Balancing your Pond's Green Bank

By Glenn Sullivan

At water’s edge, in this pond’s green bank, we see American pondweed growing among patches of declining amounts of curly leaf pondweed. Attached to that is a growth of filamentous algae. Deeper, there’s a colony of coontail. And, there’s an amount of lime green Chara.

What’s a “green bank” you ask? ”Green bank” is a pond’s combination of aquatic plants and algae. The bank analogy is a good one because, like money, if you don’t have any, there’s not much living going on. Living, healthy ponds have plants. But, ponds with too much greenery tend to get a little sloppy!

During my decade of pond vegetation management, I’ve seen only a few lakes or ponds with no plant life, usually high mountain lakes, or acid lakes of the northeast. And, I’ve seen more than my share of ponds with too much plant and algae, places often found in agricultural settings or urban spots. But, most strive for something in the middle--a balance–not just in the size of our green bank, but also composition.

Our family visited a new park the other day, and we found a four-seat teeter-totter, the kind with one seat in each direction. As we bounced around in different directions, it seemed symbolic, how each of us could participate in such simple fun. Like the four-sided playground toy, a healthy green bank works best when it exhibits different components; submersed weeds and Chara, emergent and floating plants, filamentous algae, and plankton.

As nutrients make their way into a pond, odds are they will find a home in one or more of these plant groups. Here’s where balance comes in. Quantities of one type of vegetation generally influence how much you have of others. More and more pond and lake managers are beginning to understand this concept. Consequently, I hear less of “I don’t want to see anything green in that pond,” and more “Can you get rid of that floating algae without hurting the lily pads?” This is a good thing.

Here are real examples how to balance a pond’s vegetation in the northeastern U.S. Tranquil Lake, in northwest New Jersey’s Sussex County, is about 50 acres. Every few years, Eurasian watermilfoil pokes its invasive head up early spring. We usually spank it with SePro’s Sonar, a non-contact type herbicide that attacks plants from their source, by blocking food uptake. Milfoil leaves for several years. Afterward, we look forward to a predictable, and desirable, result – chara. Within a couple weeks of milfoil’s disappearance, chara blankets the lake bottom. If weather cooperates with normal rains and moderate temperatures, chara sits well below the surface and water clarity stays exceptional throughout summer. When chara reaches the surface, we’ll receive a few tantalizing phone calls from concerned property owners. If the lake resident in charge for the year doesn’t understand the balance of, or agree with, the lake ecosystem, they may pull the trigger and order an algaecide treatment. Then, chara gives up, sinks and goes away. and along with it’s demise, clarity goes. Then, the phone rings with more concerned owners, and we chase plankton blooms and allied issues for the rest of the summer. Good for business, but not so good for this lake.

Bell’s Pond, near Albany, New York, is another good example of attaining balanced green banks. This pond was overrun with assorted submersed plants and water lilies. Plants were so thick that boating was nearly impossible by June, and invasive emergent plants like purple loosestrife were beginning to pop up out in the main body of the lake. With all nutrients locked up in plants, water clarity was excellent. But, too much plant life called the owners to action. This pond needed a fresh start. After a broad spectrum herbicide application, and a pretty big mechanical weed removal project, better than 75% of the vegetation was removed. As you might expect, the balance of nutrients shifted to plankton, and the lake color shifted to a bright green. It’s been a few years now since that pond’s “fresh start”, and each year more plants re-colonize the lake, and water clarity improves. It took an initial shock to the system, but a good balance of plants and algae has returned, which benefits all the pond’s creatures. Rearranging nutrients rearranged this pond’s life.

One more example is 16-acre Nelson Lake, in central New Jersey, near Trenton. For several years, the lake’s owners were satisfied with a perpetual plankton bloom, as long as there were no floating clumps of algae. This was accomplished mostly with bacterial additives applied every two weeks. But every so often nutrients overtook beneficial microbes and the nasty algae water net (Hydrodictyon) ran rampant. What made things worse was there was not another single plant to help balance the algae growth. After much consultation and several meetings, a number of management activities were planned, highlighted by an extensive shoreline revegetation plan. Over three seasons more than 10,000 irises, pickerelweed and other desirable plants were planted along the lake shore. Today, the lake still grows an amount of plankton, and there’s still a bit of filamentous algae along the edge from time to time, but things are far more manageable. The plants are doing a great job of assimilating nutrients in most shallow areas, right where the filamentous algae gets its start. The system has achieved a better balance, and management has become easier and more proactive.

Finding a balance isn’t a replacement for controlling nutrient loading, if less plants or algae are what you’re after. Rather, it’s learning to accept some green growth in ponds because plants are necessary components of healthy ecosystems. Finding ways to manage the pond so no one plant or algae becomes too problematic is part of management strategy.

It’s all just how you lean on the teeter-totter.

Glenn Sullivan is the President of Allied Biological Inc., a lake and wetland management firm serving NY, NJ and PA. He has a B.S. from Rutgers University, is a NALMS Certified Lake Manager and serves as Treasurer of the North East Aquatic Plant Management Society. Contact Glenn through his business website

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