Understanding and Addressing Invasive Species

Photo from: New York State Department of Environmental Conservation, water chestnut bed at Beacon

Spring is officially here! Tulips will soon be emerging from the ground, buds blossoming on trees and, unfortunately, invasive plant species will begin their annual growing cycle. No type of habitat or region of the globe is immune to the threat of invasive species (“invasives”). Invasives create major impacts on ecosystems throughout the world, and freshwater ecosystems and estuaries are especially vulnerable because the establishment of such species in these habitats is difficult to contain and reverse.

This blog provides an introduction to invasive aquatic species, including information that will help you prevent the spread of invasives in the waterways of your community.

Defining Invasive Species

Invasive species can be defined as non-native occurring in an ecosystem that is outside its actual natural or native distributional range. Although the colonization of an ecosystem by non-native species can occur naturally, it is more often a function of human intervention, both deliberate and accidental. For aquatic ecosystems some species have become established as a result of the aquarium trade, fish culture practices and/or transport of plants and animals in the bilge and ballast water of trans-oceanic shipping vessels.

One of the primary reasons invasives are able to thrive, spread rapidly, and outcompete native species is that the environmental checks and predators that control these species in their natural settings are lacking in the ecosystems and habitat in which they become introduced. The subsequent damages they cause occur on many ecological levels including competition for food or habitat (feeding, refuge and/or spawning), direct predation and consumption of native species, introduction of disease or parasites, and other forms of disruption that lead to the replacement of the native species with the invasive species. As a result, invasives very often cause serious harm to the environment, the economy, and even human health. A prominent example is the Emerald Ash Borer, a non-native, invasive beetle that is responsible for the widespread death of ash trees.

As noted above, there are a large number of aquatic invasive species. Some of the more commonly occurring non-native aquatic plant species that impact East Coast lakes, ponds and reservoirs include:

Understanding How Invasives Spread

Either intentionally or unintentionally, people have helped spread invasives around the globe. This is not a recent phenomenon but rather something that has been occurring for centuries. “Intentional introductions,” the deliberate transfer of nuisance species into a new environment, can involve a person pouring their home aquarium into a lake or deliberate actions intended to improve the conditions for various human activities, for example, in agriculture, or to achieve aesthetics not naturally available.

Photo by: Tom Britt/CC Flickr, zebra Mussels adhered to a boat propeller“Unintentional introductions” involve the accidental transfer of invasives, which can happen in many ways, including aquatic species attached to the hull of boats or contained in bilge and ballast water. A high-profile example is the introduction of zebra mussels to North America. Native to Central Asia and parts of Europe, zebra mussels accidentally arrived in the Great Lakes and Hudson River via cargo ships traveling between the regions. The occurrence, density, and distribution of Zebra mussels occurred at an alarming rate, with the species spreading to 20 states in the United States and to Ontario and Quebec in Canada. Due to their reproductive fecundity and filter-feeding ability, they are considered the most devastating aquatic invasive species to invade North American fresh waters. They alter and diminish the plankton communities of the lakes that they colonize leading to a number of cascading trophic impacts that have especially negative consequences on fisheries. Zebra mussel infestations have also been linked to increased cyanobacteria (bluegreen algae) blooms and the occurrence of harmful algae blooms (HABs) that impact drinking water quality, recreational use, and the health of humans, pets, and livestock.

Additionally, higher than average temperatures and changes in rain and snow patterns caused by climate change further enable some invasive plant species to move into new areas. This is exemplified by the increased northly spread of hydrilla (Hydrilla verticillate), a tropical invasive plant species that has migrated since its introduction in Florida in the 1950s to lakes, rivers, and reservoirs throughout the U.S.

Regardless of how any of these invasive species first became established, the thousands of terrestrial and aquatic invasive species introduced into the U.S. have caused major ecological, recreational and economic impacts.

Measuring the Impacts of Invasives

After habitat loss, invasive, non-native species are the second largest threat to biodiversity. According to The Nature Conservancy, “Invasive species have contributed directly to the decline of 42% of the threatened and endangered species in the United States. The annual cost to the nation’s economy is estimated at $120 billion a year, with over 100 million acres (an area roughly the size of California) suffering from invasive plant infestations. Invasive species are a global problem — with the annual cost of impacts and control efforts equaling 5% of the world’s economy.”

