Across

1. Zooplankton and algae, for example, are this sze.
6. Boss of the ship.
11. Metals that normally occur at very low levels in the environment.
13. Type of shark said to inhabit river mouths.
16. Toxic chemical element with the symbol Hg.
17. The ___________ gradient describes the water at a river mouth as it gets more salty flowing out to sea.
18. Two rivers join at the rivermouth. One is the Pará, but what is the other?
19. Name of the research vessel for Amazon Geotraces.
20. Colour of the water where the Amazon first mixes with the sea water.

Down

2. Crustacean very common in mangroves.
3. Equipment used for collecting water samples.
4. Metal essential for all life.
5. Plants adapted to wet soils, salt water and periodically submerged by the sea.
7. A type of plankton.
8. Tidal mouth of a large river.
9. Marajo island has 430,000 of these!
10. City at the mouth of the Amazon.
12. Adjective for an animal that can tolerate a wide range of salinity.
14. Colour of the Amazon River.
15. Equipment used to take sampls of ocean sediment.