Juergen Geist

Juergen Geist
Technische Universität München | TUM · Department of Ecology and Ecosystem Management

Prof. Dr. rer. nat.

About

336
Publications
109,573
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8,642
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January 2007 - present
Technische Universität München
Position
  • Professor (Full)

Publications

Publications (336)
Article
Population recruitment of endangered rheophilic fish species strongly depends on the survival of critical egg and larvae life stages. However, the transportation and fate of eggs after spawning is not well understood. This study analyzed the egg transport and settling patterns of the endangered European nase (Chondrostoma nasus L.), testing the tra...
Chapter
Although the costs of fish-related mitigation measures can play an important role in the adoption of mitigation measures, there is relatively little information about this aspect. This chapter presents an overview of the range of costs for different mitigation measures and compares their magnitudes. As many mitigation measures are adopted in combin...
Chapter
Full-text available
This chapter very briefly outlines site and constellation specific direct and indirect impacts of a hydropower scheme primarily on fishes. It describes potential effects of single elements of a hydropower scheme, such as available migration routes up- and downstream, impoundment, hydraulic head, turbine type and mode of operation. It summarises the...
Article
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Hydropower use of rivers can exert multiple effects on aquatic species and habitats. Due to limitations of conservation projects in the main channels of hydropower-affected rivers, there has been an increasing focus on tributaries, side channels, and fish passes as target areas for conservation and restoration. However, some of these side channels...
Article
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In context of transitioning towards renewable energy, hydroelectricity has gained global relevance. However, hydropower plants have severe impacts on aquatic habitat and biota: Dams disrupt migration routes of diad-romous and potamodromous fish species, degrade the hydro-morphology of streams and turbines cause high mortalities in fishes. To suppor...
Article
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The Chinese pond mussel, Sinanodonta woodiana, is non-native to European freshwater systems. Originating from Asia, it was brought to Europe in the 1970s and is now spreading across many countries. Management of the species is currently limited by a lack of information on the actual distribution and population characterisation of S. woodiana as wel...
Article
The abundance and persistence of plastic nanoparticles in aquatic habitats are considered a threat to marine and freshwater biota. However, the risk assessment of plastic particles is complicated due to various factors that need to be considered, including composition, size and environmental abundance. This study investigated the behavioural respon...
Article
Resolving the controversy about hydropower is only possible based on reliable data on its ecological effects, particularly fish welfare. Herein, we propose a comprehensive assessment of conventional and innovative hydropower using a data set of 52 250 fish. The effects of hydropower on fish were most harmful at sites with Kaplan turbines, showing ≤...
Chapter
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The effects of microplastics on plants and animals have not yet been fully described. Microplastics have different properties that determine whether and how they are taken up by living organisms and the extent to which they are harmful to them. Compared to other pollutants in the environment, microplastics may therefore have a more complex effect o...
Article
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Incidents with toxic benthic cyanobacteria blooms have been increasing recently. In 2019, several dogs were poisoned in the river Lech (Germany) by the benthic anatoxin-a-producing genus Tychonema. To characterize spatial and temporal distribution of potentially toxic Tychonema in this river, a systematic monitoring was carried out in 2020, focusin...
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Mountain lakes are unique and often isolated freshwater habitats that harbour a rich biotic diversity. This high conservation value may be reflected by diatoms, a group of algae that is known for its reliability as a bioindicator, but which has not been studied extensively in mountain lakes of the northern European Alps. In this study, the conserva...
Article
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An increase in river water temperatures is being detected worldwide, with some predictions of an up to 4°C rise by 2050. Such stream temperature increase is likely to affect aquatic communities, with predicted declines and range shifts of cold stenothermic species and a facilitated dispersal and population development in temperature-tolerant specie...
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Since the arrival of the invasive quagga mussels Dreissena rostriformis bugensis in Lake Constance, significant changes in the zooplankton and benthic invertebrate community were observed. Five years later the quagga mussel has become the dominating species of the benthic community. Its effects on other components of the food web, especially those...
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Mussels have been used as animal models for studying ecotoxicology, biomineralization, and bio-adhesion for many years. Despite a wealth of studies on their shell matrix and byssus proteins, few studies have focused on the extracellular matrix molecules in mussel soft tissues. Extracellular matrix molecules may play important roles in biomineraliza...
