http://dcm2.enr.state.nc.us/wetlands/Coastal_Explorers/cpfmodule/bhi/bhi_marsh2.htmhttp://dcm2.enr.state.nc.us/wetlands/Coastal_Explorers/cpfmodule/bhi/bhi_marsh2.htm http://www.texaswetlands.org/estuarine.htm Salt Marshes-biotic perspectives Modified from: Maia McGuire, PhD Florida Sea Grant Extension Agent
What is a salt marsh? • “A community of emerged halophytic vegetation in areas alternately inundated and drained by tidal action.” • “Expansive inter- or supratidal areas occupied by rooted emergent vascular macrophytes and a variety of epiphytes and epifauna.” Emerged: sticking out of the water; Halophytic: salt-loving; Inundated: flooded; macrophyte: plant that’s large enough to see; epiphyte: plant growing on another organism but not a parasite; epifauna: animal version of epiphyte
Where are salt marshes found? • Along intertidal shore of estuaries • Flat, protected waters • Extensive from Maine-Florida, along Gulf coast from Florida-Texas • Roughly 163,228 acres in Galveston Bay alone in 2005 • (NOAA 2006; Lester and Gonzalez 2008).
Salt vs. Brackish vs. Freshwater marsh • What’s the difference? • Proximity to salt water • Changes daily • Still exhibit zonation in salt and brackish marshes • Due to tidal influence • Main difference is the plant species found at brackish vs. salt marsh • Often the term “Salt” and “Brackish” marshes are used interchangeably
Salt and Brackish marsh grasses • Brackish Marsh • Spartina alterniflora • Smooth cord grass • Juncus roemerianus, • -black needlerush • Phragmites australis • - common reed • Salt Marsh • Spartina alterniflora • Smooth cord grass • Juncus roemerianus • Black needle rush • Cladium mariscoides • Swamp sawgrass • Spartina patens • Salt meadow cord grass
Associated plants Salicornia sp. • Many are succulent • Exceptions include saltgrass • Many are edible (saltwort, glasswort, sea purslane) • Form transitional zone between salt marsh and maritime forest
Zonation at the salt marsh • Zonation in general is caused by differences in climate or soil conditions.
Zonation depends on several factors: two important ones are salinity and nutrient availability. Salinity changes depending on these conditions: a. frequency of tidal inundation b. rainfall c. tidal creeks and drainage d. soil texture e. vegetation f. depth of water table g. freshwater inflow Nutrient availability also varies based on oxygen abundance
Salt/Brackish marsh zonation • Subtidal channel- channels which are permanently filled with water • Mudflat- muddy, rocky, or sandy bottom. Only exposed at low tides. Algae prevalent • Low marsh- underwater during high tides dry at high tide. Spartina, Juncus, Phragmites • High marsh (above mean high water)—Distichlis spicata, Batis maritima, Salicornia spp., Borrichia sp., Suedalinearis, Limonium carolinanum
The flooding and ebbing of the tides is one of the most important forces shaping and influencing the estuary. Tidal waters flood the estuary twice each day bringing nutrients, sediment, and oxygen rich waters from the ocean. Tidal currents also transport flora such as algae and fauna such as fish, crabs, and shrimp into the estuary. The tides shape the shoreline as they flood and ebb, moving tons of sediment and water each day.
High tides and low tides can make the same place look very different. Where rooted, flowering plants cannot withstand the strong currents and salty, murky tidewater, the mudflats are found. These areas are more properly called tide flats since they may be muddy, sandy, or even rocky. At the lowest tides, the only visible water is contained in the open water channel.
Marsh Zones– lower estuary (i.e. by the ocean, need some salt water here)
Estuary zones – lower estuary Subtidal channel Support oyster, flounder, and other invertebrates at low tide and serve as spawning and nursery areas for aquatic animals.
Estuary zones – lower estuary Subtidal channel Mud flat Mud flats are coastal wetlands that form when mud is deposited By tides or rivers. They support large populations of migratory Shorebirds, crabs, mollusks and fish.
Estuary zones – lower estuary Subtidal channel Mud flat low marsh Low Marsh is flooded daily. Is shallow, silt laden and salty. Home to many halophytes like Spartina.
The salt marsh community • Plants • Marsh grasses (various species described previously) • Associated halophytic (salt-tolerant) plants • Animals • Permanent residents • Visitors
Resident animals • Littorina irrorata • Marsh periwinkle (snail) • Crabs • Fiddler crabs (Uca spp.) • Marsh crabs (Sesarma spp.) • Geukensia demissa • Ribbed mussel
Tidal Marsh Visitors • Birds • Crabs • Shrimp • Fish • Diamondback terrapin
The majority of commercially-important marine species rely on estuaries/salt marsh at some stage of life • Examples include blue crab, oysters, hard clams, shrimp, red drum, seatrout, sheepshead, bluefish, mullet
Succession • The progressive replacement of one dominant type of species or community by another in an ecosystem until a stable climax community is established
Wrack • Wrack, a mat of dead marsh grass gets washed up on the marsh, smothering all the plants below it • The wrack is broken down or removed by flooding, leaving a bar patch of mud, or a salt pan.
Succession • 1) Water evaporates from the mud flat, leaving behind extra salt. • 2) Salt loving plants (like Salicornia) move in to the area • 3) As they grow the provide shade, which lowers water loss due to evaporation • 4) Soil salinity decreases, and other salt tolerant plants move in now that the soil isn’t as salty
Succession • This process constantly repeats itself • Leads to a definite zonation of the marsh (subtidal channel, mud flat, low marsh, high marsh)