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Politicians generally favor hosting mega sports events despite the discouraging evidence of financial benefits or direct economic gain. This paradox is surveyed from two different perspectives. First, we weighed the merits of the most prominent methods of economic analysis of mega sports events. Then, we discuss the ways in which politicians still manage to infer positive gains from hosting this type of event from the literature. Next, we look at a range of frequently intangible effects that could be used in the public debate before submitting a bid but that, paradoxically, rarely are. The most promising of these is making the people proud and happy. However, economists have so far been incapable of adequately valuing the effect of hosting a mega sport event based on happiness. Second, we analyzed the political process parallel to preparing a bid to understand why politicians are persistently keen to host, despite the bleak economic prospects. [ABSTRACT FROM AUTHOR]

Flood risk quantification is a complex process involving a chain of models. The approach contains many uncertainties which accumulate in the calculated flood risk. Risk-based flood safety standards are therefore prone to large uncertainty. This study aims to quantify the uncertainty of risk-based flood safety standards for a Dutch riverine case study. Through a systematic approach using expert elicitation, the key uncertainty sources in the Dutch safety standard derivation are identified. Uncertainty magnitudes are quantified for five main sources of uncertainty, after which these uncertainties are propagated through the model chain in a scenario analysis to derive flood safety standards. The results show that the Dutch risk-based flood safety standards are highly uncertain given the relative uncertainty bandwidth of 70%. The flood safety standards are found to be most sensitive to damage function and evacuation uncertainty. Also, we show that the impact of uncertainty strongly depends on local characteristics. [ABSTRACT FROM AUTHOR]

Usingmicro-data for Dutch firms, we argue that both the geographic component (what country is the import from) and the intensity component (what type of good is imported) is crucial for measuring and understanding productivity premia associated with importing. For example, our results indicate that the productivity premium associated with importing technology-intensive products from Taiwan differs from importing unskilled-labor-intensive products from Switzerland. We show that increasing distance and decreasing levels of development of the origin economy are negatively associated with the productivity premia of importing. Similarly, these premia are larger for technology- intensive goods and smaller for unskilled-labor-intensive goods. This implies that the geographic-intensity markets are unique and cannot be lumped together. In addition, a more dispersed import portfolio (the extensive dimension) is always positively associated with firm-level productivity. [ABSTRACT FROM AUTHOR]

Employing micro-data of Dutch local business units, we show that firm characteristics such as size, economic activity, the traded product portfolio, the focus of trade involvement and the geographic pattern of trade are important determinants of recovery following the trade collapse of 2008-2009, both in terms of speed and depth. Our findings suggest that post-crisis growth is faster for trade in goods further downstream of the value chain and thus closer to the final consumer. Trade recovery at the firm-level does not crucially hinge on locational factors such as the province in which a firm is located or regional revealed comparative advantages in particular product groups. [ABSTRACT FROM AUTHOR]

This work presents the characterisation of the Aerosol Package for the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System). Condensation particle counter (CPC) are used to measure the aerosol number concentration of the total and the non-volatile particles. The size distribution is measured by means of an optical particle counter (OPC) in the diameter range of 0.25-3 mm. In particular the OPC is characterised for (1) leakage, (2) flow and calibration stability over the expected IAGOS pressure range of 170 hPa to 1013 hPa, (3) OPC accuracy test by comparing extinction measurements with calculated values from Mie theory using the OPC size distribution and (4) the inter-instrumental precision. The CPC is characterised in the same pressure range for (1) the lower cut-off diameter, (2) the instrument accuracy by comparing with a reference instrument (Faraday Cup Electrometer, FCE) and (3) the instrument precision. We conclude that the IAGOS Aerosol Package is a fully automated, robust, low-maintenance instrument providing high precision measurements with good accuracy. [ABSTRACT FROM AUTHOR]

In December 2000, a fully automatic NOy instrument was installed on one of the five Airbus A340 aircraft used in the MOZAIC project (Measurement of Ozone and Water Vapour by Airbus in-service Aircraft) for measurements of O3 and H2O since 1994. This long-range aircraft was operated by Lufthansa, mainly out of Frankfurt and Munich. After an initial testing period, regular data collection started in May 2001. Until May 2005, 1533 flights have been recorded, corresponding to 8500 flight hours of NOy measurements. Concurrent data of NOy and O3 are available from 1433 flights and concurrent data for CO, O3 and NOy exist from 1125 flights since 2002. The paper describes the data availability in terms of geographical, vertical and seasonal distribution and discusses the quality and limitations of the data, including interference by HCN. The vast majority of vertical profiles were measured over Frankfurt, followed by Munich and North American airports. While most of the data were collected in the upper troposphere and lower stratosphere over the North Atlantic, significant data sets exist also from flights to Far and Middle East, whereas data from the tropics and the Southern Hemisphere are relatively sparse. [ABSTRACT FROM AUTHOR]

