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Mercury (Hg) is a pervasive environmental contaminant that accumulates in the organs and tissues of seabirds at concentrations capable of causing acute or long-term adverse health effects. In the present study, Hg concentrations in Adelie penguin (Pygoscelis adeliae) egg membranes and chick feathers served as a proxy for Hg bioavailability in the marine environment surrounding the northern Antarctic Peninsula. Stable isotopes were measured in conjunction with Hg to infer information regarding feeding habits (δ15 N, diet/trophic level; δ13 C, foraging habitat). The Hg concentrations were low relative to toxicity benchmark values associated with adverse health effects in birds and ranged between 0.006 and 0.080 µg g-1 dry weight (n = 65) in egg membranes and 0.140 to 1.05 µg g-1 fresh weight (n = 38) in feathers. Egg membrane δ15 N signatures suggested that females from different breeding colonies had similar diets consisting of lower and higher trophic prey prior to arrival to breeding grounds. In contrast, δ15 N signatures in feathers indicated that chick diet varied by colony. The Hg concentrations demonstrated significant positive relationships with δ15 N, providing support for the hypothesis of Hg biomagnification up the food chain. The δ13 C signatures in both tissue types provided evidence of foraging habitat segregation among populations. The differences in Hg exposure and foraging ecology suggest that each colony has localized foraging behaviors by breeding adults that warrant additional investigation. Environ Toxicol Chem 2021;40:2791-2801. © 2021 SETAC.

The Ross Sea (Antarctica) is one of the most productive marine ecosystems in the Southern Ocean and supports nearly one million breeding pairs of Adélie penguins (Pygoscelis adeliae) annually. There also is a well-preserved record of abandoned penguin colonies that date from before the Last Glacial Maximum (>45,000 14C yr B.P.) through the Holocene. Cape Irizar is a rocky cape located just south of the Drygalski Ice Tongue on the Scott Coast. In January 2016, several abandoned Adélie penguin sites and abundant surface remains of penguin bones, feathers, and carcasses that appeared to be fresh were being exposed by melting snow and were sampled for radiocarbon analysis. The results indicate the “fresh” remains are actually ancient and that three periods of occupation by Adélie penguins are represented beginning ca. 5000 calibrated calendar (cal.) yr B.P., with the last occupation ending by ca. 800 cal. yr B.P. The presence of fresh-appearing remains on the surface that are actually ancient in age suggests that only recently has snowmelt exposed previously frozen carcasses and other remains for the first time in ∼800 yr, allowing them to decay and appear fresh. Recent warming trends and historical satellite imagery (Landsat) showing decreasing snow cover on the cape since 2013 support this hypothesis. Increased δ13C values of penguin bone collagen further indicate a period of enhanced marine productivity during the penguin “optimum”, a warm period at 4000–2000 cal. yr B.P., perhaps related to an expansion of the Terra Nova Bay polynya with calving events of the Drygalski Ice Tongue.

We examined how dietary factors recorded by C and N influence Hg uptake in 347 individuals of yellowfin tuna (Thunnus albacares), an important subsistence resource from the Galápagos Marine Reserve (Ecuador) and the Ecuadorian mainland coast in 2015-2016. We found no differences in total Hg (THg) measured in red muscle between the two regions and no seasonal differences, likely due to the age of the fish and slow elimination rates of Hg. Our THg concentrations are comparable to those of other studies in the Pacific (0.20-9.60 mg/kg wet wt), but a subset of individuals exhibited the highest Hg concentrations yet reported in yellowfin tuna. Mercury isotope values differed between Δ

Phosphorus (P) chemistry and its dynamic cycling are essential for understanding aquatic primary productivity and ecosystem structure. However, there is a lack of knowledge on P chemistry in pristine aquatic ecosystems, such as in Antarctica. Here, we applied the Standards, Measurements and Testing Program (SMT) procedure and nuclear magnetic resonance spectroscopy (NMR) to reveal P speciation in two types of lacustrine sediment cores collected from Inexpressible Island, Ross Sea, East Antarctica. The Positive Matrix Factorization Model and Generalized Additive Models were applied to quantitatively identify the P sources and estimate relative effects of various environmental factors on the speciation. Our results demonstrate that orthophosphate, mainly as Ca-P, is the major component and the ortho-monoesters are the predominant organic phosphorus (OP) form in lacustrine sediments. Ornithogenic lacustrine sediments have a higher content of P as Ca-P than sediments with little or no penguin influence. Our model further suggests that penguin guano is the most important source for Ca-P, accounting for 80%, while detrital input is the predominant source for Fe/Al-P (up to 90%). The content of ortho-monoesters, as revealed by NMR, declines with depth, reflecting mineralization process of OP in the sediments. Moreover, we observed higher relative proportions of organic P in the sediments with little guano influence and the deposition of organic P are likely facilitated by microbial mats. Overall, our data suggest that burial of P in Antarctic lakes is sensitive to different P sources and sedimentary environments. The relatively higher bioavailable phosphorus in lacustrine sediments largely controls growth of aquatic microbial mats in oligotrophic lakes and ponds in Antarctica. The sediment profile data also indicate that P burial increased during the Medieval Climate Anomaly period, and climate warming is more conducive to P burial through the expansion of penguin populations and productivity of microbial mats. Our findings represent the first systematic understanding of natural P cycling dynamics and its main controlling factors in pristine ponds with different organic sources in Antarctica.

