Written by Rachel Putnam, Kroening Nature Center Naturalist
April showers bring more than flowers: spring rains also revitalize small seasonal wetlands. These wetlands may appear little more than weed-choked puddles, but look closer. A small scoop of pond water is teeming with life. In the water you can find a diversity of tiny creatures that support a complex wetland food web. For a brief season, temporary wetlands are habitats where food is abundant.
The most abundant animals in a wetland are tiny zooplankton the size of a poppy seed or sesame seed. Zooplankton are filter feeders: they dine on bacteria and bits of algae floating in the water. Many aquatic animals, in turn, feed on zooplankton. Dragonfly nymphs are fierce predators that eat everything from zooplankton to tadpoles. Tadpoles supplement their diet of algae with zooplankton. Water boatmen, insects that use their long legs to row through the water, hunt zooplankton as well.
Zooplankton aren’t the only filter feeders in a wetland. Mosquito larvae are aquatic and hang head-down to filter algae from the water. Wetlands are much more than mosquito habitat, though: mosquito larvae have several predators. Water boatmen and dragonfly nymphs hunt mosquito larvae, as do beetle larvae nicknamed “water tigers.” The aptly-named “water strider” walks on top of the water to hunt mosquito larvae and other aquatic insects. When adult mosquitoes emerge, they are hunted by adult dragonflies, which can eat over 100 mosquitoes a day.
Seasonal wetlands are temporary, so what happens to all the animals when the water dries up? Zooplankton make eggs that are dormant in the soil, waiting for water to return with the next rainy season. Water striders and water boatmen fly away, looking for another source of water. Toad tadpoles turn into tiny toadlets that can live on land in just four to six weeks. Dragonfly nymphs and mosquito larvae emerge as winged adults and leave the water behind. The wetland now looks like nothing more than a dry ditch, but keep an eye on it: the following spring it will come alive again.
Curious about what’s going on in the park this spring? Check out our upcoming programs offered at Kroening Nature Center in May (registration available at minneapolisparks.org).
Birding Watching: Feathered Friday · Friday, May 2, 9-10:30 a.m. $9, ages 18+ (activity #15603). Learn distinguishing characteristics of birds, as well as bird behaviors, diets and calls, while strolling through the park with a naturalist. Binoculars are available, and all experience levels welcome.
Nature Tots: Amazing Amphibians · Saturday, May 3, 10:30-11:30 a.m. Free, ages 2-6 with adult (activity #15440). Visit the wetland to look for signs of amphibians, then meet a live toad and salamander and watch them eat.
Spring Tree ID · Saturday, May 3, 10:30 a.m.-noon. $9, ages 18+ (activity #17687). Learn to identify trees before the leaves fully emerge using clues such as buds, flowers, bark and phenology, then go on a walk to practice your ID skills.
Homeschool Day: Macroinvertebrates · Thursday May 8, 12:30-2:30 p.m. Free for residents, ages 5-11 (activity # 15472). Explore the wetland or river with nets and search for aquatic invertebrates, then use careful observation to identify them.
Family Fun Day: Spring Blooms · Saturday May 10, 10:30-noon. Free, all ages (activity #15450). April showers bring May flowers! Go for a walk to see which plants and trees are blooming and bring in some flowers to look at under a microscope.
Nature Art: Sunprints · Saturday, May 17, 1:30-2:30 p.m. Free, all ages (activity #15444). Come inside to meet some Minnesota animals up close, touch and observe parts of animals, and create art using our animal mounts as inspiration.
Nature in Focus: Macroinvertebrates · Saturday, May 24, 1-2:30 p.m. $9, ages 18+ (activity #15718). Collect samples from one of our wetland areas to bring back and study under a microscope, then learn about the complex food webs that support aquatic life in our rivers, lakes, and ponds.
Birding Watching: Feathered Friday · Friday, May 30, 9-10:30 a.m. $9, ages 18+ (activity #15604). Learn distinguishing characteristics of birds, as well as bird behaviors, diets and calls, while strolling through the park with a naturalist. Binoculars are available, and all experience levels welcome.