Download Salt marshes

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:
1. Open Water- Subtidal
Salt marshes Tidal channels:
Eelgrass beds
Estuarine Habitats:
1. Open Water- Subtidal
2. Intertidal mudflat
Salt marshes Tidal channels:
Eelgrass beds
Intertidal mudflat
Elevation is a primary determinant of
seagrass and salt marsh location
Transitional Zone
Extreme Mudflat and/or
High Tide Seagrass
Low and Mid Salt
Marsh
High Salt Marsh
Low Tide
MLLW
Mainstem Tidal Channel
High Tide
MHHW
Tidal Inundation Period:
High Marsh- Short
Low Marsh- Long
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!
Seagrass and Salt Marsh Functions
• Primary Production
• Fish and Wildlife Habitat
(including “nursery” role)
• Sediment sink
• Shoreline protection
• Water Quality
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
Fish and Wildlife Habitat Example
• 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
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
TIDAL
WETLANDS
YEA
R
1995
1987
1971
1942
1937
WETLAND
CONVERTED TO
AGRICULTURE
1901
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
1892
ACRES
HISTORIC CHANGES OF COOS BAY TIDAL
WETLANDS, FILLED AGRICULTURAL LANDS, AND
RESIDENTIAL COMMUNITIES (1892-1995)
WETLAND
FILLED FOR
RESIDENCES
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
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
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
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