Aquatic Plants: Guardians of Our Shallow Lakes
Native aquatic plant communities protect and improve water quality and clarity in Rice Creek Watershed District waterbodies.
Shallow Lakes in Minnesota
Shallow lakes are bodies of water that are usually less than 15 feet deep. Minnesota contains many of these lakes, there are numerous shallow lakes in the Rice Creek Watershed District. They are important for water quality, flood control, recreation, habitats, and more.
However, they face challenges from pollution, mismanagement, surrounding development, and invasive species, so it's essential to protect and manage them carefully.
One important part of managing these lakes is protecting and encouraging their native aquatic plant communities along the shorelines and in the water.
Continue scrolling to learn more about why these plants are an essential piece of having a healthy shallow lake, clean and clear water, and healthy fish and aquatic life populations within the watershed.
The Role of Native Aquatic Plants in Water Quality
Aquatic plants use nutrients in the water to grow such as nitrogen and phosphorus, making them great for taking up excess amounts. This reduces the availability of nitrogen and phosphorous in the water which can create harmful algal blooms.
They also hold sediment (lake bottom soil) intact through their root systems, preventing sediment from moving into the water. When sediment gets stirred up or "kicked up" into the water that can create clarity and excess nutrient problems. The sediment or soil on the lake bottom contains nutrients like phosphorous and can be released into the water if disturbed.
By providing a protective barrier and preventing sediment from clouding the water, it also allows sunlight to shine through the clear water, thus supporting necessary plant growth.
Overview
Aquatic plants:
- absorb excess nutrients, improving water quality.
- stabilize sediments (aka lake bottom soil), reducing movement and keeping the water clear.
- release oxygen, supporting fish and other organisms.
- limit harmful algae growth, maintaining a balanced ecosystem.
Shallow Lakes and Native Plants Support Native Fish Populations and Other Aquatic Life
These plants offer important habitat and shelter, creating safe spaces for fish to breed, spawn, and find protection from predators. The dense vegetation also serves as a nursery for young fish, providing them with food and a place to grow.
They contribute to improved water quality by absorbing excess nutrients and reducing sediment runoff that come in from the shorelines and surrounding developer areas.
They also supply oxygen through photosynthesis, which puts dissolved oxygen into the water, which is needed for the survival of fish and other aquatic life. No oxygen, no fish.
Shallow lakes have a diverse range of native plants and algae species essential for supporting the overall health and biodiversity of the lake.
Here are some common native plant species found in Rice Creek Watershed lakes:
- Waterweed (Elodea spp.): A submerged aquatic plant that provides cover and food for fish and invertebrates. Its leaves and stems are consumed by various herbivorous fish species.
- Duckweed (Lemna spp.): A floating aquatic plant that reproduces rapidly, forming dense mats on the water surface. Mallards and wood ducks readily feed on it. Turtles and many other aquatic animals eat it as well and some amphibians use it as shelter.
- Cattails (Typha spp.): Emergent plants that grow in the shallow edges of lakes. They provide shelter and breeding grounds for fish and serve as a food source for various invertebrates.
- Filamentous Algae: This type of algae forms long, stringy strands and is an essential food source for many aquatic invertebrates like snails and small crustaceans.
- Green algae (Chlorophyta): Various species of green algae are important as a primary food source for small aquatic organisms like zooplankton, which are consumed by fish and other higher trophic levels.
- White water lily (Nymphaea odorata): Floating plants that provide shelter and shade for fish. Their flowers attract pollinators as well.
- Wild rice (Zizania spp.): Grows in shallow waters. It provides habitat for various aquatic species and serves as a crucial food source for waterfowl, fish, and invertebrates.
- Spadderdock (Nuphar spp.): Also known as yellow pond lily, an emergent plant with large floating leaves. It provides shelter and basking spots for fish and supports various insects.
- Flat-stem pondweed (Potamogeton zosteriformis): An important food source for waterfowl and fish, providing both habitat and nutrition.
- Coontail (Ceratophyllum demersum): A submerged aquatic plant. It offers shelter and habitat for fish and invertebrates.
The availability and abundance of these plants and algae in shallow lakes support the entire food web and ensure the survival of various fish and invertebrate species.
Common Native Aquatic Plants in Rice Creek Watershed District
- Large Leafy Pondweed
- Coontail
- White Water Lily
- Spadderdock
- Green Bulrush
- Soft Stem and Hard Stem Bulrush
- Flat-stemmed Pondweed
- Duckweeds
Below is a graphic showing the various plant communities of a lake and shoreline. There are different categories of plants some in the water and some that grow out of the water.
