissues. SedaDNA is thought to survive through mineral binding, facilitating long-term biomolecular preservation, but also challenging DNA isolation. Two common limitations in sedaDNA extraction are the carryover of other substances that inhibit enzymatic reactions, and the loss of authentic sedaDNA when attempting to reduce inhibitor co-elution. Here, we present a sedaDNA extraction procedure paired with targeted enrichment intended to maximize DNA recovery. Our procedure exhibits a 7.7–19.3x increase in on-target plant and animal sedaDNA compared to a commercial soil extraction kit, and a 1.2–59.9x increase compared to a metabarcoding approach. To illustrate the effectiveness of our cold spin extraction and PalaeoChip capture enrichment approach, we present results for the diachronic presence of plants and animals from Yukon permafrost samples dating to the Pleistocene-Holocene transition, and discuss new potential evidence for the late survival (~9700 years ago) of mammoth (Mammuthus sp.) and horse (Equus sp.) in the Klondike region of Yukon, Canada. This enrichment approach translates to a more taxonomically diverse dataset and improved on-target sequencing.

Plant taphonomy, flora exploitation and palaeoenvironments at the Middle Stone Age site of Mwulu’s Cave (Limpopo, South Africa): an archaeobotanical and mineralogical approach

The interior regions of South Africa have had less attention devoted to archaeological research than coastal regions, and palaeoenvironmental studies are also more limited. As such, little is known about the interaction between human behaviours and past environments in these semi-arid regions. Here, we present an archaeobotanical and mineralogical study from the Middle Stone Age site of Mwulu’s Cave, Limpopo Province. Our study shows the importance of using taphonomical approaches prior to interpreting archaeobotanical assemblages, while provides with novel information on the plants used by ancient inhabitants of Mwulu’s. The grass phytolith composition is of environmental significance, where a shift from C4 Panicoideae to C3 grasses is observed in the last occupation event. This tentatively suggests a shift in rainfall regime, from summer rainfall conditions to an increase in winter rain, during Marine Isotope Stage 5b in the Polokwane region, or a decrease in rainfall seasonality. Although we are unable to chronostratigraphically associate this change in the plant composition, our study adds evidence in support of previous propositions for an expansion of the winter rainfall zone into the interior regions of South Africa.

Stable isotopes of amino acids from reef fishes uncover Suess and nitrogen enrichment effects on local ecosystems

In 1979, the Suess effect was described as decreasing δ13C in the oceans linked to anthropogenic CO2 emissions. After years of over-fertilization of farming soils and runoff, we hypothesized that δ15N in coastal environments would also decline, whereby synthetic fertilizers lead to depletion of the heavy isotope 15N. We used museum-preserved and modern samples of 3 fishes from Otago, New Zealand, to reconstruct the isotopic baselines of C and N and assess specific trophic positions through time (1955-present) based on bulk and amino acid stable isotope values. Our sample set included Odax pullus, a strictly herbivorous species, and 2 commercially important species: Nemadactylus macropterus and Parapercis colias. Muscle tissue of the fishes recorded the change in δ13CBulk through time, which matched estimated Suess effect values for New Zealand. We also resolved the effects on the C isotopic baseline from natural changes in the food web using analysis of the δ13C of essential amino acids and found that while P. colias maintained a steady diet, the food web position of N. macropterus likely changed. Analysis of δ15N of phenylalanine in O. pullus indicated a decrease of 0.023‰ yr-1 since 1955, which corroborates our coastal N-enrichment hypothesis. Furthermore, we found that isotopic changes for N. macropterus were consistent with overfishing and habitat degradation in the region. These data provide vital information for our resolution and understanding of how past environments have changed in terms of both anthropogenic influences on coastal food web structure and biogeochemical cycles of C and N in marine ecosystems.

Leaf Wax Lipid Extraction for Archaeological Applications.

Plant wax lipid molecules, chiefly normal (n-) alkanes and n-alkanoic acids, are frequently used as proxies for understanding paleoenvironmental and paleoclimatic change. These are regularly analyzed from marine and lake sediments and even more frequently in archaeological contexts, enabling the reconstruction of past environments in direct association with records of past human behavior. Carbon and hydrogen isotope measurements of these compounds are used to trace plant type and water-use efficiency, relative paleotemperature, precipitation, evapotranspiration of leaf and soil moisture, and other physiological and ecological parameters. Plant wax lipids have great potential for answering questions related to human-environment interactions, being for the most part chemically inert and easily recoverable in terrestrial sediments, including those dating back millions of years. The growing use of this technique, and comparison of such data with other paleoenvironmental proxies such as pollen and phytolith analysis and soil carbonate and tooth enamel isotope records, make it essential to establish consistent, best-practice protocols for extracting n-alkanes and n-alkanoic acids from archaeological sediments to provide comparable information for interpreting past climatic, ecosystem, and hydrological changes and their interaction with human societies. © 2020 The Authors. Basic Protocol 1: Total lipid extraction Support Protocol 1: Weighing the total lipid extract Support Protocol 2: Cleaning the PSE extraction cells Alternate Protocol 1: Soxhlet total lipid extraction Alternate Protocol 2: Ultrasonic total lipid extraction Basic Protocol 2: Separation of lipids by aminopropyl column chromatography Basic Protocol 3: Separation of lipids by silver-nitrate-infused silica gel column chromatography Support Protocol 3: Preparation of silica gel infused with 10% silver nitrate Basic Protocol 4: Methylation of n-alkanoic acids Basic Protocol 5: Gas chromatography mass spectrometry (GC-MS) Basic Protocol 6: Gas chromatography isotope ratio mass spectrometry (GC-IRMS).