Les changements climatiques ont un impact sur quasiment toutes formes de vie. Des augmentations des moyennes de température ainsi que desfluctuations peuvent causer un stress, particulièrement chez les ectothermes aquatiques sessiles tels que les moules d’eau douce. Cependant, certaines espèces semblent mieux faire face à ces températures stressantes que d’autres. La tolérance au stress thermique peut par exemple expliquer le succès de certaines espèces envahissantes. Il est connu que les mitochondries peuvent jouer un rôle clé dans l’établissement de la thermo-tolérance des ectothermes. Dans cette étude, nous avons visé à caractériser la thermo-tolérance mitochondriale chez des moules d’eau douce endémiques et invasives. À travers l’utilisation de la respirométrie à haute résolution, nous avons analysé la respiration mitochondriale de deux espèces de moules d’eau douce exposées à plusieurs températures différentes. Nous avons remarqué que la moule invasive Dreissena bugensis possédait un métabolisme mitochondrial moins thermo-tolérant que la moule endémique Elliptio complanata. Cette lacune au niveau de la tolérance a été liée à une dépression métabolique aérobique plus marquée à des températures élevées. Ces résultats pourraient potentiellement être associées avec les traits de caractéristiques de vie de ces espèces, car D. bugensis est plus adaptée à des environnements instables dans lesquels les pressions de sélection pour des adaptations de résistance sont réduites. Nos résultats s’ajoutent à la littérature grandissante qui caractérise le métabolisme mitochondrial de plusieurs espèces aquatiques face aux changements climatiques / Climate change is impacting many, if not all, forms of life. Increases in extreme temperature fluctuations and average temperatures can cause stress, particularly in aquatic sessile ectotherms such as freshwater mussels. However, some species seem to thrive more than others in face of temperature-related stressors. Thermal tolerance may for example explain invasive species success. It is also known that mitochondria can play a key role in setting an ectothermic species’ thermal tolerance. In this study, we aimed to characterize the mitochondrial thermo-tolerance in invasive and endemic freshwater mussels. With the use of high-resolution respirometry, we analyzed the mitochondrial respiration of two freshwater bivalve species exposed to a broad range of temperatures. We noticed that the invasive dreissenid Dreissena bugensis displayed a less thermo-tolerant mitochondrial metabolism than the endemic unionid Elliptio complanata. This lack of tolerance was linked with a more noticeable depression of aerobic metabolism at elevated temperatures. These findings may be associated with the life history traits of both species, as D. bugensis is more adapted to unstable habitats, where selection pressures for resistance adaptations are reduced. Our findings add to the growing body of literature characterizing the mitochondrial metabolism of many aquatic ectotherms in the context of climate change.

Torpedograss (Panicum repens) was first observed in Lake Okeechobee in the 1970s and appears to have displaced an estimated 6,400 ha of native plants, such as spikerush (Eleocharis cellulosa), where inundation depths are often less than 50 cm. Two series of studies evaluated substrate exposure and water depth influences on torpedograss establishment and competitiveness. Results revealed that fragments remain buoyant for extended periods and so facilitate dispersal. Once anchored to exposed substrate fragments can readily root and establish. Subsequently, torpedograss thrives when subjected to inundations to 75 cm and survives prolonged exposure to depths greater than 1 m. These findings suggest that fluctuating water levels contribute to torpedograss dispersal and colonization patterns and that low water levels increase marsh area susceptible to invasion. The competition study found that spikerush grown in monoculture produces significantly more biomass when continually inundated to shallow depths (10 to 20 cm) than when subjected to drier conditions (-25 cm) or greater inundations (80 cm). In contrast, torpedograss establishes more readily on exposed substrate (-25 to 0 cm) compared to inundate substrates. During the first growing season biomass production increases as substrate exposure interval increases. However, during the second year, established torpedograss produces more biomass when grown on intermittently wet (0 cm) compared to permanently dry (-25 cm) or intermittently inundated (10 cm) substrates. No difference in production was observed between substrates permanently inundated (10 cm) and any other regime tested. During the first two years of torpedograss invasion, regardless of treatment, spikerush suppresses invasion and torpedograss had little effect on established spikerush, indicating that spikerush-dominated areas are capable of resisting torpedograss invasion. Even so, disturbances that might cause mortality of long hydroperiod species, such as spikerush, may create open gaps in the native vegetation and thus facilitate torpedograss establishment and expansion.

