Michigan Nature Monday: Michigan’s Many Water Resources

Michigan is well-known as the “Great Lakes State” but there is much more to the state’s freshwater ecosystem than the massive inland freshwater seas that garner all the attention. There is a true “underdog” in Michigan’s freshwater systems—groundwater.

In honor of National Groundwater Awareness Week (March 5-11, 2023), the Michigan Nature Association is proud to explore a vital component of Michigan’s groundwater system, fens, written by MNA volunteer Zoë Goodrow.

What is a fen?

When the final glaciers in Michigan retreated north about 8,000-12,000 years ago, they shaped landforms that eventually became the wetlands we see today. Fens are among the rarest types of wetlands – more specifically, peatlands – found in Michigan. What differentiates fens from other wetlands is their hydrology.

Fens are fed by a continuous flow of groundwater that filters through nutrient-rich layers of sediment, like limestone, resulting in an ecosystem rich in calcium and magnesium. The steady supply of groundwater into fens means that fen soils remain saturated throughout the year. This causes a reduced abundance of bacteria that break down plant materials (compared to other wetlands), resulting in a buildup of decayed plant debris – also known as peat.

Rare species in fens

Fens have 500 times more rare plant and animal species than the average acre of land in Michigan. They support nearly 60 rare species and are the Michigan equivalent of rainforests in terms of relative biodiversity. Typical plant species that are unique to fens across Michigan include sphagnum mosses, white lady slipper, fringed gentian, edible valerian, and carnivorous plants including sundews and pitcher plants. Rare animals that habituate fens include the yellow rail, Mitchell’s satyr, and eastern massasauga rattlesnake. Fens are extremely fragile and sensitive systems that are already being impacted by climate change, which does not bode well for the rare species that are endemic to fen ecosystems. Because of this, and their significance to Michigan’s biodiversity, it is important to know the guidelines for minimizing disturbance before you visit one.

Types of Michigan fens

Michigan is home to many types of fens, including the northern, prairie, patterned, and coastal fens. These different fens are characterized by the natural processes that formed them and the climatic conditions of the regions they reside in.

Prairie fen photo by Dave Cuthrell.

Northern fens are found in the Upper Peninsula and the northern half of the Lower Peninsula. They occur where a glacial outwash meets a more textured glacial feature like a kettle lake or an end moraine.

Prairie fens, located in the southern half of the Lower Peninsula, occur in former oak-savanna prairies. As their name suggests, they are dominated by a mix of prairie and wetland sedges, grasses, and forbs. These fens were formed via the same glacial processes as northern fens.

Patterned fens, also known as string bogs, also occur in the Upper Peninsula. What differentiates these fens from northern fens is that they are a series of alternating ridges and hollows, oriented parallel to the contours of the land. The natural processes responsible for forming these unique systems are still unknown. While there are several proposed hypotheses – researchers agree that an essential factor is the direction of water movement, as the ridges and hollows are consistently oriented perpendicular to the flow of groundwater. (See more on patterned fens with MNA’s Fox River Wetlands in the video linked below)

Click on the image above to watch “The Fox and the Fen”. Photo by Jason Whalen, Fauna Creative.

Coastal fens occur along Lake Michigan and Lake Huron in the Upper Peninsula and northern Lower Peninsula. The natural processes that formed them are inextricably linked to those of the Great Lakes. The water tables that influence these systems are subjected to seasonal and multi-year lake level fluctuations, so vegetation in coastal fens changes quickly when water levels change.

—

To experience a fen habitat first-hand, consider visiting MNA’s Lefglen Nature Sanctuary in Jackson County. The sanctuary is home to a prairie fen and a natural flowing well visible from the south trail. Visit our online sanctuary map for directions and more information.

Advertisement

Michigan Nature Monday: Dunes

Snow blankets much of Michigan now, which may have you dreaming of summer vacations to the beach, and for good reason – Michigan has plenty to choose from! But sandy shores and their hilly companions—dunes—support more than just a retreat from the daily grind.

Vegetation grows on a dune. Photo by Andrew Bacon.