Logistic regression was used to analyse the relationship between six submerged macrophyte taxa (Chara spp., Potamogeton perfoliatus, Potamogeton pectinatus, Potamogeton pusillus, Myriophyllum spicatum, Alisma gramineum and sum of all species) and four environmental variables (turbidity, effective wind fetch, water depth and sediment silt percentage, including interactions and some quadratic terms). The models were based on intensive vegetation samples (total c. 72 000) and other monitoring data carried out in five Dutch shallow lakes in the IJsselmeer area from 1988 to 1998. Water depth and light extinction were the most important factors determining the occurrence of all studied species in Veluwemeer, while effective wind fetch had a moderate effect and sediment silt had only a minor effect on the occurrence. Water depth had a negative impact on all species, except A. gramineum, which showed an optimum response. Three species showed an optimum response at intermediate turbidity (M. spicatum, P. pusillus and P. pectinatus), whereas the other taxa were negatively related. Three species (Chara spp., P. perfoliatus and M. spicatum) were positively related to wind fetch or showed an optimum response at intermediate value, whereas P. pusillus, P. pectinatus and A. gramineum were negatively related. The models including interactions between the explanatory variables showed a high goodness of fit for Veluwemeer for Chara, P. pectinatus and M. spicatum (in more than 8 of 10 instances, a cell originally scored `1' are predicted to have a higher probability than the ones originally scored `0'). The models of the other species showed a moderate goodness of fit (between 6 and 8 of 10 instances correctly predicted). The models developed for Veluwemeer were valid for Chara in all the four other lakes (more than 8 of 10 instances correctly predicted), while the models of other species were valid in some instances. A succession of vegetation was recognised based on water depth and turbidity in Veluwemeer. P. perfoliatus and P. pectinatus dominated the shallow zones under turbid conditions, but a change to dominance by Chara occurred in clear water. Based on the observation of co-occurrence, competition has played an important role for the shift from P. pectinatus to Chara. Chara became dominant 2 years after initial colonisation of Chara in P. pectinatus beds. Competition between P. perfoliatus and Chara may have been of less importance, due to a more distinct habitat (deeper colonisation) of dense P. perfoliatus beds. The analysed species showed large differences in vegetation stability from year-to-year. Chara showed the highest year to year stability (c. 65% of the cells remained covered from one year to another), while A. gramineum showed the highest dynamics (c. 10% of the cells remained covered from one year to another). Species producing specialized vegetative propagules for over wintering showed a higher local stability than species without such propagules. [ABSTRACT FROM AUTHOR]

We studied the potential role of dissolved inorganic carbon (DIC) in determining vegetation dominance of Potamogeton pectinatus L. and Chara aspera Deth. ex Willd. by monitoring the seasonal dynamics of DIC in a shallow lake and comparing the use of DIC of the two species. The HCO3−-concentration in summer dropped from 2.5 to <0.5 mM with seasonally increasing Chara biomass, whereas outside the vegetation concentrations remained at 2.5 mM. Inside Potamogeton spp. vegetation DIC decreased from 2.5 to ca. 0.75 mM HCO3−. A growth experiment showed ash-free biomass for P. pectinatus was nearly two times as high as for C. aspera at 3 mM HCO3−, but almost two times lower at 0.5 mM than at 3.0. In a separate experiment, P. pectinatus precultured at a relatively low HCO3−-level had a lower net photosynthetic rate (Pmax, 0.1 mmol O2 g−1 DW h−1) than C. aspera (Pmax, 0.1 mmol O2 g−1 DW h−1) over the range of HCO3−-concentrations tested (Pmax, 0.14 mmol O2 g−1 DW h−1). In response to CO2 no significant differences between the compensation points (P. pectinatus, 28 mM; C. aspera 66 mM), were observed, but the photosynthetic rate increased faster than for C. aspera than for P. pectinatus. Under field conditions, the use of CO2 is not important since inside vegetation CO2-concentrations were below 10 μM, and thus, not available for photosynthesis of either species during the main part of the growth season. It is suggested that C. aspera may be a better competitor for HCO3− than P. pectinatus in conditions with a low HCO3− supply. As HCO3− is a strong limiting factor for growth inside the vegetation and probably the only carbon source available, the superior ability of C. aspera to use HCO3− may be an important factor explaining its present dominance in Veluwemeer. [Copyright &y& Elsevier]

Presents some ecological aspects of charophytes and their implications for management of shallow lakes. History of Lake Veluwemeer in the Netherlands, where the charophyte vegetation disappeared coincident with cultural eutrophication but became dominant again after restoration; Main factors that regulate charophyte abundance; Effects that charophytes can have on the ecosystem; Stability of charophyte vegetation and the role of charophytes in restoration projects.

Describes the design of a solid-state microrefrigerator based on normal-insulator-superconductor tunnel junctions. Limitation of the junction area by the need for defect-free tunnel barrier; Combination of the substrate and superconducting electrode in a macroscopic superconducting single crystal.

Aerosol particle number concentration measurements are a crucial part of aerosol research. Vertical profile measurements and high-altitude/low-pressure performance of the respective instruments become more important for remote sensing validation and a vital tool for the observation of climate variables. This study tests the new, commercially available water condensation particle counter (MAGIC 210-LP) for the deployment at aircraft cruising pressure levels that the European research infrastructure IAGOS (In-service Aircraft for a Global Observing System; http://www.iagos.org , last access: 2 May 2023) is aiming for by operating measurement instrumentation onboard passenger aircraft. We conducted laboratory experiments for conditions to simulate passenger aircraft flight altitude at operation pressure. We demonstrate that this type of water condensation particle counter shows excellent agreement with a butanol-based instrument used in parallel. A Faraday cup aerosol electrometer serves as the reference instrument. Experiments are performed with test aerosol ammonium sulfate and fresh combustion soot at pressure levels ranging from 700 to 200 hPa. For soluble particles like ammonium sulfate, the 50 % detection efficiency cut-off diameter (D50) is around 5 nm and does not differ significantly for all performed experiments. For non-soluble fresh soot particles, the D50 cut-off diameter of approximately 10 nm does not vary substantially as a function of pressure, whereas the 90 % detection efficiency cut-off diameter D90 increases from 19 nm at 700 hPa to 37 nm at 200 hPa. The overall counting efficiency for particles larger than 40 nm reaches 100 % for working pressures of 200 hPa and higher. [ABSTRACT FROM AUTHOR]

