Conférence de Rachel Pilla le 1er mai à 11h

Madame Rachel Pilla, étudiante au doctorat au département de biologie de l'Université de Miami ainsi qu'au département de chimie de l'Université Laval, présentera une conférence le 1er mai 2019 à 11h00, à la salle 2422 du Centre Eau Terre Environnement de l'INRS.

Titre : The Regulatory Role of Water Transparency on Lake Ecosystem Structure and Habitat Availability

Résumé :
Lakes are valuable ecosystems that provide critical freshwater resources, but they are threatened by many human-caused stressors that can fundamentally alter their structure and function. Lake water transparency is a key response to stressors such as climate change and browning, and it in turn regulates the light environment and thermal structure of lakes. During the past several decades, many lakes have experienced changing water transparency due to increased carbon inputs caused by increases in rain and storm events plus reduced atmospheric acid deposition. In Lake Giles, a pristine lake in the Pocono Plateau (Pennsylvania, USA), three decades of detailed physio-chemical data show the effects of this browning phenomenon on the light and optical environment, thermal structure, and oxygen depletion. From these physical responses, suitable habitat for a variety of aquatic organisms is changing, as is the relative importance of the controls on total habitat availability. For zooplankton species like Daphnia, total habitat availability is defined by temperature tolerance and ultra-violet radiation exposure in the surface waters and by oxygen availability in deep waters. As these three variables change with lake browning, historical data suggest Lake Giles is at potentially critical tipping point where Daphnia may begin to experience a “habitat squeeze” due to the continually warming waters combined with increasingly prevalent oxygen depletion. The observed decrease in abundance of Daphnia in Lake Giles support this, and that a decrease in habitat availability may be leading to sub-optimal habitat use affecting the population. This may also be potentially driven by increased predator-prey overlap, where habitat availability for predatory cold-water stenotherms that are more tolerant of low oxygen conditions is increasing. Here, predictive modelling tools can be used to assess the key drivers of past and future habitat availability for aquatic organisms based on the responses to browning, underlying the importance of water transparency as a key regulator of lake ecosystem structure and biotic responses.

Bienvenue à tous!