Strontium Isotope Analysis, the Neonatal Line, and Archaeological Caribou Herd Identity in Northwest Alaska

Rangifer tarandus is a keystone species in the Arctic and has shaped human land use in this region for tens of thousands of years. The migratory ecotype requires large landscapes and long migrations between summer and winter ranges to meet their nutritional needs. The extent to which these ranges have remained the same has been controversial and uncertain. Archaeological caribou herd identity is usually ascribed based on modern caribou herd distribution. However, no study has assessed the validity of the implicit assumption of multi-thousand years of range stasis. Given that a caribou herd’s distribution and landscape use may change in response to ecological or climatic changes, it is important to assess whether past and present calving ground locations may have shifted. In this study, we applied strontium isotope analysis to identify calving grounds of archaeological caribou from the pre-contact/historic Lake Kaiyak site (MIS-00032) near the calving grounds of the modern Western Arctic caribou herd (WAH). We found that the 87Sr/86Sr values of the molars were consistent with those predicted for WAH ranges. The dental enamel from the neonatal line (NNL), a pathological marker of birth, was consistent with the modern WAH calving grounds and early summer range. These results suggest that the archaeological specimens were WAH animals. Broadly, this supports the use of strontium isotope analysis of permanent molars with an emphasis on the NNL to determine the herd identity of ungulates in the archaeological record, which has important implications for archaeology and modern wild ungulate herd management.    Dans l’Arctique, le Rangifer tarandus est une espèce clé. Depuis des dizaines de milliers d’années, cette espèce façonne l’utilisation des terres de l’Arctique par l’être humain. Afin de répondre à ses besoins alimentaires, l’écotype migratoire a besoin de vastes paysages et de longues migrations entre les aires d’estivage et les aires d’hivernage. La mesure dans laquelle ces aires sont demeurées inchangées fait l’objet de controverses et d’incertitudes. En général, l’identité d’un troupeau de caribou archéologique est déterminée en fonction de la répartition d’un troupeau de caribou moderne. Cependant, aucune étude n’a évalué la validité de l’hypothèse implicite de la stase des aires de répartition sur plusieurs milliers d’années. Puisque la répartition d’un troupeau de caribou et l’utilisation du paysage peuvent changer en réponse aux changements écologiques ou climatiques, il est important d’évaluer si les lieux de mise bas, anciens et actuels, peuvent avoir changé. Dans le cadre de cette étude, nous avons utilisé l’analyse isotopique du strontium pour déterminer les aires de mise bas du caribou archéologique au site historique et préeuropéen de Lake Kaiyak (MIS-00032), près des aires de mise bas du troupeau de caribou moderne de l’Arctique de l’Ouest (WAH). Nous avons constaté que les valeurs 87Sr/86Sr des molaires coïncidaient avec celles prévues pour les aires du troupeau de l’Arctique de l’Ouest. L’émail dentaire de la ligne néonatale, un marqueur pathologique de la naissance, correspondait aux aires de mise bas et à l’aire estivale initiale du troupeau de caribou moderne de l’Arctique de l’Ouest. Ces résultats suggèrent que les spécimens archéologiques provenaient de bêtes du troupeau de l’Arctique de l’Ouest. De manière générale, ces données viennent appuyer l’utilisation de l’analyse isotopique du strontium des molaires permanentes mettant l’accent sur la ligne néonatale pour déterminer l’identité du troupeau d’ongulés des données archéologiques, ce qui a d’importantes implications pour la gestion du troupeau sauvage d’ongulés archéologiques et modernes.Северный олень (лат. Rangifer tarandus) – ключевой вид арктической фауны, на протяжении десятков тысяч лет определяющий землепользование человека в Арктике. Этой мигрирующей популяции нужен простор и большие расстояния для миграции между летним и зимним ареалами для удовлетворения своих потребностей в питании. Однако спорным остается вопрос насколько эти ареалы сохранились. Археологическая идентичность стада северных оленей обычно определяется на основе нынешнего распределения стада. Однако не проводились исследования, оценивающие обоснованность предположения о стазисе ареала, длившегося много тысяч лет. Учитывая, что распределение и использование ландшафта стадом может измениться в ответ на климатические изменения, важно оценить, могли ли измениться места отела в прошлом и в настоящее время. В этом исследовании мы использовали анализ изотопов стронция для археологического определения мест отела северных оленей из доконтактного/исторического участка на озере Кайяк (MIS-00032) недалеко от мест отела современного западно-арктического стада (WAH). Для анализа использовались образцы со стоянки на озере Каяк (MIS-00032) и стоянки возле мест отела современного Западного арктического стада (англ. Western Arctic caribou herd, WAH). Мы обнаружили, что соотношения изотопов стронция 87Sr/86Sr в коренных зубах соответствуют прогнозам для диапазонов WAH. Зубная эмаль неонатальной линии, патологический маркер рождения, соответствует современным местам отела WAH и раннему летнему ареалу. Исходя из этого, можно предположить, что археологические образцы являются животными WAH. В целом, это обосновывает использование анализа содержания стронция в постоянных коренных зубах с акцентом на зубную эмаль неонатальной линии для определения идентичности стада из археологических свидетельств, что имеет большое значение для археологии и современного управления стадом диких оленей

