Measurements and modelling of eutrophication processes in Lake Rotoiti, New Zealand

Deterioration of water quality is a common problem for aquatic systems globally, which is accelerated by factors such as urban settlement, farming, forestry and recreation. Spatial variability of water quality in these systems hinders a more advanced understanding of their dynamics, to better enable strategies to be developed to combat their deterioration. Understanding the drivers for spatial variability is fundamentally important for predicting how lake ecosystems will respond to management scenarios and which management actions are most likely to be successful to improve lake health. Through a field study in a morphologically diverse lake in New Zealand, and the application of a lake ecosystem model, this study examined the spatial and temporal variability of phytoplankton biomass and made a detailed consideration of the performance of three-dimensional lake ecosystem models. To gain insight in the spatial variability in phytoplankton productivity, surface phytoplankton productivity measurements were carried out at three stations in morphologically complex Lake Rotoiti, North Island, New Zealand, with the objective of defining variations between sites and seasons, and the dominant environmental drivers of these variations. There was no overarching statistical relationship between measured environmental variables and primary productivity or specific production. Inorganic nutrient concentrations at the surface of the shallow station were low throughout the whole year but at the other two stations they showed a typical pattern for monomictic lakes of higher levels during winter mixing and declining concentrations during thermal stratification. The high variability between the three sites indicates that it is important to account for local differences in productivity in morphologically diverse lakes, and that whole-lake productivity estimates may vary greatly depending on the location and depth at which measurements are made. To gain understanding of the spatial variability, a higher resolution three-dimensional (3D) model, ELCOM-CAEDYM, was used to simulate the time-varying horizontal and vertical variations in water quality over one year (May 2004-May 2005). The main inflow to Lake Rotoiti arises via the Ohau Channel from adjacent eutrophic Lake Rotorua. Highly spatially resolved field data were collected monthly to validate the model performance for simulations of temperature, dissolved oxygen and chlorophyll a. The model was configured to simulate a geothermal heat source in the deepest part of the main lake basin. Model simulations of temperature, dissolved oxygen and chlorophyll a were highly correlated with measurements of these variables but simulations of spatial variations in nutrient concentration showed relatively low correlation coefficient values, in particular at a station located in a shallow embayment. An examination of the behaviour of a conservative tracer introduced into the major inflow of Lake Rotoiti, the Ohau Channel, confirmed previous findings that this inflow could enter the lake as a surface inflow, interflow or underflow, depending on temperature gradients between the inflow and the lake water column. The results showed that ELCOM-CAEDYM is capable of reproducing highly spatially resolved field data in a complex, geothermally-influenced lake, and can provide important insights into the fate of heat and constituents in major inflows. A wall to divert Ohau Channel water directly towards the outflow of Lake Rotoiti was implemented in August 2008. Based on parameter values calibrated for the time period before the inflow diversion (May 2004-May 2005), ELCOM-CAEDYM was applied to the post-diversion wall period of August 2008-August 2009. The model showed good fit with observed data for temperature, dissolved oxygen and chlorophyll a, but the model showed a poor fit when simulations were compared with in situ nutrient concentrations at all stations. Simulations with ELCOM-CAEDYM suggest that model accuracy may be improved when a simplified dynamic sediment diagenesis model is available. This could provide for less sensitivity to sediment nutrient release rates of the model and better model fit to in situ data. Ecosystem modelling is likely to play an increasingly important role in lake management and scientific understanding of lake processes as computer speed increases and models undergo further refinements. The model development is in a phase of relative maturity in which water quality simulations provide an efficient and rational tool to compare water quality outcomes and cost effectiveness of lake improvement techniques, to provide for preservation and improvement in water quality in the future

Heterogeneity in lending and sectoral growth: evidence from German bank-level data

This paper studies the sectoral and geographical dimensions of the response of bank lending to sectoral growth. We use several bank-level datasets provided by the Deutsche Bundesbank for the 1996-2002 period. Our results show that bank heterogeneity affects how lending responds to domestic sectoral growth. We document that banks? total lending to German firms reacts procyclically to domestic sectoral growth, while lending exceeding a threshold of ?1.5 million to German and foreign firms does not. Moreover, we find that the response of lending depends on bank characteristics such as the banking groups, the banks? asset size, and the degree of sectoral portfolio concentration. We find that total domestic lending by savings banks and credit cooperatives (including their regional institutions), smaller banks, and banks whose portfolios are heavily concentrated in specific sectors responds positively and, in relevant cases, more strongly to domestic sectoral growth. --bank lending,heterogeneity,sectoral growth

Temporal and spatial variations in phytoplankton productivity in surface waters of a warm-temperate, monomictic lake in New Zealand

