seagrass and salt marsh: critical coastal habitats
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Seagrass and Salt Marsh: Critical Coastal Habitats. South Slough National Estuarine Research Reserve. What is a Salt Marsh?. - PowerPoint PPT PresentationTRANSCRIPT
Seagrass and Salt Marsh: Critical Coastal Habitats
South Slough National
Estuarine Research Reserve
What is a Salt Marsh?
Salt marshes are transitional areas between land and water, occurring along the intertidal shore of estuaries and sounds where salinity (salt content) ranges from near ocean strength to near fresh in upriver marshes.
What is a Seagrass Bed? Seagrasses are flowering plants that have adapted
to living in salt water. Seagrasses are found mostly on soft sediment in estuaries and shallow coastal waters and are frequently found growing in dense beds.
In Pacific Northwest estuaries, the common species of seagrass is called eelgrass (Zostera marina), which grows in soft sediments of intertidal and subtidal zones.
Where are seagrass and salt marsh communities located?
Salt marshes
Estuarine Habitats:Salt marshes Tidal channels:
Estuarine Habitats:Salt marshes Tidal channels:
1. Open Water- Subtidal
Eelgrass beds
Estuarine Habitats:Salt marshes Tidal channels:
1. Open Water- Subtidal2. Intertidal mudflat
Intertidal mudflatEelgrass beds
High Salt MarshLow and Mid Salt Marsh
Mudflat and/or Seagrass
Transitional Zone
Elevation is a primary determinant of seagrass and salt marsh location
Tidal Inundation Period:
High Marsh- Short
Low Marsh- Long
Low Tide MLLW
Mainstem Tidal Channel
High Tide MHHW
Extreme High Tide
Why are seagrass and salt marsh communities important?
What roles do they play in the coastal ecosystem?
In ecological and economic value, they rival tropical rainforests and the world’s richest farmlands!
• Primary Production
• Fish and Wildlife Habitat (including “nursery” role)
• Sediment sink
• Shoreline protection
• Water Quality
Seagrass and Salt Marsh Functions
Primary Production
• Production• Shredding• Colonization/decomposition • Consumption by small
organisms (“grazers”)• Consumption by larger
organisms (“predators”)• Defecation/Nutrient
transformation
Eelgrass and Salt Marsh provide the critical foundation to the “detrital food web”
• Juvenile Salmon rearing habitat
• Foraging
• Physiological transitions
• Refuge from predators
Fish and Wildlife Habitat Example
• Resident and migratory bird habitat
• Shorebirds – feed on insects, fish, invertebrates
• Ducks and geese graze on vegetation – Ex. Black Brant / eelgrass
Fish and Wildlife Habitat Example
Water Quality• Nutrient uptake • Sediment trapping and baffling of wave energy• Oxygen production
Natural Variability of Salt Marsh and Seagrass Habitats
Plant distribution, species diversity, and density can vary substantially over seasons and years in response to:
– Precipitation, water table
– Light availability
– Temperature
– Nutrient availability
– Plant competition/succession
– Sediment characteristics
– Oceanic cycles (El NIÑO, PDO)
– Sea level rise
Human Impacts on Salt Marsh and Seagrass
Direct Impacts:• Dredging• Diking• Draining• Filling
Indirect Impacts:• Pollution – toxics, nutrients, sediments• Water diversions• Shading – i.e. docks, piers, bridges, boats, high water turbidity• Invasive species
HISTORIC CHANGES OF COOS BAY TIDAL WETLANDS, FILLED AGRICULTURAL LANDS, AND
RESIDENTIAL COMMUNITIES (1892-1995)
1892
1901
1937
1942
1971
1987
1995
0
1000
2000
3000
4000
5000
6000
7000
8000
900018
92
1901
1937
1942
1971
1987
1995
TIDALWETLANDS
WETLANDCONVERTED TOAGRICULTURE
WETLANDFILLED FORRESIDENCES
AC
RE
S
YEAR
Coos Bay 1900
Why Monitor Salt Marsh and Seagrass Habitat?
• To further our understanding of coastal ecology
• To document changes over time as an indicator of estuarine health
• To assess changes in sensitive estuarine habitats from long term trends in sea level rise and climate change
• To alert us to declines in key habitats and guide corrective action
• To motivate the public to protect existing habitat, restore degraded habitat, and improve upstream land use practices
South Slough’s Monitoring Strategy
South Slough National Estuarine Research Reserve (SSNERR) currently monitors a variety of physical and chemical measures as part of a nationwide effort to track the status and trends of estuarine resources in the United States.
Monitoring of eelgrass and salt marsh serve as biological indicators of ecosystem health.
A key advantage of biological indicators of estuary health is that they respond to a broad variety of environmental variables (temperature, salinity, light, pollution, etc), and therefore provide an integrated measure of how the ecosystem is functioning.
The “Big Picture” Questions:
• Within salt marshes and eelgrass beds, how are species composition, abundance, and distribution changing over time?
• What might be causing these changes?
Questions about short-term variability in these habitats:
• How closely linked are the seasonal ecological characteristics of these habitats along the estuarine gradient?
• How does the location of a habitat along the estuarine gradient affect species diversity, spatial cover, and biomass?
Questions about long-term variability in these habitats:
• How are changes in eelgrass and salt marsh habitats related to longer-term changes in the nearshore Pacific Ocean and/or freshwater inputs from the local watershed?
Guiding Concepts of Our Monitoring Approach:
• Establish monitoring sites along estuarine gradient (marine freshwater)
• Conduct representative sampling using transects and plots
• Repeatable measures• Measure both plant community attributes and
environmental variables• Testing both national (NERRS) and International
(SeagrassNet) protocols• Sample quarterly (4x per year) to assess seasonal
variability
Transects and Plots
Water Table HeightWater Table Height
Sediment elevation changesSediment elevation changes
Sediment grain size Sediment grain size
Light using loggersLight using loggers
Water temperature using loggersWater temperature using loggers
Water depthWater depth
Water salinity (salt content)Water salinity (salt content)
What do we measure at each site?
Canopy height / Blade widthCanopy height / Blade width
Shoot densityShoot density
Flowers & fruitsFlowers & fruits
Sediment descriptionSediment description
Biomass core (0.0035mBiomass core (0.0035m22))
Seagrass % cover Seagrass % cover
Species composition Species composition
PhotographPhotograph
What do we measure at each quadrat plot?
Monitoring sediment elevation changes
SeagrassNet Sites
Current project status?
• First year of project – 3 seasons of data collected
• Data analysis this Fall
• Ongoing long term monitoring to reveal trends