1. Characteristics of Coastal Waters

2. Characteristics of Coastal Waters
Salinity – freshwater runoff does not mix well with coastal seawater
Halocline – represents salinity variations with depth in water column
Isohaline – uniform salinity from surface to deeper layers

3. Characteristics of Coastal Waters
Temperature – coastal region surface water has restricted mixing
Isothermal – water temperature is uniform throughout water column
Thermocline – represents temperature variations with depth

4. Temperature Variations in the Coastal Ocean

5. Characteristics of Coastal Waters
Coastal Geostrophic Currents
Move in circular path
Generated in coastal areas by wind and runoff
Wedge of freshwater runoff on coast generates surface flow towards open ocean
Coriolis effect deflects flow

6. Characteristics of Coastal Waters
Coastal Geostrophic Currents
Northern Hemisphere – path curves northward on western coasts and southward on eastern coasts
Opposite in Southern Hemisphere
Davidson Current – coast of Washington and Oregon
More strongly developed during rainy season

7. Characteristics of Coastal Waters

8. Estuaries
Origin of estuaries – sea level rise after glacier retreat began 18,000 years ago
Four types of estuaries based on geologic origin

9. Estuaries
Coastal plain estuary – forms as sea level rises and floods existing river valleys
Chesapeake Bay
Fjord – forms as sea level rises and floods existing glaciated valleys
Coasts of Alaska, Canada, New Zealand, Chile, and Norway

10. Estuaries
Bar-built estuary – shallow and separated from open ocean by sand bars deposited parallel to coast by wave action
U.S. Gulf coast and East Coast
Tectonic estuary – forms when folding or faulting rocks generates downdropped area
San Francisco Bay

11. Estuaries Classified by Geologic Setting

12. Water Mixing in Estuaries
Vertically mixed estuary – shallow, low-volume. Net flow from head to mouth of estuary
Slightly stratified estuary – salinity increases from head to mouth at all depths. Two distinct layers
Highly stratified estuary – deep with upper-layer salinity increasing from head to mouth
Salt wedge estuary – wedge of salty water from ocean moves in under river water

13. Classifying Estuaries by Mixing

14. Estuaries and Human Activities
Most threatened where human populations are large
Estuaries are important breeding grounds and nurseries for many marine animals
Human activities can damage estuarine environments

15. Estuaries and Human Activities
Columbia River Estuary
Principal conduit for logging industry
More than 250 dams constructed
Increased sediment load
Dredging of sediment carries increased pollution risk

16. Estuaries and Human Activities
Chesapeake Bay
Slightly stratified estuary
Large seasonal changes in salinity, temperature, and dissolved oxygen
Maximum freshwater river flow in spring

17. Estuaries and Human Activities
Chesapeake Bay
Waters may become anoxic from May through August
Major kills of commercially important blue crabs, oysters, and other bottom-dwelling organisms
Increased nutrients from sewage and agriculture causing algal blooms and environmental issues

18. Lagoons Protected, shallow water bodies landward of barrier islands
Restricted circulation with ocean
Three distinct zones
Freshwater zone near head
Transitional zone in middle
Saltwater zone near mouth

19. Lagoons Laguna Madre – along Texas coast Hypersaline
Large seasonal temperature and salinity variations
Ocean water flows in wedge over denser lagoon water

20. Marginal Seas Large semi-isolated bodies of water
Result from tectonic events that isolated ocean crust between continents or created behind volcanic island arcs
Mediterranean Sea
Caribbean Sea

21. Mediterranean Sea Remnant of ancient Tethys Sea
Shallow and narrow connection to Atlantic Ocean and Black Sea
Strait of Gibraltar
Bosporous
Underwater sill separates Mediterranean into two major basins
Sill restricts flow, resulting in strong currents

22. Mediterranean Sea

23. Mediterranean Sea Mediterranean Circulation
Unique pattern caused by Middle East heat
Large surface inflow from Atlantic Ocean to replace evaporated surface water flows along north African coast, spreads
Remaining Atlantic water flows eastward to Cyprus
Water sinks and becomes Mediterranean Intermediate Water
Temperature of 15oC (59oF) and salinity of 39.1 ppt
Flows westward at depth of 200 to 600 m (660 to 2000 ft)
Temperature drops as it reaches Gibraltar
Mediterranean Circulation is opposite that of most estuaries

24. Mediterranean Circulation

25. Issues Facing Coastal Wetlands
Wetlands – ecosystems with water table close to surface
Generally saturated
Can be freshwater or coastal
Coastal wetlands occur along margins of costal waters, including estuaries, lagoons and marginal seas
Include swamps, tidal flats, coastal marshes, and bayous

26. Types of Coastal Wetlands
Salt marshes
Between 30 and 65 degrees latitude
Support salt-tolerant grasses and other halophytic low-lying plants
Along many coasts

27. Types of Coastal Wetlands
Mangroves
Tropics below 30 degrees latitude
Salt-tolerant mangrove trees, shrubs, and palms
Tall tripod-like root systems
Caribbean, Florida, Southeast Asia

28. Distribution of Salt Marshes and Mangroves

29. Characteristics of Coastal Wetlands
Home to diverse plants and animals
Highly productive ecosystems
Nurseries for more than half of commercially important fish species in southeastern U.S.

30. Characteristics of Coastal Wetlands
Soak up nutrients that run off farmlands
Remove inorganic nitrogen compounds and metals from environment
Protect shorelines from erosion
Dissipate coastal wave energy
Absorb excess water

31. Serious Loss of Valuable Wetlands
More than half of U.S. wetlands have vanished
Filled in and developed
U.S. Environmental Protection Agency (EPA) established Office of Wetlands Protection (OWP) in 1986
Future sea level rise predicted to exacerbate wetland loss

32. Serious Loss of Valuable Wetlands