The Floating Wetlands of Baltimore's Inner Harbor

Baltimore’s Inner Harbor is a welcoming destination for sailors interested in travelling to an urban Chesapeake port with easy waterfront access to its many attractions. The free Charm City Circulator can transport sailors further inland to explore the Baltimore neighborhoods that lie beyond the Waterfront Promenade. In the past several years, sailors may have noticed small green islands floating in front of the World Trade Center and next to the National Aquarium. What are these floating wetlands and why have they been installed in this highly urbanized environment?

 Photo by Laura Bankey/National Aquarium

Hundreds of years ago Baltimore’s harbor shoreline would have been lined with tidal wetlands. Bulkheads and riprap make it difficult to imagine the ecosystem that once existed on this part of the Patapsco. Today it is hard to even tell that it is part of a river. The floating wetlands seek to replicate the “ecosystems services” provided by natural wetlands. Ecosystem services is the new environmental science buzzword for describing value, both intrinsic and to humans, that a natural resource provides.

Floating wetlands are constructed of a buoyant substrate that can support native wetland plants such as Spartina patens (saltmeadow hay), Spartina alterniflora (saltmarsh cordgrass), and Hibiscus moscheutos (marsh hibiscus). Various companies construct the wetlands, and the dimensions can vary. The National Aquarium’s 200-square-foot island was constructed by Biohaven Floating Islands. The floating wetlands installed by the Waterfront Partnership of Baltimore were designed by Biohabitats and constructed with assistance from students at Living Classrooms Foundation. The original Waterfront Partnership wetlands were constructed from recycled plastic bottles, and some even came from the Waterwheel Powered Trash Interceptor at the mouth of the Jones Fall River.

Floating wetlands provide many environmental benefits to water quality and habitat enhancement, which is why the Waterfront Partnership of Baltimore has included them in their Healthy Harbor Initiative. Habitat benefits are the most concrete improvements offered by the floating wetlands. Blue herons, night herons, ducks, eels, and otters have all been observed in or around the floating wetlands. The shading and roots of the plants provide structure and refuge for fish and other nekton (cool science term that means marine and freshwater organisms that can swim freely and range in size from micro to whale). Birds and insects utilize the surface plants for habitat.

The framework of the floating wetlands itself provides a substrate for colonization of a variety of plants and animals. Interestingly, the false dark mussel has been one of the primary mollusk colonizers, a proven powerful filter feeder and water quality enhancer. Other potential benefits include nutrient removal from uptake of the plant roots which could reduce the effects of eutrophication. Heavy metal and contaminant sequestration and sediment trapping are also observable benefits to water quality. These benefits are greater in a more closed system than Baltimore’s Inner Harbor.

Floating wetlands are not going to solve the Patapsco’s water quality issues, though there are plans to install more at various locations around the harbor. Stormwater runoff, which has the biggest effect on water quality, will need to be tackled at its sources. However, the fact that the floating wetlands serve as an educational tool and provider of habitat in a highly urbanized environment is undisputed. The connection to wildlife and the river’s past ecology is now observable from both land and sea.

What can sailors do? You could have your very own floating wetland at your dock or marina! Possible sources for floating wetlands: Magothy River Association; Bluewing; Biohavens Technologies; Biohabitats Inc.

by Pamela Tenner Kellett