**Abstract**

Climate change is one of the major global concerns jeopardizing human health and wildlife. This event is considered a threat to the marine ecosystem as well. Marine algae are the leading producer in the benthic food chain. Therefore, any change in marine algal communities will disrupt the whole ecosystem. Currently, algal species face significant changes in their abundance and distribution worldwide. Toxic species are frequently invading and causing a phenomenon called the harmful algal bloom, which threatens the seafood industry and public health. This chapter will focus on the significant distribution of algal communities worldwide and the impact of climate change on these marine algal species. Besides, this chapter will shed some light on how these changes affect the marine food chain and ultimately affect human health.

**Keywords:** climate change, harmful algal bloom, Marine algae, public health, seafood
