Paleolimnological Evidence of Terrestrial and Lacustrine Environmental Change in Response to European Settlement of the Red River Valley, Manitoba and North Dakota

Limnological and terrestrial changes in three floodplain lakes are correlated with settlement of the Red River valley in Manitoba and North Dakota. Distinctive pollen, diatom and thecamoebian assemblages provide proxy evidence of the ecological changes from pre- to post-settlement periods in Horseshoe Lake, Lake Louise and Salt Lake. In the pre-settlement period (Zone I), prior to ~1812, grass and Quercus pollen dominate and are indicative of a tall grass prairie-oak riparian forest ecosystem. Diatom and thecamoebian assemblages suggest oligo- to mesotrophic limnological conditions, and more brackish water than presently occurs in Horseshoe Lake. The onset of the post-settlement period (Zone II) corresponds to distinctive terrestrial and limnological changes. A sharp decline in Quercus at the base of this zone correlates with documented regional riparian deforestation, whereas the increase in the weed taxa Salsola, Brassica, Rumex and Ambrosia is associated with the introduction of European agricultural practices and cereal grasses. Diatom and thecamoebian assemblages indicate progressive floodplain lake eutrophication, as well as increased salinity in Salt Lake. Salt Lake is the most brackish lake and supports the brackish-water foraminifera Trochammina macrescens cf. polystoma. Increased erosion and run off in the watershed has caused a more than twofold increase in lake basin sedimentation between the pre-settlement and post-settlement periods.Cette étude établit une corrélation entre les changements limnologiques et terrestres dans la plaine d’inondation de trois lacs et le peuplement de la vallée de la rivière Rouge au Manitoba et dans le Dakota du Nord. Divers assemblages polliniques, de diatomées et de thécamoébiens mettent en évidence de façon indirecte des changements écologiques entre les périodes pré- et post-peuplement aux alentours des lacs Horseshoe, Louise et Salt. Dans la période antérieure au peuplement (Zone I), soit avant 1812, la domination de la signature pollinique des graminées et du chêne indique un écosystème forestier riverain composé de graminées de haute taille et de chênes. Quant aux assemblages de diatomées et de thécamoébiens, ils permettent de penser à des conditions limnologiques d’oligo à mésotrophiques et des eaux plus saumâtres à cette période qu’actuellement dans le lac Horseshoe. La période post-peuplement (Zone II) correspond à des changements terrestres et limnologiques spécifiques. Le déclin marqué du chêne à la base de cette zone correspond en effet à la déforestation des rives de cette région, telle qu’attestée dans les documents, tandis que les taxons Salsola, Brassica, Rumex et Ambrosia correspondent à l’instauration de pratiques agricoles européennes et la culture des céréales. Les assemblages de diatomées et de thécamoébiens indiquent aussi une eutrophisation progressive de la plaine inondable de même que l’augmentation de la salinité du lac Salt, ce dernier étant le plus salé des trois lacs. Il accueille des foraminifères d’eaux saumâtres du genre Trochammina macrescens cf. polystoma. L’accroissement de l’érosion et du ruissellement dans le bassin-versant a quadruplé la sédimentation entre les périodes pré- et post-peuplement

The jellification of north temperate lakes.

Calcium (Ca) concentrations are decreasing in softwater lakes across eastern North America and western Europe. Using long-term contemporary and palaeo-environmental field data, we show that this is precipitating a dramatic change in Canadian lakes: the replacement of previously dominant pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis, a jelly-clad, Ca-poor competitor. In some lakes, this transformation is being facilitated by increases in macro-invertebrate predation, both from native (Chaoborus spp.) and introduced (Bythotrephes longimanus) zooplanktivores, to which Holopedium, with its jelly coat, is relatively invulnerable. Greater representation by Holopedium within cladoceran zooplankton communities will reduce nutrient transfer through food webs, given their lower phosphorus content relative to daphniids, and greater absolute abundances may pose long-term problems to water users. The dominance of jelly-clad zooplankton will likely persist while lakewater Ca levels remain low.This work was primarily supported by grants from the Natural Sciences and Engineering Research Council of Canada and funding from the Ontario Ministry of the Environment.This is the accepted manuscript. The final version is available at http://rspb.royalsocietypublishing.org/content/282/1798/20142449

Revealing the last 13,500 years of environmental history from the multiproxy record of a mountain lake (Lago Enol, northern Iberian Peninsula)