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Conventional flood control has emphasized structural measures such as levees, reservoirs, and engineered channels—measures that typically simplify river channels and cut them off from their floodplain, both with adverse environmental consequences. Structural measures tend to be rigid and not easily adapted to increased flooding regimes resulting fr...
Article
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Hydropower is considered an important form of renewable energy, often involving hydropeaking. While the effects of hydropeaking on aquatic communities in areas downstream the dam are well understood, there is a lack of studies investigating potential impacts on tributaries located further upstream. In this study, we tested the effects of hydropeaki...
Article
Objective The aetiology of molar-incisor hypomineralization (MIH) is currently unclear. A major hurdle in MIH research is the lack of adequate model systems. The study investigated the feasibility of zebra mussel (Dreissena polymorpha) as a novel model to screen potential MIH-related factors. Methods In four experiments with overall 46 groups (n =...
Article
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1. Freshwater mussels and crayfish provide important ecosystem functions and services. In both groups, global declines of native species are paralleled by invasions of non-native species. Knowledge on differences in predation susceptibility of native and invasive freshwater mussels exposed to native and invasive crayfish is essential for understand...
Article
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Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global...
Article
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The cover image is based on the Viewpoint A global agenda for advancing freshwater biodiversity research by Alain Maasri et al., https://doi.org/10.1111/ele.13931. Image Credit: Solvin Zankl. image
Article
Man-made, drainable aquaculture ponds have the potential to affect the water quality in the receiving waters, but whether they act mainly as a source or sink of fine sediments and nutrients is still unclear. Particularly in oligotrophic streams containing populations of the highly endangered freshwater pearl mussel (Margaritifera margaritifera), ev...
Article
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Aquatic reed beds provide important ecological functions, yet their monitoring by remote sensing methods remains challenging. In this study, we propose an approach of assessing aquatic reed stand status indicators based on data from the airborne photogrammetric 3K-system of the German Aerospace Center (DLR). By a Structure from Motion (SfM) approac...
Chapter
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Assessments of aquatic ecosystem health rely increasingly on biological indicators such as fish community structure, but national approaches differ. To use bioindicators efficiently and to allow cross-country comparisons, standardized tools and methods are required. Within this study, currently applied procedures for stream ecosystem assessment in...
Article
Decreasing yields of whitefish in upper Lake Constance have prompted considerable interest in exploring the potential for local coregonid aquaculture. This study set out to assess and compare the performance of three local species (Coregonus macrophthalmus, Coregonus arenicolus and Coregonus wartmanni) with an aquaculture-adapted strain of C. lavar...
Article
Anthropogenic alterations such as the construction of dams and reservoirs led to a loss of quantity, quality and connectivity of habitats for riverine fish species. The resulting decline of freshwater fishes has prompted many restoration efforts addressing bottlenecks in their life cycles such as improving spawning habitat quality. Whilst there is...
Article
Full-text available
Future water temperature changes may have a profound impact on fish-parasite interactions. However, while the effect of temperature on fish, and particularly salmonids, is well-understood, its combined effects with parasitic exposure are not. Here, we use a multi-stage experimental approach to explore the impact of increased water temperatures cons...
Article
Full-text available
The long-term evolutionary impacts of whole genome duplication (WGD) are strongly influenced by the ensuing rediploidization process. Following autopolyploidization, rediploidization involves a transition from tetraploid to diploid meiotic pairing, allowing duplicated genes (ohnologues) to diverge genetically and functionally. Our understanding of...
Preprint
Climate change results in altered air and water temperatures. Increases affect physicochemical properties, such as oxygen concentration, and can shift species distribution and survival, with consequences for ecosystem functioning and services. These ecosystem services have integral value for humankind and are forecasted to alter under climate warmi...
Article
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Mountain lakes are increasingly impacted by a series of both local and global disturbances. The present study reveals the eutrophication history of a remote subalpine lake (Oberer Soiernsee, Northern Alps, Germany), triggered by deforestation, alpine pasturing, hut construction, tourism and atmospheric deposition, and identifies the intertwined con...
