An object oriented modelling strategy to depict activity pattern of organisms in heterogeneous environments

The object oriented programming and simulation approach has been used at the Project Center for Ecosystems Research (Kiel) in order to advance ecological theory and in order to integrate empirical ecological field work. In this contribution we present a general scheme, which provides a framework for the development of individual based models. The scheme covers a general layout of the organism – environment interaction; the organization of (quasi‐)parallel activities of individuals (self‐scheduling of objects versus list processing); a concept to coordinate context specific activity alternatives. Basing on these considerations we give different application examples. These examples show the potential of individual based modelling to depict the modification of organismic activity pattern and population dynamics in heterogeneous environments and to study the interaction of different levels of aggregation. The model examples are simulation of a fish school in a changing environment; simulation of a robin population in a beech forest; simulation of plant development.     

Comparing measured and modelled forest carbon stocks in high-boreal forests of harvest and natural-disturbance origin in Labrador, Canada

Understanding the effects of disturbance regimes on carbon (C) stocks and stock changes is a prerequisite to estimating forest C stocks and fluxes. Live-tree, dead-tree, woody debris (WD), stump, buried wood, organic layer, and mineral soil C stock data were collected from high-boreal black spruce (Picea mariana (Mill.) B.S.P.) stands of harvest and fire origin and compared to values predicted by the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3); the core model of Canada's National Forest Carbon Monitoring, Accounting and Reporting System. Data comparing the effect of natural and anthropogenic disturbance history on forest C stocks are limited, but needed to evaluate models such as the CBM-CFS3. Results showed that adjustments to the CBM-CFS3 volume-to-biomass conversion and partitioning parameters were required for the non-merchantable and branch C pools to accurately capture live-tree C stocks in the studied black spruce ecosystems. Accuracy of the CBM-CFS3 modelled estimates of dead organic matter and soil C pools was improved relative to regional default parameters by increased snag fall and >10 cm WD base decay rates. The model evaluation process also highlighted the importance of developing a bryophyte module to account for bryophyte C dynamics and the physical burial of woody debris by bryophytes. Modelled mineral soil C estimates were improved by applying a preliminary belowground slow C pool base decay rate optimized for the soil type of the studied sites, Humo-Ferric Podzols.     

Translocation and Growth Experiments with the Macropohyte Potamogeton Lucens L. in Traunsee (Austria), with Respect to Industrial Tailings

The absence of Potamogeton lucens L. in an area of Traunsee, Austria, which is heavily impacted by industrial sludges was related to these deposits. The hypothesis that P. lucens L. is affected by the industrial tailings was confirmed by growth experiments of the translocated plants in the field. At the unpolluted reference site of the lake, the plants grew better, they were longer and produced more leaves than at the emission site.     

Reproductive toxicity of bisphenol A and cadmium in Potamopyrgus antipodarum and modulation of bisphenol A effects by different test temperature

An OECD initiative for the development of mollusc-based toxicity tests for endocrine disrupters and other chemicals has recommended three test species with respective test designs for further standardisation. Preparing a subsequent pre-validation study we performed a reproduction test with Potamopyrgus antipodarum, determining the concentration range of the selected test substances, bisphenol A (BPA) and cadmium (Cd). At 16 °C, the recommended test temperature, the number of embryos in the brood pouch was increased by BPA and decreased by Cd (NOEC: 20 μg BPA/L and 1 μg Cd/L). Coinstantaneous BPA tests at 7 °C and 25 °C demonstrated a temperature dependency of the response, resulting in lower NOECs (5 μg/L respectively). As expected, reproduction in control groups significantly varied depending on temperature. Additional observations of the brood stock showed seasonal fluctuations in reproduction under constant laboratory conditions. The recommended temperature range and test conditions have to be further investigated.     

PAH metabolites,GST and EROD in European eel (Anguilla anguilla) as possible indicators for eel habitat quality in German rivers

The stock of the European eel (Anguilla anguilla L.) continues to decline and has reached a new minimum in 2011. Poor health status of the spawners due to organic contaminants is one of the possible causes for this dramatic situation. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants, which are rapidly metabolized in vertebrates. EROD (ethoxyresorufin-O-deethylase) and GST (glutathione-S-transferase) are two enzymes involved in PAH detoxification in fish. In this study, PAH metabolites as well as EROD and GST activity in a large, comprising dataset of more than 260 migratory and pre-migratory eels from five large German river basin districts were used to describe PAH exposure and its metabolism as possible indicators for the habitat quality for eels. Eel from the river Elbe appear to be moderately contaminated with PAH. Highest mean values of PAH metabolites were analysed in fish from the river Rhine. However, the results suggest that contaminants such as PAH are metabolized in the fish and may have contributed to EROD activity in eels caught from the Elbe estuary to 600 km upstream. Since the eel’s onset of cessation of feeding is closely linked to maturation and migration, we propose bile pigments as new indicators contributing to identify the proportion of migratory eel, which is crucial information for eel management plans. We showed that PAH metabolites normalized to bile pigments as well as EROD could be used to describe the habitat quality and might be suitable parameters in search for suitable stocking habitats.     

