Harbor Wetland: Your Questions Answered

On August 9, we welcomed the public to Harbor Wetland presented by CFG Bank, our free outdoor exhibit between Piers 3 and 4. The exhibit mimics a natural salt marsh, the habitat that dominated Baltimore's Inner Harbor centuries ago. Salt marshes keep our water clean by absorbing rain or snow, filtering it slowly and releasing it back into surrounding tributaries. Today, without these natural ecosystems to keep our water clean, water rushes over sidewalks and roads, carrying trash and pollution into the harbor and beyond.

Reintroducing this important ecosystem took trial and error, starting with a 200-square-foot wetland installed in 2010. In 2017, we installed our fourth prototype, the model used as the basis for Harbor Wetland, the 10,000-square-foot exhibit open to the public today. To celebrate, we asked our audience what burning questions they had for our General Curator Jack Cover, who has been with the Aquarium's team since 1987.

Question: What is the long-term vision for Harbor Wetland?

Answer: Our goal was to build a durable, constructed tidal marsh habitat that mimics the natural Chesapeake Bay tidal marsh habitat that existed in this location before Baltimore City's founding and expansion. We hope to set the example for other highly urbanized waterfront cities: restoring biodiversity and ecological function to post-industrial, highly altered waterways is possible. The structure has been built to support living green infrastructure. We will now see how aquatic and terrestrial species use this re-created habitat and will be testing it for long-term durability.

Question: What were the biggest challenges when constructing Harbor Wetland?

Answer: We had to build a durable structure that could be mostly submerged in brackish (partly salty) water, which corrodes strong materials like metal over time. Therefore, the use of metal was minimized, and when metal was required, it had to be 316-grade stainless steel. The support structure is made of fiber-reinforced plastic (FRP), plastic lumber, and high-density polyethylene plastic (HDPE). The support structure had to be rigid yet flexible to withstand wave action.

We also had to build a floating wetland with buoyancy adjustment. As the living biomass grows, so does the weight on the wetland. To keep the wetland from sinking, we have 208 pontoons underneath it, mostly filled with water. We can add air to each pontoon to adjust for added biomass weight. Strategically placed pilings also allow Harbor Wetland to move up and down with the twice-daily tides.

The final challenging aspect was constructing this entire exhibit outside, over the water and in all kinds of weather.

Question: Have any other urban centers in Maryland (or beyond) implemented similar habitat reintroduction in their waterways?

Answer: Yes, groups in Chicago and Boston are constructing floating wetlands in highly urbanized waterways. We are in collaboration with these groups.

Question: What plants did you choose for Harbor Wetland and why?

Answer: We chose two native marsh grasses that are the dominant species in the Bay's tidal salt marshes: smooth cordgrass (found in low marsh areas) and salt meadow hay (found in high marsh areas). Additionally, three native species of woody shrubs were planted in the exhibit's high marsh areas: groundsel tree, marsh elder and bayberry. These species can withstand contact with brackish water and absorb excess nutrients like phosphorus and nitrogen. In addition to helping clean the water, these plants provide habitat for aquatic and terrestrial species.

Question: Which species have you seen on Harbor Wetland that excites you the most?

Answer: Well, seeing a video of a pair of river otters frolicking around the education dock early one morning was highly unexpected. We have found two young diamondback terrapins in the Harbor Wetland habitat as well as snapping turtles and red-eared sliders (a non-native species). Seeing schools of Atlantic silversides, mummichogs and banded killifish swimming in the shallow channels is exciting. I have also seen tiny newly hatched fish (most likely mummichog fry) swimming in the shallow flooded marsh areas, which means small fishes are reproducing in this new habitat.

Question: How long did it take to construct Harbor Wetland?

Answer: Building an exhibit usually occurs behind curtains, but Harbor Wetland came together in broad daylight—literally. The exhibit's construction and planting process took 10 months to complete. Learn more about the scientific methods behind building a wetland that mimics the intricacies of a natural salt marsh before heading to the Harbor to see it in person!

Harbor Wetland is now open to the public as a free and accessible experience available at no cost and without an Aquarium ticket. Harbor Wetland is generally open during the Aquarium's normal operating hours, barring extreme weather or other outdoor conditions. For the safety of all, the exhibit may close unexpectedly in the event of inclement weather conditions and/or when it is dark outside.