Dunes in Michigan are unique because, unlike their desert counterparts, they are impacted greatly by the water of the Great Lakes. Fluctuating lake levels contribute to dune formation by stabilizing the dunes with increased water levels as well as increased wave action in high years. These impacts are usually so slow-moving that they go unnoticed, but recent erosion along Lake Michigan due to increased lake levels had the dramatic effect of damaging some houses built close to the edges of these dunes.

One distinguishing characteristic of Michigan’s dunes is the amount of vegetation that can be found on them. There is a limited supply of sand in the Great Lakes being deposited on the dunes. This in time allows for various grasses and trees to take root and grow, further slowing or stopping the movement of the sand and allowing for more vegetation to grow. These plants are therefore critical to preventing erosion and dune migration.

Several rare plant types are supported by these dune habitats including Pitcher’s thistle, Houghton’s goldenrod, and Lake Huron tansy, just to name a few. At MNA’s Lake Huron Sand Dunes Plant Preserve in Chippewa County, a unique natural community known as a “wooded dune and swale complex” exists as a series of sandy ridges and low, swampy areas that were formed in multiple stages as lake levels receded around 12,000 years ago.

Lake Huron tansy. Photo courtesy Peggy & Jerry Keeney.

As with many natural communities throughout Michigan, a major threat to the health of this sanctuary is the impact of invasive species. Particularly at Lake Huron Sand Dunes Plant Preserve, invaders such as Spotted knapweed and European Marsh thistle are aided by habitat disturbance. MNA monitors the sanctuary regularly for signs of disturbance and works to remove invasive species before they become too widespread.

So as you plan your next Michigan beach vacation, remember that the sand is part of a much larger and ever-changing habitat complex.

Captive Rearing Strategies Could Impact Lake Sturgeon Recovery Success

by guest contributor Derek Smith

Flowing between the kitschy, Bavarian-style architecture of Frankenmuth, Michigan is the Cass River, where biologists released 104 young lake sturgeon in September 2022. Before releasing them, the biologists equipped the sturgeon with tracking and identification devices to follow the fish’s movements and survival after their release. That knowledge is critical to assess the success of sturgeon release events because there is no guarantee the sturgeon will remain where they are released.

A young lake sturgeon being released into the Cass River. The fish will leave the river after its first year, but scientists are hoping that they return when they are old enough to spawn. Photo courtesy Derek Smith.

Once numerous in North American freshwaters, lake sturgeon are considered globally endangered due in part to severe overfishing in the late 1800s and early 1900s and are absent from many rivers where they historically lived, such as the Saginaw River and its tributaries, including the Cass River. According to US Fish and Wildlife Service biologist Justin Chiotti, the goal of releasing captive-raised sturgeon is to “restore historic populations to self-sustaining levels.”

But sturgeon don’t hunker down in one place. After one year, many sturgeon leave their birth rivers to live in lakes, bays, and river mouths. When they reach sexual maturity between twelve and twenty-seven years later, the sturgeon return to their natal waters, which are better suited to spawning. There, fertilized eggs and larval fish take shelter from predators between the rock crevices in cobblestone substrate and thrive on the fast-flowing, oxygen-rich water.

How sturgeon navigate back to their rivers of origin is still largely unknown, but scientists think that larval sturgeon imprint to chemical signatures in their natal waters. Later in life, the sturgeon “sniff” their way back to their natal rivers to spawn by following those chemical queues.

Imprinting captive-reared sturgeon to rivers where they are now extirpated presents a challenge to conservation biologists When sturgeon are not raised in the waters in which biologists plan to restore self-sustaining populations, the re-introduced fish might not imprint to the historic habitat, potentially reducing the return rates when the fish are old enough to spawn. ,

A lake sturgeon fish hatchery in Genoa, WI. Photo courtesy Derek Smith.

Stream-side rearing facilities could be the solution to the imprinting challenge. At these facilities, biologists raise sturgeon directly in the river water where the sturgeon will be released. The Toledo Zoo has one such facility along the Maumee River, where they have been raising fish for release into the Maumee River since 2018. Similar facilities are located in Michigan, such as the Black River facility run by Michigan State University and the Big Manistee River facility run by the Little River Band of Ottawa Indians.