Article
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Predator-prey interactions play a key life history role, as animals cope with changing preda-tion risk and opportunities to hunt prey. It has recently been shown that the hunting success of sticklebacks (Gasterosteus aculeatus) targeting fish larvae is dependent on both the size of the prey and the prior exposure of its species to stickleback preda...
Article
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Securing genetic integrity is of key importance in conservation-oriented captive breeding programs releasing juveniles into the wild. This is particularly true for species such as the endangered freshwater pearl mussel ( Margaritifera margaritifera ) for which a number of captive breeding facilities has been established in Europe. The core objectiv...
Article
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Atlantic salmon Salmo salar L. and brown trout Salmo trutta fario L. are species of high socio-economic and ecological value. Declining populations make them target species of fisheries management. This paper reviews the direct effects of deficient longitudinal connectivity, changes in discharge, high water temperatures, oxygen depletion, changes i...
Article
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Management of biological invasions strongly depends on early and accurate detection of non-native species, yet species identification is often complicated for various reasons. One prominent example relates to the controversy about the genetic specimen assignment of Asian and Oriental weatherfish species introduced into Europe. Weatherfishes, compri...
Article
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• Fish larval drift is an essential step in the life cycle of riverine fish species as it determines dispersal and colonisation. Anthropogenic flow alterations and interruption of longitudinal and lateral connectivity by river damming and straightening can severely affect larval drift patterns. In this study, we characterised spatio-temporal drift...
Article
Full-text available
Bank habitats provide important functions for riverine fish. Yet, they have been heavily modified by land use, technical flood protection measures, and hydropower installations. Fish species requiring specific habitats to complete their life cycle have strongly declined and therefore become target species of river restoration measures. This study c...
Article
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The fish community of Lake Constance, a large, deep, oligotrophic lake has undergone drastic changes in recent years, with the sudden rise to dominance of invasive three-spined stickleback (Gasterosteus aculeatus) in the pelagic zone, a rather atypical habitat for this species in Central Europe. The core objective of this study was to compare the f...
Preprint
Full-text available
The long-term evolutionary impacts of whole genome duplication (WGD) are strongly influenced by the ensuing rediploidization process. Following autopolyploidization, rediploidization involves a transition from tetraploid to diploid meiotic pairing, allowing duplicated genes (ohnologues) to diverge genetically and functionally. Our understanding of...
Article
Full-text available
Scanning electron microscopy (SEM) has been widely used to describe interspecific differences in egg quality of teleost freshwater fish, but potential intraspecific differences are poorly studied. Eggs of many rheophilic cyprinids are covered with adhesive structures such as attaching villi facilitating egg attachment at substrates of spawning grou...
Article
Oxygen is one of the most crucial elements on earth and equally affects life and inorganic redox processes. After its transition to water with moderate solubility and slow diffusion rates, most aquatic organisms depend on permanent renewal of dissolved oxygen (DO). Recharge of this pivotal aqueous gas may become hampered by anthropogenic and climat...
Article
Full-text available
Increased deposition of fine sediments in rivers and streams affects a range of key ecosystem processes across the sediment-water interface, and it is a critical aspect of river habitat degradation and restoration. Understanding the mechanisms leading to fine sediment accumulation along and across streambeds and their effect on ecological processes...
Article
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The global decline of freshwater bivalves (Unionida) has prompted many programmes for their conservation and augmentation, which often include a captive breeding component. One key point to such programmes is the collection, maintenance and use of mussel glochidium larvae, which require attachment to a fish host in a sensitive parasitic stage of th...
Poster
Full-text available
Increased deposition of fine sediments in streams affects a range of key ecosystem processes across the sediment-water interface, and it is a critical aspect of river habitat degradation and restoration. Understanding the mechanisms leading to fine sediment accumulation along and across streambeds, and their affectation to ecological processes is t...
Article
Full-text available
Captive breeding programs are widely applied by conservation practitioners as a means of conserving, reintroducing, and supplementing populations of imperilled freshwater fishes and mussels. We conducted a systematic map to provide an overview of the existing literature base on the effectiveness of captive breeding and release programs. A key findi...
Article
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Fish passes facilitate fish movement in fragmented river systems, yet they can also provide important habitat functions. This study investigated the fish community composition of different constructed habitat types (fluvial habitats, floodplain ponds) within fish passes in relation to habitat characteristics in order to deduce recommendations for f...
