The last ten seminars:

Sedimentation and aggregation in stratified water
(with preliminary data from field experiment in Gokyo lakes, Sagarmatha National Park)

Presenta: Roberto Camassa

University of North Carolina

Particle settling through density stratified fluids experience hydrodynamic interactions that can significantly alter their behavior with respect to their homogeneous fluids counterpart. These are ultimately due to the complex interplay between diffusion, advection, and geometry (through physical boundary conditions). This talk will review results from an ongoing investigation of the relative and overall importance of some newly identified mechanisms that govern the settling and aggregation behavior of particles under different conditions. Preliminary water column sampling data from a field experiment in the Gokyo lake II and IV, Sagarmatha National Park, will be presented.

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Freshwater mussels vs climate change: to be or not to be?

Presenta: Paulo Castro

Department of Biology, University of Minho, Portugal

Humans are now appropriating more than 50% of freshwater runoff, many species are overexploited, ecosystems are polluted, over 1 million dams globally widespread fragment rivers and species introductions in freshwater ecosystems. In ecosystems already disturbed, climate change will most likely exacerbate this state. Freshwater mussels (FM: Bivalvia: Unionida) are one of the most imperiled faunal groups on Earth, and their conservation is urgent. Indeed, FM are responsible for numerous important ecosystem services (e.g. water purification), and are a link for the interaction of other aquatic organisms (e.g. pelagic-benthic processes). In addition, due to their high vulnerability, FM can be used as a model organism to assess how may climate change, and its interaction with other stressors, affect freshwater ecosystems. This project is focused on assessing the limits and responses of native mussels to climate change, with a multidisciplinary approach including physiology, phenology, distribution and molecular tools (gene expression and genetic diversity). Composition and salinity of the copepod Leptodiaptomus cf. sicilis from one of the hyposaline lakes will be shown.

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Effect of salinity and ionic composition on biological diversity in tropical volcanic lakes, Mexico

Presenta: J. Salvador Hernandez Aviles

Limnology Lab. UMIEZ. Biology Department. FES Zaragoza,
Universidad Nacional Autónoma de México

Six lakes are among a series of maar, athalassohaline lakes that are located in the Trans Volcanic Belt in central Mexico. They are between 2,300 and 2,510 m a.s.l., and have a warm monomictic thermal regime with mixing during the cold-dry period (December-March). By being in an endorheic basin these lakes are in a process of increasing their salinity and changing ionic specific composition. In addition, the extraction of groundwater that feeds these aquatic ecosystems with deep wells has increased the process of salinization. These chemical parameters have an important influence in certain limnological processes such as the whiting event and the formation of microbialites which are mainly associated with changes in the water alkalinity. The whiting event is a process in which small particles of calcium carbonate are precipitated by changes in different concentrations of forms of carbon which in turn are produced to bacterial activity. Microbialites are organosedimentary deposits product of the biomineralization processes induced by microorganisms and the formation of extracellular matrix. In this seminar, the specific taxonomic composition of bacteria in the whiting event and the diatoms richness of the microbialites in subsaline and hyposaline lakes will be shown. In addition, the experimental ecophysiological response to changes in ionic composition and salinity of the copepod Leptodiaptomus cf. sicilis from one of the hyposaline lakes will be shown.

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Fluitazione dei sedimenti degli invasi:
biodisponibilità di elementi in traccia e tossicità per organismi macrobentonici

Presenta: Laura Marziali

CNR-IRSA sede di Brugherio (MB)

I sedimenti accumulati negli invasi lombardi vengono rimossi generalmente tramite fluitazione nel corpo idrico di valle, causando un impatto prevalentemente di tipo fisico sulle comunità acquatiche fluviali. In alcuni casi, tuttavia, sostanze microinquinanti, quali elementi in traccia o composti organici, accumulate nei sedimenti possono indurre effetti tossici a lungo termine sugli organismi acquatici. Uno studio sperimentale in corso sull'invaso di Pagnona (LC) e altri invasi lombardi è focalizzato sulla caratterizzazione chimica dei sedimenti degli invasi e dei corpi idrici di valle prima e dopo la fluitazione, sulla valutazione del bioaccumulo e degli effetti su organismi test e sulle comunità macrobentoniche del fiume a valle.

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