Neogastropods (Melongenidae, Fasciolariidae, Turridae) from the Cannonball Formation (Paleocene: Thanetian), North Dakota and South Dakota

The Cannonball Formation of Paleocene age is a shallow-marine, clastic sequence exposed primarily in southwest-central North Dakota and northwestern South Dakota. The formation is characterized by alternating, poorly consolidated, relatively thin sandstone and thick mudstone units. The Cannonball neogastropod families Melongenidae, Fasciolariidae, and Turridae contain 20 species assigned to 15 genera based on 334 individuals from 50 localities. Four genera, Alticollarum, Obtusicarina, Vitticoncha, and Ericksonia are new, whereas Serrifusus, Mesorhytis, Rhombopsis, and Deussenia are first reported occurrences from Tertiary strata. Marshallaria is newly reported from North America and likely from the Northern Hemisphere. Twelve species are additions to the Cannonball fauna; of these, Acamptogenotia varicosta, Serrifusus sohli, Deussenia minuta, and Ericksonia clivilinea are newly described. Mesorhytis dakotensis is the most abundant species; the other species are generally rare. No stratigraphic zonation of species was observed. The middle informal unit has the most diverse fauna with 16 species, followed by that of the lower with 15 and the upper with 11. The larger number of occurrences is in the sandstone lithology, whereas the greater number of individuals occurs in the mudstone. Cluster analyses indicate little or no correlation between substrate type and species occurrence and that these neogastropods have no paleoenvironmental significance. These neogastropods are inferred to have been semi-infaunal or shallow infaunal predators. Comparisons between the neogastropod faunas of the Cannonball and Late Cretaceous Fox Hills and Pierre Formations suggest that 60 percent of the Late Cretaceous genera and all of the species became extinct prior to Cannonball time. Five Cannonball neogastropods occur in the Agatdal Formation of West Greenland, two in the greensands of Copenhagen, Denmark, and one in the Aquia Formation of Maryland and Virginia. A northerly or northeasterly source for the Cannonball Sea is inferred as the simplest explanation for the large number of Cannonball species occurring in West Greenland. Furthermore, a connection with the North Atlantic most readily explains the mixture of cool and warmer water gastropod and bivalve genera in the Cannonball fauna, since most of these genera also occur in the West Greenland fauna. Absence of West Greenland tropical\u27\u27 forms in the Cannonball fauna is attributed to oceanic cooling caused by mixing of North Atlantic and Arctic waters. Occurrences of Cannonball neogastropods are restricted entirely to other late Paleocene faunas, and, therefore, a late Paleocene (Thanetian) age for the Cannonball Formation is tentatively suggested

Global Trends in Type 1 Diabetes in Adolescents and Young Adults (1990–2019)

The study by Gong et al. examines the increases in the incidence, prevalence, and burden trends of type 1 diabetes (T1D) in adolescents and young adults over a 30-year span (1990 – 2019) by age, sex, and geographical regions based on the data from the 204 countries and territories included in the Global Burden of Disease (GBD) collaborative.1 Burden is defined as a combination of mortality rates and disability adjusted life year (DALY) indexes. The results of this 3-decade study should be interpreted within the milieu of improvements in the diagnosis and treatment of T1D over this period as well as economic and political regional changes to inform further research, policy development, and advocacy to mitigate the disease burden

Nitrogen dynamic in Eurasian coastal Arctic ecosystem: Insight from nitrogen isotope

Primary productivity is limited by the availability of nitrogen (N) in most of the coastal Arctic, as a large portion of N is released by the spring freshet and completely consumed during the following summer. Thus, understanding the fate of riverine nitrogen is critical to identify the link between dissolved nitrogen dynamic and coastal primary productivity to foresee upcoming changes in the Arctic seas, such as increase riverine discharge and permafrost thaw. Here, we provide a field-based study of nitrogen dynamic over the Laptev Sea shelf based on isotope geochemistry. We demonstrate that while most of the nitrate found under the surface fresh water layer is of remineralized origin, some of the nitrate originates from atmospheric input and was probably transported at depth by the mixing of brine-enriched denser water during sea-ice formation. Moreover, our results suggest that riverine dissolved organic nitrogen (DON) represents up to 6 times the total riverine release of nitrate and that about 62 to 76% of the DON is removed within the shelf waters. This is a crucial information regarding the near-future impact of climate change on primary productivity in the Eurasian coastal Arctic

Tracing Carbon Sources through Aquatic and Terrestrial Food Webs Using Amino Acid Stable Isotope Fingerprinting

Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring delta C-13 patterns among amino acids (delta C-13(AA)) could distinguish between multiple aquatic and terrestrial primary production sources. We found that delta C-13(AA) patterns in contrast to bulk delta C-13 values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their delta C-13(AA) patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk delta C-13 values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer delta C-13 patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs