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We report additional fossil evidence for pygoscelid penguins breeding on King George (25 de Mayo) Island, South Shetland Islands, in the Holocene beginning at ~7000 cal. yr BP. This evidence comes from a raised marine beach deposit formerly studied and described as Pingfo I at Stranger Point, Potter Peninsula. We relocated and exposed deposits at this site and recovered additional samples of penguin bones from five stratigraphic beds that are redescribed here. Most of these bones are from juvenile penguins and exhibit little or no wear indicating minimal transport to the beach deposits. Some of the bones are developed enough to be identifiable to Adélie ( Pygoscelis adeliae), Gentoo ( Pygoscelis papua), and Chinstrap ( Pygoscelis antarctica) penguins, indicating that all three species were breeding at Stranger Point from ~7320 to 4865 cal. yr BP. This breeding occupation corresponds with the first warming and deglaciation that occurred in the northern Antarctic Peninsula by this time and ends with the onset of reglaciation of the Peninsula. At least 31 abandoned penguin mounds and ornithogenic soils also were located and sampled at Stranger Point and indicate that the current occupation of this area by all three pygoscelid penguins dates no older than ~535 cal. yr BP. The absence of ornithogenic soils from earlier Holocene breeding was probably due to glacial activity and soil solifluction during periods of warming in the mid to late Holocene.

The Upper Gunnison Basin (UGB), Colorado, is a montane region characterized by unusual physiography and topographic isolation. Excavations of three caves in the UGB provide one of the most diverse records of high-elevation late Quaternary vertebrates in North America. The localities, Haystack Cave (2450 m above sea level [m asl]), Cement Creek Cave (2860 m asl), and Signature Cave (3055 m asl), together provide a near-continuous record of vertebrate communities that extends from before the last glacial maximum to the present. These communities largely represent a sagebrush (Artemisiaspp.) steppe-tundra environment that prevailed throughout the UGB in the late Pleistocene. At least five taxa of extinct large mammals disappear from the UGB by the Early Holocene; one small mammal (the short-faced skunkBrachyprotomacf.B.brevimala) also became extinct. The fossil record further indicates that only four small extant mammals (Sorex preblei,Dicrostonyxsp.,Lemmiscus curtatus, andUrocitellus elegans) were extirpated from the UGB by the Early Holocene, in part because of community restructuring and loss of open habitats with expansion of forests to higher elevations. An analysis of taxonomic richness and evenness at Cement Creek Cave indicates high resilience in the small mammal community despite major climate shifts over the past 40,000+ yr.

We performed stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of 12 ancient Adelie penguin (Pygoscelis adeliae) chick mummies recovered from abandoned colonies in the Ross Sea region, Antarctica, to investigate isotopic variation and fractionation over time. We also examined latitudinal variation in penguin diet to address if the modern dietary pattern (an increase in krill as dominant prey to the north) in this region has existed in the past or if this is a recent phenomenon. The ancient mummies range in age from > 48,000 14C years before present (BP) to ~ 500 calendar years BP. Feather, skin, bone, and toenail samples were analyzed from each individual where available. Identical analyses were performed on five modern mummified Adelie penguin chick carcasses and breast feathers of ten recently dead chicks from each of two active colonies, Cape Hallett and Adelie Cove. We found significantly lower δ15N values in Cape Hallett modern chicks as compared to those from Adelie Cove, indicating an entire trophic-level difference in modern diet that agrees with other studies in this region. The ancient mummies exhibited consistent isotopic fractionation of δ13C among the four different tissues through time. Variation in δ15N and δ13C values was greater in bone and skin than in feather or toenail, but δ15N in all four tissues indicated similar dietary trends with latitude as occurs in this region today. These results provide insight into the dietary variability of Adelie penguins across the Ross Sea region and a framework for similar analyses with other avian species.

Mercury (Hg) is a pervasive environmental contaminant that accumulates in the organs and tissues of seabirds at concentrations capable of causing acute or long-term adverse health effects. In the present study, Hg concentrations in Adélie penguin (Pygoscelis adeliae) egg membranes and chick feathers served as a proxy for Hg bioavailability in the marine environment surrounding the northern Antarctic Peninsula. Stable isotopes were measured in conjunction with Hg to infer information regarding feeding habits (δ

In this study, total mercury (THg) was analyzed in archaeological human bone from 23 sites dating to between the Middle Neolithic and the Antiquity. A total of 370 individuals from individual or collective burials was sampled, mostly using cortical bone from the humerus. These individuals were recovered from over 50 different funerary structures ranging from tholoi, pits, caves, and hypogea. Although cinnabar (HgS) is a likely cause of mercury poisoning and toxicity for people exposed to this mineral from mining or use as a paint or pigment, not all sites investigated here had cinnabar associated with the burials or other excavated areas. We found unusual levels of THg in many of the sampled individuals that we assume were caused by exposure to cinnabar in life, and not by diagenetic processes or other exposures to mercury such as through diet, which would only cause negligible accumulation of THg in bone. Our data, based on the largest sampling ever undertaken on contamination of human bone through archaeological evidence, provide a baseline for additional research on cinnabar and its use in Prehistory. Moderate to high levels of THg in human bone are mainly associated with societies dating from the second half of the 4th to late 3rd millennia B.C. (Late Neolithic to Middle Chalcolithic) in southern Iberia. By the Late Chalcolithic and Early Bronze Age, the use of cinnabar decreased significantly and became minimal or absent. The use and abuse of cinnabar appears to have been pervasive throughout the above-mentioned period and particularly between c. 2900-2300 B.C. This occurred in connection with the high symbolic and probably sacred value of the substance, which was sought after, traded, and extensively used in a variety of rituals and social practices. info:eu-repo/semantics/publishedVersion