DOC export is exceeded by C fixation in May Creek: A late-successional watershed of the Copper River Basin, Alaska.

Understanding the entirety of basin-scale C cycling (DOC fluxes and CO2 exchanges) are central to a holistic perspective of boreal forest biogeochemistry today. Shifts in the timing and magnitude of dissolved organic carbon (DOC) delivery in streams and eventually into oceans can be expected, while simultaneously CO2 emission may exceed CO2 fixation, leading to forests becoming stronger CO2 sources than sinks amplifying rising trace gases in the atmosphere. At May Creek, a representative late-successional boreal forest watershed at the headwaters of the Copper River Basin, Alaska, we quantified the seasonality of DOC flux and landscape-scale CO2 exchange (eddy covariance) over two seasonal cycles. We deployed in situ fDOM and conductivity sensors, performed campaign sampling for water quality (DOC and water isotopes), and used fluorescence spectroscopy to ascertain DOC character. Simultaneously, we quantified net CO2 exchange using a 100 ft eddy covariance tower. Results indicate DOC exports were pulse-driven and mediated by precipitation events. Both frequency and magnitude of pulse-driven DOC events diminished as the seasonal thaw depth deepened, with inputs from terrestrial sources becoming major contributors to the DOC pool with decreasing snowmelt contribution to the hydrograph. A three-component parallel factorial analysis (PARAFAC) model indicated DOC liberated in late-season may be bioavailable (tyrosine-like). Combining Net Ecosystem Exchange (NEE) measurements indicate that the May Creek watershed fixes 142-220 g C m-2 yr-1 and only 0.40-0.57 g C m-2 yr-1 is leached out as DOC. Thus, the May Creek watershed and similar mature spruce forest dominated watersheds in the Copper River Basin are currently large ecosystem C sinks and exceeding C conservative. An understanding of DOC fluxes from Gulf of Alaska watersheds is important for characterizing future climate change-induced seasonal shifts

Reactive Oxygen Species and Chromophoric Dissolved Organic Matter Drive the Aquatic Photochemical Pathways and Photoproducts of 6PPD-quinone under Simulated High-Latitude Conditions

