Freshwater & Marine Ecosystems

Eutrophic lakes are characterized by...

• low nutrients, low oxygen
• low nutrients, high oxygen
• high nutrients, low oxygen
• high nutrients, high oxygen

Which zone contains the most life in a lake or pond?

• Littoral zone around the shoreline
• Profundal zone in the deep and dark
• Benthic zone in the sediment
• Limnetic zone in the open lake as far as light reaches

Plankton are NOT....

• top carnivores of pond food webs
• tiny, microscopic organisms
• easy prey for other aquatic life
• producers

True of False: The temperature of the ocean water decreases as the depth of the water increases.

• True
• False

An area where fresh water from streams and rivers spills into the ocean is called an _____________.

• plankton
• estuary
• sargassums
• coral reefs

Estuaries

• are always saltwater ecosystems

• are always freshwater ecosystems

• are ecosystems where both fresh water and salt water are present

• prevent the development of salt marshes

land consisting of marshes or swamps

• Pond

• Stream

• Wetland

• Tributary

Which is NOT a freshwater ecosystem?

• a river
• a lake 
• an estuary
• a stream

Estuaries form where 

• a lake evaporates
• a river meets the sea
• a river becomes dammed
• a wetland becomes filled in

Estuary water should have 

• less salt than the ocean
• more salt than the ocean
• no salt