Published on OpenChannels (https://www.openchannels.org) Aquaculture and marine ecosystems: Friend or foe? Aquaculture production is an increasingly important component of global seafood production. Seafood production from aquaculture has expanded nearly six-folds ince 1990, while capture fisheries production has remained relatively stagnant. According to the UN Food and Agricultural Organization’s most recent analysis of global fisheries and aquaculture, seafood production from aquaculture [i] (excluding seaweeds) exceeded production from marine capture fisheries for the first time in 2016. Aquaculture’s reputation is mixed, however. It obviously has the potential to feed many people, but it has is associated with an umber of observed and potential negative environmental impacts, including: Altering and destroying habitat, such as mangrove forests, for aquaculture facilities Escapes of farmed species into the wild, enabling species invasions and altering the genetics of wild populations Spreading diseases and parasites to wild populations Releasing fecal waste, uneaten food, and pesticides into the local environment, decreasing water quality Contributing to the overfishing of wild fish populations because of the use of wild fish to feed farmed fish. This negative view obscures the incredible diversity of aquaculture types and their diverse interactions with marine environments. Aquaculture enterprises vary in: What species are cultivated (e.g., seaweeds, mollusks, crustaceans, finfish) and what they feed on (e.g., whether they are photosynthesizers, filter feeders, deposit feeders, herbivores, carnivores) How intense production is (e.g., total biomass per cage, the degree to which fertilizer and supplementary feeds are used) The type of environment production takes place in (e.g., freshwater streams or lakes, fully enclosed tanks, ponds, intertidal, sheltered bays, open ocean, sea pens, ponds, tanks). Careful siting and management of aquaculture facilities can avoid many of the negative impacts listed above, and new research is calling attention to how many types of aquaculture (particularly that of primary producers and filter and deposit feeders) can provide conservation benefits (e.g., serving as de facto marine protected areas and alleviating wild harvest through replacement or supplementation) and a range of other ecosystem services (e.g., providing habitat, removing excess nutrients in the water column, attenuating wave energy, and sequestering and storing carbon). In this issue we feature five areas where aquaculture’s interactions with marine ecosystems (and/or our understanding of them) are evolving. We interviewed experts about recent research and developments related to: Ecosystem services that marine aquaculture can provide Ecosystem implications of offshore aquaculture and integrated multi-trophic aquaculture Whether aquaculture is reducing pressure on wild finfish and invertebrate stocks Aquaculture food sources and their implications for the marine environment. We also speak with a biotechnology researcher about thec urrent status of “cellular aquaculture” – the cultivation of seafood tissue in a laboratory or factory envrionment rather than in an aquatic environment. Rebecca Gentry: Marine aquaculture can remove nutrients Editor’s note: Rebecca Gentry is a postdoctoral researcher in the Department of Geography at Florida State University. Her research focuses on spatial ecological and socioeconomic questions related to marine aquaculture development. The Skimmer: In a recent paper, you reviewed research on a variety of ecosystem services that marine aquaculture can provide in addition to fulfilling its principal commercial objectives of providing food, pharmaceuticals, and other products. These additional ecosystem services include augmenting wild fisheries catches, sequestering carbon, regulating ocean acidification, protecting coastlines, removing nutrients from the water, improving water clarity, and providing artificial habitat. For which of these services is there the strongest evidence right now, and what types of aquaculture provide those services? Gentry: In our research we found nutrient removal to be the most thoroughly documented ecosystem service provided by marine aquaculture (aside from directly producing food and other materials). This ecosystem service has been widely studied using a range of techniques, including laboratory studies, modeling exercises, and direct measurement of nutrient removal. Algae and bivalves (e.g., clams and mussels) are the most commonly studied species with regard to nutrient removal. But we found that there is evidence for nutrient removal for a range of other species, such as polychaetes and sea cucumbers. Although the potential for nutrient removal is promising, it is important to remember that many types of marine aquaculture (such as most types of finfish farming) add nutrients to the environment and that even some species that are noted for their nutrient removal ability (e.g., bivalves) can also release nutrients into the water column. Understanding that different species interact with the environment in a variety of ways can help inform marine aquaculture development that maximizes ecosystem service benefits and minimizes negative environmental impacts. The Skimmer: If aquaculture can provide these other ecosystem services, it would be optimal for ocean planning to begin to incorporate consideration of them when siting aquaculture. Are there currently any examples of entities siting aquaculture in ways that maximize other ecosystem services? Gentry: There are certainly places, such as Jamaica Bay in New York, that are usingr estorative aquaculture techniques (e.g., aquaculture methods used to promote ecosystem health) to harness the water quality, substrate stabilizing, and habitat provisioning services provided by shellfish. There is also continued interest in integrated multi-trophic aquaculture (IMTA), the co-locating of farms of different species together so that the wastes from one type of farming can be assimilated by other species (e.g., the culturing of finfish, mussels, and seaweed together). [Editor’s note: Read more about IMTA here.] There are IMTA farms in places ranging from Sanggou Bay, China, to pilot projects in the Bay of Fundy, Canada. Most marine spatial planning for marine aquaculture that I am aware of has focused on avoiding the negative effects of marine aquaculture development, but I think that future planning would benefit from integrating the ecosystem services from aquaculture into the process. One example of the types of analyses needed to do this include a 2014 project that mapped locations in the Maryland state waters of the Chesapeake Bay where shellfish aquaculture could contribute to water quality goals and coastal zone enhancement. Hot off the presses: Global analysis of locations for restorative aquaculture A paper published in October 2019 provides a global analysis of locations where shellfish and seaweed aquaculture have the greatest potential to restore coastal ecosystems and provide benefits to people. Researchers found the greatest opportunities for restorative shellfish aquaculture in Oceania, North America, and Asia, and the greatest opportunities for seaweed aquaculture distributed throughout Europe, Asia, Oceania, and North and South America. View the map. Gesche Krause: Siting aquaculture offshore can reduce environmental impacts and stakeholder conflicts Editor’s note: Gesche Krause is a social scientist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Researcher in Germany. Her research focuses on the social dimensions of marine resource use and social and economic dimensions of sustainable aquaculture. The Skimmer: Can you tell us a little bit about the status of offshore aquaculture right now? Krause: As the global population increases, the growing demand for seafood and stagnating supply from capture fisheries creates pressure on aquaculture to fill this gap. Aquaculture production has grown at an average rate of more than 6% annually over the past decade, and today, aquaculture supplies over half of the seafood consumed globally. Further expansion of aquaculture in nearshore environments is difficult, however. Coastal populations and maritime uses have soared in abundance and intensity over the past few decades, and there is tremendous competition for marine space. In Europe, this has created scope to research radical new ways of using marine space efficiently, such as the recently completed EU-funded Multi-Use in European Seas (MUSES) project. As a result of this new thinking, offshore aquaculture is gaining prominence. Situating aquaculture farther offshore can reduce both the environmental impacts on and the environmental impacts from aquaculture (e.g., nutrient input from terrestrial systems and nutrient effluents from aquaculture) as well as reduce stakeholder conflicts. Moving aquaculture offshore may also enable the large-scale growth in the aquaculture sector necessary to enhance food security for a growing world population. [ii] Several industrialized countries – including China, South Korea, and Norway – are rapidly developing futuristic open ocean finfish systems. For instance, in 1 Norway, the government granted production licenses, known as “development licenses”, to companies that committed themselves to developing prototypes of installations for offshore salmon (Salmo salar) aquaculture. Once the prototypes are developed, the companies can convert the development licenses