Archives For Bob Kirschner

What’s black and white and spread all over? Zebra mussels—but they’re no joke.

If you noticed more aquatic “weeds” and algae growing in the Garden Lakes this year—or that our beloved Smith Fountain was MIA after mid-summer—read on to find out why.

Invasive plants and the problems they pose have been the topic of frequent postings here on the Chicago Botanic Garden’s blog. Now we have another invasive species to tell you about—and this time, it’s an animal: zebra mussels.

PHOTO: Adult zebra mussel (Dreissena polymorpha).

Adult zebra mussels (Dreissena polymorpha) are about the size of your thumbnail.

Like many invasive plants and animals, zebra mussels’ native range is a faraway place; in this case, eastern Europe and western Russia. In the past 200 years, they have spread throughout all of Europe and Asia. Here in North America, the first account of an established population was in 1988 in Lake St. Clair (located between Lakes Huron and Erie), likely arriving here as tiny hitchhikers in the ballast water of a single commercial cargo ship traveling from the north shore of the Black Sea.

Somewhat remarkably, over the next two years they had spread throughout the entire Great Lakes. Just a year later in 1991, zebra mussels had escaped the Great Lakes and begun their march across North America’s inland waters. (Watch an animation of their spread). Today they are found in at least 29 states.

A zebra mussel may live up to five years and produce up to one million eggs each year—that’s five million eggs over their lifetime. A freshwater species of mollusk, they prefer to live in lakes and rivers with relatively warm, calcium-rich water (to help support their shell development). They feed by filtering microscopic algae from the surrounding water, with each adult zebra mussel filtering up to one liter of water per day.

Though tiny in size (adults are typically ½ to 2 inches long), their ecological and economic impacts can be enormous. Adult zebra mussels prefer to attach to hard surfaces such as submerged rocks, boat hulls, and pier posts—but they also cling to water intake structures as well as the interior of most any pipe that has flowing water in it (such as drinking water supply and irrigation system piping). From an ecological perspective, zebra mussels’ removal of microscopic algae often causes the afflicted waterway to become much more “clear.” While this clearer water may otherwise seem like a good thing, the now-removed microscopic algae is an important food source for many native aquatic animals. The clearer water also allows sunlight to penetrate deeper into the water, thereby stimulating much more rooted aquatic plant growth.

Nearby, zebra mussels were first identified in 2000 at the Skokie Lagoons, just south of the Garden. In 2013 and again in 2014, just a few zebra mussel shells were found at the Garden on the intake screens for our irrigation system’s South Pumphouse. Since so few mussels were found, we were hoping that the Garden’s lakes were simply not a hospitable place for the zebra mussels to flourish. Unfortunately, that thinking all changed in 2015….

PHOTO: Waterfall Garden label covered in zebra mussels.

These zebra mussels, only a few months old at the time, completely covered this plant label that had inadvertently fallen to the bottom of the Waterfall Garden’s upper pool.

At our Waterfall Garden, 1,000 gallons per minute of lake water are pumped to the top of the garden, after which the water flows down through the garden’s channels and then back into the lake. When Garden staff drained the Waterfall Garden for cleaning in June 2015, there were no apparent zebra mussels present—but by September 2015, the entire bottom of the Waterfall Garden’s upper pool was completely encrusted with attached zebra mussels. Needless to say, we were more than a little alarmed.

Realizing that the Garden’s lakes could indeed support massive growth of zebra mussels, the Garden’s science, horticulture, and maintenance staff quickly came together to devise a remediation strategy that would protect two critical components of the Garden’s infrastructure from “clogging” by zebra mussels: our irrigation system (which utilizes lake water to irrigate nearly all of our outdoor plant collections) and our building cooling systems (three of our public buildings extract lake water to support their air conditioning systems).

PHOTO: One of the Garden's lake water filtration systems.

Automatic backwash filters like the ones pictured here will be added to each of the Garden’s three pumping stations that withdraw lake water to irrigate nearly all of our outdoor plant collections.

The Garden’s zebra mussel remediation team drew upon the best scientific expertise available in North America, which confirmed that there is no scientifically proven approach for removing all zebra mussels from a body of water. The team explored all potential options for eliminating zebra mussel impacts on our infrastructure, and ultimately settled on two approaches: first, the installation of automatic backwash filters to keep even the tiniest of zebra mussels from getting into our irrigation system (the youngest zebra mussels are about 70 microns in size, or about the width of a human hair), and second, the installation of conventional closed-loop “cooling towers” on the three Garden buildings that currently use lake water for air conditioning (thereby discontinuing all withdrawals of the lake water for building cooling). Final design of the backwash filtration systems and the cooling towers is currently underway, and our intent is to have everything installed and operational by spring 2017.

PHOTO: The Garden’s aquatic plant harvester cuts and removes excessive aquatic vegetation and algae from the Garden lakes.

The Garden’s aquatic plant harvester cuts and removes excessive aquatic vegetation and algae from the Garden lakes.

