Progress and knowledge gaps in ocean acidification and aquacultured seaweeds

ocean acidification

This study reviews progress and knowledge gaps in ocean acidification and aquacultured seaweeds and concludes current knowledge gaps regarding mitigation approaches are unbalanced and mostly focused on seaweed monitoring and cultivation methods. Photo of seaweed farming at Uroa, a fishermen’s village on Zanzibar’s east coast, by Moongateclimber, via Wikimedia Commons.

The global seaweed aquaculture industry contributes significantly to the production of various downstream and upstream products like food, biopolymers, cosmetics, nutraceuticals, bioenergy compounds, and pharmaceuticals. And the production of seaweed-based biofuel as an alternative to fossil fuel has managed to reduce up to 1,500 tons of carbon dioxide per square kilometer per year when compared to emissions from fossil fuels. Among its other functions, the open ocean aquaculture of seaweeds provides shoreline protection from storms and waves.

Seaweed production can also help to reduce ocean eutrophication by absorbing nutrients required for seaweed growth. With a wide distribution of biomass at the global level, Seaweed Aquaculture Beds (SABs) have the potential to at least act as a temporary carbon sink to mitigate the immediate effects of climate change. This is due to the capacity of seaweeds for carbon assimilation and accumulation, and carbon dioxide sequestration in a relatively short period.

On the other hand, there is evidence indicating that certain naturally growing seaweeds have the capacity for carbon sequestration and accumulation, which can be exported and buried in deep-sea regions. However, with the elevation in atmospheric carbon dioxide, ocean acidification (OA), as one of the impacts of climate change, will negatively affect entire marine systems. Although this is a globally pressing matter, the discourse on the potential ecological or economic impacts of seaweed production is still limited.

The physiological responses of non-calcifying seaweed towards OA are species-specific and inconsistent at different developmental stages, mostly due to different carbon-uptake strategies. Furthermore, the interactive effects of OA and other environmental variables such as temperature complicate any definitive prediction about the exact impacts of OA effects on fleshy seaweed.

This article – adapted and summarized from the original publication (Hengjie, T. et al. 2023. Ocean Acidification and Aquacultured Seaweeds: Progress and Knowledge Gaps. J. Mar. Sci. Eng. 2023, 11(1), 78) – discusses how the increase in dissolved carbon dioxide with pH variation will affect the physiological responses of aquacultured seaweeds.

Mohammad Rozaimi, Global Seafood Alliance, 17 January 2023. Full article.

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