Science·New Canada's lakes are changing because of warming caused by the burning of fossil fuels. Here's why scientists are concerned. Researchers dig deep to find answers in sediment cores from Canadian lakes Jaela Bernstien · CBC News · Posted: Aug 06, 2025 3:57 PM EDT | Last Updated: 3 minutes ago Swirls of green, captured from space by a satellite, show a 2015 blue-green algae bloom in Lake Erie, off the shore of Point Pelee in southwestern Ontario. (NASA) If you guessed algae, you're right.