1. Wetlands: nature’s unique aquatic systems
Allison Parnell
Coastal & Wetlands Ecology Lab
Texas A&M University at Galveston

2. A transition zone between land and water bodies;
WHAT ARE WETLANDS?
A transition zone between land and water bodies;
neither “land” nor “water”.
Refers to a variety of habitats:
Coastal salt marshes
Forested swamps
Freshwater marshes
Brackish (intermediate salinity) marshes
Photo: A.R. Armitage
3 distinguishing characteristics define wetlands:
Hydrology-presence of water
Hydric soils-soils that are anoxic
Hydrophytic vegetation

3. All marshes are wetlands BUT not all wetlands are marshes.
WHAT ARE WETLANDS?
All marshes are wetlands BUT not all wetlands are
marshes.
Wetlands can be divided into two main habitats:
Marshes-dominated by herbaceous (non-woody) vegetation
Example: salt marsh
Swamps-dominated by trees
Example: Cypress -tupelo
swamp
Photo: A.R. Armitage
Photo: Conservationfund.org

4. SALTWATER VS FRESHWATER WETLANDS
Salt marshes are regularly tidally inundated.
Some fully marine (salinity ~32‰).
Many are estuarine-where freshwater from rivers or streams mixes with ocean water (Gulf of Mexico water).
Estuarine marshes result in brackish salinities (~0.5-30‰).
Brackish conditions may be temporary (only after large rain events) or may be constant if nearby source of freshwater (river output).

5. ARE WETLANDS ESTUARIES?
An estuary is defined by Pritchard (1967) as:
“a semi-enclosed coastal body of water which has a free connection with the open sea and within which seawater
is measurably diluted with freshwater derived from land drainage”.

6. ARE WETLANDS ESTUARIES?
Upper Texas Coast
River discharge
Salt marsh
Tidal flooding
Photo: A.R. Armitage
Photo:

7. SALTWATER VS FRESHWATER WETLANDS
Swamps remain flooded for extensive period of time and may only dry out occasionally.
Occur in low lying areas of floodplains (depressions).
Dominant source of water is from overbank flooding or may be runoff from precipitation.

8. INHABITANTS OF SALTWATER WETLANDS
Vegetation:
Cordgrass of the Spartina genus most prominent.
Smooth cordgrass-low elevation.
Maritime saltwort-mid elevation.
Indian blanket, Fire wheel-upland elevation.
Maritime saltwort
Indian Blanket, Fire wheel
Smooth cordgrass
Photos: A.R. Armitage

9. INHABITANTS OF SALTWATER WETLANDS
Invertebrates:
Shrimp, fiddler & blue crabs & oysters.
Vertebrates:
Waterfowl, wading & shore birds.
Variety of fish species.
Alligators, bobcats, raccoons, snakes & river otters.
Photo: chesapeake-bay.org
Photo: flickr.com
Photos: A. Parnell
Photo: coolcreatureshotplanet.com

10. INHABITANTS OF FRESHWATER WETLANDS
Vegetation:
Water tupelo & bald cypress-dominant trees.
Water hickory, water locust, black tupelo & many others are common to swamps.
Water tupelo
Bald cypress
Water locust
Water hickory
Photo: jcho.masgc.org
Photo: statesymbolsusa.org
Black tupelo
Photo: forestryimages.org
Photo: aggie-horticulture.tamu.edu
Photo: my-photo-gallery.com

11. INHABITANTS OF FRESHWATER WETLANDS
Invertebrates:
Variety of insects (flies, beetles, dragonflies & damselflies).
Spiders & scorpions.
Mollusks-slugs & snails & freshwater bivalves.
Vertebrates:
Bald eagles, woodpeckers, ducks & wading birds.
Variety of reptiles & amphibians.
Bats, rabbits, beaver, foxes & deer.
Variety of freshwater fish species (gars, catfish, bass & minnows).
Photos: C. Nunnally
Photo: permies.com
Photo: A. Parnell
Photo: ecotravel.ctaudubon.org

12. THE IMPORTANCE OF WETLANDS
Ecological:
In coastal areas nurseries for estuarine organisms, habitat for migratory birds & spawning & feeding areas for recreational and game fish species.
Wetlands support regional biodiversity-threatened &
endangered species.
Photo: fws.gov
Photo: tpwd.state.tx.us
Wetland plants help improve water quality & may take up CO₂ from the atmosphere and subsequently influence climate change patterns.

13. THE IMPORTANCE OF WETLANDS
Economic:
Coastal wetlands reduce wave energy subsequently reducing flooding and protecting shorelines from erosion.
Inland wetlands store floodwaters thus controlling flood damage and erosion and stabilize river flows & groundwater levels.
Salt marshes-oyster production, commercial fisheries (>$400 million/year), employ ~30,000 coastal residents , sport fishing ($2 billion/year industry).
Swamps-contribute to the timber & crayfish industry.

14. THE IMPORTANCE OF WETLANDS
Social:
High biodiversity in wetlands provide fishing, nature tourism (kayaking & boating), hunting & bird watching.
Photo: txstate.edu
Photo: A. Parnell
Photo: bird-watching.purzuit.com

15. Questions?
Photos: A. Parnell