This work presents the characterisation of the Aerosol Package for the European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System). Condensation particle counter (CPC) are used to measure the aerosol number concentration of the total and the non-volatile particles. The size distribution is measured by means of an optical particle counter (OPC) in the diameter range of 0.25–3 µm. In particular the OPC is characterised for (1) leakage, (2) flow and calibration stability over the expected IAGOS pressure range of 170 hPa to 1013 hPa, (3) OPC accuracy test by comparing extinction measurements with calculated values from Mie theory using the OPC size distribution and (4) the inter-instrumental precision. The CPC is characterised in the same pressure range for (1) the lower cut-off diameter, (2) the instrument accuracy by comparing with a reference instrument (Faraday Cup Electrometer, FCE) and (3) the instrument precision. We conclude that the IAGOS Aerosol Package is a fully automated, robust, low-maintenance instrument providing high precision measurements with good accuracy. [ABSTRACT FROM PUBLISHER]

In December 2000, a fully automatic NOy instrument was installed on one of the five Airbus A340 aircraft used in the MOZAIC project (Measurement of Ozone and Water Vapour by Airbus in-service Aircraft) for measurements of O3 and H2O since 1994. This long-range aircraft was operated by Lufthansa, mainly out of Frankfurt and Munich. After an initial testing period, regular data collection started in May 2001. Until May 2005, 1533 flights have been recorded, corresponding to 8500 flight hours of NOy measurements. Concurrent data of NOy and O3 are available from 1433 flights and concurrent data for CO, O3 and NOy exist from 1125 flights since 2002. The paper describes the data availability in terms of geographical, vertical and seasonal distribution and discusses the quality and limitations of the data, including interference by HCN. The vast majority of vertical profiles were measured over Frankfurt, followed by Munich and North American airports. While most of the data were collected in the upper troposphere and lower stratosphere over the North Atlantic, significant data sets exist also from flights to Far and Middle East, whereas data from the tropics and the Southern Hemisphere are relatively sparse. [ABSTRACT FROM AUTHOR]

An evaluation of the operation and performance of a Cavity Attenuated Phase-Shift Particle Extinction Monitor (CAPS PMex) was performed for use on board commercial aircraft as part of the research infrastructure IAGOS (In-service Aircraft for a Global Observing System,www.iagos.org). After extensive laboratory testing, a new flow system, using mass flow controllers, was installed to maintain constant purge and sample flows under low and varying pressure conditions. The instrument was then tested for pressures as low as 200 hPa and evaluated against particle-free compressed air and CO2. Extinction coefficients for the studied gases were in close agreement with literature values with differences between 2.2% and 8%, proving that the CAPS technology works at low pressures. The instrument's limit of detection, with respect to 3 times the variability of the background signal for the full pressure range, was 0.2 Mm−1for 60s integration time. During its first research aircraft operations, the IAGOS instrument prototype, composed of one CAPS PMex and one OPC, showed excellent results regarding the stability of the instruments and the potential for characterizing different aerosol types and for estimating the contribution of sub- and super-μm sized particles to aerosol light extinction. Copyright © 2017 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Aerosol intensive optical properties, including Ångström exponents for aerosol light extinction (EAEs), scattering (SAEs) and absorption (AAEs) as well as and the single-scattering albedo (SSA), are indicators for aerosol size, chemical composition, radiative behaviour and particle sources. Derivation of these parameters requires the measurement of aerosol optical properties at multiple wavelengths, which usually involves the use of several instruments. Our study aims to quantify the uncertainties in the determination of these intensive properties using an optical closure approach. In our laboratory closure study, we measured the full set of optical properties for a range of light-absorbing particles with different properties externally mixed with ammonium sulfate to generate aerosols with controlled SSA values. The investigated absorbing particle types were fresh combustion soot emitted by an inverted flame soot generator (SOOT; fractal agglomerates), Aquadag (AQ; compact aggregates), Cabot black (BC; compact agglomerates) and an acrylic paint (magic black, shape unknown). The instruments used in this study were two cavity attenuated phase shift particle monitors for single-scattering albedo (CAPS PM SSA 's; λ=450 , 630 nm) for measuring light-extinction and light-scattering coefficients, one integrating nephelometer (λ=450 , 550, 700 nm) for light-scattering coefficients, and one tricolour absorption photometer (TAP; λ=467 , 528, 652 nm) for filter-based light-absorption coefficients. One key finding is that the coefficients of light absorption, scattering and extinction derived from combing the measurements of two independent instruments agree with measurements from single instruments; the slopes of regression lines are equal within reported uncertainties (i.e. closure is observed). Despite closure for measured absorption coefficients, we caution that the estimated uncertainties for absorption coefficients, propagated for the differential method (DM; absorption = extinction minus scattering), can exceed 100 % for atmospherically relevant SSA values (>0.9). This increasing estimated uncertainty with increasing SSA yields AAE values that may be too uncertain for measurements in the range of atmospheric aerosol loadings. We recommend using the DM for measuring AAE values when the SSA < 0.9. EAE- and SAE-derived values achieved closure during this study within stated uncertainties for extinction coefficients greater than 15 Mm -1. SSA values for 450 and 630 nm wavelengths internally agreed with each other within 10 % uncertainty for all instrument combinations and sampled aerosol types, which fulfils the defined goals for measurement uncertainty of 10 % proposed by Laj et al. (2020) for GCOS (Global Climate Observing System) applications. [ABSTRACT FROM AUTHOR]

