Toward the Establishment of Nature-Based Solution (NbS) Using Seagrasses and Macroalgae to Control Harmful Algal Bloom

The global population is estimated to grow to around 8.5 billion in 2030 and 9.7 billion in 2050, an increase of approximately 2 billion people worldwide in the next 30 years, as the United Nations World Population Prospect 2022 report. To improve global food security, fisheries and aquaculture are crucial in responding to increased seafood demand. However, expanding anthropogenic activities will likely worsen the impact on aquatic ecosystems. Harmful algal blooms (HABs) are a global environmental issue that indiscriminately kill and/or contaminate seafoods. In extreme cases, humans die from exposure to toxic seafood products. Over the past few decades, there has been growing evidence of an acceleration in geographic expansion and an increase in the severity of HABs related to climate change. Therefore, establishing sustainable control measures against HAB outbreaks is urgently needed. Biological control using naturally-living bacteria that kill and/or inhibit the growth of HAB species has been extensively studied worldwide as an environmentally friendly measure. This chapter introduces and discusses the relationship between climate change and HAB outbreaks and countermeasures, focusing on the possibility of controlling HABs using bacteria inhabiting macroalgal and seagrass beds as a Nature-based Solution (NbS), adding value to efforts to establish a carbon-neutral society.