Vanishing Glaciers Project
Unraveling the microbiome of glacier-fed streams around the world
Glaciers are melting worldwide at a rapid pace and it becomes critical to better understand how invisible key players in aquatic ecosystems, such as microbes, respond to changing environmental conditions. The River Ecosystems Laboratory (RIVER) at EPFL and collaborators are exploring glacier-fed streams around the world to unravel their associated microbial biological diversity, and specific mechanisms developed by microbes to cope in such extreme environments. The results will help predict, among others, how global climate change may impact the structure and specific functions of stream microbiomes, and its cascading effects on the biogeochemical cycles, as glaciers further retreat. The Vanishing Glaciers project represents a massive collaborative effort and involves Technical specialists, Civilists, Microbiolgists, Ecologists, Glaciologists from the RIVER lab. at EPFL and collaborators around the globe.
The Vanishing Glaciers project is funded by the NOMIS Foundation.
For more information, please visit: glacierstreams.ch and the RIVER lab. website at EPFL.
The Vanishing Glaciers project is funded by the NOMIS Foundation.
For more information, please visit: glacierstreams.ch and the RIVER lab. website at EPFL.
Coral reefs in the Anthropocence
Coral reefs are increasingly threatened by numerous global and local stressors such as climate change, nutrient pollution, and overfishing. Effects of global climate change are mainly evident as sustained periods of high seawater temperature can induce coral bleaching events (i.e. the loss of coral symbionts and/or photopigments) - as well as coral disease outbreaks. Local stressors such as overfishing and pollution, resulting from among others sewage outfalls and coastal runoff, can also have deleterious effects on coral reefs by affecting the trophic interactions within the whole ecosystem. For example, removing herbivorous fishes together with changing nutrient regimes induce growth of fleshy algae, which compete with corals for nutrients, light and space. Under these stressors, the balance of many reefs is shifting towards a competitive advantage for algae, which grow faster than corals and foster a higher microbial biomass.
My research aims to better understand how human-induced stressors alter important trophic and biotic interactions in coral reefs - from micro to macro scales (microbiome, physiology, community).
Trophic and biotic interactions between reef fishes and corals in the Anthropocene
Coral microbiome plays a key role in a number of host functions including coral immune response and nutrient cycling. However, the processes behind shifts in the coral microbiome that contribute to microbiome dysbiosis (i.e. the loss of beneficial symbionts and increase in opportunits/pathogens) remain poorly understood. There is an urgent need to investigate how human-induced stressors can interact with common biotic interactions (i.e. corallivory, release of fecal material) to disrupt coral-associated microbial communities in ways that promote dysbiosis and mortality. This is especially the case for interactions involving ecologically and economically important taxa such as reef fishes, which are fundamental to both reef ecosystem function and human societies. Identifying the mechanisms and conditions under which fishes can contribute to the disruption of coral microbiomes and compromise coral health will improve our ability to predict the dynamics of reef communities in the Anthropocene. Our results shed a light on underappreciated pathways linking parrotfish and surgeonfish to microbial dysbiosis and to the spread of opportunists and potential pathogens in coral reefs.
The associated research projects were funded by the Swiss National Science Foundation
Thanks to the many collaborators which made this project possible: People from the Burkepile and Vega Thurber Labs at UCSB and OSU respectively, Dr. Cody Clements at Georgia Institute of Technology, Dr. Thomas Lamy and Dr. Quentin Schull at UMR MARBEC, Sarah Merolla at UC Davis and to the undergrads who participated in the experiments.
Effects of nutrient pollution on the physiological responses of tropical corals in the
context of climate change
My past and ongoing research addresses how climate change and nutrient pollution alter the nutrional exchanges within the coral-dinoflagellate symbiosis. Employing controlled studies in both the tanks at the Scientific Centre in Monaco and in the field (Eilat, Israel), my Ph.D. research has assessed: 1) how tropical corals take up and use inorganic nitrogen and phosphorus depending on environmental parameters and 2) the effects of nitrogen and/or phosphorus limitation or anthropogenic pollution on reef coral physiology. Our studies showed that corals respond differently depending on the chemical form of the nutrient, source of nitrogen and the availability of phosphorus in the reef environment. We also found that, in the presence of low phosphorus concentrations, ammonium supplementation (i.e. fish-dervied nutrients) enhanced coral metabolism and allowed coral colonies to overcome thermal stress increasing coral survival. Conversely, nitrate enrichments (i.e. human-mediated enrichments) negatively impacted photosynthesis and calcification processes increasing coral bleaching susceptibility. These deleterious effects were enhanced when combined with organic matter supplementation (heterotrophic feeding), but suppressed with addition of phosphorus. My results highlighted the importance of phosphorus availability for symbionts health. Under thermal stress, different coral species differentially increased their uptake rates of phosphorus. This latter nutrient turned out to be a key element to sustain the holobiont metabolism. These outcomes shed light on how marine symbioses cope with eutrophication and highlight the tight relationship between the biogeochemical factors characterizing the reef environment and coral health.
Many thanks to the current and past members of the Scientific Centre of Monaco and to the Sorbonne University