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s10933-009-9387-7.We present the Holocene sequence from Lago Enol (43°16′N, 4°59′W, 1,070 m a.s.l.), Cantabrian Mountains, northern Spain. A multiproxy analysis provided comprehensive information about regional humidity and temperature changes. The analysis included sedimentological descriptions, physical properties, organic carbon and carbonate content, mineralogy and geochemical composition together with biological proxies including diatom and ostracod assemblages. A detailed pollen study enabled reconstruction of variations in vegetation cover, which were interpreted in the context of climate changes and human impact. Four distinct stages were recognized for the last 13,500 years: (1) a cold and dry episode that includes the Younger Dryas event (13,500–11,600 cal. year BP); (2) a humid and warmer period characterizing the onset of the Holocene (11,600–8,700 cal. year BP); (3) a tendency toward a drier climate during the middle Holocene (8,700–4,650 cal. year BP); and (4) a return to humid conditions following landscape modification by human activity (pastoral activities, deforestation) in the late Holocene (4,650–2,200 cal. year BP). Superimposed on relatively stable landscape conditions (e.g. maintenance of well established forests), the typical environmental variability of the southern European region is observed at this site.The Spanish Inter-Ministry Commission of Science and Technology (CICYT), the Spanish National Parks agency, the European Commission, the Spanish Ministry of Science, and the European Social Fund

Limnological Characteristics of a High Arctic Oasis and Comparisons across Northern Ellesmere Island

Rapidly warming temperatures in the Arctic are predicted to markedly alter the limnology of tundra lakes and ponds. These changes include increases in aquatic production, pH, specific conductivity, and nutrient levels. However, baseline limnological data from High Arctic regions are typically restricted to single sampling events or to repeated samplings of a few select sites, which limits our ability to assess the influence of climatic change. We employ two techniques to examine the influence of a warmer climate on High Arctic aquatic ecosystems. First, we compare limnological characteristics in July 2003 of 23 ponds and lakes from an atypically warm High Arctic oasis on Ellesmere Island to those of 32 ponds and lakes located across northern Ellesmere Island, where climatic conditions are much cooler and more typical of High Arctic environments. Second, we resample 13 sites originally analyzed in 1963 to assess the influence that 40 years of rising temperatures (as documented by meteorological records) have had on the limnological characteristics of these freshwater ecosystems. The specific conductivity values, as well as the concentrations of nutrients and related variables (especially dissolved organic carbon, DOC), from the Arctic oasis sites are among the highest yet reported from the Canadian High Arctic, and they are significantly higher than those from the polar desert around northern Ellesmere Island. Comparison of the modern and historical data indicated that most oasis sites currently have higher pH than they did in 1963, which is consistent with the documented warming of temperatures.On prévoit que les températures en hausse rapide dans l’Arctique auront pour effet de modifier considérablement la limnologie des lacs et étangs de la toundra. Parmi ces changements, notons l’augmentation de la production aquatique, du pH, de la conductibilité spécifique et des niveaux de nutriments. Toutefois, les données limnologiques de base des régions de l’Extrême-Arctique se limitent typiquement à des événements d’échantillonnage unique ou à des échantillonnages répétés de quelques sites choisis, ce qui a pour effet de restreindre notre aptitude à évaluer l’influence des changements climatiques. Nous avons eu recours à deux techniques pour examiner l’influence d’un climat plus chaud sur les écosystèmes aquatiques de l’Extrême- Arctique. Premièrement, nous comparons les caractéristiques limnologiques de juillet 2003 de 23 lacs et étangs d’oasis atypiquement chaudes de l’Extrême-Arctique sur l’île d’Ellesmere à celles de 32 étangs et lacs parsemés dans le nord de l’île d’Ellesmere, où les conditions climatiques sont beaucoup plus fraîches et plus typiques des milieux de l’Extrême-Arctique. Deuxièmement, nous avons rééchantillonné 13 sites qui avaient d’abord été analysés en 1963 et ce, dans le but d’évaluer l’influence qu’ont eu 40 années de températures à la hausse (d’après les données météorologiques) sur les caractéristiques limnologiques de ces écosystèmes d’eau douce. Les valeurs de conductibilité spécifique, de même que les concentrations en nutriments et les variables connexes (surtout le carbone organique dissous ou COD) des oasis de l’Extrême-Arctique figurent parmi les valeurs les plus élevées signalées dans l’Extrême-Arctique canadien, et sont considérablement plus élevées que celles des déserts polaires du nord de l’île d’Ellesmere. La comparaison des données contemporaines aux données historiques laisse entrevoir que la plupart des oasis ont un pH plus élevé actuellement qu’en 1963, ce qui coïncide avec la constatation documentée de l’augmentation des températures

Revealing the last 13,500 years of environmental history from the multiproxy record of a mountain lake (Lago Enol, northern Iberian Peninsula)

