Tidal Freshwater Marshes

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Found where major rives come into the ocean carrying a lot of volume.

Definitions:

• Euhaline - "true" marine zone, below 30 ppt salinity
• Polyhaline - 18 to 30 ppt salinity, dominated by grasses like Spartina
• Mesohaline - middle zone, 5 ppt salinity
• Oligohaline - less than 5 ppt salinity, diverse plants and animals, high productivity.  Tidal energy subsidy: a "flushing" effect brings water and nutrients

Distributions:

• 200,000 hectares on the Atlantic Coast (South Atlantic Area)
• 500,000 hectares in the Gulf of Mexico (Associated with the Mississippi River Delta)
• Heavily influenced by human population and human sprawl (Pfesteria piscicida outbreaks are popular here)

Soils and Chemistry:

• Anaerobic soils: no oxygen, no nitrate, not much ammonia
• Cannot support much plant growth
• Lots of organic matter because of slow decomposition (10% to 100% peat)
• No salt problems (no NaCl), no acidic soils (low in nutrients)

Plants:

• Low Tide- Submerged Aquatic Plants: Elodea (Waterweed), Potamogeton (Pondweed), and Nupar
• High Tide- A natural levee: Ambrosia (Ragweed)
• Low Zone- Emergent vegetation: Peltandra (Arrow Arum)
• High Zone- Typha, Spartina, and Zizania (wild rice)

3 Types:

• Mature - ~ 500 years old, peat substrate in the banks
• Floating islands of vegetation or mats
• Areas where new marshes are still building

Floating Marshes: Tigris and Euphrates Rivers have floating marshes. Mats of vegetation that float up and down with the tide are so thick that trees, cattails, and even people live on them. They can also be found in Louisiana.

Animal Diversity:

• Supports largest density and diversity of birds. Houses 280 species of birds, 44 species of ducks and other waterfowl. Supported by the mass amount of food built up in the backs of the marshes.
• Supports a large variety of mammals                                                                                                                        beavers, otters, muskrat, mink, and nutria (an introduced spp that looks like a small beaver or muskrat but is taking over the muskrats habitat)

Fish and Crustacean Life Cycle:

• Catadromous: spawns out at sea (example: eel)
• Anadromous: spawns in freshwater, lives out at sea (examples: striped bass, herring, shad, sturgeons, and some shrimp)

Productivity:

• Produce 10 to 30 tons/dry matter/ hectare/ year (only the plants)
• More species richness, but less productivity
• Soils are exporters of nutrients here: lose nutrients