If you visited the Garden in 2016, you probably witnessed some of the zebra mussels’ ecological impacts to our lakes. Mid-summer lake water transparency in our lakes typically is about 3 to 4 feet—but in 2016, this increased dramatically to about 6 feet (likely due to the zebra mussels’ filtering abilities described earlier). This clearer water resulted in much great submerged aquatic plant growth in our lakes, and our aquatic plant harvester struggled to keep up. Many visitors commented that there was much more aquatic “weed” growth in the lakes this year—and they were correct.

In fact, there was so much aquatic plant growth in our lakes this summer that the water intake for Smith Fountain in the North Lake became clogged and the pump burned out. Look for a repaired Smith Fountain (with a more clog-resistant intake) to reappear next spring.

PHOTO: The Smith Fountain (which is illuminated at night) is an acclaimed feature in the North Lake.

The Smith Fountain (which is illuminated at night) is an acclaimed feature in the North Lake.

While there currently is no known way to eliminate zebra mussels from freshwater lakes and streams, Garden researchers intend to utilize the new aquatic research facilities in the emerging Kris Jarantoski Campus to explore experimental approaches, such as biological control agents, to potentially lessen the zebra mussels’ ecological impacts to our 60-acre system of lakes. Stay tuned.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

Look up! In partnership with Friends of the Chicago River (FOCR) and the Forest Preserves of Cook County (FPCC), an osprey nesting platform was installed on Friday, January 29, along the North Branch Trail at the south end of the Chicago Botanic Garden near Dundee Road.

MAP

The Garden’s new osprey nesting platform is located near Dundee Road and is viewable from the North Branch Trail.

The osprey is listed as an endangered species in Illinois, which means it’s at risk of disappearing as a breeding species. Fish-eating raptors that migrate south and winter from the southern United States to South America, osprey are often seen during their migrations—yet few remain in Illinois to nest. The lack of suitable nesting structures has been identified as a limiting factor to their breeding success here.

Males attract their mates to their strategically chosen nesting location in the spring. In order for a nest to be successful, it must be located near water (their diet consists exclusively of fish, with largemouth bass and perch among their favorites), the nest must be higher than any other nearby structure, and it must be resistant to predators (think raccoons) climbing the nest pole and attacking the young.

FOCR and the FPCC sought out the Garden as a partner for an installation site, in large part owing to the Garden’s strong conservation messaging and proximity to other nearby nesting platforms that have been recently installed (two are located alongside the FPCC’s Skokie Lagoons just to the south).

The Garden’s nesting platform was installed atop an 80-foot “telephone pole,” set 10 feet into the ground and extending upwards by 70 feet. The 40-inch hexagonal nest platform atop the pole has a wire mesh on the bottom so that water can pass through the sticks and stems that the osprey will bring to construct the nest.

PHOTO: Installing and osprey nesting pole.

A truck-mounted auger and crane set the nesting pole and platform into place.

PHOTO: Installing an osprey nesting pole.

The nesting platform sits atop the pole and is ideally sized for a future osprey nest; notice that we even “staged” the new osprey home with a few sticks of our own!

PHOTO: Installing an osprey nesting pole.

A metal band was wrapped near the bottom of the pole to prevent predators from being able to climb it.

PHOTO: Installing an osprey nesting pole.

The nesting pole and platform is fully installed and is visible from the North Branch Trail that runs through the Garden.

With the osprey nesting platform now in place, our hope is that within the next few years, a migrating male will select the site and pair with a female. Osprey generally mate for life, though they’re together only during the breeding and rearing seasons.

You can learn more about the how and why of the osprey nesting platform project at the FOCR website. Follow the links on that webpage for images, video, and a press release relating to the installation of an identical osprey platform at the Skokie Lagoons last spring.

Read more about the long-term effort, and about ospreys making a comeback in Cook County. Discover birding at the Garden and find our full bird list online at chicagobotanic.org/birds.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

Coming of Age for the Garden’s Cygnets

Two juvenile trumpeter swans transported to Iowa last week to join wild populations

Bob Kirschner —  September 16, 2013 — Leave a comment

In early June, the Garden’s resident pair of adult trumpeter swans (Cygnus buccinator) gave birth to two offspring, called cygnets, in their nest near the Visitor Center. Much to the delight of Garden visitors, over the ensuing months the proud parents have enjoyed showing off their family as they paddle about the Garden Lakes.

Trumpeter swans on their nest near the Garden's Visitor Center in spring 2013

Trumpeter swans on their nest near the Garden’s Visitor Center in spring 2013

A little background on trumpeter swans: the trumpeter swan is North America’s largest waterfowl, with a wingspan of more than 7 feet.  Famed for their French-horn call and immortalized by author E.B. White’s The Trumpet of the Swan, by the late 1800s the swans were nearly hunted to extinction in much of the United States and Canada for their meat, feathers, down, and quills. By the 1930s, just 69 trumpeter swans were known to exist in the continental United States. But thanks to the ambitious conservation efforts in our region and beyond that began in the 1980s, trumpeter swan populations are making an incredible recovery.