Source: Michigan State University
Shallow Lakes: Ecosystems for Flourishing Aquatic Plants
Shallow lakes tend to have higher nutrient levels, which helps native aquatic plants grow. Nutrient-rich sediments accumulate in shallow lake bottoms, providing good soil for these plants to flourish. Deep lakes, on the other hand, often have lower nutrient levels, limiting the growth of native plants.
The fluctuation of water levels in shallow lakes creates a environment that favors the establishment of native plants adapted to such conditions.
Sunlight can usually reach the lake bottom because of the shallow depths and helps the growth of plants. Deep lakes, with their greater depth, have reduced light, making it more challenging for plant growth.
The graphic below shows two different pictures of a shallow lake. In the top picture, the lake is clear, and there are lots of plants growing in the water. The water is see-through, and we can see the plants underwater. This is called a "vegetation-dominated clear state."
In the bottom picture, the water is murky and not clear. This is because there are too many tiny plants called phytoplankton in the water. These plants grow a lot when there are too many nutrients in the water. In this state, there are few plants growing underwater, and the bottom of the lake is being stirred up by fish and waves.
Scheffer, Marten. (2001). Alternative Attractors of Shallow Lakes. TheScientificWorldJournal. 1. 254-63. 10.1100/tsw.2001.62.
Sometimes shallow lakes can be clear and full of plants, and other times they can be murky and dominated by phytoplankton. These changes happen because of different things like excess nutrients in the water, how many fish are in the lake, and what humans do around the lake.
The study by Marten Scheffer, called "Alternative Attractors of Shallow Lakes," talks about these different states and what causes the lake to switch between them.
Resources for Aquatic Plant Identification
Visit a Few Shallow Lakes in RCWD
Map Tour Below
Howard Lake
Otter Lake
Spring Lake
Rice Lake
Part of the Lino Chain of Lakes
Lakeshore Owners: Best Practices to Protect Native Aquatic Plants and Improve Water Quality
Promoting conservation practices is important to protecting native aquatic plants in our lakeshores. Limiting chemical use around the lake and using responsible boating practices (for example less wakes/no wake zones) play key roles in protecting these valuable plants. Shoreline stabilization and restoration through planting native plants have additional benefits, as they act as natural filters, preventing erosion and maintaining water clarity by trapping sediments and pollutants. Never kill or remove native vegetation around your shoreline or in the water unless necessary.
Lakeshore owners hold a huge responsibility in protecting and appreciating aquatic plants for their contribution to clean water and good water quality, ultimately ensuring the health and sustainability of our lake ecosystems.
Example of a shoreline with a severe lack of native vegetation and active erosion versus a stabilized shoreline with native plants (Photo 2 from Natural Shore Technologies in Minnesota
Soft Stem Bulrush along Spring Lake shoreline in Spring Lake Park, MN
Three-Square Bulrush along Lake Josephine shoreline in Roseville, MN
Native plants and a natural shoreline on Golden Lake in Circle Pines MN
Preserving Shallow Lake Ecosystems: 10 Actions for Protecting and Restoring Aquatic Plant Populations
Educate and Raise Awareness: Anyone can highlight the importance of aquatic plants in shallow lakes. Host workshops, seminars, and informational sessions to help people understand their ecological benefits. Join local lake associations to advocate for best practices.
Implement Responsible Land Use Practices: Encourage lakeshore owners and communities to minimize runoff and nutrient pollution by using natural landscaping, managing stormwater, and limiting fertilizers and pesticides.
Support Native Plant Projects: Work with local environmental groups or government agencies on native plant restoration. Planting native vegetation along shorelines can prevent erosion or loss of shoreline, provide homes for fish and wildlife, and improve water quality.
Adopt Shoreline Buffer Zones: Encourage lakeshore owners to establish buffer zones with native plants to filter sediments and nutrients, provide wildlife habitat, and prevent erosion.
Implement Invasive Species Management: Prevent invasive plants from displacing native species by encouraging early detection and management.
Advocate for Water Quality Regulations: Support policies and regulations that protect shallow lakes and their native plant populations.
Foster Community Engagement: Involve the community in lake cleanup events and conservation initiatives to cultivate a sense of responsibility for the lake's well-being.
Promote Sustainable Recreation: Encourage responsible recreation to minimize disturbances to native aquatic plants. Respect designated areas and guidelines to protect ecosystems. Use low wake or no wake zones to prevent shoreline erosion.
Collaborate with Experts and Scientists: Seek advice from environmental experts to develop effective management and conservation strategies for aquatic plant populations in shallow lakes.
