NATURALIST NOTES: Winter Wonders Beneath the Ice: How Michigan's Aquatic Creatures Survive the Chill
When Michigan's lakes and ponds freeze over, the underwater world transforms into a chilly, oxygen-limited environment. Yet, it's not lifeless—beneath the ice, a host of creatures have incredible strategies to survive the winter months. From turtles to tiny insects, let's dive into the fascinating lives of these winter survivors.
Oxygen availability is the biggest challenge for underwater life during winter. As ice covers the surface, gas exchange with the atmosphere decreases. Plants and algae under the ice continue photosynthesis during daylight hours, producing oxygen, but this slows dramatically with reduced sunlight. Despite these challenges, aquatic ecosystems are resilient, maintaining a delicate balance until spring’s thaw.
Michigan's turtles, like the painted turtle and snapping turtle, are masters of winter survival. As ectothermic (cold-blooded) animals, their body temperature drops with their surroundings. When winter arrives, turtles bury themselves in the muddy bottoms of ponds and lakes, entering a state called brumation—a reptilian version of hibernation.
But how do they breathe under the ice? Turtles have an amazing adaptation: cloacal respiration. This means they can absorb oxygen through blood vessels in their cloaca (a multi-purpose opening), allowing them to survive even when oxygen levels are low. This "butt breathing" may sound odd, but it's a life-saving trick!
When oxygen becomes extremely scarce, turtles switch to anaerobic respiration, a process that doesn’t require oxygen but leads to the buildup of lactic acid. To counter this, their shells act as a buffer, releasing calcium carbonate to neutralize the acid and keep their bodies in balance.
Michigan’s aquatic insects, like dragonfly nymphs and caddisfly larvae, also weather the winter with impressive strategies. Many spend their juvenile stages underwater, protected from the harshest conditions above the ice.
Dragonfly nymphs, for example, remain active under the ice, hunting smaller aquatic organisms. Their gills, located inside their rectum, extract oxygen directly from the water. These nymphs are patient predators, biding their time until spring when they’ll emerge as adults.
Caddisfly larvae, known for their ability to build protective cases out of sand, leaves, or tiny sticks, hunker down for the winter in these shelters. These cases offer insulation and camouflage, helping the larvae survive until warmer weather returns.
The next time you see a frozen lake or pond in Michigan, remember that life thrives just beneath the surface. From turtles breathing through their cloacas to dragonfly nymphs stealthily hunting, these creatures embody resilience. Winter may be harsh, but for Michigan’s aquatic life, it’s simply another chapter in their incredible survival story.