Pollution & Runoff

What is Pollution & Runoff?

Pollution and runoff are land-based problems that flow into the ocean — often without us even noticing.

Whenever it rains, water runs off streets, farms, factories, and cities — carrying trash, chemicals, fertilizers, sewage, and plastics into rivers and eventually the ocean.

This pollution ends up right where coral reefs live — along coastlines and shallow waters.

How Pollution affect Reefs?

Nutrient Pollution → Algae Overgrowth

  • Fertilizers used on farms or lawns contain nitrogen and phosphorus.

  • These nutrients cause harmful algae blooms in the ocean.

  • Algae grow too fast → Block sunlight → Smother corals.

Without sunlight, corals can’t photosynthesize and get energy.

A plastic bag floating underwater above a coral reef.

Sediment Runoff → Coral Suffocation

Construction, deforestation, or farming causes loose soil to wash into the ocean.

Sediments cloud the water and choke corals by covering them in mud.

Four bottles of sunscreen lotion with orange packaging labeled 'SUN screen SPF 30+' on a sandy beach with palm trees and ocean in background, bright sunlight.

Sunscreen causes coral bleaching!

Satellite image of a large body of water with dark blue and greenish swirling patterns, possibly a river delta or coastal area with sediment and algae.

Plastic Pollution → Physical Damage

  • Floating plastics (bags, bottles, fishing nets) get stuck on reefs.

  • Plastics break coral branches, cut into tissue, and block growth.

  • Microplastics can even be ingested by marine life.

Logs of wood stacked on dirt ground in a wooded area, with a yellow bulldozer parked nearby.

Toxic Chemicals → Coral Poisoning

Pesticides, oil spills, industrial waste, and sewage introduce harmful substances into reef waters.

Some chemicals directly damage coral cells.

Certain sunscreen chemicals (like oxybenzone) can even cause coral bleaching.