Estuaries: Vital Ecosystems at Risk

Estuaries are where rivers or streams meet the ocean, often bordered by salt marshes or intertidal mudflats. Out of the 32 largest cities in the world, 22 are located on estuaries. These unique habitats are crucial for nesting and breeding of various animals. Additionally, most of the fish and shellfish consumed by humans have spent part of their lives in estuaries. Estuaries also play a vital role in filtering out sediments and pollutants.

However, estuaries are facing numerous threats due to coastal development, introduction of invasive species, overfishing, dams, and global climate change. These factors have made estuaries one of the most threatened ecosystems on earth.

Types of Estuaries

• Salt Wedge: Formed by rivers like the Mississippi, Columbia, and Hudson, where saltwater creates a wedge shape.
• Fjord: Occurs when river input flows into a deep hole, causing freshwater to go over the saltwater. Examples include British Columbia, Alaska, Chile, New Zealand, and Scandinavian countries.
• Slightly Stratified: Tidal flow erases the salt wedge, but the water is still saltier at the bottom.
• Vertically Mixed: Strong tides and weak river flow result in a well-mixed estuary.

Types of Estuarine Habitats

• Oyster Reefs
• Kelp Forests
• Rocky and Soft Shorelines
• Submerged Aquatic Vegetation
• Coastal Marshes
• Mangrove Forests
• Deepwater Swamps and Riverine Forests
• Mud Flats
• Tidal Streams
• Barrier Beaches
• Salt Marshes

Wastewater Treatment

• Bar Screening
• Grit Removal
• Primary Clarifier
• Aeration
• Secondary Clarifier
• Chlorination
• Water Analysis and Testing
• Effluent Disposal

Potable Water Treatment

• Coagulation
• Flocculation
• Sedimentation
• Filtration
• Disinfection

Nitrogen Cycle in Estuaries

• Nitrogen Fixation: Conversion of N2 to NH3 by an enzyme called nitrogenase
• Nitrification: Conversion of NH3 to NO2 by bacteria
• Assimilation: Process carried out by Cyanobacterium
• Ammonification: Conversion of N to NH3 by ammonifying bacteria
• Denitrification: Conversion of NO3 to N2 in wet soils by bacteria

Chemical Analysis Areas

• Salinity
• Temperature
• Aragonite (Calcium Carbonate) Saturation - for Marine Environments, especially coral reefs
• pH
• Turbidity - Water Clarity
• Dissolved Oxygen
• Biochemical Oxygen Demand
• Phosphates
• Nitrates
• Total Solids
• Fecal Coliform - Bacteria from feces