The Garden’s two adult trumpeters are flightless, so cygnets born here at the Garden aren’t able to learn important skills. For quite a few years, the Garden has been a partner with the Iowa Department of Natural Resources’ Trumpeter Swan Restoration Program. More than a dozen cygnets born at the Garden have been brought to Iowa, where they’re assimilated with wild populations of trumpeters.

Just last week, our two cygnets (together with five born at the Lincoln Park Zoo this spring) were transported to Iowa, where they’ll be kept in a safe area over the winter. Come next spring, they’ll be able to interact with wild populations and begin the journey of becoming proud parents themselves one day.

Mom, dad, and the kids going for a paddle around the Garden Lakes

Mom, dad, and the kids going for a paddle around the Garden Lakes

While it may be with some sadness that we bade farewell to our cygnets, we can take comfort knowing that they are helping to bring renewed hope for a species that, until recently, seemed headed for extinction.

Interested in learning more about trumpeter swans?  Check out The Trumpeter Swan Society, and read more about the successful restoration programs in Iowa, Minnesota, and Wisconsin.


©2013 Chicago Botanic Garden and my.chicagobotanic.org

It’s been a fairly cold and snowy winter in the Chicago area (though some of us longer-term residents might call it rather normal!). But the temperatures now are moderating, and signs of spring are popping up all over. The daffodils are quickly breaking the ground surface, and bits of green are reappearing at the crowns of our native plants.

After last summer’s record-breaking heat and drought, our first thoughts this spring may not be about rain or flooding. But heavy rains are sure to return at some point, and how we manage that water runoff can have a big impact on flooding, on groundwater levels, on water quality, and on the health and beauty of our garden landscapes.

A remarkably simple and effective approach to capture excess rain water is rapidly gaining popularity, especially in residential settings. Rain gardens are aptly named, nifty landscape features that capture rain water traveling across a lawn before it reaches a waterway or storm sewer, allowing much of that water to percolate down into the soil. Rain gardens truly are a win-win-win trifecta: 1) they help reduce flooding (and recharge ground water) by allowing more rainfall to soak into the ground; 2) they improve the quality of water reaching our streams and lakes by slowing the runoff and allowing soil particles and related contaminants to settle out; and 3) with a little thoughtful design, they become a spectacular native plant garden that’s rich in seasonal color and texture—as well as an important habitat for butterflies, dragonflies, and insects that songbirds love to eat.

Around homes and apartments, a rain garden often is situated downslope of a roof downspout so that it can capture the roof’s runoff water before it reaches the street or storm sewer. Think of a rain garden as a shallow “bowl” depression in the ground, with the downslope lip of the bowl just a bit higher than the surrounding land so that water is trapped behind it. A modestly sized rain garden often can be easily installed as a weekend project: a few shovels, a rototiller to loosen the soil, about 100 native plants, and some mulch are all that’s needed to create a 10-foot by 10-foot rain garden.

Rain Water Glen

Rainwater Glen at the Garden’s Plant Science Center

The Chicago Botanic Garden advocates the use of native plants in rain gardens including sedges, rushes, grasses, and various forbs (flowering species). Native plants recommended for rain gardens are particularly well-suited for both submerged conditions that occur right after it rains, as well as the dry conditions that develop between rainfall events. These native plants also help support our native populations of wildlife. Chicago Wilderness has great information about using native plants in the landscape. 

You can assure yourself (and your neighbors) that there’s no need to worry about your rain garden becoming a breeding site for mosquitos. When installed in soils that drain reasonably well, a rain garden’s standing water will disappear within a day or so (and that’s far shorter than the seven to 12 days needed for mosquitos to lay and hatch eggs).

There are many guides available on how to design, install, and maintain a rain garden, including quite a few on the Internet. One particularly well-written resource was prepared by experts in Wisconsin and is titled “Rain Gardens: A How-to Manual for Homeowners.”  This manual provides excellent information about how to site a rain garden in your yard, and suggests good native plants to use for both sun and shade conditions.

You can learn more about rain gardens at the Chicago Botanic Garden on Saturday, June 1, 2013, as we celebrate World Environment Day. A how-to rain garden station will be set up alongside the Woman’s Board of the Chicago Horticultural Society Rainwater Glen at the Daniel F. and Ada L. Rice Plant Conservation Science Center.

On a related note: Perhaps you’ve heard recently in the news about the dire situation for monarch butterflies this spring (for example, see this National Geographic bulletin). If you’ve thought in the past about planting milkweed to help the monarchs but still haven’t, 2013 could be an especially important year for you to add some to your garden. The native swamp milkweed (Asclepias incarnata) can be a great rain garden plant!


©2013 Chicago Botanic Garden and my.chicagobotanic.org