AP Enviro: Aquatic Biomes

Aquatic biomes are characterized by different means, such as salinity, depth, and water flow.
They fall under 2 categories: freshwater and marine.
Freshwater includes: streams, rivers, lakes, and wetlands.
- Freshwater biomes have low salinity and are categorized as streams, rivers, lakes, ponds, and freshwater wetlands.
Marine include: estuaries, coral reefs, and the open ocean.
- Marine biomes are characterized by salt water.
- They include:
  - Estuaries/salt marshes
  - Mangrove swamps
  - Intertidal zones
  - Open ocean
The Earth is covered by 70% of water, not all accessible.
Another form of freshwater biome is freshwater wetlands, which are land that is saturated by water for at least part of the year, but shallow enough to support vegetation.
- Many bird species depend on wetlands during migration and breeding seasons.

Rivers and streams, besides being low salinity, are specifically characterized by flowing freshwater.
Fast-moving streams tend to combine, forming rivers, which then slow down.
Streams tend to have few plants and algae, and when combined into a river, more sediments and organic material settle so plant growth can occur.

Lakes and ponds tend to have standing water, and may be too deep to support vegetation except near the shorelines, or the littoral zone.
In deeper lakes there is an area where sunlight penetrates to the deepest it can, known as the limnetic zone.
Floating algae, known as phytoplankton, can live in the limnetic zone.
Where sunlight can’t reach is the profundal zone.
Once you reach the bottom of the lake, pond or ocean, that is the benthic zone.

Lakes with low nutrients are considered oligotrophic.
Lakes with moderate nutrients are considered mesotrophic.
Lakes with high nutrients are considered eutrophic.
Eutrophic lakes can have high concentrations of algae and block light due to high turbidity.

Major Marine Biomes

Estuaries are near coast lines where rivers of freshwater and saltwater from the ocean combine.
- They tend to carry nutrients from rivers to become very productive areas, and can filter contaminants.
Salt marshes similarly contain nonwoody emergent vegetation.
The safety provided by both biomes mean that they tend to be nurseries for fish and other organisms.
Mangrove swamps occur near tropical and subtropical coasts, and are characterized by mangroves with roots that rise above water to survive high salt content.
Intertidal zones are narrow bands of coastline that exist between high and low tide.
- Many species must adapt to extreme temperatures and desiccation.
Coral Reefs are Earth’s most diverse marine biome, found in warm shallow waters beyond the shoreline in tropical regions.
- They are characterized by symbiotic coral species that are prone to coral bleaching.
- Areas of open ocean are deep and far away from the shoreline, where the ocean floor is not visible through the water due to lack of sunlight.