Tag Archives: lakes

Destiny of Waters

Is it a lake or a pond or a wetland?

Recently someone asked me about the body of water beyond my backyard—if it was a lake or a pond and what’s the difference? My first answer was that it is a pond by name. A pond or lake may be named as such the way “street,” “lane,” or “road” are often interchangeable. Secondly, a lake and a pond have differences at the ecological level—in terms of aquatic life, and in terms of limnology.  I also explained that the differences had to do with acreage and depth of the water body. Sometimes a “pond” can be bigger and deeper by comparison to a nearby lake, as in the case of Long Pond (113’ deep) and Echo Lake (66’ deep) in Acadia National Park. In that case, Echo Lake is technically considered a “great pond” under Maine state law because it’s a natural pond greater than 10 acres.  But usually lakes are bigger and deeper than ponds. State definitions generally include both lakes and natural ponds as “waters of the state.” Under the Cowardin classification system, ponds are wetlands.

What I did not explain to my friend very well was the natural gradation of lakes into ponds into wetlands, and their evolution as waters.  What made sense to me as an ecologist, that one type would naturally grade into another water type, was harder to explain. What’s even harder to illustrate is the concept of an ecotone—the transitional area between two ecological communities adjacent to one another. As usual, I thought of movies.

The phenomenon of distinct communities existing side by side can be observed in film.  For example, the liminal space between cultures—a cultural transition area—can be viewed as bordercrossings, illustrated effectively in films like “Night on Earth” (1991). Jim Jarmusch’s film took place entirely in taxi cabs in five different time zones throughout the world. The concept is that no matter where you go, at one point in time, there are eerily similar transactions and interactions taking place in taxi cabs—a kind of cultural habitat, if you will—for humans migrating from one place to another. Some water bodies, like taxi cabs, are mobile; some are stationary, like an ‘off-duty’ cab.  And that’s where the changes from lake to pond to wetland, or the line between adjacent ecological communities, can get a little fuzzy to someone standing on the curb, er, the edge of the water.

Over what period of time do lakes become ponds? How long does it take for ponds to become wetlands? For wetlands to become meadows? The short answer is several thousand years, if nothing has interrupted (or accelerated) the natural evolution of these waters. This is called succession. Biology students learning about wetland succession in a classroom can experiment with an aquarium—starting with a mini pond or wetland habitat. For a biology teaching guide written by BioMedia (Russell) that outlines the key ingredients to such an experiment for a year-long study,click here. Limnologists say, “lakes are destined to die,” whereas ponds are the “death of a lake” and the “birth of a marsh.” For an explanation on pond succession, click here.

So how does a pond become a wetland? The first stage, called the ‘pioneer’ stage of wetland succession, starts with the pond without plant life at the bottom. Plankton, which inhabit the pond, and carry miniscule plant and animal life, arrive on the winds or wings of insects.  Over time, plankton die on the pond bottom and create a mucky layer, which is rich enough for water emergent plants to grow, such as water lilies, ancient wetland plants. As water lilies form a blanket over the surface of the water, they cut off the sunlight to the bottom, killing off the submergent plants. These processes can take a variety of timeframes from a matter of years to a matter of millennia. Trees, shrubs and grasses move into the space that was once the pond and a wetland takes shape. This is a dynamic process with many variables. Some wetland ecologists have argued against the idea of wetland succession because of these variables.

Succession is not a sure thing. It does not occur with all lakes in the U.S.. (For instance, there is no scientific concern that the Great Lakes will eventually turn into ponds, or meadows.) There are many factors that can interrupt a “natural” succession process such as a changing climate, soils, drainage, land development, introduction of invasive plants or other aquatic species, phosphorus run-off (causing dissolved oxygen) or other factors.

In addition to the possible succession pattern of pond to wetland, some wetlands can be turned into ponds. In the U.S. Fish & Wildlife Service’s Status & Trends of Wetlands in the Conterminous United States 2004-2009, ponds are recognized as a type of freshwater wetland. The report indicates a net increase of 207,200 acres of ponds between 2004-2009, an increase of 3.2% in ponds nationally (FWS).  The trouble with ponds, for example, farm ponds, being created while another type of freshwater wetland is lost, is that there is a difference between constructed ponds and wetlands—including natural ponds, in terms of their ecological functions. According to the Status & Trends Report, the majority of ponds in the U.S. are constructed farm ponds. Only 31% of the ponds in the lower 48 states are natural.

Mankind has a dramatic impact on natural landscapes frequently disrupting succession. This means it’s an uncertain destiny for our lakes, ponds, streams, rivers and wetlands. For those working to protect wetlands, and to harness the power of wetlands to sequester carbon and provide unique and solvent ways to fight climate change’s impact on our planet, this is cause for concern. Save wetlands, save ourselves.

