I was out and about this summer and spent a fair bit of time exploring lakes. One of my companions on some of these jaunts was a 4-year old. This was great. She helped me see things in a whole new way.
Hey granddad, “What are all these squiggly lines?”
I waded out to where she was standing waist deep (her waist) in the cool, clear lake waters. I still had my glasses on so I bent over and waited for the ripples to subside. As the waters calmed, sure enough there were lines in the sand as if she had drawn them with a stick. They were 5 to 10 ft long and often looped back on themselves. I considered but dismissed hydrologic origins to these phenomena – the lines cut right across the ripple marks on the lake bottom. I started wondering what creature could have done this pattern in the sand.
“Look, they are all over the bottom. What are they?”
The more I looked, the more I came to believe they were tracks. We had seen snails the day before and also small intricately patterned water snakes. They were both interesting possibilities but not quite right. I looked more and more carefully at the lines as she became more animated and started churning up the water, her energetic side overtaking her scientific interest in our discovery.
The flashes of light from her frolicking reflected off shiny nubs at the end of several of the lines. I reached down and scooped up a handful of sand, silt, and pebbles.
As I watched the sand and silt sift through my fingers, I discovered something larger left in my hand.
“Hey, come look at what I found.” She came over wide-eyed, splashing me in the process.
“What is it? What did you find?” She asked. I opened my hand and showed here a bluish-black mussel about two inches across, with a shiny nubby hinge on one side.
“It’s a mussel,” I said.
“I can make a muscle.” She flexed here bicep, grinning ear to ear.
“Not that kind. This is what we call a shellfish. A bi-valve. It has two shells. It moves by filtering water and sand through the edges of their shells. That process propels it along the bottom, leaving these tracks behind. Let’s put several in a bucket for a few minutes and see what happens.”
We put 2 inches of sand and 6 inches of water into a bucket and placed 2 mussels, lying flat on their sides on top of the sand. We then put the bucket in the shade sitting in a few inches of water to keep it cool.
Nothing happened while we watched so she was off exploring other things. Five minutes later we took another look and found both mussels to be standing on edge and puffing water out of their shells.
“They are making tracks in the sand in our bucket! Let’s put some more in.”
She was right. They had already made 4-inch long tracks in the sand. We had tested and proven our theory that these mussels had created at least some of the tracks that we had discovered. She was excited about her discovery.
Someday she will ask more questions about some of these discoveries. She will learn that mussels are important filter feeders that help keep our lakes and rivers cleaner. We did ask the locals about eating them but were discourage from doing so for two reasons. First, they are not as tasty as their saltwater relatives. Secondly, since they are long-lived filter feeders, pollutants from the burning of fossil fuels and storm water runoff that settle to the bottom of our lakes, can build up inside them making them distasteful and potentially harmful. That put a slight damper on things for me.
But we loved talking about our discovery of the day, amazed at how easy it was to discover something new to us, simply by exploring nature.