We report the first radiocarbon ages on vertebrate fossils from Labor-of-Love Cave, White Pine County, Nevada, based on purified collagen in teeth and bone, as well as a description of the cave's vertebrate paleontology. This cave was discovered in 1982 with the recovery of an associated partial skeleton of the extinct giant short-faced bear (Arctodus simus). Subsequent excavations in 1985 recovered additional fossil material of birds and mammals from stream deposits in the cave. These fossils, along with fossils collected from the surface during surveys in 2018, are reported here. Radiocarbon ages indicate that most fossil material was deposited in the cave before and during the Last Glacial Maximum (LGM; 21,441–27,774 cal yr BP) and eroded from stream deposits inside the cave following the LGM, presumably from increased precipitation and stream flow. The vertebrate assemblage includes 4 other extinct taxa including 1 carnivore (Panthera atrox) and 3 ungulates (Equus sp., Oreamnos harringtoni, Euceratherium collinum) and the first record of Canada lynx (Lynx canadensis) from the Great Basin. If contemporaneous, the assemblage as a whole indicates an open grassland/sagebrush/tundra environment in Spring Valley during the late Pleistocene, with coniferous forest on mountain slopes facing this valley and where the cave is situated. Although the entrance to the cave is now blocked by slumped talus and breakdown, in the Pleistocene it was likely a large accessible opening at the base of a limestone cliff, with stream flow emerging and flowing into the valley below during the late Pleistocene, when bears and other species possibly used the cave as a shelter or den.

Soils in Antarctica support simple but unique biological assemblages in one of the most extreme terrestrial habitats on Earth. Among terrestrial fauna, microscopic invertebrates (nematodes, rotifers and tardigrades) are the most abundant and diverse, but the paucity of surveys still limits a more thorough understanding of their diversity and distribution patterns. To address this gap in knowledge, we conducted a survey across soil environments with differing biogeochemical characteristics (i.e., fellfields, moss communities, wetlands, and ornithogenic soils) at Edmonson Point. Our primary objective was to identify local diversity and drivers of distribution patterns of soil microfauna assemblages at the species level for all phyla. Presence of a broad range of soil habitats supported abundant and diverse microfauna of 24 species, including 18 rotifers, 4 nematodes, and 2 tardigrades. While nematode and tardigrade fauna were generally consistent with previous reports in the region, rotifers consisted mostly of bdelloids, newly-recorded and likely endemic species. Bdelloid rotifers were generally the most abundant followed by nematodes and tardigrades in similar numbers, with very patchy distributions and only nematodes found across all soil habitats. The type of soil environment was the most significant predictor of species distributions, with the richest and most abundant microfauna found in moist soils associated with cryptogamic vegetation and the poorest in dry fellfields and ornithogenic soils. Species distributions were also highly variable within particular environments and were related primarily to moisture, nutrients and organic matter, but availability and quality of food resources was the major underlying driver. Given the exceptionally wide range of terrestrial environments, Edmonson Point represents one of the most important biodiversity hot-spots for microfauna in the Ross Sea region, emphasizing its outstanding ecological importance and conservation value.

Lacustrine sediments from ice-free areas of Antarctica record both paleoecological and paleoclimatic information. Four sediment profiles (IIL1, IIL3, IIL4 and IIL9) were collected at Inexpressible Island, Ross Sea, to establish a robust late-Holocene chronology using accelerator mass spectrometry (AMS) 14C dating and geochemical and lithological analyses. The IIL1 and IIL4 sediments were strongly affected by penguin guano, and their bottom (oldest) ages were dated to 1659 and 4820 yr BP, respectively, using a Mixed Marine SoHem mode. By contrast, the organic matter of IIL3 and IIL9 sediments were predominantly sourced from aquatic microbial mats with the bottom ages of these two cores at 3179 and 2945 yr BP, respectively, based on a SHCal13 mode. The mass accumulation rates of the four sediment profiles inferred from this chronology showed peaks during ~1400–800 yr BP, corresponding to greater mean grain size and higher sand fraction ratios in the IIL3 and IIL9 profiles, suggesting a strengthened hydrodynamic effect in this period. Our results indicate a relatively warm period occurred in the study area, in accordance with an ‘optimum’ warming in the Ross Sea region. From a regional view, this warm period was also consolidated with climatic records from the western Ross Sea, most likely corresponding to a well-recognized climate perturbation known as the Medieval Climate Anomaly (MCA) in many parts of the world.

