Seminar: from Michael Paterson (IISD Experimental Lakes Area)

This week we will have a seminar from Michael Paterson (IISD Experimental Lakes Area)

There will be coffee and snacks before the seminar. Please bring your own mug.

Thursday 4:00PM, HSC 1A5 and on zoom (Passcode: cElegans)

Dark waters: Assessing the effects of brownification at the IISD-Experimental Lakes Area

In recent decades, many lakes on the Boreal Shield have become darker (browner) because of increases in dissolved organic carbon (DOC). The potential causes and effects of changes in DOC will be assessed using data from the IISD Experimental Lakes Area (ELA) in northwestern Ontario. I will compare results using 3 different approaches: 1) a survey of lakes with different DOC concentrations undertaken in 2017-2018 (space-for-time-substitution); 2) long-term data collected over 56 years from 4 unmanipulated reference lakes; and 3) a whole-lake manipulation experiment designed to decrease concentrations of DOC. Changes in DOC concentrations were primarily associated with changes in hydrology and affected light, temperature, and oxygen conditions in the study lakes. Relationships between DOC concentrations and the aquatic food web (phytoplankton, zooplankton, benthos, and fish) varied depending on the data set. Overall, the results suggest that increases in DOC are likely to cause decreases in phytoplankton productivity but that changes in consumer communities (zooplankton, fish) may be more variable and harder to predict.