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Abstract Ocean oxygen content is decreasing with global change. A major challenge for modelling future declines in oxygen concentration is our lack of knowledge of the natural variability associated with marine oxygen inventory on interannual and multidecadal timescales. Here, we present 10 annually resolved 200 year-long records of denitrification, a marker of deoxygenation, from a varved sedimentary archive in the North Pacific oxygen minimum zone covering key periods over the last glacial–interglacial cycle. Spectral analyses on these records reveal strong signals at periodicities typical of today’s Atlantic multidecadal oscillation. Modern subsurface circulation reanalyses regressed on the positive Atlantic and Pacific Climatic Oscillation indices further confirm that North Atlantic temperature patterns are the main control on the subsurface zonal circulation and therefore the most likely dominant driver of oxygen variability in the tropical Pacific. With currently increasing temperatures in the Northern Hemisphere high latitudes and North Atlantic, we suggest deoxygenation will intensify in the region.

Abstract Marine sedimentary rocks deposited across the Neoproterozoic Cryogenian Snowball interval, ~720-635 million years ago, suggest that post-Snowball fertilization of shallow continental margin seawater with phosphorus accelerated marine primary productivity, ocean-atmosphere oxygenation, and ultimately the rise of animals. However, the mechanisms that sourced and delivered bioavailable phosphate from land to the ocean are not fully understood. Here we demonstrate a causal relationship between clay mineral production by the melting Sturtian Snowball ice sheets and a short-lived increase in seawater phosphate bioavailability by at least 20-fold and oxygenation of an immediate post-Sturtian Snowball ocean margin. Bulk primary sediment inputs and inferred dissolved seawater phosphate dynamics point to a relatively low marine phosphate inventory that limited marine primary productivity and seawater oxygenation before the Sturtian glaciation, and again in the later stages of the succeeding interglacial greenhouse interval.

Abstract Repetitive DNA make up a considerable fraction of most eukaryotic genomes. In fish, transposable element (TE) activity has coincided with rapid species diversification. Here, we annotated the repetitive content in 100 genome assemblies, covering the major branches of the diverse lineage of teleost fish. We investigated if TE content correlates with family level net diversification rates and found support for a weak negative correlation. Further, we demonstrated that TE proportion correlates with genome size, but not to the proportion of short tandem repeats (STRs), which implies independent evolutionary paths. Marine and freshwater fish had large differences in STR content, with the most extreme propagation detected in the genomes of codfish species and Atlantic herring. Such a high density of STRs is likely to increase the mutational load, which we propose could be counterbalanced by high fecundity as seen in codfishes and herring.

The volume of human carbon (δ13C) and nitrogen (δ15N) isotope data produced in archaeological research has increased markedly in recent years. However, knowledge of bone remodelling, its impact on isotope variation, and the temporal resolution of isotope data remains poorly understood. Varied remodelling rates mean different elements (e.g., femur and rib) produce different temporal signals but little research has examined intra-element variability. This study investigates human bone remodelling using osteon population density and the relationship with carbon and nitrogen isotope data at a high resolution, focusing on variation through femoral cross-sections, from periosteal to endosteal surfaces. Results demonstrate considerable differences in isotope values between cross-sectional segments of a single fragment, by up to 1.3‰ for carbon and 1.8‰ for nitrogen, illustrating the need for standardised sampling strategies. Remodelling also varies between bone sections, occurring predominantly within the endosteal portion, followed by the midcortical and periosteal. Therefore, the endosteal portion likely reflects a shorter period of life closer to the time of death, consistent with expectations. By contrast, the periosteal surface provides a longer average, though there were exceptions to this. Results revealed a weak negative correlation between osteon population density and δ15N or δ13C, confirming that remodelling has an effect on isotope values but is not the principal driver. However, a consistent elevation of δ15N and δ13C (0.5‰ average) was found between the endosteal and periosteal regions, which requires further investigation. These findings suggest that, with further research, there is potential for single bone fragments to reconstruct in-life dietary change and mobility, thus reducing destructive sampling.