We excavated active and abandoned Adelie Penguin (Pygoscelis adeliae) colonies at Seymour Island and Hope Bay, Antarctic Peninsula, to determine an occupation history for this species at these sites. Previous research at Hope Bay has indicated an occupation there since the middle Holocene, based on a sediment record from Lake Boeckella. Excavations revealed only shallow and relatively fresh ornithogenic soils in the active colonies at the two localities. At least 53 abandoned pebble mounds were located at Hope Bay of which nine were excavated and four were sampled by probing to recover organic remains to determine their age. Radiocarbon dating of egg membrane, feather, and bone from both sites revealed a young occupation dating to less than ~600 years after correcting for the marine carbon reservoir effect. The mismatch in the geologic record of Adelie Penguin occupation in the northern Antarctic Peninsula, including Lake Boeckella sediments and geologic deposits and lake sediments on King George Island, with more direct evidence of breeding colonies from ornithogenic soils from active and abandoned colonies is hereby referred to as the ‘northern enigma’ as it does not occur in other regions of Antarctica including the southern Antarctic Peninsula, East Antarctica, or the Ross Sea, where the penguin record extends to the early to middle Holocene and matches well with the geologic record of deglaciation and penguin occupation. As yet, there is no convincing explanation for the ‘northern enigma’., Facultad de Ciencias Naturales y Museo

Methylmercury biomagnifies in food chains and can lower reproductive success in many organisms, particularly in top predators such as Brown Pelicans (Pelecanus occidentalis). To determine and compare variability in mercury exposure in this species, chick feathers and egg membranes were collected from seven breeding sites located in the remote Pamlico Sound and the more human-impacted Cape Fear River in North Carolina, USA. The average concentration of total mercury in egg membrane was 0.20 ± 0.14 ppm dry weight, a level associated with slightly reduced reproductive success in some birds, while chick feather total mercury concentrations (1.13 ± 0.02 ppm fresh weight) were well below the lowest observable adverse effects level. Mercury exposure did not vary between the Cape Fear River and Pamlico Sound, but did vary significantly among three Cape Fear River colonies. Diet analysis using δ13C and δ15N revealed minimal differences in the trophic level and foraging location of prey between islands in close proximity, indicating that differences in mercury availability are not due to differences in diet composition. The source of mercury variation in Brown Pelicans remains unknown and in need of further study.

Penguin colonies in Antarctica offer an ideal "natural laboratory" to investigate ecosystem function and the nitrogen (N) cycle. This study assessed the spatial distribution of penguin-derived N from guano and quantitatively assessed its impact on plant N utilization strategies in Victoria Land, Ross Sea region, Antarctica. Soil, moss, and aquatic microbial mats were collected inside and outside an active Adélie penguin (Pygoscelis adeliae) colony and analyzed for δ

Seabirds are ideal model organisms to track mercury (Hg) through marine food webs as they are long-lived, broadly distributed, and are susceptible to biomagnification due to foraging at relatively high trophic levels. However, using these species as biomonitors requires a solid understanding of the degree of species, sexual and age-specific variation in foraging behaviors which act to mediate their dietary exposure to Hg. We combined stomach content analysis along with Hg and stable isotope analyses of blood, feathers and common prey items to help explain inter and intra-specific patterns of dietary Hg exposure across three sympatric Pygoscelis penguin species commonly used as biomonitors of Hg availability in the Antarctic marine ecosystem. We found that penguin tissue Hg concentrations differed across species, between adults and juveniles, but not between sexes. While all three penguins species diets were dominated by Antarctic krill (Euphausia superba) and to a lesser extent fish, stable isotope based proxies of relative trophic level and krill consumption could not by itself sufficiently explain the observed patterns of inter and intra-specific variation in Hg. However, integrating isotopic approaches with stomach content analysis allowed us to identify the relatively higher risk of Hg exposure for penguins foraging on mesopelagic prey relative to congeners targeting epipelagic or benthic prey species. When possible, future seabird biomonitoring studies should seek to combine isotopic approaches with other, independent measures of foraging behavior to better account for the confounding effects of inter and intra-specific variation on dietary Hg exposure.

We sampled clapper rail (Rallus crepitans) feathers from museum specimens collected between 1965 and 2010 to investigate changes in mercury (Hg) availability in coastal marshes of New Hanover County, North Carolina. Stable isotope analysis (δ(13)C and δ(15)N) was conducted to control for dietary shifts that may have influenced Hg exposure. Hg concentrations ranged from 0.96 to 9.22 μg/g (ppm), but showed no significant trend over time; diet (δ(15)N) or foraging habitat (δ(13)C) also provided little to no explanatory power to the variation in Hg concentrations among clapper rails. Our findings suggest the bioavailability of Hg to clapper rails in coastal North Carolina salt marshes has remained consistent over time, despite the global trend of increasing mercury in many other bird species, providing an excellent baseline for any future assessment of Hg availability to salt marsh birds in coastal North Carolina.