Surface phytoplankton productivity measurements were carried out in morphologically complex Lake Rotoiti with the objective of defining variations between sites and seasons, and the dominant environmental drivers of these variations. Measurements were carried out monthly at two depths at each of three morphologically diverse stations for 1 year throughout the lake. Productivity at the surface of the shallow embayment was significantly higher in most months of the year compared with the surface of the other two stations but there were no significant differences from September to December 2004. There were no relationships between measured environmental variables and primary productivity or specific production. Inorganic nutrient concentrations at the surface of the shallow station were low throughout the whole year but at the other two stations they showed a typical pattern for monomictic lakes of higher levels during winter mixing and declining concentrations during thermal stratification. The high variability between sites found in this study indicates that it is important to account for local differences in productivity in morphologically diverse lakes, and that whole lake productivity estimates may vary greatly depending on the location and depth of productivity measurements

Does diversification improve the performance of German banks? Evidence from individual bank loan portfolios

Should banks be diversified or focused? Does diversification indeed lead to enhanced performance and, therefore, greater safety for banks, as traditional portfolio and banking theory would suggest? This paper investigates the link between banks? profitability (ROA) and their portfolio diversification across different industries, broader economic sectors and geographical regions measured by the Herfindahl Index. To explore this issue, we use a unique data set of the individual bank loan portfolios of 983 German banks for the period from 1996 to 2002. The overall evidence we provide shows that there are no large performance benefits associated with diversification since each type of diversification tends to reduce the banks? returns. Moreover, we find that the impact of diversification depends strongly on the risk level. However, it is only for moderate risk levels and in the case of industrial diversification that diversification significantly improves the banks? returns. --focus,diversification,monitoring,bank returns,bank risk

Zusammenhang zwischen Schadstoffen aus der Elbe und missgebildeten Fischembryonen in der Deutschen Bucht.

The trends of malformation prevalence in embryos of dab, Limanda limanda, in the southern North Sea after the year 1990 mirrored the drop in major pollutants in the rivers draining into the German Bight. Despite this general decline we detected a pollution event in the southern North Sea in winter 1995/1996 employing the prevalence of malformations in dab embryos as an indicator. An abrupt rise in malformation prevalence in the embryos of dab, corresponded to a dramatic increase in DDT levels in parent fish from the same area, indicating a hitherto unnoticed introduction of considerable quantities of DDT into the system. This input could be traced back to discharges of unknown origen into the River Elbe

Predicting COVID-19 Infections Using Multi-layer Centrality Measures in Population-scale Networks

Understanding the spread of SARS-CoV-2 has been one of the most pressing problems of the recent past. Network models present a potent approach to studying such spreading phenomena because of their ability to represent complex social interactions. While previous studies have shown that network centrality measures are generally able to identify influential spreaders in a susceptible population, it is not yet known if they can also be used to predict infection risks. However, information about infection risks at the individual level is vital for the design of targeted interventions. Here, we use large-scale administrative data from the Netherlands to study whether centrality measures can predict the risk and timing of infections with COVID-19-like diseases. We investigate this issue leveraging the framework of multi-layer networks, which accounts for interactions taking place in different contexts, such as workplaces, households and schools. In epidemic models simulated on real-world network data from over one million individuals, we find that existing centrality measures offer good predictions of relative infection risks, and are correlated with the timing of individual infections. We however find no association between centrality measures and real SARS-CoV-2 test data, which indicates that population-scale network data alone cannot aid predictions of virus transmission.Comment: Updated Acknowledgement sectio

Biodiversity and species-environment relationships of the demersal fish assemblage at the Great Meteor Seamount (subtropical NE Atlantic), sampled by different trawls

Quantitative data collected with different bottom trawls at the Great Meteor Seamount (subtropical NE Atlantic, 30°N; 28.5°W) in 1967, 1970 and 1998 are compared. Bootstrap estimates of total catch per unit effort increased from 6.96 and 10.8 ind. m–1 h–1 in 1967 and 1970, respectively, to 583.98 ind. m–1 h–1 in 1998. Gear effects and an effect of gear over time accounted for 47.1% and 20% of species variability. Further significant factors were time of day and habitat, while season was not significant. A total of 43 species was collected. Including supplementary species information, a grand total of 46 species was found associated with the Great Meteor Seamount. Diversity was higher in 1967 and 1970 (Shannon's diversity: H′=2.5 and 1.6) than in 1998 (H′=0.9). Species–environment relationships are discussed in terms of a sound-scattering layer–interception hypothesis, i.e. utilisation of prey from a diurnally moving sound-scattering layer for the bentho-pelagic community. This is probably augmented by concentration effects in a circular current around the seamount (Taylor-column). Long-term changes are discussed with respect to a decrease in biodiversity due to considerable increases in Macroramphosus scolopax and Capros aper. In 1998, the increase of abundance of Trachurus picturatus and the respective decreases for genuine benthic species were likely to have been caused by a change of gear