Programmering og modellering har i de senere år blitt innført i høyere utdanning og ble innført i skolen med fagfornyelsen fra høsten 2020. Det har skapt behov for mer kunnskap om motivasjon og læring i emner som integrerer programmering som et nytt element i ellers veletablerte fagdisipliner. Denne studien undersøkte motivasjon for beregningsorientering (programmering og modellering) ved studieprogrammet biovitenskap ved Universitetet i Oslo. Spørreundersøkelser basert på Eccles’ forventning-verdi-modell ble gjennomført ved semesterstart og -slutt i to påfølgende år (2018 og 2019), før og etter innføring av krav om matematikk R2 (R2-kravet). Motivasjonsvariabler ble validert ved faktoranalyse og undersøkelse av indre konsistens. Resultatene viste at studentene hadde mye lavere mestringsforventning og mye større interesse for et emne som integrerer programmering i biologi enn for studieprogrammet generelt. Nytteverdien var den sterkeste motiverende faktoren for emnet. Studenter med matematikk R2 hadde litt større mestringsforventning til emnet enn de som ikke hadde denne fordypningen. Studentene med R2 opplevde likevel bare litt mindre utfordring med matematikk i emnet, og ingen forskjell i utfordringer knyttet til programmering i emnet, sammenlignet med studenter uten R2. Samtidig opplevde studenter med R2 litt større utfordring med biologien i emnet, og det viste seg at studenter med full fordypning i R2 hadde mindre biologi fra videregående opplæring enn studenter uten R2. Resultatene drøftes i lys av motivasjonsteori med tanke på implikasjoner for undervisning, inntakskrav og videre forskning.

The volume of human carbon (δ13C) and nitrogen (δ15N) isotope data produced in archaeological research has increased markedly in recent years. However, knowledge of bone remodelling, its impact on isotope variation, and the temporal resolution of isotope data remains poorly understood. Varied remodelling rates mean different elements (e.g., femur and rib) produce different temporal signals but little research has examined intra-element variability. This study investigates human bone remodelling using osteon population density and the relationship with carbon and nitrogen isotope data at a high resolution, focusing on variation through femoral cross-sections, from periosteal to endosteal surfaces. Results demonstrate considerable differences in isotope values between cross-sectional segments of a single fragment, by up to 1.3‰ for carbon and 1.8‰ for nitrogen, illustrating the need for standardised sampling strategies. Remodelling also varies between bone sections, occurring predominantly within the endosteal portion, followed by the midcortical and periosteal. Therefore, the endosteal portion likely reflects a shorter period of life closer to the time of death, consistent with expectations. By contrast, the periosteal surface provides a longer average, though there were exceptions to this. Results revealed a weak negative correlation between osteon population density and δ15N or δ13C, confirming that remodelling has an effect on isotope values but is not the principal driver. However, a consistent elevation of δ15N and δ13C (0.5‰ average) was found between the endosteal and periosteal regions, which requires further investigation. These findings suggest that, with further research, there is potential for single bone fragments to reconstruct in-life dietary change and mobility, thus reducing destructive sampling. [ABSTRACT FROM AUTHOR]

The δ13C composition of Cibicidoides wuellerstorfi and other Cibicidoides spp is an important tool to reconstruct past changes in the deep ocean carbon cycle. The species are expected to match the δ13C of ambient dissolved inorganic carbon (DIC), although it has been recognized that substantial offsets can occur. Here, I present a compilation of modern δ13C and δ18O data for named Cibicidoides species in combination with fully resolved carbonate chemistry at each core location. The data show for C. wuellerstorfi that the offset from the expected value in both carbon (∆13C) and oxygen (∆18O) is correlated with seawater carbonate chemistry. The result is comparable to, but not identical with, published culture experiments in which marine organisms were grown under variable pH‐conditions. Overall, ∆13C in C. wuellerstorfi correlates positively with carbonate saturation, [DIC], and temperature. The three variables together explain 47.1% of the variation in ∆13C. The trend for ∆18O is similar, except that the effect of temperature has been removed through correction with a published δ18O‐temperature equation. Up to 35% of the remaining variation in ∆18O can be explained by ambient carbonate chemistry. Data for other named Cibicidoides species are broadly similar, but are too sparse for a detailed analysis. The results indicate that strongly negative ∆13C occurs predominantly in the deep Atlantic in response to a combination of low [DIC], low temperature, and undersaturation within the lysocline. Implications for paleoceanographic reconstructions are discussed. Key Points: The offset between the measured and expected δ13C and δ18O of Cibicidoides wuellerstorfi correlates with seawater carbonate chemistryNegative ∆13C occurs mainly in the deep Atlantic due to a combination of low temperature, under‐saturation, and low to intermediate dissolved inorganic carbon [ABSTRACT FROM AUTHOR]

Prior to ~1 million years ago (Ma), variations in global ice volume were dominated by changes in obliquity; however, the role of precession remains unresolved. Using a record of North Atlantic ice rafting spanning the past 1.7 million years, we find that the onset of ice rafting within a given glacial cycle (reflecting ice sheet expansion) consistently occurred during times of decreasing obliquity whereas mass ice wasting (ablation) events were consistently tied to minima in precession. Furthermore, our results suggest that the ubiquitous association between precession-driven mass wasting events and glacial termination is a distinct feature of the mid to late Pleistocene. Before then (increasing), obliquity alone was sufficient to end a glacial cycle, before losing its dominant grip on deglaciation with the southward extension of Northern Hemisphere ice sheets since ~1 Ma.