The implementation of the Water Framework Directive requires EU member states to establish and harmonize ecological status class boundaries for biological quality elements. In this paper, we describe an approach for defining ecological class boundaries that delineates shifts in lake ecosystem functioning and, therefore, provides ecologically meaningful targets for water policy in Europe., We collected an extensive data set of 810 lake-years from nine Central European countries, and we used phytoplankton chlorophyll a, a metric widely used to measure the impact of eutrophication in lakes. Our approach establishes chlorophyll a target values in relation to three significant ecological effects of eutrophication: the decline of aquatic macrophytes, the dominance of potentially harmful cyanobacteria and the major functional switch from a clear water to a turbid state., Ranges of threshold chlorophyll a concentrations are given for the two most common lake types in lowland Central Europe: for moderately deep lakes (mean depth 3-15 m), the greatest ecological shifts occur in the range 10-12 μg L−1 chlorophyll a, and for shallow lakes (<3 m mean depth), in the range 21-23 μg L−1 chlorophyll a., Synthesis and applications. Our study provides class boundaries for determining the ecological status of lakes, which have robust ecological consequences for lake functioning and which, therefore, provide strong and objective targets for sustainable water management in Europe. The results have been endorsed by all participant member states and adopted in the European Commission legislation, marking the first attempt in international water policy to move from physico-chemical quality standards to harmonized ecologically based quality targets. [ABSTRACT FROM AUTHOR]

Aerosol intensive optical properties like the Ångström exponents for aerosol light extinction, scattering and absorption, or the single-scattering albedo are indicators for aerosol size distributions, chemical composition and radiative behaviour and contain also source information. The observation of these parameters requires the measurement of aerosol optical properties at multiple wavelengths which usually implies the use of several instruments. Our study aims to quantify the uncertainties of the determination of multiple-wavelengths intensive properties by an optical closure approach, using different test aerosols. In our laboratory closure study, we measured the full set of aerosol optical properties for a range of light-absorbing aerosols with different properties, mixed externally with ammonium sulphate to generate aerosols of controlled single-scattering albedo. The investigated aerosol types were: fresh combustion soot emitted by an inverted flame soot generator (SOOT, fractal aggregates), Aquadag (AQ, spherical shape), Cabot industrial soot (BC, compact clusters), and an acrylic paint (Magic Black, MB). One focus was on the validity of the Differential Method (DM: absorption = extinction minus scattering) for the determination of Ångström exponents for different particle loads and mixtures of light-absorbing aerosol with ammonium sulphate, in comparison to data obtained from single instruments. The instruments used in this study were two CAPS PMssa (Cavity Attenuated Phase Shift Single Scattering Albedo, ? = 450, 630 nm) for light extinction and scattering coefficients, one Integrating Nephelometer (? = 450, 550, 700 nm) for light scattering coefficient and one Tricolour Absorption Photometer (TAP, ? = 467, 528, 652 nm) for filter-based light absorption coefficient measurement. Our key finding is that the coefficients of light absorption sap, scattering ssp and extinction sep from the Differential Method agree with data from single reference instruments, and the slopes of regression lines equal unity within the precision error. We found, however, that the precision error for the DM exceeds 100% for sap values lower than 10-20 Mm-1 for atmospheric relevant single scattering albedo. This increasing uncertainty with decreasing sap yields an absorption Ångström exponent (AAE) that is too uncertain for measurements in the range of atmospheric aerosol loadings. We recommend using DM only for measuring AAE values for sap > 50 Mm-1. Ångström exponents for scattering and extinction are reliable for extinction coefficients from 20 up to 1000 Mm-1 and stay within 10% deviation from reference instruments, regardless of the chosen method. Single-scattering albedo (SSA) values for 450 nm and 630 nm wavelengths agree with values from the reference method ssp (NEPH)/sep (CAPS PMSSA) with less than 10% uncertainty for all instrument combinations and sampled aerosol types which fulfil the defined goals for measurement uncertainty of 10% proposed by Laj et al., 2020 for GCOS (Global Climate Observing System) applications. [ABSTRACT FROM AUTHOR]

An important problem in lake management is the replacement of submerged plant species by competing species with undesirable properties. Although dynamics of rooted aquatic macrophytes have been extensively modeled, competition between different species has hardly been addressed so far. We present an individual-based spatially explicit model (‘Charisma’) designed to simulate the growth of one or more competing species of submerged macrophytes. The model behavior easily becomes rather complex and puzzling if we study more than one species. This probably reflects the complexity as it really occurs in nature, but poses a challenge for calibrating and understanding the model. To control this complexity, we used a flexible design facilitating the elimination of feedback loops and processes to trace the causes of the complex behavior of the model. The resulting ‘realistic, yet transparent’ model appeared useful in many aspects for bridging the existing gap between theory and reality. As an example, we present an analysis of competition between the charophyte Chara aspera Deth. ex Willd. and pondweed Potamogeton pectinatus L. The model suggests that alternative equilibria may arise as a result of two positive feedbacks: the enhancement of transparency by macrophytes and a feedback caused by bicarbonate competition. [Copyright &y& Elsevier]