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s10933-009-9387-7.We present the Holocene sequence from Lago Enol (43°16′N, 4°59′W, 1,070 m a.s.l.), Cantabrian Mountains, northern Spain. A multiproxy analysis provided comprehensive information about regional humidity and temperature changes. The analysis included sedimentological descriptions, physical properties, organic carbon and carbonate content, mineralogy and geochemical composition together with biological proxies including diatom and ostracod assemblages. A detailed pollen study enabled reconstruction of variations in vegetation cover, which were interpreted in the context of climate changes and human impact. Four distinct stages were recognized for the last 13,500 years: (1) a cold and dry episode that includes the Younger Dryas event (13,500–11,600 cal. year BP); (2) a humid and warmer period characterizing the onset of the Holocene (11,600–8,700 cal. year BP); (3) a tendency toward a drier climate during the middle Holocene (8,700–4,650 cal. year BP); and (4) a return to humid conditions following landscape modification by human activity (pastoral activities, deforestation) in the late Holocene (4,650–2,200 cal. year BP). Superimposed on relatively stable landscape conditions (e.g. maintenance of well established forests), the typical environmental variability of the southern European region is observed at this site.The Spanish Inter-Ministry Commission of Science and Technology (CICYT), the Spanish National Parks agency, the European Commission, the Spanish Ministry of Science, and the European Social Fund

Neoglacial lake-ecosystem changes above and below the subarctic Fennoscandian treeline inferred from changes in diatom functional groups

Algal communities act as sensitive indicators of past and present climate effects on northern lakes, but their responses can vary considerably between ecosystems. Functional trait-based approaches may help us better understand the nature of the diverse biotic responses and their underlying ecosystem changes. We explored patterns in diatom (Bacillariophyceae) growth forms and species composition during the Neoglacial in two shallow lakes typical of subarctic regions, including a dark-colored woodland lake and a clear tundra lake. Sediment carbon and nitrogen elemental and isotope biogeochemistry and spectral indices were used to track broadscale changes in lake productivity, the inflow of organic carbon from land, and benthic substratum over the past three millennia. The biogeochemical indices tracked declines in land-lake connectivity as well as lake-water and sediment organic enrichment above and below the subarctic treeline driven by Neoglacial cooling. This broadscale environmental transition was intercepted by periods of elevated primary production associated with transient Neoglacial warm anomalies and, in particular, the twentieth century warming. Although the Neoglacial development of the lakes showed conspicuous similarities, diatom functional and taxonomic responses were not uniform between the lakes pointing to intrinsic differences in the development of benthic habitats and underwater-light regimes. Many of the observed biotic shifts aligned with expectations based on earlier research linking diatom functional traits to changing light and organic levels but the results also point to further research needs, particularly to better differentiate the individual and interactive effects of substratum and light. Despite distinct anthropogenic imprints in the biogeochemical record, the scale of human impact on the lakes' biota has not, as yet, been profound, but the changes are nonetheless clear when compared to the previous three millennia of natural lake development.Peer reviewe

Integrated atomic quantum technologies in demanding environments: Development and qualification of miniaturized optical setups and integration technologies for UHV and space operation

Employing compact quantum sensors in field or in space (e.g., small satellites) implies demanding requirements on components and integration technologies. Within our work on integrated sensors, we develop miniaturized, ultra-stable optical setups for optical cooling and trapping of cold atomic gases. Besides challenging demands on alignment precision, and thermo-mechanical durability, we specifically address ultra-high vacuum (UHV) compatibility of our integration technologies and optical components. A prototype design of an UHV-compatible, crossed beam optical dipole trap setup and its application within a cold atomic quantum sensor is described. First qualification efforts on adhesive micro-integration technologies are presented. These tests are conducted in application-relevant geometries and material combinations common for micro-integrated optical setups. Adhesive aging will be investigated by thermal cycling or gamma radiation exposure. For vacuum compatibility testing, a versatile UHV testing system is currently being set up, enabling residual gas analysis and measurement of total gas rates down to 5•10-10mbar l/s at a base pressure of 10-11 mbar, exceeding the common ASTM E595 test

Integrated atomic quantum technologies in demanding environments: Development and qualification of miniaturized optical setups and integration technologies for UHV and space operation

Employing compact quantum sensors in field or in space (e.g., small satellites) implies demanding requirements on components and integration technologies. Within our work on integrated sensors, we develop miniaturized, ultra-stable optical setups for optical cooling and trapping of cold atomic gases. Besides challenging demands on alignment precision, and thermo-mechanical durability, we specifically address ultra-high vacuum (UHV) compatibility of our integration technologies and optical components. A prototype design of an UHV-compatible, crossed beam optical dipole trap setup and its application within a cold atomic quantum sensor is described. First qualification efforts on adhesive micro-integration technologies are presented. These tests are conducted in application-relevant geometries and material combinations common for micro-integrated optical setups. Adhesive aging will be investigated by thermal cycling or gamma radiation exposure. For vacuum compatibility testing, a versatile UHV testing system is currently being set up, enabling residual gas analysis and measurement of total gas rates down to 5•10-10mbar l/s at a base pressure of 10-11 mbar, exceeding the common ASTM E595 test