“And this, my little friends, is a leech!” Despite the collective chorus of “ewws,” every kid in the group rushed forward to get a better look at the wriggling creature I held out in my plastic spoon. We were standing on a path near Meadowgrass Ave. in Cottage Grove where a group of about 30 children and adults had gathered to learn about their neighborhood ponds. My very first scoop of water had netted a goldmine – a handful of snails, dozens of spiraling daphnia, and one small black leech. Within minutes, the children had fanned out between the two nearby ponds, armed with extremely scientific collection devices (clear plastic take-out containers and plastic spoons) and intent on catching creepy crawlies of their own. We found tiny toads and chorus frogs in every stage of development from tadpole to adult, snails, scuds, crawling water beetles, and a water boatman. It was obvious that these two little neighborhood ponds were actually quite full of life.
Scientists use a variety of techniques to measure the health of our lakes, rivers and streams. The Washington Conservation District and citizen volunteers collect surface water samples from around 80 lakes in Washington County, which are then sent to a lab at the Metropolitan Council to be analyzed for phosphorus, nitrogen, and chlorophyll-a (a measure of how much algae is in the water). Water monitors also lower secchi disks into the water to measure how clear it is, and record other factors such as temperature and water elevation. In streams, researchers measure the amount of sediment suspended in the water, phosphorus and nitrates, chloride (salt), flow rate and one other critical factor – the abundance and diversity of macroinvertebrates.
Aquatic macroinvertebrates are small animals that live in the water and are big enough to see with the naked eye (hence the prefix “macro”). Unlike fish and reptiles, which have backbones, invertebrates include aquatic insects, snails, clams, shrimp, leeches and other creepy crawlies that have shells, exoskeletons, or no hard body parts at all. Though these kinds of critters may seem unimportant, they are foundational to aquatic food webs and become food for larger animals such as frogs, fish and birds. The presence or absence of certain species of aquatic macroinvertebrates can be considered an indicator of a water body’s overall health. For example, stonefly, caddisfly and mayfly nymphs can only survive in streams with good water quality, whereas dragonfly nymphs and scuds can tolerate a wider range of conditions.
This summer, my colleague Jenn Radtke and I have been organizing neighborhood “pond dipping” events around the east metro as a fun way to teach children and adults about their local water resources. The activity is a favorite with young families; the kids love getting their hands and feet wet and, unlike in fishing, they don’t need specialized equipment or endless patience to succeed. Exploring a neighborhood pond or stream can also help people to see these waterways with a new perspective. During the event in Cottage Grove, more than one parent remarked to me that the trail and ponds were “right there, next to my house,” and yet they’d never paid much attention to them before. People were also surprised when they looked at a watershed map and saw that water from these two ponds eventually flows to the Mississippi River, via a series of pipes and ponds that crosses Hwy 61 and continues south to the river. A recent event along Keller Creek in Maplewood highlighted a stretch of creek where Ramsey County and the Ramsey-Washington Metro Watershed District have been working to remove invasive species, repair eroding streambanks, plant native habitat, and improve a kayak and canoe portage. The creek connects Lake Phalen to Keller Lake and is now easily accessible from a new bike trail.
If you’re interested in doing a little exploring on your own, you can find an easy-to-use aquatic invertebrate identification guide online here. In addition to the previously mentioned “scientific” sampling equipment, I’ve found that an ice cube tray also comes in handy for separating and sorting the things that you find. Be prepared to get a little bit wet and dirty and maybe even creeped out.