Waterfront Cities Around The World Are Encouraging Marine Biodiversity With Life-Enhancing Designs

Source: Hakai Magazine/Tyee Bridge 

Photo: Chen Hu/Unsplash


I’m swimming under a sidewalk. The cantilevered slab of concrete is a couple of meters over my head, part of Seattle’s Central Waterfront area that is famous for Pike Place Market and the tourist stroll of chowder houses and souvenir shops. It’s not your average sidewalk: it’s been embedded with translucent glass bricks that allow light to hit the seawater. Like many of the other enhancements to the recently rebuilt sea wall, it’s an act of eco-engineering intended to improve marine habitat in the waters of Elliott Bay, in Washington State.

Thanks to the glass bricks, I can see some of the other subsurface innovations. Most obvious is what’s right in front of me: the concrete face of the sea wall itself, which has a cobbled, river stone texture and angled shelves that encourage the growth of algae and invertebrates. Below me, the seafloor has been built up with mesh bags stuffed with rocks, known as marine mattresses; these reduce the water depth and make the sea wall area more hospitable to juvenile salmon, which are evolutionarily programmed to prefer shallow, nearshore waters. As for the light-delivering sidewalk, it’s intended to boost seaweed growth and create a more inviting passage to shade-avoidant salmon smolts.

It’s mid-September, still technically summer. Bobbing in a drysuit and snorkel in the polluted waters of Elliott Bay would not usually be my first choice for ocean recreation, but I’m tagging along with two University of Washington (UW) habitat biologists who are counting fish and other marine creatures near the sea wall to see these enhancements close-up. They’re all elements of the US $688-million Central Waterfront redesign and, together, they help create habitat that more closely mimics a natural shoreline. This includes niches, hidden surfaces, shadow, sunlight, and micro-currents that promote the growth of the tiny organisms young salmon feed on—and shallower waters that provide juvenile fish greater safety from predators.

While the improvements may sound humble, they’ve made Seattle a pioneer in a growing trend: cities that want to have their sea walls and their sea life too.

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Photo: Chen Hu/Unsplash

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