Climate change is often discussed in terms of rising temperatures, melting ice, and sea-level rise. But scientists at Scripps Institution of Oceanography are drawing attention to another environmental threat happening beneath the surface: the loss of oxygen from our oceans and other bodies of water.
A recent Scripps-led scientific review warns that aquatic deoxygenation—the decline of dissolved oxygen in oceans, rivers, lakes, and streams—could threaten the stability of ecosystems around the world. Researchers argue that oxygen loss is significant enough that it should be considered alongside major global environmental threats such as climate change, ocean acidification, biodiversity loss, and chemical pollution.
Several human activities contribute to the problem. As the planet warms, warmer water holds less oxygen. At the same time, nutrient pollution from sources such as fertilizers and wastewater can stimulate excessive algae growth. When that organic material decomposes, the process consumes oxygen, sometimes creating areas where marine organisms struggle to survive.
The consequences extend throughout the food web. Low-oxygen conditions can alter habitats and threaten everything from microscopic organisms to fish and sharks. Even marine mammals that breathe at the surface can be affected when oxygen loss changes where their prey can live.
What makes this research especially important is that deoxygenation does not occur by itself. It interacts with climate change, pollution, biodiversity loss, and other pressures already affecting marine environments. Scripps researchers are therefore calling for aquatic oxygen levels to receive greater attention in how scientists and policymakers evaluate the health of the planet.
Protecting our oceans requires more than responding to environmental damage after it occurs. Reducing greenhouse gas emissions and nutrient pollution while expanding ocean monitoring can help address the causes of oxygen loss. Research like this demonstrates why continued ocean observation is essential: changes happening underwater can ultimately affect ecosystems—and communities—far beyond the coastline.
Diya Comar