Radionuclides including (210)Pb, (226)Ra and (137)Cs were analyzed in eight ornithogenic sediment profiles from McMurdo Sound, Ross Sea region, East Antarctica. Equilibration between (210)Pb and (226)Ra were reached in all eight profiles, enabling the determination of chronology within the past two centuries through the Constant Rate of Supply (CRS) model. Calculated fluxes of both (210)Pb and (137)Cs varied drastically among four of the profiles (MB4, MB6, CC and CL2), probably due to differences in their sedimentary environments. In addition, we found the flux data exhibiting a clear decreasing gradient in accordance with their average deposition rate, which was in turn related to the specific location of the profiles. We believe this phenomenon may correspond to global warming of the last century, since warming-induced surface runoff would bring more inflow water and detritus to the coring sites, thus enhancing the difference among the profiles. To verify this hypothesis, the deposition rate against age of the sediments was calculated based on their determined chronology, which showed ascending trends in all four profiles. The significant increase in deposition rates over the last century is probably attributable to recent warming, implying a potential utilization of radionuclides as environmental indicators in this region.

Sedimentary n-alkanoic acids are ubiquitous in the environment and their carbon isotopic composition is increasingly used to identify the source of organic matter and to reconstruct past climatic and ecological changes. Here we investigate the distribution and carbon isotope ratios of n-alkanoic acids in two sediment profiles influenced by animal excrement in Antarctica. We found that organic matter input from animal excrement is the predominate source of short- and mid-chain n-alkanoic acids in the ornithogenic sediments. Decreased δ13C values are closely related to increased excrement input of penguins and seals that occupied the study site, especially in C16 n-alkanoic acid. Long-chain (>C24) n-alkanoic acids likely originate from moss and heterotrophic microbes, and the δ13C values of C26 n-alkanoic acid were consistent with organic biomarkers and bio-elements from animal excrement. Two possible processes are suggested to explain the close relationship between C26 n-alkanoic acid δ13C values and animal excrement input. All the results indicate that the carbon isotopes of n-alkanoic acids in ornithogenic sediments can be used to indicate historical population change of penguins or seals in Antarctica.

We report new discoveries and radiocarbon dates on active and abandoned Adélie penguin ( Pygoscelis adeliae ) colonies at Cape Adare, Antarctica. This colony, first established at approximately 2000 BP (calendar years before present, i.e. 1950), is currently the largest for this species with approximately 338 000 breeding pairs, most located on low-lying Ridley Beach. We hypothesize that this colony first formed after fast ice began blocking open-water access by breeding penguins to the Scott Coast in the southern Ross Sea during a cooling period also at approximately 2000 BP. Our results suggest that the new colony at Cape Adare continued to grow, expanding to a large upper terrace above Ridley Beach, until it exceeded approximately 500 000 breeding pairs (a ‘supercolony’) by approximately 1200 BP. The high marine productivity associated with the Ross Sea polynya and continental shelf break supported this growth, but the colony collapsed to its present size for unknown reasons after approximately 1200 BP. Ridley Beach will probably be abandoned in the near future due to rising sea level in this region. We predict that penguins will retreat to higher elevations at Cape Adare and that the Scott Coast will be reoccupied by breeding penguins as fast ice continues to dissipate earlier each summer, restoring open-water access to beaches there.

The wide geographic distribution of penguins (Order Sphenisciformes) throughout the Southern Hemisphere provided a unique opportunity to use a single taxonomic group as biomonitors of mercury among geographically distinct marine ecosystems. Mercury concentrations were compared among ten species of penguins representing 26 geographically distinct breeding populations. Mercury concentrations were relatively low (62.00 ppm) in feathers from 18/26 populations considered. Population-level differences in trophic level explained variation in mercury concentrations among Little, King, and Gentoo penguin populations. However, Southern Rockhopper and Magellanic penguins breeding on Staten Island, Tierra del Fuego, had the highest mercury concentrations relative to their conspecifics despite foraging at a lower trophic level. The concurrent use of stable isotope and mercury data allowed us to document penguin populations at the greatest risk of exposure to harmful concentrations of mercury as a result of foraging at a high trophic level or in geographic ‘hot spots’ of mercury availability. Fil: Brasso, Rebecka L.. University Of North Carolina; Estados Unidos Fil: Chiaradia, André. Philip Island Nature Park, Research Department; Australia Fil: Polito, Michael J.. State University Of Louisiana; Estados Unidos Fil: Raya Rey, Andrea Nélida. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Emslie, Steven D.. University Of North Carolina; Estados Unidos

High performance liquid chromatography (HPLC) combined with mass spectrometry (MS) was used to analyse deposited pigments (including chlorophyll a, phaeophytin a, canthaxanthin, echinenone, zeaxanthin, scytonemin and mycosporine-like amino acids) from two sediment profiles of ponds in the Ross Sea area, East Antarctica. We explored the sources and characteristics of each pigment, reconstructed an 800-year record of ultraviolet radiation (UVR) and total incoming light intensity, and identified the possible factors that may have influenced historical UVR changes in this region. The results indicated at least four UVR peaks during the past 800 years, corresponding to c. AD 1950–2000, 1720–1790, 1560–1630 and 1350–1480, with the intensity from the most recent sediments being the highest. A comparison between the changes in UVR and total incoming light intensity showed similar patterns between AD 1720 and 1830, suggesting that factors controlling the UVR intensity in the Ross Sea area may be related to insolation fluctuation at that time. The two proxies are, however, weakly correlated during other periods. Historically, there is a relationship between the reconstructed UVR and solar activity, but this natural process may be strongly affected by multiple factors, including climate parameter change and anthropogenic activities during the modern times.