The photochemical degradation pathways of 6PPD-quinone (6PPDQ, 6PPD-Q), a toxic transformation product of the tire antiozonant 6PPD, were determined under simulated sunlight conditions typical of high-latitude surface waters. Direct photochemical degradation resulted in 6PPDQ half-lives ranging from 17.5 h at 20 °C to no observable degradation over 48 h at 4 °C. Sensitization of excited triplet-state pathways using Cs+ and Ar purging demonstrated that 6PPDQ does not decompose significantly from a triplet state relative to a singlet state. However, assessment of processes involving reactive oxygen species (ROS) quenchers and sensitizers indicated that singlet oxygen and hydroxyl radical do significantly contribute to the degradation of 6PPDQ. Investigation of these processes in natural lake waters indicated no difference in attenuation rates for direct photochemical processes at 20 °C. This suggests that direct photochemical degradation will dominate in warm waters, while indirect photochemical pathways will dominate in cold waters, involving ROS mediated by chromophoric dissolved organic matter (CDOM). Overall, the aquatic photodegradation rate of 6PPDQ will be strongly influenced by the compounding effects of environmental factors such as light screening and temperature on both direct and indirect photochemical processes. Transformation products were identified via UHPLC-Orbitrap mass spectrometry, revealing four major processes: (1) oxidation and cleavage of the quinone ring in the presence of ROS, (2) dealkylation, (3) rearrangement, and (4) deamination. These data indicate that 6PPDQ can photodegrade in cool, sunlit waters under the appropriate conditions: t1/2 = 17.4 h tono observable decrease (direct); t1/2 = 5.2-11.2 h (indirect, CDOM)

DOC export is exceeded by C fixation in May Creek:a late-successional watershed of the Copper River Basin, Alaska

Abstract Understanding the entirety of basin-scale C cycling (DOC fluxes and CO₂ exchanges) are central to a holistic perspective of boreal forest biogeochemistry today. Shifts in the timing and magnitude of dissolved organic carbon (DOC) delivery in streams and eventually into oceans can be expected, while simultaneously CO₂ emission may exceed CO₂ fixation, leading to forests becoming stronger CO₂ sources than sinks amplifying rising trace gases in the atmosphere. At May Creek, a representative late-successional boreal forest watershed at the headwaters of the Copper River Basin, Alaska, we quantified the seasonality of DOC flux and landscape-scale CO₂ exchange (eddy covariance) over two seasonal cycles. We deployed in situ fDOM and conductivity sensors, performed campaign sampling for water quality (DOC and water isotopes), and used fluorescence spectroscopy to ascertain DOC character. Simultaneously, we quantified net CO₂ exchange using a 100 ft eddy covariance tower. Results indicate DOC exports were pulse-driven and mediated by precipitation events. Both frequency and magnitude of pulse-driven DOC events diminished as the seasonal thaw depth deepened, with inputs from terrestrial sources becoming major contributors to the DOC pool with decreasing snowmelt contribution to the hydrograph. A three-component parallel factorial analysis (PARAFAC) model indicated DOC liberated in late-season may be bioavailable (tyrosine-like). Combining Net Ecosystem Exchange (NEE) measurements indicate that the May Creek watershed fixes 142–220 g C m-2 yr-1 and only 0.40–0.57 g C m-2 yr-1 is leached out as DOC. Thus, the May Creek watershed and similar mature spruce forest dominated watersheds in the Copper River Basin are currently large ecosystem C sinks and exceeding C conservative. An understanding of DOC fluxes from Gulf of Alaska watersheds is important for characterizing future climate change-induced seasonal shifts

Aerobic versus Anaerobic Microbial Degradation of Clothianidin under Simulated California Rice Field Conditions

Microbial degradation of clothianidin was characterized under aerobic and anaerobic California rice field conditions. Rate constants (<i>k</i>) and half-lives (DT₅₀) were determined for aerobic and anaerobic microcosms, and an enrichment experiment was performed at various nutrient conditions and pesticide concentrations. Temperature effects on anaerobic degradation rates were determined at 22 ± 2 and 35 ± 2 °C. Microbial growth was assessed in the presence of various pesticide concentrations, and distinct colonies were isolated and identified. Slow aerobic degradation was observed, but anaerobic degradation occurred rapidly at both 25 and 35 °C. Transformation rates and DT₅₀ values in flooded soil at 35 ± 2 °C (<i>k</i> = −7.16 × 10^–2 ± 3.08 × 10^–3 day^–1, DT₅₀ = 9.7 days) were significantly faster than in 25 ± 2 °C microcosms (<i>k</i>= −2.45 × 10^–2 ± 1.59 × 10^–3 day^–1, DT₅₀ = 28.3 days). At the field scale, biodegradation of clothianidin will vary with extent of oxygenation