You may have noticed something new in the water at Rockland Lake State Park.  These are floating treatment wetlands!  Read our post below to find out more about these water treatment platforms.

Why are they here? 
In recent years, harmful algal blooms have become common in Rockland Lake. These algae blooms are largely caused by an unhealthy increase in nutrients such as phosphorous in the lake.  The nutrients come from many sources nearby, including excess lawn/garden fertilizers that wash into storm ditches after a rainfall, then drain into Rockland Lake.  One culvert (inlet) with consistently high nutrient levels is located near Parking Field 5 and it was chosen as the location for a new floating treatment wetland.  The goal of adding a floating wetland to the lake is to reduce the amount of nutrients – and by extension, harmful algal blooms – in the lake.

What are they?
Floating treatment wetlands (a.k.a. floating wetlands/islands) help to bring the benefits of natural wetlands to polluted water. They filter water to improve water quality and they provide important habitat for a variety of plants and animals. Floating wetlands can come in different shapes and sizes, but in general, wetland plants are supported atop a buoyant platform, with roots exposed in the lake water below.

What do they do?
Floating treatment wetlands help to create the right balance of submerged and non-submerged wetland habitat based on each individual site’s needs. As the plants grow, they use-up excess nutrients in the water. In addition, communities of beneficial bacteria form a film around the roots, further helping to filter nutrients and pollutants. Higher/lower elevations create areas with varying oxygen levels, promoting these different biological filtering methods. The floating platform blocks sunlight, preventing the growth of algae. Lastly, fish and wildlife enjoy the new addition to their habitat.

Floating wetland materials arrive by truck in late July 2017, photo by State Parks

More floating wetland materials. Plants from a local nursery include: tussock sedge (Carex stricta), swamp rosemallow (Hibiscus moscheutos), Blueflag iris (Iris versicolor), and soft rush (Juncus effuses), photo by State Parks

Floating wetland materials. These special polyester supports will help hold the plants in-place for years to come., photo by State Parks

Constructing the floating wetland! Some of the plants are submerged, while others are elevated on an island., photo by State Parks

One of several floating wetland units., photo by State Parks

Constructing the floating wetland! Units are assembled near the shore, to be later brought to the target location., photo by State Parks.

Another close-up, with thin netting around the edge to protect the young plants from birds., photo by State Parks.

Close-up of a floating wetland unit. Brick weights help keep the plants evenly balanced, with roots below water, photo by State Parks.

Floating wetland at Parking Field 5 culvert, September 2017, photo by State Parks.

Finished floating wetland, installed at Parking Field 5 culvert. The green “spilled paint” look on the water is a harmful algal bloom. Photo from early August 2017, photo by State Parks.

This is the first time that floating treatment wetlands have been used in New York State Parks.  Environmental staff will determine the effectiveness of this project by monitoring water quality changes over time (e.g. harmful nutrient levels and algal blooms by the inlet as well as lake-wide).  If successful, then floating wetlands may be used to help treat stormwater pollution and improve other aquatic habitats in New York.

Post by April Brun, Gabriella Cebada Mora, and Erin Lennon.

Rockland photos by Gabriella Cebada Mora, Aissa Feldmann, Matt Brincka, and Erin Lennon.

Resources

Floating Island/Wetland images and information

US Environmental Protection Agency information on nutrient pollution and harmful algal blooms:
(Website)                   (Video)

NYS Dept. of Environmental Conservation information on fertilizers and how to reduce nutrient runoff:

(Website)                   (Video)