Water-birds were almost absent from Lake Veluwemeer during the 1970s and 1980s, due to low food availability related to eutrophication. Several restoration measures have resulted in the recolonization of the lake by Chara spp. during the 1990s. Bird numbers in autumn and winter have increased along with charophyte biomass. Linear regression analysis was used to relate bird numbers to the abundance of their potential food sources Chara, pondweeds, filamentous macro-algae (FA) and zebra mussels (Dreissena polymorpha) within the depth range available to each species. Numbers of mute swan (Cygnus olor), pochard (Aythya ferina), tufted duck (A. fuligula), coot (Fulica atra) (R2≥0.98), gadwall (Anas strepera) (R2=0.78), Bewick’s swan (Cygnus columbianus) (R2=0.79), red-crested pochard (Netta rufina) (R2=0.76) and pintail (Anas acuta) (R2=0.38) showed significant correlations with these food sources. Chara biomass explained most of the variance in all species except for gadwall. Both bird numbers and their duration of stay were closely associated with the presence of Chara. Grazing pressure was low during spring and summer and Chara colonized the lake in spite of consumption. It is argued that birds did not slow down colonization of the lake by Chara during the 1990s, but may have accelerated succession from pondweeds Potamogeton spp. to charophytes. As more birds foraged on Chara compared to any other food resource, the preservation of large areas of Chara is of great importance to the water-bird community in Lake Veluwemeer. [Copyright &y& Elsevier]

Promoting indigenous submerged macrophytes is considered an important measure to restore shallow lakes. On the other hand, dense stands of aquatic vegetation often cause nuisance for boating, swimming and by obstruction of water flow. Consequently, the interests of recreational users may conflict with nature conservation. At first sight, aiming lake management at intermediate vegetation biomass seems a good solution for this controversy. However, as can be shown with a simple economical model, such a compromise may not always be an optimal solution in terms of total welfare across all users of a lake. Here, we show that a management strategy aimed at moderate plant biomass can also be unfeasible for ecological reasons. This is shown by applying two very different models: a minimal logistic model of plant growth which is easy to understand, and the relatively complex and realistic simulation model Charisma which, among other things, includes the seasonal cycle and a detailed description of the dynamics of light availability for macrophytes. The qualitative results of both models were remarkably similar. If the ecosystem has no alternative stable states, it is possible to set vegetation to any desired sustainable level using an appropriate harvesting strategy. However, if an intermediate vegetation biomass is to be realized the costs of harvesting are high, because the yield is predicted to be maximal in that case. If the ecosystem has alternative stable states, harvesting becomes risky because the vegetation may collapse entirely below a certain, in practice unknown, biomass. Also, even moderate harvesting may reduce the resilience of the vegetated state, making the ecosystem more vulnerable to adverse conditions such as unfavorable weather conditions or bird grazing. [Copyright &y& Elsevier]

Submerged plant dominance and a turbid state with few submerged plants have been hypothesized to represent alternative stable states in eutrophic shallow lakes. Here, we analyze the conditions for occurrence of alternative stable states in shallow lakes further, using Charisma, a simulation model describing the growth of Chara aspera. The model includes seasonality and spatial structure, aspects which were absent in earlier models predicting alternative equilibria. The parameterization of the model is largely based on experimental results and field observations. Over a range of conditions, the model does indeed predict alternative stable states. The range of conditions over which alternative stable states exist, appeared most sensitive to the assumed reduction of local turbidity by plants and the maximum growth rate of the plants. Aboveground biomass disappears during winter in most lakes in temperate regions. Our analysis indicates that from an evolutionary perspective there is an optimum biomass allocation strategy with respect to investment in overwintering structures. Too little investment reduces chances to regain dominance in the subsequent year, whereas too much investment in dormant overwintering structures such as seeds and tubers reduces photosynthesis. Interestingly, the optimal investment is lower for obtaining maximal summer biomass than for realizing the maximum stability of the vegetated state.The model also suggests that a short clear-water phase enhances the probability of vegetation survival. The optimal timing for a clear-water phase is at the end of May or in June, as is indeed the case in many lakes.In line with earlier theory, shallow lakes with a ‘flat’ depth profile are predicted to have the strongest hysteresis. In lakes with a depth gradient, the response to changes in turbidity is predicted to depend strongly on horizontal mixing of the water between vegetation stands and the open water. Hysteresis disappears predominantly due to a strong horizontal mixing of water. In case of little mixing, on the other hand, local alternative stable states are predicted to occur. [Copyright &y& Elsevier]

