Seagrass and Salt Marsh: Critical Coastal Habitats

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Seagrass and Salt Marsh Critical Coastal Habitats

• South Slough National
• Estuarine Research Reserve

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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.

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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.
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Where are seagrass and salt marsh communities
located?
Salt marshes
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Estuarine Habitats
Salt marshes
Tidal channels
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1. Open Water- Subtidal
Estuarine Habitats
Salt marshes
Tidal channels
Eelgrass beds
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1. Open Water- Subtidal
Estuarine Habitats
2. Intertidal mudflat
Salt marshes
Tidal channels
Intertidal mudflat
Eelgrass beds
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Elevation is a primary determinant of seagrass
and salt marsh location
Transitional Zone
Low and Mid Salt Marsh
Mudflat and/or Seagrass
High Salt Marsh
Mainstem Tidal Channel
Tidal Inundation Period High Marsh- Short Low
Marsh- Long
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Why are seagrass and salt marsh communities
important? What roles do they play in the
coastal ecosystem?
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• In ecological and economic value, they rival
  tropical rainforests and the worlds richest
  farmlands!

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Seagrass and Salt Marsh Functions

• Primary Production
• Fish and Wildlife Habitat (including nursery
  role)
• Sediment sink
• Shoreline protection
• Water Quality

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Primary Production
Eelgrass and Salt Marsh provide the critical
foundation to the detrital food web

• Production
• Shredding
• Colonization/decomposition
• Consumption by small organisms (grazers)
• Consumption by larger organisms (predators)
• Defecation/Nutrient transformation

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Fish and Wildlife Habitat Example

• Juvenile Salmon rearing habitat
• Foraging
• Physiological transitions
• Refuge from predators

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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

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Water Quality

• Nutrient uptake
• Sediment trapping and baffling of wave energy
• Oxygen production

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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

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• 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

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HISTORIC CHANGES OF COOS BAY TIDAL WETLANDS,
FILLED AGRICULTURAL LANDS, AND RESIDENTIAL
COMMUNITIES (1892-1995)
ACRES
YEAR
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Coos Bay 1900
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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

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South Sloughs 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.

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• 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.

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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?

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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?

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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?

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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

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Transects and Plots
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What do we measure at each site?

• Water depth
• Water salinity (salt content)

• Water Table Height
• Sediment elevation changes
• Sediment grain size
• Light using loggers
• Water temperature using loggers

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What do we measure at each quadrat plot?

• Canopy height / Blade width
• Shoot density

• Flowers fruits

• Sediment description
• Biomass core (0.0035m2)

• Seagrass cover
• Species composition

• Photograph

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Monitoring sediment elevation changes
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Current project status?

• First year of project 3 seasons of data
  collected
• Data analysis this Fall
• Ongoing long term monitoring to reveal trends

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