Current research themes
Cumulative stressors and freshwater biodiversity patterns
Biodiversity is often higher in rivers and lakes with relatively undeveloped watersheds. While many studies have documented biodiversity change in response to watershed land use, such studies have traditionally focused on 'horizontal communities' and rarely incorporated compositional information across the food web ('multitrophic diversity'). Moreover, it remains unclear how watershed land use impacts facets and scales of biodiversity other than local taxonomic diversity, which has been the focus of most large-scale analyses. We are involved in various data synthesis projects documenting land use impacts on freshwater biodiversity in Canada, considering multiple dimensions of biodiversity and multiple trophic levels from microorganisms to fish. |
Disentangling impacts of multiple land use-related stressors
Agricultural land use influences multiple physical and chemical parameters in inland waters, for example nutrient loading, pesticide concentrations, water turbidity, and hydrological variables such as mean and maximum water flow. Disentangling the individual and interactive effects of multiple, co-occurring stressors requires manipulative experiments in which stressors are applied alone or in combination. We are conducting such experiments in aquatic mesocosms, i.e. simplified ecosystems that are small enough to be replicated many times, but which nonetheless contain a complex food web and a large number of species. While compromising on ecological realism, mesocosms provide the necessary statistical power to dissect the cumulative effects of multiple stressors. For example, working with Andrew Gonzalez and the 'Large Experimental Array of Ponds' (LEAP) group at McGill University, we have conducted several mesocosm experiments testing the cumulative effects of eutrophication, pesticides, and acidification. You can find out more about the LEAP project here. |
Rapid adaptation to watershed land use
While myriad studies have documented community and ecosystem-level impacts of land use on lakes and rivers, very few studies have looked at contemporary trait change in aquatic populations in relation to watershed land use. Thus, it is currently hard to predict whether evolutionary adaptation or phenotypic plasticity will allow populations to adjust their traits and maintain their performance in the new, human-influenced environmental conditions typical of water bodies in agricultural areas. To fill this gap and better define the 'limits of adaptation' in aquatic animals facing land-use related stressors, we are documenting trait variation across populations of species that occur in both natural and degraded habitats. |
Applying eDNA metabarcoding methods in freshwater systems
Traditional methods of surveying freshwater communities are time and labour-intensive, limiting the spatial and temporal scope of datasets. This is especially problematic for surveys of multitrophic diversity, which require expert taxonomic knowledge of multiple taxa (algae, benthic invertebrates, fish...). Molecular methods such as eDNA metabarcoding could help solve this problem. Although we are not a molecular ecology lab, we are very much excited to collaborate with molecular ecologists to validate and apply metabarcoding methods in our study systems. For example, through a collaboration with various government agencies and not-for-profit organizations, we are currently sampling streams and river floodplain habitats in the St-Lawrence lowlands, collecting eDNA and so-called 'morphological' data across the food web, and characterizing impacts of land use on multitrophic diversity estimated with traditional methods vs. a multimarker metabarcoding approach. |
Interactive effects of land use and climate change
Warming waters and novel hydrological conditions brought about by climate change are another leading threat to freshwater biodiversity. Similar abiotic changes are triggered by watershed deforestation, which could either pre-adapt communities to future climates or create environmental extremes that few species can tolerate. To better understand how climate change will affect freshwater communities in agricultural landscapes, we are measuring ecophysiological traits of populations along land use gradients, conducting warming experiments, and using large biomonitoring datasets to quantify the climatic niche of species that respond to watershed land use. |