Abstract Passive acoustic monitoring was used to detect the sounds of rarely sighted Antarctic blue and fin whales to investigate their seasonal occurrence (as presence or absence of whale calls) and behaviour (as determined from call rates) in the Benguela ecosystem. Data were collected using autonomous acoustic recorders deployed on oceanographic moorings for 16.26 months off the west coast of South Africa in 2014 and 2015. Satellite derived environmental variables were used as predictors of whale acoustic occurrence and behaviour. Migratory Antarctic blue and fin whales were acoustically present in South African waters between May and August with call occurrence peaks in July whereas some fin whales extended their presence to November. No whale calls were recorded in summer for either species, suggesting whales use the Benguela ecosystem as an overwintering ground and migration route. Antarctic blue whales produced both their characteristic Z -call and their feeding associated D-call. Fin whales produced calls characteristic of animals from the eastern Antarctic fin whale acoustic population. Random forest models identified environmental variables such as sea surface temperature anomaly, sea surface height, wind speed, months of the year, Ekman upwelling index and log-transformed chlorophyll-a as the most important predictors of call occurrence and call rates of blue and fin whales. Here we present the first acoustic recordings of Antarctic blue and fin whales in the Benguela ecosystem, and provide preliminary information to investigate seasonal abundance and distribution of these large baleen whale populations. This work demonstrates the feasibility of cost-effectively monitoring Antarctic top-consumer baleen whales in the Benguela ecosystem. Highlights • Whale calls were detected from May to November but peaked in July. • First acoustic records of sympatric whale occurrence off the west coast of South Africa. • Acoustic evidence of Antarctic blue whales feeding in the Benguela ecosystem • Call occurrences indicate the west coast of South Africa as an overwintering ground and migration route. • Environmental conditions influenced whale call occurrence and diel acoustic behaviour. [ABSTRACT FROM AUTHOR]

The Prince Edward Islands (PEIs) lie within the Antarctic Circumpolar Current (ACC), in a transition zone bordered by the sub‐Antarctic Front (SAF) to the north and the Antarctic Polar Front (APF) in the south. A climate‐driven southward shift of the ACC and its frontal systems, the SAF and APF, in the vicinity of the PEIs is associated with a long‐term decline in the frequency of island‐associated phytoplankton blooms. These oceanographic perturbations coincide with significant declines in top predator populations attributed to shifts in the distribution and availability of prey, illustrating the interconnectedness between the marine and terrestrial ecosystems of the PEIs. This study investigated the influence of oceanographic variability on the marine ecosystem of the PEIs. A shift in phytoplankton and bacterial communities was observed that coincides with the position of the southern branch of the SAF, which was located to the north of the PEIs during 2014 and to the south during 2012, 2013, and 2015. These shifts in the diversity and structure of marine microbial communities correlate with significant perturbations in the position of the SAF relative to the islands leading us to conlclude that bacterial and phytoplankton communities in the PEI region are strongly influenced by shifts in the position of the SAF relative to the PEIs. This study highlights the critical need to link on‐going physical time series measurements with biological observations to provide a better understanding of the direct role that the upstream dynamics has on the near‐shore island environment and its productivity. [ABSTRACT FROM AUTHOR]

The European Water Framework Directive has been adopted by Member States to assess and manage the ecological integrity of surface waters. Specific challenges include harmonizing diverse assessment systems across Europe, linking ecological assessment to restoration measures and reaching a common view on ‘good’ ecological status. In this study, nine national macrophyte-based approaches for assessing ecological status were compared and harmonized, using a large dataset of 539 European lakes. A macrophyte common metric, representing the average standardized view of each lake by all countries, was used to compare national methods. This was also shown to reflect the total phosphorus (r 2  = 0.32), total nitrogen (r 2  = 0.22) as well as chlorophyll- a (r 2  = 0.35–0.38) gradients, providing a link between ecological data, stressors and management decisions. Despite differing assessment approaches and initial differences in classification, a consensus was reached on how type-specific macrophyte assemblages change across the ecological status gradient and where ecological status boundaries should lie. A marked decline in submerged vegetation, especially Charophyta (characterizing ‘good’ status), and an increase in abundance of free-floating plants (characterizing ‘less than good’ status) were the most significant changes along the ecological status gradient. Macrophyte communities of ‘good’ status lakes were diverse with many charophytes and several Potamogeton species. A large number of taxa occurred across the entire gradient, but only a minority dominated at ‘less than good’ status, including filamentous algae, lemnids, nymphaeids, and several elodeids (e.g., Zannichellia palustris and Elodea nuttallii ). Our findings establish a ‘guiding image’ of the macrophyte community at ‘good’ ecological status in hard-water lakes of the Central-Baltic region of Europe. [ABSTRACT FROM AUTHOR]

We present here sea surface salinity (SSS) and temperature (SST) data collected on board the S.A. Agulhas-I and S.A. Agulhas-II research vessels, in the framework of the South African National Antarctic Programme (SANAP). Onboard Sea-Bird thermosalinographs were regularly calibrated and continuously monitored in-between cruises, and no appreciable sensor drift emerged. Water samples were taken on a daily basis and later analyzed with a Portasal salinometer; some CTD measurements collected along the cruises were used to validate the data. No systematic differences appeared after a rigorous quality control on continuous data. Results show that salinity measurement error was a few hundredths of a unit on the practical salinity scale. Quality control included several steps, among which an automatic detection of unreliable values through selected threshold criteria and an attribution of quality flags based on multiple criteria, i.e., analysis of information included in the cruise reports, detection of insufficient flow and/or presence of air bubbles and ice crystals in the seawater pipe, visual inspection of individual campaigns, and ex post check of sea ice maps for confirming ice field locations. This data processing led us to discard about 36% of acquired observations, while reliable data showed an excellent agreement with several independent SSS products. Nevertheless, a sea ice flag has been included for identifying valid data which could have been affected by scattered sea ice contamination. In our opinion, this dataset, available through an unrestricted repository at https://doi.org/10.7289/V56M3545, contributes to improving the knowledge of surface water features in one of the most important regions for global climate. The dataset will be highly valuable for studies focusing on climate variability in the Atlantic sector of the Southern Ocean, especially across the Antarctic Circumpolar Current and its fronts. Furthermore, we expect that the collected SSS data will represent a valuable tool for the calibration and validation of recent satellite observations provided by SMOS and Aquarius missions. [ABSTRACT FROM AUTHOR]