High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~ 1 cal ka BP. We coupled isotopic and radiocarbon measurements (δ18O, δD, δ15N, δ13C, and14C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene.

Specialization is a common mechanism of niche differentiation that can lead to eco- logical co-existence among species. However, species with specialized habitat or dietary require- ments often exhibit a high degree of sensitivity to environmental change. Understanding patterns of specialization and niche segregation among Antarctic marine predators is of increased impor- tance because of recent climate-driven reductions in a key prey species, Antarctic krill Euphausia superba. We examined the stomach contents and stable isotope values of sympatric chinstrap Pygoscelis antarctica and gentoo P. papua penguins across 5 breeding seasons at Cape Shirreff, Livingston Island, Antarctica. Our goal was to examine foraging niche segregation and the degree of specialization between species during the chick-rearing period. Dietary and isotopic foraging niches indicated consistent niche partitioning with higher krill consumption and greater use of off- shore foraging habitats by chinstrap relative to gentoo penguins. While chinstrap penguin diets were dominated by krill with little variation, gentoo penguins exhibited broader dietary and iso- topic niches with a higher degree of variation. There was little evidence that shifts in the availabil- ity of adult krill influenced penguin diets or foraging niches during our study, though the contrast- ing foraging strategies identified provide insight into the differing population trends observed between penguin species. The narrower foraging niche observed in declining chinstrap penguin populations indicates that they are likely highly sensitive to declines in the abundance of Antarc- tic krill. In contrast, the generalist niche exhibited by recently expanding gentoo penguin popula- tions is likely better suited to the rapidly changing environmental conditions in the Antarctic Peninsula.

AIM: Our aim was to determine the age and dispersal history of Colorado pinon (Pinus edulis) in western Colorado during the early to late Holocene using radiocarbon‐dated needles and nutshells from packrat (Neotoma spp.) middens. LOCATION: The Uncompahgre Plateau (UP) comprises more than 600,000 ha of public and private lands in west‐central Colorado, USA. Elevations within UP range from 1400 to 3140 m and it is characterized by numerous deep canyons and flat‐topped mesas. The Upper Gunnison Basin (UGB) encompasses a 243,000‐ha area enclosed within the southern Rocky Mountains in south‐western Colorado, USA. It spans 2200–4300 m in elevation, with no outlet apart from the Black Canyon of the Gunnison lower than 2650 m. METHODS: Middens were sampled by breaking off small sections of solidified deposits located in caves and crevices that were then disaggregated in water with repeated rinsing to separate all the plant remains. Single conifer needles and nutshells from 28 middens were radiocarbon dated to determine the age and timing of dispersal into western Colorado. RESULTS: Thirty‐two midden samples were collected, of which 28 produced identifiable plant remains that were radiocarbon dated. Pinon needles and/or nutshells were identified and radiocarbon dated from 20 of these middens from seven localities in UP. The results indicated that pinon did not become established in UP until c. 6000 yr bp, which contrasts with the nearby UGB, where pinon charcoal has been identified from seven archaeological sites with dates ranging from 8000 to 3000 yr bp. MAIN CONCLUSIONS: Our data are consistent with a model of late Pleistocene/early Holocene pinon migration into the Colorado Plateau from Arizona and New Mexico before becoming established in western Colorado. The timing of the pinon migration into south‐central Colorado along the Rio Grande corridor from New Mexico remains uncertain. While pinon–juniper woodlands currently dominate the lower elevations of UP, pinon had disappeared from UGB by c. 3000 yr bp and remains absent there today except for a few isolated trees.

Ornithogenic or bird-formed soils have accumulated in many coastal regions around Antarctica as a result of breeding activities by pygoscelid penguins, especially the Adelie penguin ( Pygoscelis adeliae ). These soils are often deep, range from hundreds to thousands of years old, and contain a natural archive of penguin tissues and those of their prey. In some regions, these tissues are extremely well preserved by the dry, cold environment and include complete and partial penguin mummies, feathers, bone, and eggshell. Hard parts of prey (fish bones, otoliths, and squid beaks) also commonly occur in these deposits from the penguin guano as it accumulates during soil development. Here, we review how research on these soils and the tissues they contain has progressed since they were first identified and described. These studies have provided not only valuable information on penguin occupation history with climate change since the Pleistocene, but also whole ecosystem responses to perturbations such as the ‘krill surplus’ that is hypothesized to have occurred following historic depletion of seals and whales in the 18th–20th centuries. New findings in the Ross Sea indicate how penguin occupation and abandonment cycles have progressed over millennia in relation to climate change. In addition, stable isotope analysis of δ 15 N and δ 13 C in ancient and modern Adelie penguin tissues (feathers, bone, eggshell and membrane) and guano support the ‘krill surplus’ hypothesis in showing a dietary shift from fish to krill over the past ∼200 years. Other recent studies have focused on stable isotope analyses of penguin prey remains, as well as ancient DNA and mercury analyses of penguin tissues recovered from ornithogenic soils. An analysis of fish otoliths recovered from ancient guano provide a means to investigate values of otolith carbonate δ 18 O, which correlates with other paleoclimatic records, and can be used as a proxy for changing ocean temperatures through time. In addition, measurements of total mercury (Hg) in penguin egg membrane from abandoned colonies up to 800 years old indicate significantly higher mercury levels in the past compared to modern penguins, likely due to a greater reliance on higher trophic prey prior to the proposed ‘krill surplus’. All of these studies indicate that ornithogenic soils and the natural archive of tissues they contain provide a unique means to integrate both terrestrial and marine records with ecosystem studies and climate change, past and present, in Antarctica.

