Natural Connections: Treasures Of The Big Bay Lagoon

The calm waters of Lake Superior glimmered in midday sunshine, and dozens of families enjoyed the sandy beach of Big Bay Town Park on Madeline Island. I hiked past them all, my steps echoing slightly on the boardwalk that winds through pine forest behind the beach.

When a little path diverted from the boardwalk and disappeared into the alder thicket on the inland side, I followed it through the brush. Threading my way through the alders, and then stepping carefully through drifts of dry grasses, I gained a view of the Big Bay lagoon. Brightly colored canoes carried families past waterlilies into the calm, protected water. I scanned the low mat of grasses and shrubs between me and them. Nope, I didn’t see what I was looking for.

This beautiful juxtaposition of clear, cold water in Lake Superior, the long sandy strip, and the dark waters of the lagoon, tell a geologic tale. First, the Mid-Continent Rift started to tear North America apart roughly 1.1 billion years ago. Immense amounts of magma erupted through cracks created by the rift, then cooled into lava flows many miles thick. Now unsupported, the crust subsided, creating a huge basin.

In that time, before land plants had evolved, rain fell on bare rocks and braided streams carried sediments into the basin. Over 4,000 feet of sand accumulated, and over time was cemented by quartz and iron oxide precipitated by water seeping through the sand. Fast forward millions of years, and a series of glaciers scraped through the area, carving softer rocks out of the Lake Superior basin, and leaving behind more resistant areas of sandstone that became the Apostle Islands.

The northeast-trending shape of Madeline Island tracks the direction of ice flow. And for some reason, the glaciers were able to carve a little deeper into the northeast-facing pocket we now call Big Bay. When the ice melted away from the area about 15,000 years ago, water levels dropped in stages, and the waves of Lake Superior carried sand across the entrance to Big Bay. The resulting bay mouth bar closed off the back half of the bay to the waters of Lake Superior, and vegetation began to accumulate in the calm water. Eventually, shoreline currents built another bay mouth bar, with the lagoon trapped between the two.

This long history resulted in a variety of unique habitats for tourists as well as plants. Some brave souls swam in the chilly waters of Lake Superior, while groups of kids chose to play in the warm waters of the lagoon just a few feet away. Sea kayakers can explore the sandstone cliffs of the island when the winds are right, but many families prefer the quiet waters of the lagoon for paddling.

A diversity of plants find their own niches here, too. Beach grasses face the lake and anchor sand against the wind. A red pine forest carpeted with wintergreen, bearberry, and other drought-tolerant vegetation inhabits the sand spit. And in the stagnant lagoon where decomposition has slowed and organic matter has accumulated over time, a floating mat of Sphagnum moss and sedges holds numerous treasures in a type of wetland called a fen. Treasures I was hunting!

On about my third try, when I pushed through the alders and looked out over the grassy mat, I found what I was looking for: a cluster of odd-looking flowers poking up above the grass. On stalks over a foot tall, there were deep-red, five-lobed umbrellas, each with five delicate petals drooping underneath. Like periscopes, they peek above the wispy blades of sedges. Like marking flags, they indicate something special hides below.

Wading through the sedges, water seeping into my sandals from the sponge-like mat of Sphagnum moss, I found the cup-shaped leaves of pitcher plants clustered around the base of each flower. These carnivorous plants trap insects in their leaf pools and host a little community of beings to help digest those insects. This provides nitrogen and phosphorus nutrients that are in short supply in the peat soils.

Pink caught my eye next, and I admired a large patch of rose pogonia orchids. On each, a few light pink petals surrounded a fringed lower petal with hot pink stripes and yellow anthers. Instead of eating insects, orchids in bogs get nutrients from fungi attached to their roots.

Sunny yellow flowers beckoned then, and I balanced on a rotting log to get closer. These horned bladderwort flowers look harmless enough, but in the wet soil their roots have set little traps to catch tiny aquatic macroinvertebrates who supplement their diet of sunshine.

Lining the same log was a row of sundew rosettes—their tiny spoon-shaped leaves prickling with hairs, each tipped with a shining drop of dew. On several leaves, tiny gnats lay trapped in the sweet, sticky droplets while dew filled with enzymes released their nutrients for the plant to absorb.

I snapped photos happily, then checked the time. Gazing wistfully across the expanse of the lagoon I still hadn’t explored, I turned back anyway. At the Madeline Island Museum, I quickly added local photos to my slideshow for the Madeline Island Wilderness Preserve Speaker Series. With a crowd gathered, the title of my talk flashed up on the screen: “Treasures of the Secret Fen.” I couldn’t wait to tell them about the delights I’d found just a few miles away and a million years in the making.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too. Natural Connections 3 is in the works—and needs illustrators from the community! Find out more at: https://www.cablemuseum.org/books/.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our Summer Calendar is open for registration! Visit our new exhibit, “Becoming the Northwoods: Akiing (A Special Place). Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.