Six years of simultaneous moored observations near the western and eastern boundaries of the South Atlantic are combined with satellite winds to produce a daily time series of the basin-wide meridional overturning circulation (MOC) volume transport at 34.5°S. The results demonstrate that barotropic and baroclinic signals at both boundaries cause significant transport variations, and as such must be concurrently observed. The data, spanning ~20months during 2009-2010 and ~4 years during 2013-2017, reveal a highly energetic MOC record with a temporal standard deviation of 8.3 Sv, and strong variations at time scales ranging from a few days to years (peak-to-peak range = 54.6 Sv). Seasonal transport variations are found to have both semiannual (baroclinic) and annual (Ekman and barotropic) timescales. Interannual MOC variations result from both barotropic and baroclinic changes, with density profile changes at the eastern boundary having the largest impact on the year-to-year variations. [ABSTRACT FROM AUTHOR]

We present here sea surface salinity (SSS) and temperature (SST) data collected onboard the SA Agulhas-I and SA Agulhas-II research vessels, in the framework of the South African National Antarctic Programme (SANAP). Onboard SeaBird ThermoSalinoGraphs were regularly calibrated and continuously monitored in-between cruises, and no appreciable sensor drift emerged. Water samples were taken on a daily basis and later analysed with a Portasal salinometer; some CTD measurements collected along the cruises were used to validate the data. No systematic differences appeared after a rigorous quality control on continuous data. Results show that salinity measurement error was a few hundredths of a unit on the practical salinity scale. Quality control included several steps, among which an automatic detection of unreliable values through selected thresholds criteria and an attribution of quality flags based on multiple criteria, i.e. analysis of information included in the cruise reports, detection of insufficient flow and/or presence of air bubbles in the seawater pipe, visual inspection of individual campaigns, ex-post check of seaice maps for confirming icefields locations. This data processing led to discard about 36% of acquired observations, while reliable data showed an excellent agreement with several independent SSS products. Nevertheless, a seaice flag has been included for indentifying valid data which could have been affected by scattered seaice contamination. In our opinion this dataset, available through an unrestricted repository at https://doi.org/10.7289/V56M3545, contributes to improve the knowledge of surface water features in one of the most important regions for global climate. That will be highly valuable for studies focusing on climate variability in the Atlantic sector of the Southern Ocean, especially across the Antarctic Circumpolar Current and its fronts. Furthermore, we expect that the collected SSS will represent a valuable tool for the calibration and validation of recent satellite observations provided by SMOS and Aquarius missions. [ABSTRACT FROM AUTHOR]

The Water Framework Directive is the first international legislation to require European countries to establish comparable ecological assessment schemes for their freshwaters. A key element in harmonising quality classification within and between Europe's river basins is an “Intercalibration” exercise, stipulated by the WFD, to ensure that the good status boundaries in all of the biological assessment methods correspond to similar levels of anthropogenic pressure. In this article, we provide a comprehensive overview of this international comparison, focusing on the assessment schemes developed for freshwater lakes. Out of 82 lake ecological assessment methods reported for the comparison, 62 were successfully intercalibrated and included in the EC Decision on intercalibration, with a high proportion of phytoplankton (18), macrophyte (17) and benthic fauna (13) assessment methods. All the lake assessment methods are reviewed in this article, including the results of intercalibration. Furthermore, the current gaps and way forward to reach consistent management objectives for European lakes are discussed. [ABSTRACT FROM AUTHOR]

In this paper we analyze a long-term dataset on the recovery from eutrophication of Lake Veluwe (The Netherlands). Clear hysteresis was observed in a number of ecosystem variables: the route to recovery differed significantly from the route that led to loss of clear water. The macrophyte dominated state disappeared in the late 1960s at TP above 0.20 mg l−1, whereas its return occurred at less than 0.10 mg TP l−1. Several regime shifts resulting in the occurrence of three alternative stable states were observed over a period of 30 years. The turbid state showed resistance to change, despite a strong and prompt reduction in Chl -a following reduction of external P-loading. The most important component that determined hysteresis in the return to clear water was not internal P-loading, but a high level of nonalgal light attenuation (through sediment resuspension) maintained by the interaction between wind and benthivorous fish. Although Chara was able to re-colonize the most shallow parts of the lake, recovery stalled and for a number of years clear (above charophyte beds) and turbid (deeper parts of the lake) water co-existed, as a separate alternative state on route to full recovery. Lake-wide clear water was re-established after bream density had been reduced substantially. This allowed a return of zebra mussels to the lake, whose high filtration capacity helped in maintaining clear water. In this study, we were able to identify the main drivers of hysteresis and regime shifts, although formal demonstration of cause and effect was not possible on the basis of field data alone. We argue that resilience of the present clear water state of Lake Veluwe very much depends on sizable populations of a few keystone species, especially Chara (stoneworts) and Dreissena (zebra mussels), and that careful management of these species is equally important as control of nutrients. Lake management should strive to maintain and strengthen resilience of the ecosystem, and this should offer protection against a renewed collapse of the clear state. [ABSTRACT FROM AUTHOR]

