ECOLAB > Agenda > Motility of aquatic invertebrates: response to environmental factors, behavioral adaptations, and their ecological consequences

Motility of aquatic invertebrates: response to environmental factors, behavioral adaptations, and their ecological consequences

Séminaire le 31 oct 2019 à 10h00
François-Gaël MICHALEC

Institute of Environmental Engineering, ETH Zürich

Motility of aquatic invertebrates: response to environmental factors, behavioral adaptations, and their ecological consequences 

 

Jeudi 31 octobre 2019, 10h00, Salle de Conférences, 4R1

 

François-Gaël MICHALEC

Institute of Environmental Engineering, ETH Zürich

 

Small aquatic organisms such as plankton in the ocean or benthic invertebrates in rivers have been frequently described as being carried along by the flow because they are too small or unable to swim sufficiently strongly to move against currents. This description is not strictly true, as many species propel themselves, sometimes vigorously. Motility mediates processes that are fundamental to their fitness, for instance predation, reproduction, or dispersal, and that affect the structure and functioning of the ecosystem at multiple scales. Motility is in turn affected by the physical, biological, and chemical features of the environment. Despite their ecological significance, the nature and consequences of these interactions remain elusive, primarily because of the difficulties in resolving accurately the motion of organisms swimming and interacting in three dimensions. 

 

I will start my presentation by outlining recent experimental results on the effects of fluid flow on the motility of planktonic and benthic copepods. Fluid flow is a fundamental physical feature of aquatic habitats. It competes with the limited swimming abilities of aquatic invertebrates and this directly affects their movement, spatial distribution, and behavior. However, copepods and many species of zooplankton are not simply passively at the mercy of flow. They can sense and respond to the hydrodynamic features of their environment, and their interactions with turbulence are not purely physical consequences of the forces exerted by the flow, for instance on their shape and inertia, but are also active, behavioral responses. I will show that both planktonic and benthic copepods can modulate their swimming activity in response to turbulence, thereby maintaining the ability to direct their motion and to maintain their distribution despite the physical constraints that turbulent advection imposes on their navigation. These results mirror those obtained by other groups with other organisms such as oyster and sea urchin larvae, and suggest that active response to ambient hydrodynamic conditions is a pervasive behavioral trait among small aquatic invertebrates, with large ecological implications, from drift avoidance in stream invertebrates to the vertical displacement of zooplankton populations in the pelagic ocean.

 

In the second part of my presentation, I will illustrate how aquatic invertebrates react to the presence of anthropogenic toxicants in their environment, drawing from results obtained collaboratively at ETH Zurich and Lille University. Our approach combines optical particle tracking techniques from the field of turbulence research with nano-chemistry and microscopy imaging to develop new experimental techniques that allow more realistic and reproducible exposure conditions, to reconstruct the motion of plankton swimming in three dimensions, and to quantify changes in the kinematic and geometric properties of their trajectories at an unprecedented level of accuracy. Results show that sublethal concentrations of pollutants result in hyperactivity during the first stages of exposure and depressed activity at longer exposure duration, irrespectively of the mode of action of the toxicant, except for nano-materials that display unexpected effects on behavior even at very low concentrations. This approach offers new opportunities to assess the impacts of contaminants on biota through the lens of organism motility, and can be used to study a range of problems in both marine and freshwater ecosystems, with direct applications for their sustainable management. 

Afficher le pied de page