Sub-project 1: Determination and quantification of flow traits of benthic invertebrates in river ecosystems

Expected alterations in community structure of aquatic invertebtrates under global change can be estimated only if hydrological/hydraulic preferences and tolerances of target species get assessed numerically
Sub-project 1 details

The river flow regime is one of the key parameters in river ecosystems as it controls physical habitat conditions, biological and ecological processes and river ecosystem functioning. River flow conditions have been substantially altered globally due to water regulation and climatic changes resulting in detrimental impacts on the functioning and health of river ecosystems. Species of benthic invertebrates are a major organism group in river ecosystems that are highly sensitive to environmental changes. It is crucial to better understand the quantitative changes in e.g. species’ abundance to environmental stressors such as flow alterations. Empirically-driven predictive relationships might be established for individual species by linking their abundance along wide ranges of environmental gradients to any environmental variables, e.g. different flow conditions. Any changes in flow can be described by indicators of hydrologic alterations (IHA metrics) that provide information on duration, frequency, magnitude, rate and timing of flow events. These predictive relationships can be used to assess species responses to climate-change-induced flow alterations.

The work is divided into three parts: Firstly, a non-linear modelling approach is applied for a German-wide dataset which enables to link the abundance of species to river flow to quantify flow preferences of benthic invertebrates for various IHA metrics. Secondly, this approach is used in two contrasting river catchments in the lowland and lower mountainous region of Germany to quantitatively assess potential changes in species’ abundance due to projected changes in flow conditions under the worst climate scenario RCP 8.5. Thirdly, potential variability in projected abundance of individual species under 16 climate models derived from various combinations of global and regional climate models are examined. The effects of variability in climate model predictions on species’ abundance and functional trait composition are tested. The results provide empirical evidence that the functional trait compositions will be affected by flow alterations, but the effects would be regionally different. For example, flow alterations lead to increasing abundance of rheophilic and tolerant rhithral species in the lowland area, which is referred to as “rhithralisation effect”.

These results go one step further than the qualitative assessment of species responses to environmental changes, and support the current knowledge that flow alterations and their effects on species’ abundance might be a global phenomenon. The main findings underline the high susceptibility of stream macroinvertebrates to ongoing climate-change-induced flow alterations. Concerning the methodology, a clear recommendation for future predictions is to reduce uncertainty inherent in climate change models and thus to improve future predictability of e.g. species’ abundance.

The analyses applied in this sub-project are applicable to forecast climate change impacts at different spatial and temporal scales as well as for different stressors or species.

Contact for sub-project 1
Karan Kakouei,
Tel.: +49 (0)30 64181 690, Website

Sub-project 2: Quantification of global change impacts on hydrological conditions

A simulation model depicts the recent past and current conditions regarding hydrological parameters, followed by a prediction model showing explicit data on flow conditions under climate change.
Sub-project 2 details

This subproject deals with the simulation of hydrologic parameters in three German catchments in different eco-regions: The Treene in the northern lowlands, the Kinzig in the low mountain range and the Ammer in the alpine region. In each catchment, the hydrological model was applied and optimized to ideally depict the flow preferences (indicators of hydrologic alteration, IHA) of benthic invertebrates. A thorough sensitivity analysis is carried out to assess the influence of different model settings on the simulation of biota. The resulting baseline simulation of the detailed spatio-temporal IHA is complemented by a comprehensive climate change impact analysis including the consideration of uncertainties. These uncertainties are crucial information to correctly interpret and assess the relevance of predicted species changes under climate change.

Contact for sub-project 2
Dr. Jens Kiesel,
Tel: +49 (0)30 6392 4086 or +49 (0)9742 931077, Website

Sub-project 3: Improvement of climate change projections for benthic invertebrates

Existing models for species range changes will be improved by adding riverine characteristics and stressor functions
Sub-project 3 details

Species’ distribution models (SDMs) are predictive models that are increasingly applied to river ecosystems. Hydrological flow regime is cited as one of the most important drivers of lotic systems, influencing the abundance and distribution of river biota. The main goal is to advance the predictive ability of SDMs for riverine benthic invertebrates by integrating hydrological predictors that describe flow regime. The work is divided into three parts: First, a high resolution spatio-temporal dataset of stream flow, and a set of hydrological metrics for the German stream network will be developed. Second, a variable selection method to select the optimal environmental variables for use in SDMs will be proposed, and the impact of predictor set choice in SDMs will be investigated. Third, the role of hydrology in SDMs will be disentangled, by investigating the influence of climate and hydrology related datasets.

The hydrological variable is found to be the most important individual factor for species’ distributions in terms of both variable importance and proportional explained variance. Hydrology variables contribute to a high proportion of explained variance. The larger predicted range sizes may be due to the better description of the river discharge regime provided by the hydrological variables.

In this sub-project hydrological variables are created and integrated in SDMs, and effective methods to improve prediction performance of riverine species’ distribution to advance freshwater SDM research are developed and validated. The introduced methods can be applied in different geographical regions as well as under alternative time periods and spatial scales. Due to the implications associated with altered model accuracy and predicted range size, applying SDMs with hydrological variables has the potential to aid river management decisions and conservation efforts.

Contact for sub-project 3
Katherine Irving,
Tel: +49 (0)30 6392 4089, Website

Sub-project 4: Analysis of flow related changes at large spatial scales

Consideration of the effects of changed discharge conditions on the habitat availability for aquatic invertebrates and fish on a European and global level allows the consideration of pronounced spatial gradients
Sub-project 4 details

The analysis on data rich model catchments from three important ecoregions in Germany (lowland, mountainous, alpine) will be complemented by analyzing large-scale flow changes and their ecological effects. Depending on the data availability the focus region might be a north-south European gradient from the Mediterranean to the Scandinavian region, but preferably a global approach will be sought. The regions chosen are expected to react differently to global change (i. e. increase/decrease in mean annual precipitation or enhanced summer droughts) and thus allow a comprehensive overview on potential effects.

It is planned to obtain macroinvertebrate data from rivers where flow characteristics have been altered. Such preferred sampling areas have been identified by modeled river flow alterations due to dams and water withdrawals as computed by the global water model WaterGAP. Furthermore, regions with semi-arid and conditions will be identified, where strong influence of water flow variations on freshwater biota is always expected.

Contact for sub-project 4
Martin Friedrichs,
Tel: +49 (0)30 6392 4082, Website