Atmospheric CO2 cycles of the Quaternary likely imposed major constraints on the physiology and growth of C3 plants worldwide. However, the measured record of this remains both geographically and taxonomically sparse. We present the first reconstruction of physiological responses in a late Quaternary high-elevation herbaceous plant community from the Southern Rocky Mountains, USA. We used a novel proxy—fossilized tooth enamel of yellow-bellied marmots (Marmota flaviventris)—which we developed using detailed isotopic analysis of modern individuals. Calculated C isotopic discrimination ( $$\Delta$$ ) of alpine plants was nearly 2 ‰ lower prior to the Last Glacial Maximum than at present, a response almost identical to that of nonherbaceous taxa from lower elevations. However, initial shifts in $$\Delta$$ aligned most closely with the onset of the late Pleistocene bipolar temperature “seesaw” rather than CO2 increase, indicating unique limitations on glacial-age high-elevation plants may have existed due to both low temperatures and low CO2. Further development of system-specific faunal proxies can help to clarify this and other plant- and ecosystem-level responses to past environmental change.

Concentrations of rare earth elements (REEs) were determined in three ornithogenic sediment profiles excavated at active Adelie penguin ( Pygoscelis adeliae ) colonies in McMurdo Sound, Ross Sea, Antarctica. The distribution of REEs in each profile fluctuated with depth. REEs measured in environmental media (including bedrock, guano, and algae) and analysis on the correlations of ΣREE–lithological elements and ΣREE–bio-elements in the profiles indicated that sedimentary REEs were mainly from weathered bedrock in this area, and the non-crustal bio-genetic REEs from guano and algae were minor. Further discussion on the slopes and Ce and Eu anomalies of chondrite-normalized REE patterns indicated that a mixing process of weathered bedrock, guano and algae was the main controlling factor for the fluctuations of REEs with depth in the sediments. An end-member equation was developed to calculate the proportion of REEs from the three constituents in the sediments. The calculation functioned well in estimating bedrock-derived REEs and the magnitude of ornithogenic influence in different profiles. In general, REEs in the ornithogenic sediments showed anti bio-element patterns and thus can be used as an additional proxy to reconstruct historical penguin populations.

Positioned near the top of the food web, the dietary composition of Antarctic penguins and seals can be an excellent indicator of the regional food web and thus the status of the marine ecosystem. The dietary composition of modern penguins and seals has been well investigated; a long-term time series of data on penguin and seal diets, however, are rare. Such data, especially any predating the initiation of human harvesting of fish, whales and seals in Antarctica, are crucial for understanding and predicting responses of regional marine food webs to natural climate changes. Here we review recent progress on research of paleodietary change in Antarctic penguins and seals, specifically the Adelie penguin (Pygoscelis adeliae) and Antarctic fur seal (Arctocephalus gazella). These studies indicate that the dietary changes of penguins correspond quite well with fluctuations in climate and sea ice extent during the Holocene. The depleted δ 15N ratios found in modern Adelie penguins support the “krill surplus hypothesis” in relation to historic human depletion of krill-eating fish, seals and whales.

Biological responses to climate and environmental changes in remote polar regions are of increasing interest in global change research. Terrestrial and marine polar ecosystems have suffered from impacts of both rapid climate change and intense human activities, and large fluctuations in the population sizes of seabirds, seals, and Antarctic krill have been observed in the past decades. To understand the mechanisms driving these regime shifts in polar ecosystems, it is important to first distinguish the influences of natural forcing from anthropogenic activities. Therefore, investigations of past changes of polar ecosystems prior to human contact are relevant for placing recent human-induced changes within a long-term historical context. Here we focus our review on the fossil, sub-fossil, archaeological, and biogeochemical remains of marine vertebrates in polar sediments. These remains include well-preserved tissues such as bones, hairs and feathers, and biogeochemical markers and other proxy indicators, including deposits of guano and excrement, which can accumulate in lake and terrestrial sediments over thousands of years. Analyses of these remains have provided insight into both natural and anthropogenic impacts on marine vertebrates over millennia and have helped identify the causal agents for these impacts. Furthermore, land-based seabirds and marine mammals have been shown to play an important role as bio-vectors in polar environments as they transport significant amounts of nutrients and anthropogenic contaminants between ocean and terrestrial ecosystems.

Hundreds of split-twig figurines have been recovered from caves in Grand Canyon and are associated with a hunting ritual that dates from 4200–3100 14C yrs before present (BP). The caves chosen for this ritual all have Pleistocene remains of big game animals visible in packrat middens or surface deposits at the entrances. Presumably, Archaic hunter-gatherers identified these sites as entrances to the Underworld where the fossil remains represented ancestral animals. We examine the known chronology for these sites in Grand Canyon and postulate that the origin of this ritual is correlated with a period of rapid climate change that occurred on both global and regional scales beginning at ∼4000 BP. Increasingly variable conditions and the onset of modern El Nino Southern Oscillation (ENSO) patterns in the eastern Pacific at that time probably negatively affected productivity of big game species in years with decreased winter precipitation. Thus, the caves became foci for a hunting ritual with figurine...