Of the $120 billion, about $100 million per year is spent on aquatic invasive plant control to address such deleterious issues as:

  • Human health (West Nile Virus, Zika Virus)
  • Water quality impacts (Canada geese)
  • Potable water supplies (Zebra mussel)
  • Commercial fisheries (Snake head, lamprey, Eurasian ruffe, round goby)
  • Recreational activities (Eurasian watermilfoil, water chestnut, hydrilla)
  • Biodiversity (Purple loosestrife, common reed, Japanese knotweed)

Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. As the National Wildlife Federation explains, “The invasive species may provide little to no food value for native wildlife. Invasive species can also alter the abundance or diversity of species that are important habitat for native wildlife. Additionally, some invasive species are capable of changing the conditions in an ecosystem, such as changing soil chemistry…”

Addressing Invasives

Our native biodiversity is an irreplaceable and valuable treasure. Through a combination of prevention, early detection, eradication, restoration, research and outreach, we can help protect our native heritage from damage by invasive species.

What Can We Do?

  • Reduce the spread
  • Routinely monitor
  • Document and report
  • Spread the word

Reducing the Spread:
The best way to fight invasive species is to prevent them from occurring in the first place. There are a variety of simple things each of us can do to help stop the introduction and spread of invasives.

  • Plant native plants on your property and remove any invasive plants. Before you plant anything, verify with your local nursery and check out this online resource for help in identifying invasive plants.
  • Thoroughly wash your gear and watercraft before and after your trip. Invasives come in many forms – plants, fungi and animals – and even those of microscopic size can cause major damage.
  • Don’t release aquarium fish and plants, live bait or other exotic animals into the wild. If you plan to own an exotic pet, do your research to make sure you can commit to looking after it. Look into alternatives to live bait.

The Lake Hopatcong Foundation Water Chestnut prevention brochureInvasive plant monitoring is one of the most valuable site­-level activities people can support. Contact your local watershed organizations to inquire about watershed monitoring volunteer opportunities. For example, the Lake Hopatcong “Water Scouts” program was established to seek out and remove any instances of the invasive water chestnut species.

If you are a lake or watershed manager, the best way to begin an invasive plant monitoring project is with an expert invasive plant survey to determine which invasives are most likely to be problematic in your watershed and identify the watershed’s most vulnerable areas. Contact us to learn more.


Documenting and Reporting:
It’s important to learn to identify invasive species in your area and report any sightings to your county extension agent or local land manager. For example, in New Jersey there is the Invasive Species Strike Team that tracks the spread of terrestrial and aquatic invasives and works with local communities in the management of these species. Additionally, consider developing a stewardship plan for your community to help preserve its natural resources. Princeton Hydro’s team of natural resource scientists can help you get the ball rolling by preparing stewardship plans focused on controlling invasive species and protecting the long-term health of open spaces, forests habitats, wetlands, and water-quality in your community.

Spreading the word:
Many people still don’t understand the serious implications of invasive species. Education is a crucial step in stopping the spread of invasives, which is why it’s so important to talk with your neighbors, friends and family about the hazards and ecological/economic impacts of invasive species.

Also consider talking with your community lake or watershed manager about hosting an educational workshop where experts can share their knowledge about invasives specific to your area and how best to address them. Princeton Hydro’s Director of Aquatic Programs Dr. Fred Lubnow recently gave a presentation to the Lake Hopatcong Foundation titled, “Invasive Species in Watershed Management.” View it here.


We encourage you to share this article and spread your invasive species knowledge so that together we can help stop the introduction and spread of invasive species.

This Month’s Events: March Update from Princeton Hydro

Princeton Hydro is proud to participate in a number of exciting conferences throughout March. The conferences, which take place in Pennsylvania, New Jersey and Virginia, cover a wide variety of topics centered around protecting water resources.

March 2: New Jersey Conservation Rally

The 22nd Annual NJ Land Conservation Rally is a one-day educational conference about preserving open space and farmland in New Jersey. The event consists of training workshops, roundtable discussions, a keynote speech from David Case, author of “Nature of Americans,” exhibitors, and a farmers market.

Princeton Hydro, a proud sponsor of the rally, is giving two presentations:
  • “Recognizing The Power of Dam Removal To Reconnect & Restore Our Ecosystem”
    The Nature Conservancy ’s River Restoration Manager Beth Styler Barry and Princeton Hydro’sDirector of Engineering Services Mary Paist-Goldman , P.E. will present the most effective ways to approach a comprehensive, all-inclusive dam removal in New Jersey, with particular emphasis on the Musconetcong Watershed.
  • “Nonprofit Social Media Hacks”
    Rally Planning Committee member Lindsay McNamara and Communication Strategist for Princeton Hydro Dana Patterson present ways to punch up your social media presence. The course is designed for social media beginners and experts alike, and will cover cross-channel techniques to help increase engagement, event attendance, and social buzz around your organization.



March 4 – 6: Virginia Water Conference

Held by the Virginia Lakes and Watershed Associationand the Virginia Floodplain Management Association, the Virginia Water Conference will host 400 participants, and will include exhibits and breakout sessions on topics ranging from floodplain management to dam safety to water resource engineering.

