Today’s Forecast: A Look at the Seasonality of the Mississippi
With daylight savings time giving us a coveted hour of more light and temperatures in the 40’s creeping into the Twin Cities, life on campus began to wake up a bit. The sun was shining; there were happier faces, and even a few brave souls who thought it was time to bring out the shorts. It may be such a Minnesotan thing to constantly discuss the weather, but we are so strongly tethered to Mother Nature that weather truly is one thing that binds our culture together. We all know that the changing seasons impact our lives in both tangible and subtle ways, but not all of us know, or take the time to think about how seasons influence the river. That’s why on March 11th River Life gathered with fish ecologist, Jay Hatch for a Water Walk across Bridge 9 on the Mississippi River to talk about seasonal changes and the river.
According to Hatch, “It’s already happening, things are beginning to move”.
Despite the piles of snow and layers of ice on the river, the group took a moment to take in the physical changes of our scenery noting the budding trees, groups of joggers, and the charming bald eagles that flew overhead. Hatch explained that the changes we see and the biological changes in the river and its ecosystems that are about to take place come down to a combination of part temperature and part photoperiod (length of daylight). With Minnesota’s variable temperatures the river can rely on day length to get things started as we move into spring.
As snow melts and the sun shines for longer periods throughout the day, more inorganic and organic nutrients will bring high rates of productivity throughout the river’s ecosystem. The vegetation along both sides of the gorge will change as trees bud, leave and flower at different rates due to temperature. Assuming our winter ends in at least May this year, the warming water will also trigger more biological life to wake up. Aquatic vegetation will take off as ice melts, letting in more sunlight. The river will start to see fish like the northern pike, sturgeon, flathead catfish, and walleye return to the area after their winter break in warmer waters downstream. The increase in daylight will queue female fish to put yolk in their eggs, until warmer temperatures trigger the final maturation stage. Similarly we’ll see an influx of migratory birds like the red-winged blackbird, heron, duck, and eagles. Although, Jay Hatch pointed out that some eagles stay around despite the cold weather, especially in areas like St. Anthony Falls where open water is more common. From the bridge we spotted a large nest looming above the falls, which indicates that eagles keep returning to this area, suggesting some success in the revival of the species.
However, humans and urbanization also have an effect on the seasonal changes of the river. We may be excited for the snow to melt but what’s going into the river is whatever is in its watershed including salt, sand, car grease and oil, as well as agricultural runoff from upstream. Hatched described that the city has largely separated its sanitary sewers from its storm sewers meaning these pollutants from city streets go directly into the Mississippi, which helps to give the river that rather repulsive appearance we see during the spring. Likewise as the ice and snow melt the river’s current speeds up, increasing erosion and mixing sediments with the particles and dissolved particles of organic matter from pollutants to form a frothy layer in some parts of the river. The melt also brings along the threat of flooding and the potential for immense damage throughout the length of the Mississippi River.
Our Water Walk taught us that there are some things like photoperiod and temperature that we have no power over, and then there are others like pollution, policy, and planning that we can control to help the Mississippi and its ecosystems safely transition into spring. Either way things are changing, we can only hope that means warmer and sunnier weather are coming our way so that we can stop talking about the expected accumulation of snowfall and freezing rain we’ll be receiving, and start enjoying time along the river in spring.
Join us at our next Water Walk in April…and keep those fingers crossed!
Tagged Water Walks