Coastal Tidal Marshes

Transcription

1 Virginia s Wetlands

2

3 Coastal Tidal Marshes Hydrology driven by lunar tides; Stresses include tidal inundation and/or salts; Found along high latitudes along intertidal coasts; Comprise ~ 70% wetlands of the mid- Atlantic coastal plain; Marshes replaced by mangroves between 25 N- 25 S lat.

4 Factors Affecting Tidal Marshes 1. Distance from tidal source 2. Tide Range 3. Basin profile 4. Size of Watershed

5 Polyhaline Tidal Freshwater Mesohaline Oligohaline Wetland Diversity: Role of Gradients Tide Species Richness Distance from Mouth 90K Distribution of estuarine environmental parameters and plant species richness of Chesapeake Bay estuaries (modified from Perry and Atkinson 2007).

6 Salinity (note: tide range remains constant) Decrease Spatial Diversity Estuary/River Profile Headwater System Tidal Freshwater Marshes Oligohaline Saltmarshes Tidal River/ Lagoon Flood Mesohaline Saltmarshes Ebb Ocean Polyhaline Saltmarshes

7 Virginia s Coastal Wetlands Tidal Salt Marshes Polyhaline Mesohaline Oligohaline

8 Salinity of an area is a function of: Salt content and volume of incoming ocean water; Volume of incoming freshwater Salinity = tidal volume/freshwater input

9 Salt Marsh Vertical Profile Tall Cordgrass Short Cordgrass Saltmeadow Hay Salt Bush MHW Mean tide MLW

10 Tall Cordgrass Short Cordgrass MHW Mean tide MLW

11 Saltmeadow Hay Salt Bush MHW Mean tide MLW

12 Tidal Freshwater Marshes

13 TFM Vertical Profile MHW MLW Seasonal Variation

14 Spring and Early Summer Spatter Dock Arrow Arum

15 Mid- to Late Summer Spatter Dock Rice Cutgrass/Northern wild rice/bidens

16 October Spatter Dock ecreasing abundance Rice Cutgrass/Northern wild rice/bidens/knotweed

17 Tidal Freshwater Swamps

18 Table 1. Physical description of York River component CBNERRVA sites. Tide range was approximately the same at each site ( m.). SITE TOTAL # SPECIES DIVERSITY DISTANCE UPSTREAM (Km) SALINITY RANGE (ppt) Goodwin Islands Polyhaline Catlett Islands Mesohaline Taskinas Creek Oligohaline Sweet Hall Marsh (TFW)

19 Table 2. Dominant species and Shannon=s diversity index for each site. Dominance is defined as the sum of Relative Importance Values (RIV) of species, when ranked in descending order, that total greater than 50%. RIV is calculated by dividing the individual species IV by the sum of all IV's for that site. SITE DOMINANT SPECIES % TOTAL RIV Goodwin Islands: Distichlis spicata 33.5 Spartina alterniflora 32.0 Catlett Islands: Spartina alterniflora 48.0 Distichlis spicata 30.7 Taskinas Creek: Spartina patens 48.0 Distichlis spicata 30.7 Sweet Hall Marsh: Peltandra virginica 18.3 Carex stricta 9.8 Leersia oryzoides 8.8 Polygonum punctatum 6.9 Polygonum arifolium 6.7

20 Tidal Wetlands Response to Sea Level Change Depend upon: 1. sed. + organic accretion; 2. changes in relative sea level.

21 Marsh Stability: Accretion Accretion from natural sources: - Inorganic: Erosion of river banks, minor runoff. Resuspension from stochastic events; - Organic: Rootstock, small amount of allogenic input. Resuspension from stochastic events. Accretion from anthropogenic sources: - Inorganic: Surface runoff (high), resuspension of sediments can be high; - Organic: Terrestrial allogenic input, resuspension of sediments moderate.

22 Marsh Stability: Sea Level Relative sea level is the sea level felt by the marsh. It is combination of Eustatic sea level, isotectonic activities, and local conditions. 1. Eustatic sea level: The elevation of sea level taken from a point in space. 2. Isotectonic rebound: melting of glaciers have allowed NE landmasses to rebound; SE is sinking.

23 Marsh Stability NE SE Iso-stasis With Glaciers Post-Glaciers

24 Marsh Stability: Sea Level Relative sea level is the sea level felt by the marsh. It is combination of Eustatic sea level, isotectonic activities, and local conditions. 1. Eustatic sea level: The elevation of sea level taken from a point in space. 2. Isotectonic rebound: melting of glaciers have allowed NE landmasses to rebound; SE is sinking. 3. Local impacts: availability of sediments, storms, ground water withdrawal,

25 On to the plants, Folks!