Seasonal variations in the nitrogen isotopic composition of settling particles at station K2 in the western subarctic North Pacific

Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific western subarctic gyre (WSG) revealed seasonal changes in δ15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting traps (DST; 100-200 m) and moored traps (MST; 200 and 500 m). All particles showed higher δ15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ15N(SUS) of 0.4-3.1 ‰ in the euphotic zone (EZ). The δ15N(SUS) signature was reflected by δ15 N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ15 N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ15 N(DST) variations of 2.4-7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ15 N(DST) vs. PP regression to δ15 N(MST) of 1.9-8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. Moreover, the monthly export ratio at 500 m was calculated using both estimated PP and measured organic carbon fluxes. Results suggest a 1.6 to 1.8 times more efficient transport of photosynthetically-fixed carbon to the intermediate layers occurs in summer/autumn rather than winter/spring

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Isotopic and molecular distributions of biochemicals from fresh and buried Rhizophora mangle leaves†

Rhizophora mangle L. (red mangrove) is the dominant species of mangrove in the Americas. At Twin Cays, Belize (BZ) red mangroves are present in a variety of stand structures (tall >5 m in height, transition ~2–4 m and dwarf ~1–1.5 m). These height differences are coupled with very different stable carbon and nitrogen isotopic values[1] (mean tall δ(13)C = -28.3‰, δ(15)N = 0‰; mean tall δ(13)C = -25.3‰, δ(15)N = -10‰). To determine the utility of using these distinct isotopic compositions as 'biomarkers' for paleoenvironmental reconstruction of mangrove ecosystems and nutrient availability, we investigated the distribution and isotopic (δ(13)C and δ(15)N) composition of different biochemical fractions (water soluble compounds, free lipids, acid hydrolysable compounds, individual amino acids, and the residual un-extractable compounds) in fresh and preserved red mangrove leaves from dwarf and tall trees. The distribution of biochemicals are similar in dwarf and tall red mangrove leaves, suggesting that, regardless of stand structure, red mangroves use nutrients for biosynthesis and metabolism in a similar manner. However, the δ(13)C and δ(15)N of the bulk leaf, the biochemical fractions, and seven amino acids can be used to distinguish dwarf and tall trees at Twin Cays, BZ. The data support the theory that the fractionation of carbon and nitrogen occurs prior to or during uptake in dwarf and tall red mangrove trees. Stable carbon and nitrogen isotopes could, therefore, be powerful tools for predicting levels of nutrient limitation at Twin Cays. The δ(13)C and δ(15)N of biochemical fractions within preserved leaves, reflect sedimentary cycling and nitrogen immobilization. The δ(15)N of the immobilized fraction reveals the overlying stand structure at the time of leaf deposition. The isotopic composition of preserved mangrove leaves could yield significant information about changes in ecosystem dynamics, nutrient limitation and past stand structure in mangrove paleoecosystems

The Nature of the Dietary Protein Impacts the Tissue-to-Diet 15N Discrimination Factors in Laboratory Rats

Due to the existence of isotope effects on some metabolic pathways of amino acid and protein metabolism, animal tissues are 15N-enriched relative to their dietary nitrogen sources and this 15N enrichment varies among different tissues and metabolic pools. The magnitude of the tissue-to-diet discrimination (Δ15N) has also been shown to depend on dietary factors. Since dietary protein sources affect amino acid and protein metabolism, we hypothesized that they would impact this discrimination factor, with selective effects at the tissue level. To test this hypothesis, we investigated in rats the influence of a milk or soy protein-based diet on Δ15N in various nitrogen fractions (urea, protein and non-protein fractions) of blood and tissues, focusing on visceral tissues. Regardless of the diet, the different protein fractions of blood and tissues were generally 15N-enriched relative to their non-protein fraction and to the diet (Δ15N>0), with large variations in the Δ15N between tissue proteins. Δ15N values were markedly lower in tissue proteins of rats fed milk proteins compared to those fed soy proteins, in all sampled tissues except in the intestine, and the amplitude of Δ15N differences between diets differed between tissues. Both between-tissue and between-diet Δ15N differences are probably related to modulations of the relative orientation of dietary and endogenous amino acids in the different metabolic pathways. More specifically, the smaller Δ15N values observed in tissue proteins with milk than soy dietary protein may be due to a slightly more direct channeling of dietary amino acids for tissue protein renewal and to a lower recycling of amino acids through fractionating pathways. In conclusion, the present data indicate that natural Δ15N of tissue are sensitive markers of the specific subtle regional modifications of the protein and amino acid metabolism induced by the protein dietary source