According to Matt Cross, the Toledo Zoo’s Conservation Coordinator,“the idea with the stream-side facility is that the fish will pick up on the different chemical cues from the river, which they will use to return to the river to spawn.” By raising sturgeon in the waters to which they will later be released, the Zoo’s biologists are increasing the chances that the sturgeon are in the river water during the developmental stage when imprinting occurs, which Cross says is “a big question mark.”

But the stream-side facilities are costly and have water quality issues that off-site hatchery facilities optimized to grow large amounts of fish are better equipped to manage. The National Fish Hatchery in Genoa, Wisconsin is one such facility. There, U.S. Fish & Wildlife biologists rear sturgeon from eggs in Genoa well water. The facility raises hundreds to thousands of sturgeon for release into rivers each year, but there is a chance that hatchery-raised fish miss the crucial period at which imprinting occurs before they are large enough to be released. The unknown timing of when sturgeon can imprint to rivers obscures the relative effectiveness of these two rearing strategies.

Larval lake sturgeon swim around a tank filled with well water at the Genoa National Fish Hatchery. Biologists refer to the fish at this age as “free-living embryos” because they still have a yolk sac that provides all their nutrition. Photo courtesy Derek Smith.

According to Cross, “it’s a cost-benefit problem.” If sturgeon raised in well water still reliably return to the rivers where they are released, the large number of fish raised at the Genoa Hatchery could be a boon to sturgeon conservation across the Great Lakes region. On the other hand, if the hatchery-raised sturgeon wander, additional streamside facilities may prove necessary to re-introduce self-sustaining sturgeon populations to target rivers. The Cass River, for example, lacks a stream-side rearing facility and may potentially benefit from one.

To better assess the costs and benefits of each rearing strategy, biologists at the Toledo Zoo, US Fish and Wildlife Service, Ohio Division of Wildlife, Michigan State University, and the University of Toledo will test whether the two rearing-strategies impact how sturgeon return to rivers. In the summer of 2022, the biologists collected eggs and sperm from the same spawning adults in the St. Clair River, where healthy, self-sustaining populations exist today. Fertilized eggs were created by mixing sperm and egg, then half of the eggs were raised at the Genoa Hatchery while the other half were raised at the Toledo Zoo’s stream-side facility.

Once the fish were fingerling size, the biologists equipped them with PIT tags. The tags are similar to the microchips implanted into pet dogs and cats and encode an identification number linked to information about where an individual fish was released and in which facility it was raised. Whenever a released sturgeon is recaptured, scanning its PIT tag will allow biologists to identify how many fish from each rearing facility returned to the Maumee River to spawn

Both institutions have partnered to release sturgeon into the Maumee River in this manner since 2018, so the oldest fish released in this program are only 4 years old. The team must wait until the first of the released sturgeon mature eight to twenty-three years from now before they get their answers.

Michigan Nature Monday: Poweshiek skipperling

One of the rarest butterflies, the Poweshiek skipperling, is truly on the brink of extinction. Once abundant in the tall prairie grasslands and the prairie fens of several states and provinces in the upper Midwest, the tiny butterfly is now found only in a handful of sites in Manitoba and northern Oakland County, including an MNA nature sanctuary. Loss of habitat and other factors contributed to a decades-long—and now a relatively recent and rapid—population decline that has scientists scratching their heads and worried about what their disappearance may mean for other pollinators.

The globally endangered Poweshiek is now so rare that only 100 individual butterflies were counted in a 2021 census. Recovery plans—aided by an international partnership that includes MNA—call for captive breeding efforts to headstart individuals and increase survival to adulthood in order to build a reserve population that can be reintroduced to the wild. The Minnesota Zoo, John Ball Zoo in Grand Rapids, Michigan State University’s Haddad Lab, and the Michigan Nature Association are specifically collaborating within the Poweshiek Skipperling International Partnership to annually produce more individuals for wild releases in 2022 and beyond in what is known as ex situ or “offsite” conservation.

Poweshiek skipperling photo by Cale Nordmeyer, Minnesota Zoo

MNA is proud to protect habitat critical for the Poweshiek skipperling’s survival, and to be part of the important partnership that is working to save this species from extinction. We look forward to continuing participation in this partnership effort to increase the Poweshiek skipperling population in the wild in the coming years.

Learn more about our conservation work and how you can contribute at michigannature.org.