Interannual and decadal variability in zooplankton communities of the southeast Bering Sea shelf

The southeastern Bering Sea shelf ecosystem is an important fishing ground for fin- and shellfish, and is the summer foraging grounds for many planktivorous seabirds and marine mammals. In 1997 and 1998, Northern Hemisphere climate anomalies affected the physical and biological environment of the southeastern Bering Sea shelf. The resulting anomalous conditions provided a valuable opportunity to examine how longer-term climate change might affect this productive ecosystem. We compared historical and recent zooplankton biomass and species composition data for the southeastern Bering Sea shelf to examine whether or not there was a response to the atmosphere–ocean–ice anomalies of 1997 and 1998. Summer zooplankton biomass (1954–1994) over the southeastern shelf did not exhibit a decline as previously reported for oceanic stations. In addition, zooplankton biomass in 1997 and 1998 was not appreciably different from other years in the time series. Spring concentrations of numerically abundant copepods (Acartia spp., Calanus marshallae, and Pseudocalanus spp.), however, were significantly higher during 1994–1998 than 1980–1981; spring concentrations of Metridia pacifica and Neocalanus spp. were not consistently different between the two time periods. Neocalanus spp. was the only taxon to have consistent differences in stage composition between the two time periods—CV copepodites were much more prevalent in May of the 1990s than early 1980s. Since relatively high zooplankton concentrations were observed prior to 1997, we do not attribute the high concentrations observed in the summers of 1997 and 1998 directly to the acute climate anomalies. With the present data it is not possible to distinguish between increased production (control from below) and decreased predation (control from above) to explain the recent increase in concentrations of the species examined.     

Impacts of Present and Future Climate Change and Climate Variability on Agriculture in the Temperate Regions: North America

The potential impact of climate variability and climate change on agricultural production in the United States and Canada varies generally by latitude. Largest reductions are projected in southern crop areas due to increased temperatures and reduced water availability. A longer growing season and projected increases in CO₂ may enhance crop yields in northern growing areas. Major factors in these scenarios analyzes are increased drought tendencies and more extreme weather events, both of which are detrimental to agriculture. Increasing competition for water between agriculture and non-agricultural users also focuses attention on water management issues. Agriculture also has impact on the greenhouse gas balance. Forests and soils are natural sinks for CO₂. Removal of forests and changes in land use, associated with the conversion from rural to urban domains, alters these natural sinks. Agricultural livestock and rice cultivation are leading contributors to methane emission into the atmosphere. The application of fertilizers is also a significant contributor to nitrous oxide emission into the atmosphere. Thus, efficient management strategies in agriculture can play an important role in managing the sources and sinks of greenhouse gases. Forest and land management can be effective tools in mitigating the greenhouse effect.     

The Cloud Ice Mountain Experiment (CIME) 1998: experiment overview and modelling of the microphysical processes during the seeding by isentropic gas expansion

The second field campaign of the Cloud Ice Mountain Experiment (CIME) project took place in February 1998 on the mountain Puy de Dôme in the centre of France. The content of residual aerosol particles, of H₂O₂ and NH₃ in cloud droplets was evaluated by evaporating the drops larger than 5 μm in a Counterflow Virtual Impactor (CVI) and by measuring the residual particle concentration and the released gas content. The same trace species were studied behind a round jet impactor for the complementary interstitial aerosol particles smaller than 5 μm diameter. In a second step of experiments, the ambient supercooled cloud was converted to a mixed phase cloud by seeding the cloud with ice particles by the gas release from pressurised gas bottles. A comparison between the physical and chemical characteristics of liquid drops and ice particles allows a study of the fate of the trace constituents during the presence of ice crystals in the cloud.In the present paper, an overview is given of the CIME 98 experiment and the instrumentation deployed. The meteorological situation during the experiment was analysed with the help of a cloud scale model. The microphysics processes and the behaviour of the scavenged aerosol particles before and during seeding are analysed with the detailed microphysical model ExMix. The simulation results agreed well with the observations and confirmed the assumption that the Bergeron–Findeisen process was dominating during seeding and was influencing the partitioning of aerosol particles between drops and ice crystals. The results of the CIME 98 experiment give an insight on microphysical changes, redistribution of aerosol particles and cloud chemistry during the Bergeron–Findeisen process when acting also in natural clouds.     

Behaviour of H2O2, NH3, and black carbon in mixed-phase clouds during CIME

We investigated the partitioning of trace substances during the phase transition from supercooled to mixed-phase cloud induced by artificial seeding. Simultaneous determination of the concentrations of H₂O₂, NH₃ and black carbon (BC) in both condensed and interstitial phases with high time resolution showed that the three species undergo different behaviour in the presence of a mixture of ice crystals and supercooled droplets. Both H₂O₂ and NH₃ are efficiently scavenged by growing ice crystals, whereas BC stayed predominantly in the interstitial phase. In addition, the scavenging of H₂O₂ is driven by co-condensation with water vapour onto ice crystals while NH₃ uptake into the ice phase is more efficient than co-condensation alone. The high solubility of NH₄⁺ in the ice could explain this result. Finally, it appears that the H₂O₂–SO₂ reaction is very slow in the ice phase with respect to the liquid phase. Our results are directly applicable for clouds undergoing limited riming.     