Princeton Hydro’s Dr. Fred Lubnow, Director of Aquatic Programs, and Michael Hartshorne, Senior Limnologist, are conducting a Water Quality and Quantity breakout session titled,  “A Limnological Assessment of a 250-Acre Impoundment in Virginia for the Consideration of Nutrient Inactivation.”



March 7 – 8: PA Lake Management Society Conference

The Pennsylvania Lake Management Society is hosting its 28th annual conference during which lake professionals, students, recreation enthusiasts, lakeside residents and community members will come together to explore a variety of topics related to managing lakes and reservoirs. Visit the Princeton Hydro booth to discuss the latest advancements in pond, lake and watershed management.

The conference offers a collection of professional presentations, workshops and panel discussions. Princeton Hydro is giving two presentations during the conference:

  • “Continued Management of Hydrilla in Harveys Lake, Luzerne County, Pennsylvania”
    Lead by Michael Hartshorne, Senior Limnologist, and Scott Churm, Associate: Director of Aquatic Operations
  • “Conducting a Nutrient Inactivation Treatment for Internal Phosphorus Load Control for a Small Glacial Lake in Northern Pennsylvania”
    Lead by Dr. Fred Lubnow, Director of Aquatics Programs



March 10: Schuylkill Watershed Congress

The Watershed Congress is an annual event that seeks to advance the best available information and techniques for protecting and restoring watersheds by combining science, policy, and practical applications into one program.

The one-day conference offers a keynote discussion on Landscape-Scale Forest Loss in the Delaware Basin, 21 concurrent sessions covering a broad range of watershed topics, poster sessions and exhibits. Dr. Fred Lubnow‘s breakout session, titled “Ecology/Management of Cyanotoxin Producing Blue-Green Algae in the Schuylkill River,” reviews the basic ecology of nuisance blue-green algae and how to monitor, manage and prevent cyanotoxins particularly in potable water supplies.



March 15: Land Ethics Symposium

The theme for this year’s 18th Annual Land Ethics Symposium, which is presented by Bowman’s Hill Wildflower Preserve, is “Creative Approaches for Ecological Landscaping.” The conference will focus on ways to create low-maintenance, economical and ecologically balanced landscapes using native plants and restoration techniques.

Participants can take part in presentations, for which continuing education credits are available, on topics, including Installation and Management of Stormwater Basins, Landscaping for Carbon Storage and Resilience, and Watershed Restoration. The conference also offers a variety of networking events and an exhibitor hall. Princeton Hydro, a “Friends Sponsor” of the event, will have an exhibitor table. We hope to see you there!



March 19: SAME Philadelphia Post Small Business Conference

The Philadelphia Post is hosting its 12th Annual Small Business Conference and Industry Day, which aims to promote engagement between agency, industry, and small businesses. The program consists of networking events, small business exhibits, a variety of speakers and much more.

The Society of American Military Engineers (SAME) gives leaders from the A/E/C, environmental, and facility management industries the opportunity to come together with federal agencies in order to showcase best practices and highlight future opportunities for small businesses to work in the federal market. If you’re in attendance, please stop by the Princeton Hydro booth.


Princeton Hydro Founder Receives Lake Management Achievement Award

We’re thrilled to announce that Princeton Hydro Founder Dr. Stephen J Souza received the North American Lake Management Society’s “2017 Lake Management Success Stories Award” for his work with Lake Mohawk.

While accepting his award Dr. Souza stated, “this would not have been possible had it not been for the foresight of the Lake Mohawk Country Club and the support we have received over the years from the Lake Board, the current General Manager Barbara Wortman, Steve Waehler and the Lake Committee, Ernie Hofer and Gene DePerz of the Lake Mohawk Preservation Foundation, and of course the late Fran Smith.”

Steve went on to thank his staff at Princeton Hydro, especially Chris Mikolajczyk and Dr. Fred Lubnow, for their efforts over the years “collecting and analyzing a variety of lake data and implementing the innovative restoration practices responsible for the lake’s water quality improvements.”

Since 1990, Dr. Souza has worked with the Lake Mohawk Country Club and the Lake Mohawk Preservation Foundation to develop and implement successful lake management strategies to restore and protect the health of the lake and its surrounding watershed.

The NALMS award recognizes an individual or team with notable accomplishment of lake and reservoir management efforts that demonstrate improvements in lake/reservoir condition or watershed management in a cost-effective manner.

Many thanks to Lake Mohawk for the continued partnership and steadfast commitment to water quality. And, thanks to NALMS for bestowing Dr. Souza with this great honor.

Click here to see the complete 2017 awards recap from NALMS.