The oceans are missing their rivers
In a rhythm that’s pulsed through epochs, a river’s plume carries sediment and nutrients from the continental interior into the ocean, a major exchange of resources from land to sea. More than 6,000 rivers worldwide surge freshwater into oceans, delivering nutrients, including nitrogen and phosphorus, that feed phytoplankton, generating a bloom of life that in turn feeds progressively larger creatures. They may even influence ocean currents in ways researchers are just starting to understand. … Many of the harms caused by dams are well-documented. They block fish passage and starve subsistence fishers; radically alter natural river regimes and aquatic creatures’ lifecycles; and flood forests, wetlands, villages, and historical sites. … Now scientists are describing another impact that has received relatively little attention but appears to also be profound: Dams block sediment-carrying river pulses into the ocean.