Differences in grain growth of calcite: a field-based modeling approach

Normal grain growth of calcite was investigated by combining grain size analysis of calcite across the contact aureole of the Adamello pluton, and grain growth modeling based on a thermal model of the surroundings of the pluton. In an unbiased model system, i.e., location dependent variations in temperature-time path, 2/3 and 1/3 of grain growth occurs during pro- and retrograde metamorphism at all locations, respectively. In contrast to this idealized situation, in the field example three groups can be distinguished, which are characterized by variations in their grain size versus temperature relationships: Group I occurs at low temperatures and the grain size remains constant because nano-scale second phase particles of organic origin inhibit grain growth in the calcite aggregates under these conditions. In the presence of an aqueous fluid, these second phases decay at a temperature of about 350 °C enabling the onset of grain growth in calcite. In the following growth period, fluid-enhanced group II and slower group III growth occurs. For group II a continuous and intense grain size increase with T is typical while the grain growth decreases with T for group III. None of the observed trends correlate with experimentally based grain growth kinetics, probably due to differences between nature and experiment which have not yet been investigated (e.g., porosity, second phases). Therefore, grain growth modeling was used to iteratively improve the correlation between measured and modeled grain sizes by optimizing activation energy (Q), pre-exponential factor (k₀) and grain size exponent (n). For n=2, Q of 350 kJ/mol, k₀ of 1.7×10²¹ mⁿs^–1 and Q of 35 kJ/mol, k₀ of 2.5×10^-5 mⁿs^–1 were obtained for group II and III, respectively. With respect to future work, field-data based grain growth modeling might be a promising tool for investigating the influences of secondary effects like porosity and second phases on grain growth in nature, and to unravel differences between nature and experiment.Editorial responsibility: J. Hoefs     

Die Gasvakuolen der BlaualgeMicrocystis aeruginosa

Zusammenfassung Lichtoptisch sind inMicrocystis aeruginosa Zellen mit und ohne Gasvakuolen vorhanden. Dieses Ph?nomen kann erkl?rt werden durch die Abbildungsverh?ltnisse der gasgefüllten, submikroskopischen Elemente der Gasvakuolen, der Hohlspindeln, die mehr oder weniger geh?uft auftreten und dadurch das Vorkommen verschiedener Zelltypen vort?uschen.

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Summary Cells ofMicrocystis aeruginosa have been investigated by light- and electron-microscopy. In the light-microscope cells with and without gas vacuoles are observed. This fact can be confirmed by submicroscopic findings.

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Résumé En observantMicrocystis aeruginosa avec le microscope photonique on voit des cellules avec et sans vacuoles gazeuses. Ce fait s'explique par les observations submicroscopiques.

     

Zur Resistenz von Blaualgen gegen kurzwellige Strahlung

Zusammenfassung 13 Klone von Blaualgen verschiedener taxonomischer Stellung (Chroococcales, Chamaesiphonales, Nostocales) und verschiedener ?kologischer Gruppen (Plankter, Litoralformen, Aerophyten schattiger und sonniger Standorte), wurden mit Gamma-und UV-Strahlen behandelt. Plankter erwiesen sich unabh?ngig von ihrer taxonomischen Stellung als wenig widerstandsf?hig: Die maximale Gammastrahlentoleranz betrug je nach Klon 65 bis 260 krad bei Bestrahlungszeiten von rund 10 bis 40 Minuten, die maximale UV_Strahlentoleranz belief sich (mit einer Ausnahme) unter unseren Versuchsbedingungen auf eine Bestrahlungszeit von 32 Minuten. Begleitbakterien tolerierten durchwegs h?here Strahlendosen. Dagegen erwiesen sich Aerophyten bzw. Lithophyten von Standorten mit extremem natürlichem Strahlungsklima auch im Experiment als sehr resistent. So überlebtenChamaesiphon polonicus undScytonema burmanicum siebenstündige Exposition in Gammastrahlen (totale Dosis 2500 krad) sowie vierstündige UV-Bestrahlung. Begleitbakterien überlebten zwar die UV-Behandlung, nicht aber die hohen Gammastrahlendosen. Behandlung mit Gammastrahlen eignet sich daher zur Gewinnung axenischer Kulturen von Cyanophyten extremer Naturstandorte. Mehrere Monate alte axenische Kulturen vonScytonema burmanicum und vonS. lyngbyoides riechen übel, w?hrend bakterienhaltige Kulturen geruchlos bleiben. Vermutlich bauen die Begleitbakterien von den Algen ausgeschiedene, übelriechende Stoffwechselprodukte zu geruchlosen Verbindungen ab.