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Legal regulation of alien species of plants and animals Abstract This thesis deals with the legal regulation of invasive non-native species of plants and animals, i.e., preventing their spread and minimizing the negative consequences that these species cause on individual ecosystems and biodiversity in general. The aim of this work is to analyse the related effective international, EU and Czech national legislation and to define the most significant changes concerning the relevant Czech laws in connection with the implementation of Regulation (EU) No. 1143/2014 and Regulation (EC) No. 708/2007. At the beginning, the work deals with the history of the spread of non-native species, as identifying the critical pathways of their spread is also an important knowledge necessary for creating effective legislation and also the definition of fundamental terms - non-native species, invasive non-native species, and biodiversity. Furthermore, the work deals with the most important international treaties in this area, i.e., the Convention on Biological Diversity, the Convention on the Conservation of Migratory Species of Wild Animals, the Convention on the Conservation of European Fauna and Flora and Habitats and the Madrid Protocol to the Antarctic Treaty, with the relevant European Union legislation, i.e., a network...

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Development of selected invasive species and meadow vegetation classification algorithm in the Krkonoše Mountains using hyperspectral data Abstract The thesis deals with utilization of airbone APEX hyperspectral image data for selected invasive species and meadow vegetation classification in the study area of the Krkonoše Mountains National Park. The mian goal of the thesis was to develop of classification algorithm based on proposed vegetation indices. The approach was based on the utilization of in-situ LAI, fAPAR, chlorophyll content data and analysis of their relation with vegetation spectral properties. The work also deals with several problems regarding LAI - vegetation indices relationship, namely saturation of LAI and mutual correlation of LAI and chlorophyll content. Tha classification was focued on invasive species Rumex alpinus and Lupinus polyphyllus, meadow vegetation with dominant Nardus stricta and dominant Trisetum flavescens and cutted lawns. Besides the proposed approach, the presented work resulted in several classification maps of study area and in spectral libraries, containing ground level spectra of studied invasive species, meadow vegetation types and several other meadow species. Keywords: hyperspectral image data, APEX, LAI, fAPAR, vegetation indices, invasive species, meadow...

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The prevalence of hypoxia in aquatic systems has increased in recent decades and climate change is expected to worsen the extent and severity of hypoxic phenomena worldwide. Moreover, aquatic hypoxia has produced adverse ecological consequences and stimulated research interest within the Laurentian Great Lakes. The physiological stress imposed by hypoxia reduces habitat quality for most aquatic biota and causes changes in patterns of resource use and food web dynamics. We conducted a review of the primary literature to identify trends in prevalence of Great Lakes hypoxia research and broadly classify the unique hypoxic conditions afflicting Great Lakes ecosystems. We found that the majority of research effort toward Great Lakes hypoxia is focused on the Lake Erie central basin. Our review further revealed that this does not characterize the breadth of hypoxic phenomena that occur throughout the Great Lakes region. We then utilized a long-term monitoring dataset provided by the U.S. Environmental Protection Agency Great Lakes National Program Office to quantify the impact of Lake Erie central basin hypoxia on habitat quality of several fish species. We found that bioenergetics-based growth-rate potential models have a potential application as the framework for the development of biological endpoints that measure the effects of hypoxia on aquatic biota. Finally, we utilized stable isotope analysis to look for broad spatial and temporal trends in resource utilization within distinct regions of the Lake Erie central basin, with hypoxia and large-scale hydrodynamic patterns serving as potential driving patterns for spatial differences.

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