Seabirds have substantial influence on geochemical circulation of elements, serving as a link for substance exchange between their foraging area and colonies. In this study, we investigated the elemental and carbon isotopic composition of five penguin-affected sediment profiles excavated from Ross Island and Beaufort Island in the Ross Sea region, Antarctica. Among the three main constituents of the sediments (including weathered bedrock, guano and algae), guano was the main source of organic matter and nutrients, causing selective enrichment of several elements in each of the sediment profiles. In the 22 measured elements, As, Cd, Cu, P, S, Se and Zn were identified as penguin bio-elements in the Ross Sea region through statistical analysis and comparison with local end-member environmental media such as weathered bedrock, fresh guano and fresh algae. Carbon isotopic composition in the ornithogenic sediments showed a mixing feature of guano and algae. Using a two-member isotope mixing equation, we were able to reconstruct the historical change of guano input and algal bio-mass. Compared with research in other parts of Antarctic, Arctic, and South China Sea, we found apparent overlap of avian bio-elements including As, Cd, Cu, P, Se, and Zn. Information on the composition and behavior of bio-elements in seabird guano on a global scale, and the role that bio-vectors play in the geochemical circulation between land and sea, will facilitate future research on avian ecology and paleoclimatic reconstruction.

The ‘krill surplus’ hypothesis in Antarctica posits that the historic depletion of krill-eating whales and seals in the 18–20th centuries provided a surplus of krill in the Southern Ocean that benefited penguins. A previous study which examined stable isotopes in ancient and modern tissues of Adélie penguin (Pygoscelis adeliae) provides support for this hypothesis. Specifically, a significant decrease in δ13C and δ15N values occurred in modern versus ancient tissues from an apparent dietary shift from fish to krill associated with the purported krill surplus. Here, we present new data on gentoo penguin (Pygoscelis papua) tissues from active and abandoned colonies at three locations in the Antarctic Peninsula. We found an overall, but weak, decrease in modern versus fossil δ15N and δ13C values of gentoo penguin egg membrane with considerable variation across three breeding sites. Dietary mixing models suggest that shifts between fish and krill in gentoo penguins were likely not as strong as those previously observed in Adélie penguins. This weaker signal probably results from the greater reliance on fish in their diets, past and present, though we cannot rule out declines in primary productivity or other ecosystem shifts which also could account for declines in δ13C and δ15N values.

Antarctic krill (Euphausia superba) occupy a key position in the Southern Ocean linking primary production to secondary consumers. While krill is a dominant grazer of phytoplankton, it also consumes heterotrophic prey and the relative importance of these two resources may differ with ontogeny. We used stable isotope analyses to evaluate body size-dependent trophic and habitat shifts in krill during the austral summer around the South Shetland Islands, Antarctica. We found evidence for an asymmetric, ontogenetic niche expansion with adults of both sexes having higher and more variable δ15N values but consistent δ13C values in comparison with juveniles. This result suggests that while phytoplankton likely remains an important life-long resource, krill in our study area expand their dietary niche to include higher trophic food sources as body size increases. The broader dietary niches observed in adults may help buffer them from recent climate-driven shifts in phytoplankton communities that negatively affect larval or juvenile krill that rely predominately on autotrophic resources.

Three species of coastal sparrows (Ammodramus nelsoni, Nelson's Sparrow; A. caudacutus, Saltmarsh Sparrow; and A. maritimus, Seaside Sparrow) reside in North Carolina salt marshes in winter during their nonbreeding periods. We analyzed the timing of migration, survivorship, and site fidelity of these species with mark—recapture data from five winters (2006–2010). By determining the percentage of individuals captured more than once, we documented a shift from transient to settled individuals during and following migration and used linear regressions to test whether this shift was related to mean monthly minimum temperatures. We also used MARK and capture histories over five winters to estimate probabilities of apparent survival and capture. On the basis of recapture data, the three species' populations were composed largely of transient individuals from October until the sparrows settled for the winter by late November. Our recapture data indicate that when coastal sparrows settle for the winter ...

The vertebrate fossil record of Cement Creek Cave, Colorado, spans from ≫ 45,000 yr ago to the present and represents the richest stratified series of high-elevation (≫ 2900 m) mammal remains known from the late Quaternary of North America. Stable carbon and oxygen isotope analyses of tooth enamel were used to assess potential ecological responses of two species found commonly throughout the cave, Yellow-bellied marmots (Marmota flaviventris) and Bushy-tailed woodrats (Neotoma cinerea), to late Quaternary climate and environmental changes of the Southern Rocky Mountains. Results indicate that despite such perturbations, the dietary ecologies of both species were maintained across this period. Neither taxon shifted to consuming C4 taxa or different C3 functional groups; similarly, no significant shifts in surface water use were detected. Variations in enamel δ13C were observed, however, that represent the physiological responses of high-elevation plants to changing levels of late Quaternary atmospheric CO2. While our findings extend both the geographic and elevational record of this plant CO2 response, they simultaneously highlight the ecological stability of high-elevation M. flaviventris and N. cinerea during climate changes of late Quaternary magnitude.