Urban Aquaculture: Farming the Urban Sea

Conventional aquaculture has rightly earned a reputation for producing low quality seafood at high environmental costs. According to the FAO, major environmental impacts of aquaculture range from changes in benthic communities to the massive eutrophication of lakes. Much of the current controversy centers around inadequate coordination and management of  intensive farming systems, and many do not believe aquaculture can be conducted sustainably.

But not all. A new form of ocean-friendly farming has emerged right outside of New York City. These small-scale vertical farms are designed to grow multiple species of seaweed and shellfish. They go beyond minimizing environmental impacts, instead providing an array of environmental benefits. Brendan Smith, the owner of Thimble Island Oyster Co, the first vertical multi-species ocean farm in Long Island Sound describes the farms as “three-dimensional gardens, where seaweed, mussels and scallops grow at the top of the water column, stacked above oysters and clams below.”

Already restaurants in Manhattan are clamouring for the locally produced seafood.With 91% of the seafood consumed in North America imported from foreign waters there is increased interest in restoring local watersheds to full productivity. While local seaweed might seem like a strange concept, a native seaweed like Nori contains more vitamin C than orange juice, more calcium than milk, and more protein than soybeans.

These farms do more than grow food, they restore ecosystems rather than deplete them. Vertical aquaculture systems can potentially be much more sustainable and much less intensive compared to land-based counterparts. Seaweed and shellfish require no inputs — no land, no fertilizer, no fresh water — and since they grow three-dimensionally, they use space more efficiently.

Shellfish and seaweed also act as filters, drawing out nitrogen and heavy metals from sea water. Excess nitrogen from residential and agricultural activities regularly runs off into marine ecosystems, triggering large-scale algae blooms that deplete oxygen levels, decimate marine life and force beach closures.  A single oyster can filter up to 50 gallons of water a day. This means that even small farms can have measurable impacts on water quality.

One local NY initiative, spearheaded by the Bronx-based nonprofit Rocking the Boat and Charles Yarish of the University of Connecticut, grows kelp and mussels in the Bronx River to  not for food, but instead to filter out mercury and other pollutants. Other local projects are even building oyster reefs to protect New York from storm surges and flooding.

Another interesting component of aquaculture is it’s emerging potential for viable renewable energy production. As one of the fastest-growing plants in the world, kelp is capable of producing over 2,000 gallons of biofuel per acre annually. This is five times more than the ethanol produced by corn and up to 30 times more per acre than soybeans. Companies like RPM Sustainable Technologies are already working with Long Island Sound farmers to source kelp for their biofuel operations.

One billion people live in coastal urban areas, almost 50% of which are threatened by development-related activities. Urban aquaculture has enourmous potential for sustainable urban food, jobs and economies. Check out  Thimble Island Oyster Co for more information.

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