Influence of a heavy rainfall event on the leaching of [14C]isoproturon and its degradation products in outdoor lysimeters

In four different agricultural soils the long-term leaching behaviour of [14C]isoproturon was studied in outdoor lysimeters (2 m length, 1 m2 surface area). The herbicide was applied in spring 1997 and spring 2001. At the end of the first 4-year-investigation period between 0.13% and 0.31% of the applied radioactivity was leached. Isoproturon or known metabolites could not be detected in the leachate. However, shortly after the second application isoproturon and its degradation products 2-hydroxy-isoproturon and monodemethyl-isoproturon were leached via preferential flow in one of the lysimeters (Mollic gleysol) in concentrations of 4.5 microg L-1, 3.1 microg L-1 and 0.9 microg L-1, respectively, thus considerably exceeding the EU threshold limit of 0.1 microg L-1 for ground and drinking water. The results indicate that in soils where mass flow transfer dominates, leaching of isoproturon to groundwater is of low probability whereas in highly structured soils which have the tendency to form macropores, isoproturon can be transported via preferential flow to the groundwater.     

Steady states and sensitivities of commonly used pelagic ecosystem model components

Pelagic, coupled ocean circulation-ecosystem models, are widely used in climate research. These tools aim to quantify fluxes of nutrients and carbon in the ocean and are, increasingly, the base of future projections. For this purpose it is crucial to quantify and identify the sources of uncertainties. In contrast to physical models, the underlying equations for ecosystem models are derived from empirical relationships rather than based on first principles. This resulted in the development of a multitude of different ecosystem models - different in respect to both, underlying principles and complexity. Clearly, the question arises, to what extent the sensitivities of these models are comparable.This study focuses on the intrinsic dynamics of some widely used, simple (containing 2-3 prognostic variables) ecosystem models in a 0-D framework (i.e., comprising only the well-mixed oceanic surface layer). A suite of differing model approaches is tuned such that their behavior is similar. The setup resembles the well-mixed oceanic surface layer in the Baltic proper. It is illustrated that strong differences between the model approaches appear due to exemplary, anticipated changes in the external nutrient and light conditions. Herewith, we demonstrate the well-known, but rarely demonstrated fact that, apparent consistency between modeled prognostic variables with today's data bases is not necessarily a good measure of forecast skill. The causes which lead to the different sensitivities are illustrated by considering the steady state solutions. It is pointed out, that apparently small changes in the model formulations can result in very different dynamical behavior and an enormous spread between the model approaches, despite the feasibility to tune a common behavior in a limited range of light and nutrient supply. In our examples, the sensitivity is mainly a function of the formulation of the loss rate of phytoplankton. It is thus, in particular, the formulation of highly unknown heteorotrophic processes that determines the model sensitivity.     

A new approach to investigate the interactions between sediment transport and ecotoxicological processes during flood events

Purpose

The 'step-by step' principle was introduced into the European Union legislation on genetically modified organisms as a means to cope with uncertainty about environmental risks from the release of genetically modified organisms into the environment. The approval process is orientated along the stepwise reduction of containment which reflects a precautionary approach towards the risks of genetically modified organism release. Thus, the gradual reduction of containment should keep pace with the gradual generation of risk-related knowledge. This paper strives to clarify the meaning, legal status and practical importance of the principle. It also looks at whether non-European Union countries have adopted the principle as well, and how they practice it.

Methods

The article is based on research of the relevant legal texts, court cases and legal literature. In addition, a number of dossiers of applications for the European Union authorisation of release and placing on the market of genetically modified seed were analysed.

Results and conclusions

Although 'step-by-step' is not a precise legal rule it does have legal meaning as a principle guiding the risk assessment and management of genetically modified organism introduction into the environment. Assuming a process of gradual reduction of containment and scaling up of release ranging from closed systems via experimental release to cultivation the 'step-by-step principle' requires that the knowledge on environmental risks of genetically modified organisms should be generated on stages previous to the ones where the risk can result in damage. The analysis of the legislation of China, the United States of America and Brazil showed a differentiated approach towards the step-by-step principle.