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Habitat Benefits from Shellfish and Seaweed Aquaculture

July 14, 2021

The growing aquaculture industry has exciting implications for Alaskan communities. Research shows aquatic farming provides many ecological benefits.

Close up of kelp from Seagrove Kelp Co Seagrove Kelp Co. located in Doyle Bay, Alaska. Credit: Seagrove Kelp Co.

The growing aquaculture industry has exciting implications for Alaskan communities, both human and marine. In recent years, the State of Alaska has seen a significant increase in aquatic farm applications and notably, the farm acreage amount applied for. According to the 2021 Mariculture Task Force Final Report (PDF, 169 pages), if the state approved all applications currently under review, it would result in approximately an 850 percent increase in the acreage for aquatic farms in state waters over the last five years. Not only does this growth have exciting economic implications, research is increasingly showing the ecological benefits of aquatic farming. As Alaskans apply for more and bigger farms, that means more habitat for everything from crab to salmon smolt to barnacles and mussels.

Tommaso Shellfish farmer
Tommaso Shellfish located near Prince of Wales Island. Credit: Tommaso Shellfish

As with real estate, location is one of the most important considerations in setting up a farm. An understanding of the surrounding ecosystem helps farmers choose the right kind of aquaculture to grow a marketable product while also decreasing potential impacts and maximizing ecosystem services. When combined with their wild counterparts, farmed shellfish and seaweed can positively impact their surroundings. A recent paper by Dr. Seth Theuerkauf and colleagues (PDF, 19 pages) explores the habitat value of shellfish and seaweed aquaculture for fish and invertebrates: “A growing body of scientific evidence indicates that the commercial cultivation of bivalve shellfish and seaweed can deliver valuable ecosystem goods and services, including provision of new habitats for fish and mobile invertebrate species.” For example, a small fish might hide from a predator inside an oyster cage or among cultivated kelp fronds, feeding on mussel spat growing on the lines. Looking across 65 studies, they noted that shellfish and seaweed aquaculture were associated with higher species diversity.

Close up of kelp from Seagrove Kelp Co
Close up of kelp from Seagrove Kelp Co. Credit: Seagrove Kelp Co.

Beyond providing structural habitat and food sources, both shellfish and seaweed positively impact habitat and provide ecosystem services thanks to their own biological processes. Oysters are efficient filter feeders, removing nitrogen from the waters surrounding them and incorporating it into their shells and tissue. An adult oyster can filter up to 50 gallons of water a day. A farm with 100,000 oysters per acre can potentially filter up to 5,000,000 gallons of water per day, per acre. Reduced nitrogen levels in turn reduces rapid growth of harmful algaes that can overwhelm other species and reduce oxygen levels in the water. Algal blooms can lead to die offs in fish, crabs, and other aquatic life. Fortunately, shellfish aquaculture has emerged as a promising, low-cost tool to help improve water quality.

Seaweeds both pull carbon dioxide out of the waters around them and also produce oxygen, greatly benefiting the nearby ecosystem. The harmful effects of ocean acidification on calcium carbonate-dependent species (e.g., oysters, clams, and some plankton) growing near the seaweed is reduced along with the revival of low-oxygen zones that are more prevalent as ocean waters continue to warm.

While Alaskan waters continue to provide healthy habitat for myriad species of marine life, global trends of habitat reduction and stressors, like ocean warming and acidification, will likely impact Alaskan habitat, too. Aquaculture can provide a buffer for species affected by these changes, all while creating jobs in coastal communities and growing healthy, low-impact, sustainable seafood. Alaskan aquatic farms are described as “low to no input” farms because feed, fresh water, and fertilizers aren’t necessary to grow their crops. By raising shellfish and seaweed, farms improve access to local seafood and mitigate harmful effects of excess nutrients, ocean acidification, and provide habitat for our robust fisheries.

Last updated by Alaska Regional Office on November 21, 2022