Happy Thursday, everyone! This week’s topic is quite special to me because it blends my fascination with a really cool habitat and a very interesting evolutionary occurrence. I started my career in environmental education by teaching about wetlands, I did my graduate research on isolated and riverine wetlands, and I’m currently getting into stormwater wetlands. I love them. They are amazing.
Wetlands are areas of land where water is present constantly or at least six months out of the year. That hydric regime creates an ecosystem that has regular water level fluctuations and requires plants and animals to be adapted to the ever-changing, sometimes low-water, conditions. If you read the 10 Things post on soils, you know that hydric soils are one of the components that determine a wetland. The other defining characteristic is the presence of hydric plants which have adaptations that allow them to survive in those conditions. Adaptations are characteristics that allow an organism to survive in a particular habitat or ecosystem. So this week’s 10 Things focuses on the adaptations wetland plants and animals have developed in order to survive on those wonderful habitats.
1. Those tiny green dots on the surface of the water are a floating plant called duckweed
In terms of living conditions, wetland plants can be submergent and live completely underwater, emergent and have roots firmly in the soil and erect stems that emerge from the water’s surface, or floating and have roots that dangle freely in the water. Duckweed is a tiny, free-floating flowering plant with little roots. Examples of submergent and emergent plants are pondweeds and bulrush, respectively. Duckweed can also be found in ponds.
Bonus: Cattail leaves—along with the leaves and stems of many emergent plants—are sturdy to allow them to remain standing tall during varying water levels.
Image credit: Lake Restoration Incorporated
2. American bitterns have the looks and behavior to make them practically invisible
Not only does the American bittern have patterns on its feathers that make it resemble the grasses where it likes to hang out, but it also thrusts its beak into the air and remains completely still when it senses a predator for total and complete camouflage.
Side note: I’ve gotten close to a bittern and had no idea it was there until it squawked and flew away. They can blend in very well and startle you if you aren’t paying attention.
3. Beavers’ tails, feet, fur, and skulls make them wetland adaptation overachievers
Webbed feet? Perfect for swimming. Flattened tail? Rudder and warning signal for predators. They have eyes on top of their head that allow them look around while swimming without their whole body being out of the water, they have large lungs that allow them to hold their breath for up to 15 minutes, they can close their ears and nostrils while underwater, and special eyelids that are basically goggles to protect their eyes while swimming. Oh, did I mention waterproof fur? Because the oils from their musk glands does that, too. Yeah, beavers are like the Hermoine of wetlands.
4. Some wetland plants have roots that come up for air
Roots need oxygen to carry out the functions that make nutrients available to the rest of the plant. In upland areas, that oxygen is available in the soil; however, wetland soils are anaerobic (lacking oxygen) because the soil pores are filled with water. To remedy this dilemma, aerial roots known as pneumatophores grow above the water’s surface to get air from the atmosphere. A classic example of this are the aerial roots of a grey mangrove.
Image credit: Chenille Williams
5. Mosquitoes, like many insects, spend the first portion of their lives in the water and have an organ to help them breathe (not gills)
Because of the standing water, wetlands are an ideal nursery for mosquitoes. To capitalize on this optimal habitat, the larva have a breathing tube called a siphon that pierces the water’s surface and allows the larva to get oxygen while remaining underwater.
Image credit: Wiki Commons
6. Whirligig beetles have double vision and can see on top of and under the water
With two sets of eyes on top of one another—one for looking at the water’s surface, one for looking underwater—whirligig beetles are able to search for prey while also being on the lookout for hungry birds.
7. Aerenchyma cells and lenticels create oxygen highways from the plant’s leaves, stem, or trunk to its roots
The names alone are pretty amazing and fun to say. As mentioned earlier, the anaerobic conditions of the soil force plants to provide oxygen to their roots in other ways. Aerenchyma cells are a porous tissue in plant leaves that allow that leaf-to-root oxygen transport. Lenticels function in the same manner except they are located on the bark. If you ever get a chance, cut off a small piece of a cattail leaf and examine it to see the aerenchyma. But don’t do it in a nature park because those plants are protected.
Image credit: San Elijo Lagoon Conservancy
8. Lung fish live up to their names and can breathe without water
In times of extremely low water levels or in conditions where there is little oxygen in the water, the specialized respiratory system of lungfish allow them to breathe air to compensate for the low dissolved oxygen. When water levels are extremely low, they can burrow in the mud, cover themselves in a mucus to prevent their skin from drying out, and breathe oxygen.
9. Wading birds have feet that prevent them from being a “stick in the mud”
The long, wide-spaced toes of wading birds like herons and egrets allow them to have stability while walking through shallow water and not get stuck. Because of this characteristic, they can move stealthily while looking for fish to eat.
Image credit: Chenille Williams
10. Dragonfly nymphs are fierce predators with mouth parts like retractable grappling hooks
As with mosquitos, dragonflies spend the first portion of their lives as nymphs (i.e. “babies”) in an aquatic environment. The lower lip of a dragonfly nymph forms a mask that shoots out, grabs prey (including mosquito larva!) with its hooks, and pulls it back into the dragonfly’s mouth for a tasty meal. They are savvy and efficient hunters who don’t need a khaleesi.
Image credit: Sam Velder