Photo of the Day
Tannin-darkened waters of Rio Negro flowing across the sand on the coast of Brazil
April 24, 2011
Rio Negro, Brazil
This Month in Photo of the Day: Nature and Weather Photos
Water dark with tannin inspired the name Rio Negro, or "black river," which swirls across virgin sand in Lençóis Maranhenses National Park. In the park's ponds, thriving communities of algae can turn the water blue or green.
See more pictures from the July 2010 feature story "A Sea of Dunes".
See more pictures of freshwater »
See more of Your Brazil Photos »
DON'T MISS THE REST OF THIS STORY!
Create a free account to continue and get unlimited access to hundreds of Nat Geo articles, plus newsletters.
Go Further
Animals
- How can you tell if a wild animal really needs your help?How can you tell if a wild animal really needs your help?
- Fireflies are vanishing—but you can help protect themFireflies are vanishing—but you can help protect them
- Could this simple plan save Africa's most mysterious cat?Could this simple plan save Africa's most mysterious cat?
- This ray is vanishing from our oceans—and being made into jewelryThis ray is vanishing from our oceans—and being made into jewelry
Environment
- Why are so many dead whales washing up on the East Coast?Why are so many dead whales washing up on the East Coast?
- What the Air Quality Index measures—and what to do when it’s code redWhat the Air Quality Index measures—and what to do when it’s code red
- Seaweed may play a big role in the fight against climate changeSeaweed may play a big role in the fight against climate change
History & Culture
- Discover Austin, Texas, with a Nat Geo photographer
- Paid Content for Advertiser
Discover Austin, Texas, with a Nat Geo photographer - Soccer is the world's most popular sport. But who invented it?Soccer is the world's most popular sport. But who invented it?
- 2,000 years of shipwrecks discovered on ancient sea route2,000 years of shipwrecks discovered on ancient sea route
Science
- 5 green towers inspired by nature and striving to protect it
- Paid Content for Advertiser
5 green towers inspired by nature and striving to protect it - Sugar doesn’t actually make kids hyper—here’s why so many believe it doesSugar doesn’t actually make kids hyper—here’s why so many believe it does
- When it’s too cold, these octopuses just rewire their brainsWhen it’s too cold, these octopuses just rewire their brains
- What is yerba mate—and is this caffeinated drink really good for you?What is yerba mate—and is this caffeinated drink really good for you?
- Is organic food healthier? That’s the wrong question.Is organic food healthier? That’s the wrong question.
Travel
- 5 of the best new nature books to explore the UK's wild isles.5 of the best new nature books to explore the UK's wild isles.
- 4 wild and wonderful places for outdoor adventures in Canada4 wild and wonderful places for outdoor adventures in Canada
- Discover Austin, Texas, with a Nat Geo photographer
- Paid Content for Advertiser
Discover Austin, Texas, with a Nat Geo photographer