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Summary Thirteen strains of blue-green algae including members of the Chroococcales, Chamaesiphonales and Nostocales and belonging to various ecological groups have been exposed to various doses of gamma and UV radiation. Tolerances were independent of the taxonomic position but correlated with the ecological behaviour of the taxa involved. While planktonic species were quite sensitive to both UV and gamma radiation (maximum tolerance in the range of 65 to 260 krad) aerophytic and lithophytic species tolerated up to more than 2500 krad of gamma radiation and more than 4 hours of exposition to UV radiation. In cultures of planktonic species, gamma radiation killed the algae prior to the associated bacteria so that no axenic cultures could be obtained. In some cultures of aerophytic and lithophytic taxa however, bacteria were killed prior to the algae. Thus, axenic cultures of these strains could be obtained. Old axenic cultures ofScytonema burmanicum and ofS. lyngbyoides display a bad smell, whereas cultures with bacteria are odourless. Probably, the bacteria are reducing to odourless compounds the smelling substances excreted by the algae.

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Résumé Treize souches cloniques de Cyanophycées d’eau douce appartenant aux ordres des Chroococcales, des Chamaesiphonales et des Nostocales et représentant divers types écologiques à savoir des formes du plancton et du littoral ainsi que des espèces saxicoles aériennes et subaériennes de habitats ombreux et fort ensoleillés ont été traité aux rayons et UV. Les espèces planctoniques se montraient peu résistantes, indépendemment de leur position taxonomique: Dans nos conditions, elles supportaient au maximum 32 minutes d’irradiation de rayons UV, et, selon la souche clonique, de 65 à 260 krad de rayons gamma. Les bactéries accompagnant les algues supportaient partout des doses d’irradiation plus élevées. Par contre, les espèces saxicoles provenant de stations aériennes ou subaériennes se montraient très résistantes.Chamaesiphon polonicus etScytonema burmanicum par exemple supportaient dans nos conditions une irradiation UV de 4 heures et une exposition aux rayons gamma de 6 heures (dose totale: 2500 krad). Les bactéries accompagnant ces espèces supportaient les rayons UV, mais non les rayons gamma. Le traitement avec des rayons gamma peut donc aboutir à des cultures axéniques de Cyanophycées d’habitats aériens ou subaériens. Les cultures axéniques deScytonema burmanicum et deS. lyngbyoides agées de quelques mois sentent mauvais, tandis que les cultures parallèles dont les algues sont accompagnées de bactéries restent sans odeur. Il semble que les bactéries décomposent les substances d’odeur désagréable produites par les deux espèces.

     

On the consequences of a long-term perspective for coastal management

The potential impacts of climate change on coastal zones combined with the ever increasing number of people living in these areas, motivate a more long-term perspective in coastal management. To explore whether such a perspective raises the need for developing coastal management strategies at larger spatial scales, this paper presents a case study for the dune-protected Holland coast. Long-term (200 years) coastal management strategies are set-up at different levels of spatial aggregation, accounting for specific characteristics of the coast itself and for types of land use in the hinterland. Using a combination of multi-criteria analysis and cost-benefit analysis the new coastal management strategies are compared to the long-term continuation of present coastal management practice. It appears that the large uncertainties that inevitably accompany a long-term perspective do not preclude the comparison of long-term coastal management strategies. Additionally, it appears that a long-term perspective favors solutions for coastal defense enhancement that are more spatially extended and alongshore uniform than those emerging from continuing today's coastal management practice for two centuries.     

Does upward seepage of river water and storm water runoff determine water quality of urban drainage systems in lowland areas? A case study for the Rhine–Meuse delta

The water quality of urban drainage ditches in lowlands in the Rhine‐Meuse delta was analysed with principal component analysis (PCA) during a dry period and a rain storm, and related to the seepage of polluted river water and effective impervious area (EIA). This was done in order to test the hypothesis that seepage of river water and storm water runoff from impervious areas strongly determine the water quality of urban drainage systems along large lowland rivers. Our analysis revealed that upward seepage of groundwater originating from rivers Rhine and Meuse was positively correlated with nitrate, potassium, sodium and chloride and negatively correlated with alkalinity, calcium, magnesium and iron. EIA was correlated with very few environmental variables (i.e. phosphate, pH and iron in the dry period and iron during the rain storm). Nickel and zinc concentrations generally exceeded the maximum allowable concentrations (MAC), while lead and phosphorus concentrations were just above the nutrient standards and MAC in a few locations during the rain storm. To optimize water quality in urban water systems, attention should be paid to all sources of pollution and not only to EIA. The impact of local groundwater seepage originating from large rivers in lowlands on the chemistry of urban water systems is often underestimated and should be taken into account when assessing water quality and improving water quality status. Copyright © 2009 John Wiley & Sons, Ltd.