For too long, the ocean has been viewed as the solution for waste disposal. The practice of collecting and disposing of human waste is what has allowed people to live closely together in densely packed cities, without being hit again and again by devastating epidemics of infectious disease. But in many regions of the world, wastewater management is nonexistent or inadequate, with tremendous consequences to ocean health and human health.

For hundreds if not thousands of years, people have mistakenly assumed that the ocean is vast enough to absorb and dilute human waste without consequence. Historically, scientists have mostly ignored the impacts of human waste, by instead focusing on the role of agriculture and other land-use change in degrading water quality. Consequently, the impacts have not been well documented, and leave us in need of high-quality data.

More recently, scientists have begun documenting wastewater pollution’s role in the decline of coastal ecosystems, including coral reefs, sea grasses, salt marshes, mangroves, and shellfish beds. Scientists have demonstrated how wastewater triggers harmful algal blooms that coat everything in slime, poison the water with invisible neurotoxins, create deoxygenated dead zones that are uninhabitable for fish and other marine life, and shift the ocean’s nitrogen cycle into a low-oxygen mode, which produces nitrous oxide (N₂O) — a potent greenhouse gas 300 times more powerful than carbon dioxide (Breitburg et al., 2018). We are continuing to learn about the complex and negative impacts wastewater pollution has on coastal communities to raise awareness about the threat and identify solutions to end it.