A month’s worth of satellite images of Lake Erie show big changes ushered in by spring.

A huge sheet of ice that covered nearly half the lake broke apart on March 6 and had dwindled significantly by March 16.

Even before the ice broke up, light blue smudges swirled in the water. That’s sediment, or fine-grained mud that’s been stirred up from the lake bottom and stays suspended, said David Schwab, a physical oceanographer with National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Lab.

“It reflects light better than pure lake water so it appears lighter than the surrounding lake water,” he said.

Throughout March, the water on Lake Erie’s surface is around the same temperature as the water on the bottom. That makes it easier for the top and bottom water to mix, which stirs up sediment, said Thomas Bridgeman, assistant professor of Environmental Sciences at the University of Toledo.

“This period after the ice out is the spring turnover or mixing time, so that’s going to stir up a lot of sediment,” he said.

All that sediment that gets stirred up has to come from somewhere, and the one important source is the Great Lakes’ tributaries like Ohio’s Maumee River. Their annual donation of spring sediment picked up from agricultural and urban runoff is plainly visible in satellite images starting March 16. You can hit the pause button at any date for a closer look.

Last year, Bridgeman and graduate student Justin Chaffin found that sediment plumes can incubate Lake Erie’s harmful algae blooms. Direct sunlight can damage Microcystis, one of the more noxious algae species. But the floating mud can block enough sun to protect the algae while still letting enough through to power photosynthesis.

But these March plumes probably won’t be helping any harmful blooms. The water is still too cold, Bridgeman said.

“Even if all the other conditions are right – the nutrients and the sediment and everything – right now it’s just too cold for that kind of harmful algae to grow.”

The left side of the satellite images shows the ice breakup on the southern tip of Lake Huron as it dribbled down the St. Clair River into Lake St. Clair. That ice jammed up, snarling freighters and dropping Lake St. Clair two feet, though the lake’s level is rebounding and should recover completely.