Article
Full-text available
Understanding stream thermal heterogeneity patterns is crucial to assess and manage river resilience in light of climate change. The dual acquisition of high-resolution thermal infrared (TIR) and red–green–blue-band (RGB) imagery from unmanned aerial vehicles (UAVs) allows for the identification and characterization of thermally differentiated patc...
Article
Full-text available
Since historical times, the inherent human fascination with pearls turned the freshwater pearl mussel Margaritifera margaritifera (Linnaeus, 1758) into a highly valuable cultural and economic resource. Although pearl harvesting in M. margaritifera is nowadays residual, other human threats have aggravated the species conservation status, especially...
Preprint
Full-text available
Freshwater biodiversity is declining dramatically, and the current biodiversity crisis requires defining bold goals and mobilizing substantial resources to meet the challenges. While the reasons are varied, both research and conservation of freshwater biodiversity lag far behind efforts in the terrestrial and marine realms. We identify fifteen pres...
Article
The biological communities of mountain lakes are suspected to be highly sensitive to global warming and associated catchment changes. To identify the parameters determining algal community responses, subfossil pigments from 21 different mountain lakes in the Bavarian‐Tyrolean Limestone Alps were investigated. Sediment cores were radio‐isotopically...
Preprint
Full-text available
Freshwater biodiversity is declining dramatically, and the current biodiversity crisis requires defining bold goals and mobilizing substantial resources to meet the challenges. While the reasons are varied, both research and conservation of freshwater biodiversity lag far behind efforts in the terrestrial and marine realms. We identify fifteen pres...
Article
Full-text available
A recent global meta‐analysis reported a decrease in terrestrial but increase in freshwater insect abundance and biomass (van Klink et al., Science 368, p. 417). The authors suggested that water quality has been improving, thereby challenging recent reports documenting drastic global declines in freshwater biodiversity. We raise two major concerns...
Article
Full-text available
Male alternative mating strategies are a widespread life history choice, yet they have hardly been assessed in the context of fish invasions. As established proxies for alternative life-history strategies, body length and sexual maturity of Ponto–Caspian round goby (Neogobius melanostomus) from the recently invaded upper Danube River were contraste...
Article
Securing adequate supply of high-quality water is of increasing global importance and relies in large part on ecosystem services provided by freshwater biota. Unionid mussels are important keystone species and habitat engineers that shape freshwater ecosystems through water filtration, nutrient cycling and provision of habitats; their rapid global...
Article
Extensive fish production in earthen ponds is a common aquaculture practice, which requires draining of the ponds for fish harvesting. Despite their value for biodiversity and water retention, the impact of fish ponds on the receiving streams as regards fine sediment and nutrient pollution remains controversial. This holds particularly true for str...
Article
Full-text available
Ecotoxicological effect assessment of particulate materials and sparingly soluble substances (SSS) is an emerging field. Current standard toxicity tests of aquatic organisms are based on soluble substances which are added to the aqueous phase. While soluble substances distribute homogeneously, particles can form aggregates resulting in inhomogeneou...
Article
Full-text available
Monitoring of fish passage at hydropower plants largely relies on stow-fyke-net captures installed downstream of turbine outlets, yet little is known about which fish behavior contributes to reduced catch efficiency. We studied fish-net interactions as well as biological and physical factors potentially influencing behavior in three experiments: (i...
Preprint
Full-text available
Since historical times, the inherent human fascination with pearls turned the freshwater pearl mussel Margaritifera margaritifera (Linnaeus, 1758) into a highly valuable cultural and economic resource. Although pearl harvesting in M. margaritifera is nowadays residual, other human threats have aggravated the species conservation status, especially...
Article
Oxygenated streambeds are considered a key requirement for the successful recruitment of stream fauna, including highly endangered freshwater pearl mussel Margaritifera margaritifera. Excessive amounts of fines impede exchange between open water and interstitial, leading to colmation and low oxygen levels in the juvenile habitat. Understanding the...
Article
Full-text available
Male alternative mating strategies are a widespread life history choice, yet they have hardly been assessed in the context of fish invasions. As established proxies for alternative life-history strategies , body length and sexual maturity of Ponto-Caspian round goby (Neogobius melanostomus) from the recently invaded upper Danube River were contrast...