Marshes

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Slide 1

Coastal Ecosystems: Salt Marshes and Mangroves

Marine Biology

Dr. Ouida Meier

Slide 2

Factors Driving Coastal Ecosystems

Latitude

temperature

light, seasonality

Tidal cycles

amplitude

frequency

Wave energy

Degree of riverine input

freshwater input

alluvial sediments and deposition

turbidity

Slide 3

Factors Driving Coastal Ecosystems

Geological characteristics

rock

sand

sediment

Hydrological characteristics

nearshore currents

transport

Continental proximity

nutrient input

anthropogenic impacts

(cont.)

Slide 4

Recap: Rocky Intertidal

Our example (Pacific Northwest): high latitude, so

Cold Pacific waters, strong seasonality

Tidal cycle: high amplitude, semi-diurnal

Wave energy high

Freshwater input – riverine characteristics modified by bay / estuary

Geology: rocky cliffs, interspersed w/sandy beach

Hydrology: strong nearshore currents & transport

Continental edge, input via interaction with terrestrial systems

Slide 5

Salt Marsh Ecosystems

Our example (southeastern U.S.: Gulf and Atlantic coasts): moderate latitude, so

“Warm” Atlantic and warmer Gulf and Gulf stream waters, moderated seasonality

Tidal cycle: low amplitude

Wave energy low

Freshwater input often critical – deltaic riverine input can result in extensive marsh systems, abundant alluvial sediment input. Salt accumulation a challenge.

Geology: long-term alluvial sediment accumulation

Hydrology: nearshore currents & transport important

Continental edge, nutrient input via runoff, rivers

Slide 6

Salt marsh and tidal channels in coastal Georgia

Slide 7

Plants of the Salt Marsh Community

Spartina alterniflora – marsh cordgrass

height depends on riverine or tidal flushing

export of dried mats during winter storms

exclude salt from roots

Salicornia – a succulent

Salt pans

Fresher water and soils / higher ground: other grasses (Spartina patens), rushes (Juncus romerianus), sedges

Zonation based on topography, inundation of freshwater, fresh/salt fluctuation, tidal flushing, relative stresses, anoxia of soils, latitudinal gradient (e.g., east coast U.S.).

Slide 8