Ecosystem #3 The Estuary

What is an Estuary? A semi-enclosed body of water where freshwater and saltwater mix Other names for estuaries: Bay Sound Lagoon Inlet

Estuary Classification Origin Degree of Mixing

Types of Estuaries by Origin Coastal Plain Tectonic Bar Built (or Barrier Island Estuary) Fjord

#1: Coastal Plain Estuary Most common Sometimes called a Drowned River Valley Formed at the end of the last ice age when rising water flooded (or drowned) existing river valleys Examples: Tampa Bay Chesapeake Bay (MD), Narragansett Bay (RI)

Coastal Plain Estuary Chesapeake Bay (MD)

#2: Tectonic Estuary Caused by earthquakes where folding or faulting may create bays with narrow inlets to the sea Examples: San Francisco Bay

Tectonic Estuary

#3: Bar Built Estuary Also called Barrier Island Estuaries These are most commonly barrier islands that are separated from land by a shallow lagoon Usually shallow with reduced tidal action Examples: Common along the Texas and Florida Gulf Coasts and the Outer Banks of NC

Bar Built Estuary

#4: Fjords Valleys that have been cut deeper by moving glaciers and then invaded by the sea Usually narrow, straight, long and with steep sides Examples: Alaska, Canada, Norway, etc.

Fjords

Estuary Classification by Stratification Degree of Mixing

Degree of Mixing? Estuaries can be classified by how the freshwater and saltwater mix The basic flow pattern Freshwater flows on the surface toward the ocean while seawater flows into the estuary below the surface

Most Common Types of Mixing Vertically Mixed Salinity is consistent from top to bottom Slightly Stratified/Partially Mixed Lower layers of water typically saltier than upper layers (Ex. Tampa Bay) Highly Stratified/Salt Wedge Least mixed Forms when a rapidly flowing large river enters the ocean in an area where tidal range is low Example: Mississippi River

Salt Wedge Vertically Mixed Partially Mixed

Use 2 colors to indicate freshwater vs. saltwater and be sure to label In your notes, draw a sketch of what each type of mixing would look like! Use 2 colors to indicate freshwater vs. saltwater and be sure to label

Why are Estuaries Important? Video Clip Record in your notes

Why are Estuaries Important? Habitat for may plants and animals (including land dwellers like humans & birds) Nursery ground Protect water quality by filtering out dirt and pollution Recreation (fish, swim, kayak, bird watch, etc.) Economy (food, fishing charters and other recreation)

Importance Cont’d… Estuaries trap and accumulate sediment that comes from rivers which makes the estuary rich in nutrients (elements & compounds) and biologically productive (lots of plants & animals) What problems can you foresee with this process…

Eutrophication An overabundance of nutrients that causes an ecological imbalance Fertilizer runoff is also trapped in estuaries

What limits productivity in an estuary? White Boards: What limits productivity in an estuary? In other words, what may keep living things from spending time in an estuary?

What Limits Productivity in an Estuary? Organisms must be able to tolerate a wide range of salinities Osmotic stress caused by tides Decomposition depletes the oxygen in nutrient rich sediment The rotten egg smell is a result of sulfides released by anaerobic sulfur bacteria

Everything is Connected! How do estuaries contribute to the productivity of adjacent ecosystems? By increasing the number of individuals that survive to adulthood Safer than the open ocean By providing nutrients while reducing eutrophication & other damage that could make its way out to the open ocean