Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes

Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial–aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)—the messenger between terrestrial and lake ecosystems—with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change‐driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice‐out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans.     

Comparative effects of ammonium,nitrate and urea on growth and photosynthetic efficiency of three bloom‐forming cyanobacteria

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Evidence for iron‐regulated cyanobacterial predominance in oligotrophic lakes

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Genome-Wide Association Study Dissects the Genetic Architecture of Seed Weight and Seed Quality in Rapeseed (Brassica napus L.)

Association mapping can quickly and efficiently dissect complex agronomic traits. Rapeseed is one of the most economically important polyploid oil crops, although its genome sequence is not yet published. In this study, a recently developed 60K Brassica Infinium^® SNP array was used to analyse an association panel with 472 accessions. The single-nucleotide polymorphisms (SNPs) of the array were in silico mapped using ‘pseudomolecules’ representative of the genome of rapeseed to establish their hypothetical order and to perform association mapping of seed weight and seed quality. As a result, two significant associations on A8 and C3 of Brassica napus were detected for erucic acid content, and the peak SNPs were found to be only 233 and 128 kb away from the key genes BnaA.FAE1 and BnaC.FAE1. BnaA.FAE1 was also identified to be significantly associated with the oil content. Orthologues of Arabidopsis thaliana HAG1 were identified close to four clusters of SNPs associated with glucosinolate content on A9, C2, C7 and C9. For seed weight, we detected two association signals on A7 and A9, which were consistent with previous studies of quantitative trait loci mapping. The results indicate that our association mapping approach is suitable for fine mapping of the complex traits in rapeseed.     

The relationship of retrobulbar hematomas to vision in cynomolgus monkeys

An experimental model has been developed to measure the effect of retrobulbar hematomas on functional vision in cynomolgus monkeys. In this model, functional vision was quantitated using flashed evoked visual potentials in five monkeys following creation of retrobulbar hematomas. In one monkey used as a control, functional vision remained impaired for 180 minutes following induction of retinal ischemia by increased intraorbital pressure. In two monkeys in which increased intraorbital pressure was relieved by anterior chamber paracentesis following 15 minutes of retinal ischemia, flashed evoked visual potential promptly returned to baseline level. In two additional monkeys in which increased intraorbital pressure was relieved following 30 minutes of retinal ischemia, flashed evoked visual potentials improved but never returned to baseline levels. This study demonstrates the usefulness of flashed evoked visual potentials in measuring functional vision in cynomolgus monkeys. This experimental model should prove useful in evaluating the effects of increased intraorbital pressure on functional vision and the effect of intervention on impaired vision due to retrobulbar hematomas. Further studies with larger numbers of animals are needed to clarify these preliminary studies and document longer-term effects of retinal ischemia secondary to retrobulbar hematomas.     

Bromodeoxyuridine combined with UV light and gamma irradiation promotes the production of asymmetric somatic hybrid calli

Summary The degree of gamma- or X-ray-induced donor chromosome elimination in asymmetric somatic hybrids is highly variable. Here the beneficial use of bromodeoxyuridine and UV light as additional chromosome destabilizing agents is described. Protoplasts of Nicotiana tabacum were fused with protoplasts of Nicotiana plumbaginifolia (Np) that carried the kanamycin-resistance and glucuronidase (GUS) genes on separate chromosomes. Prior to fusion, the Np donor protoplasts were pretreated with bromodeoxyuridine and then were inactivated by treatment with iodoacetate ± UV light ± 200 Gy gamma irradiation. Hybrids were selected on medium containing kanamycin. The elimination of Np DNA was assessed by scoring of the fraction of hybrid calli that expressed GUS and by dot-blot analysis using a Np-specific probe. Gamma irradiation alone resulted in elimination of 50% of Np DNA. Pretreatment with bromodeoxyuridine (10 M) followed by 2.5 to 5 min UV light resulted in the elimination of 35–45% of the donor genome, but incorporation of bromodeoxyuridine (10 M) followed by 2.5 to 5 min UV light and 200 Gy gamma irradiation resulted in 85 to 90% elimination of Np DNA.Abbreviations BrdU bromodeoxyuridine (5-bromo-2-deoxyuridine) - GUS glucuronidase - HPT hygromycin B phosphotransferase - KmR kanamycin resistant - Np Nicotiana plumbaginifolia - NPT neomycin phosphotransferase II - Nt Nicotiana tabacum - UV ultraviolet