Helpful Resources:

Massachusetts Lake and Pond Guide

Wisconsin’s Natural Communities

Michigan DNR: Succession – Changing Land, Changing Wildlife

Wetland Ecosystems by William J. Mitsch, James G. Gosselink et. al. (2009)

Wetland Ecology: Principles and Conservation, 2nd Edition by Paul Keddy, (2010)

ASWM’s Wetland Science web resources

Other recent blogs on wetland succession:

Conservation Maven: Study finds post-restoration wetland succession highly variable

Ian Lunt’s Ecological Research Site: There’s a wetland in my grassland

Constantine Alexander’s blog: Artificial wetlands can provide benefits over the long haul(on Bill Mitsch’s work on wetland creation and succession)

Save the Eels – New Book by Trout Illustrator, James Prosek

Growing up on a lake in Maine, my brother and I liked to lean over the end of the dock, shine a flashlight into the water on summer nights and lure the eels. They’d swim over to the beam, poke their heads out of the water and kiss the flashlight. I used to feel them slip passed my legs when I swam at night. They felt slippery because eels cover their bodies with a layer of mucous. But over the years, I’ve encountered fewer eels in the lake. Their population has decreased. In lakes and streams and rivers all over the world, eels are disappearing.

In the 1880s, the New York Times claimed that the eels in the St. Lawrence River were abundant; the population could never be diminished. Freshwater eels are the only fish that spends its adult life in freshwater and then returns to oceans—namely the dark Sargasso Sea, to spawn and then die. Juvenile (elver) eels travel up streams and tributaries of the Mississippi River and migrate into other freshwaters—lakes, wetlands, ponds—where they live until they reach maturity. For some eels, this can take many years, even 100 years. Once they reach reproductive maturity, they migrate back down the streams and rivers to the ocean, back to the Sargasso Sea, to spawn. They don’t come back. This is because eels go into their silver stage of development and their whole system degenerates. Their reproduction cycle has a “will self-destruct” button after they spawn. Unfortunately, nowadays eels are increasingly threatened by destruction of habitat caused by coastal development and construction of dams as well as overfishing. In the last 20 years, the population has been diminished by possibly as much as 99%. (FWS)

FWS released a status review of the American eel in 2007 which showed that while the eel population has decreased in some areas, the overall world population was not endangered. The eel was not added to the Endangered Species list. “Overfishing and hydropower turbines continue to impact eels in some regions, such as Lake Ontario and Chesapeake Bay, although these factors do not fully explain the reduced number of eels migrating up the Saint Lawrence Seaway and into Lake Ontario,” explained FWS biologist Heather Bell on the 2007 report.http://www.greenenvironmentnews.com/Environment/Wildlife/Endangered+Species+
 For more information on the American eel and the FWS research on considering it for protection, go to:http://www.fws.gov/northeast/newsroom/eels.html FWS mapped a model of eel habitat in 2001:http://www.fws.gov/r5gomp/gom/habitatstudy/metadata/American_eel_model.htm

Meanwhile, one man is calling for eel conservation. Check out this article by James Prosek, on Yale’s Environment 360 blog: “A Steady, Steep Decline for the Lowly, Uncharismatic Eel”http://e360.yale.edu/feature/a_steady_steep_decline_for_the_lowly_uncharismatic_

Prosek’s new book is titled, Eels – An Exploration, From New Zealand to the Sargasso, of the World’s Most Amazing and Mysterious Fish. According to a New York Times review, Eels is more than a “fish book.” It is an “impassioned defense of nature itself, rescued from the tired rhetoric of 1970s-style environmentalism by good, honest shoe-leather reporting.” Prosek takes the reader to eel haunts around the world: a river in the Catskills of New York; the traditional Maori eeling grounds of New Zealand; and an odd little volcanic island…http://www.nytimes.com/2010/10/24/books/review/Greenberg-t.html Prosek previously won a Peabody Award in 2003 for his documentary about traveling through England in the footsteps of Izaak Walton, the 17th-century author of The Compleat Angler. Prosek’s watercolor paintings of fish first appeared in his book, Trout: an Illustrated History http://www.amazon.com/Trout-Illustrated-History-James-Prosek/dp/067944453X

In the U.S., most people have a general dislike for eels. But in other parts of the world, eels are treated with respect, having a place in ancient myths and sacred beliefs, for example, in New Zealand.   Scotland just published its first eel conservation management plan in 2010. http://www.scotland.gov.uk/Topics/marine/Salmon-Trout-Coarse/eelsNorway passed new laws that assign fishing quotas, lowering the allowable number of eels caught starting in 2010. http://marinesciencetoday.com/2009/07/03/norway-helps-endangered-european-eels-conservation/ Scientists in England are also calling attention to the problem of eels vanishing from the Thames River.http://www.telegraph.co.uk/earth/environment/conservation/7046249/Eels-vanishing-from-River-Thames-scientists-warn.html

Also check out a related article in the Orion Magazine:http://www.orionmagazine.org/index.php/articles/article/5610

Related video: http://www.orionmagazine.org/index.php/audio-video/item/orion_original_video_eel_water_rock_man/

Related link: New York Department of Environmental Conservation led an eel conservation project this year (2010): http://www.dec.ny.gov/lands/49580.html

Additionally, check out the photos of “tame eels” eating crackers in this album:http://www.thewildernesslodge.org/biche_images.htm