The fish community in the shallow Lake Veluwe (3400 ha) has recently changed in composition. The total biomass of fish decreased to ca. 35% of the original biomass. The change in fish biomass followed the introduction of a commercial fishery and was in its turn followed by a rapid expansion of macrophyte beds dominated by Chara aspera Deth. ex Willd.An individual-based fish model was used to evaluate the causation of these events. We estimated natural mortality of the bream population (Abramis brama L.) using data on growth, recruitment and size distribution. The model predicted that without the fishery the biomass of the bream population would hardly change and that the fishery could explain the change in the biomass and size composition.The rapid expansion of C. aspera was unlikely without the fishery, as Chara needs transparency down to the bottom and undisturbed sediment. The reduction of the bream population created favourable conditions for zebra mussels Dreissena polymorpha (Pallas) to settle which in turn created the clear water, necessary for the development of the Chara beds. [Copyright &y& Elsevier]

While the influence of the Agulhas Current on the larger basin and global-scale circulationand climate has been extensively studied, much less research effort has been focussed on theimpacts of the Agulhas Current on its adjacent shelf system. In particular, in situ samplingalong the South-East African shelf has been conducted at either a very coarse spatialresolution, or along single transects, or has been limited to more focussed bay-scale studies.Two recent hydrographic surveys of the South-east African shelf and slope duringJanuary/February and July/August 2017, provide the first high-resolution shelf-wideobservations of the region. During each survey, a cyclonic eddy associated with a largesolitary Agulhas Current meander (commonly referred to as Natal Pulses) was observed tomodify surface, central, and intermediate water masses on the shelf and slope. Satellitealtimetry indicated that the core of the January/February 2017 cyclonic eddy was locatedalong the 2000 m isobath, with its inshore limb roughly along the 1000 m contour. Thiseddy resulted in substantial uplift of colder, nutrient-rich central (&#x003C;15 ˚ C; 26.4&#x003C; γn &#x003C; 27.0 kg m−3), and intermediate (&#x003C;9 ˚ C; &#x003E;27.0 kg m−3) waters ontothe shelf. While such eddies have previously been associated with the uplift ofcentral waters, this study provides the first evidence of intermediate water uplift, withintermediate waters observed as shallow as 100 m. Further offshore, along the continentalslope, clear separation between intermediate waters was evident for the first time,with Antarctic Intermediate Water (AAIW) occurring within the eddy and Red SeaWater (RSW) observed at stations outside of the eddy&#x2019;s influence. In contrast, theJuly/August cyclonic eddy was much larger, with its core located beyond the 3000 misobath and its inshore limb along the 2000 m contour. Despite its larger size andstronger intensity, the July/August cyclonic eddy appeared to have much less influenceon shelf waters, with only central waters (&#x003C;15 ˚ C) being uplifted onto the shelf.Although there was less distinction between AAIW and RSW along the slope duringJuly/August 2017, larger proportions of AAIW were once again observed at stationswithin the eddy, while larger proportions of RSW were observed outside the eddy. [ABSTRACT FROM AUTHOR]

The southeast African shelf is situated between the southeast coast of South Africa and thewestern edge of the Agulhas Current. Similar to the other western boundary currents of theworld, the Agulhas Current strongly influences the oceanographic conditions of its adjacentshelf system. Limited societal drivers have resulted in an in situ sample deficit which has ledto the majority of studies conducted in the region to have been carried out using satellite dataand modelling. In this study, high-resolution in situ data, acquired during two hydrographicsurveys in January/February (austral summer) and July/August (austral winter) 2017, wereused to identify and characterise the physical oceanographic processes modifyinghydrographic conditions on the shelf. The same five water masses, Tropical Surface Water(TSW), Subtropical Surface Water (STSW), South Indian Central Water (SICW), Red SeaWater (RSW) as well as Antarctic Intermediate Water (AAIW), were observedduring each survey. Indications of seasonality in temperature and salinity, wereobserved in the upper water masses (TSW and STSW) but not within the deeper watermasses (SICW, AAIW and RSW). The influence of river outflow on the nearshoreupper waters, located in close proximity to the river mouth, was found to be moreintense during January/February than in July/August. The Agulhas Current, as well ascyclonic mesoscale eddies along the inshore edge of the Current, were observed tostrongly drive conditions on the shelf region during each survey. Three types ofsubsurface upwelling (i.e. divergence induced upwelling, Ekman pumping at thecentre of cyclonic eddies and Ekman veering in the bottom boundary layer alongthe slope) were found to essentially prime the lower levels of the shelf with coldnutrient-rich water. The 'secondary pump&#x2019; known as wind-driven upwelling, inducedby offshore Ekman transport and vertical mixing, resulted in the surfacing of thiscold (10-15 ˚ C) nutrient-rich water from below at several inshore sites. Theseprocesses, which introduce nutrient-rich water onto an essentially mesotrophic shelf,strongly influence ecosystem functioning, as evidenced by substantially higherchlorophyll a concentrations in response to upwelling induced by the cyclonic eddyduring January/February 2017. While the observations of these processes along thesoutheast African shelf are not new, this study provides a description of the firsthigh-resolution shelf wide hydrographic surveys of the region, setting a baseline ofoceanographic conditions occurring on the shelf as well as the processes affecting it. [ABSTRACT FROM AUTHOR]