Transcript RINHSPlenaryWeis

SALT
MARSHES
AND
COASTAL
Issues for coastal marshes and ponds
PONDS:
MANAGEMENT
ISSUES
Judith S.
Weis
Rutgers University
RI Natural History Survey 2011
JUDITH S. WEIS RUTGERS UNIVERSITY
RHODE ISLAND NATURAL HISTORY SURVEY
APRIL 2011
Functions of Salt Marshes
• Breeding grounds for: Fish (menhaden,
striped bass, summer flounder, alewife,
shad) shrimp, crabs, birds. Two-thirds of all
marine species depend on tidal wetlands
for a portion of their life cycle.
• Stopping place for migratory birds.
• Habitat for mammals: Racoons, muskrats,
etc.
• High productivity – comparable to coral reef
or rain forest - supports lots of life
Other Ecosystem Services
•
•
•
•
Fisheries – source of food for humans
Removing pollutants
Sequestering carbon
Flood control – shoreline protection
MARSHES vs HURRICANES
• Storm protection - buffer
• Emergent wetlands greatly diminish wind
penetration and wave strength
• Maintain elevation by trapping sediments
• Economic damage inversely proportional to
amount of wetland area
Human Impacts on Salt Marshes: Physical Changes
Mosquito ditching. By the 1930s, most salt marshes ditched for
mosquito control. Impacts - drainage of marsh pools, lowered water
table, vegetation changes. Ditching drains all standing water. Not very
effective in controlling mosquitoes, but reduced populations of birds
and fish that used marsh pools
Open marsh water management (OMWM).
Creating or restoring natural shallow pools, allowing water to remain on
marsh at low tide; fish stay and eat mosquito larvae. Birds attracted to the
pools and also eat mosquito larvae. More effective in controlling
mosquitoes.
FILLING
These deep marshes were filled in for homes and lawns. Many acres
filled during development of East Coast cities. Major airports on filled
marshes.
LAND USE
Residential land-use change impacts run-off. More
impervious surface --> more runoff - impairs water quality.
ROADS AND RAILROADS
Bridges and culverts built over creeks restrict water flow
Areas became less saline since less seawater reaches them, allowing
less salt-tolerant plants to invade, like common reed, loosestrife, and
cattails.
Shoreline Hardening: Bulkheads
Bulkheads - vertical structures to control erosion
Revetments - large rocks or boulders.
Remove shallow water habitat and prevent marshes from
migrating inland as sea level rises.
Straightened creek channel makes currents run faster, narrower and
deeper, preventing sediments from settling in nearby wetlands.
CCA-TREATED WOOD IN ESTUARIES
(From Weis, J.S., and P. Weis (1992). J. Exp. Mar. Biol. Ecol. 161: 189-199.)
EPIBIOTA:
• UPTAKE BY RESIDENT ORGANISMS
• TOXIC EFFECTS IN OYSTERS – GENOTOXIC
AND HISTOPATHOLOGICAL
• SETTLEMENT OF EPIBIOTA ON
EXPERIMENTAL PANELS DELAYED
• UPTAKE AND EFFECTS GREATEST FROM
NEW WOOD AND IN POORLY FLUSHED
CONDITIONS
SEDIMENTS & BENTHOS
• GRADIENT OF METALS IN SEDIMENT (FINE
FRACTION) AND IN BENTHOS GOING OUT
FROM BULKHEAD
• REDUCED BENTHIC COMMUNITY –
ABUNDANCE, SPECIES RICHNESS AND
DIVERSITY – BY CCA BULKHEADS
• BY 10 M AWAY, COMMUNITY IS
COMPARABLE TO REFERENCE SITE
(BULKHEADS OF OTHER MATERIALS)
• TROPHIC TRANSFER FROM ALGAE
GROWING ON WOOD TO SNAIL GRAZERS –
TOXIC TO SNAILS
CURRENT SALT MARSH
PROBLEMS
• Subsidence = sinking
• Channelling rivers (levees) to prevent
flooding deprives marshes of new soil to
build up its elevation, so marsh sinks
(Louisiana)
• Sea level rise
LESS MARSH, MORE
OPEN WATER.
Healthy
Marsh
Eroding
Marsh
Normal
Booming
Busting
(more edge habitat)
Depleted
Marsh
Marsh Dieback in Cape Cod
The culprit Sesarma reticulatum, a native marsh
crab that is growing out of control, probably
because of depletion of its natural predators
Global sea level rises due to thermal expansion of the
oceans, and melting of glaciers. The rate of sea-level rise
during the 20th century was about 10 times higher than the
average rate during the last 3,000 years and is accelerating.
INTERTIDAL SALT MARSHES
MUST INCREASE ELEVATION,
MOVE INLAND, OR BE
SUBMERGED.
MARSH MIGRATION INLAND
• WILL THEY RUN INTO ROUTE 1, MAIN
STREET, AND PARKING LOTS?
• IRONICALLY, THE INVASIVE PLANT
PHRAGMITES, WHICH IS OFTEN
REMOVED, INCREASES ELEVATION,
AND MAY ALLOW MARSHES TO KEEP UP
WITH SEA LEVEL.
Chemical Changes - Pollution
Biomagnification. Concentration of some contaminants, such as mercury,
increases as it moves up the food chain. Organisms higher in the food web
have higher concentrations, represented by size of the dot.
EUTROPHICATION
• EXCESSIVE INPUTS OF NUTRIENTS
• CAN BE FROM POINT SOURCES –
SEWAGE TREATMENT PLANTS
• CAN BE FROM NON-POINT
SOURCES – INTERMITTENT
RUNOFF- AGRICULTURE AND
URBAN ENVIRONMENTS
Excess nutrients lead to algal blooms.
When blooms die and sink, their decomposition uses up the
oxygen in deeper water.
HARMFUL ALGAL BLOOMS
• Some algal blooms are toxic. Toxins they produce
can make their way up the food chain, causing
animal mortality.
• Algal toxins are taken up by shellfish (mussels,
oysters), that humans can eat.
Alexandrium, the
cause of PSP
“Red tide”
3. BIOLOGICAL ALTERATIONS:
INVASIVE SPECIES – COMMON REED
PRESENT IN HIGH MARSH FOR 1,000 YEARS BUT IN ’60S
STARTED SPREADING AND MOVING DOWN
NEW VARIETY INVADING EAST COAST BRACKISH
MARSHES, REPLACING CORDGRASS IN LOW MARSH,
GREATLY REDUCING PLANT DIVERSITY IN HIGH MARSH.
Research Sites
Saw Mill Creek:
Spartina alterniflora
Phragmites australis
Mill Creek:
Restored Spartina
Mean Number of Taxa
12
Benthic Community
10
8
Creek Bank Habitat
6
4
2
0
Jun-99
Jul-99
Aug-99
Sep-99
Date
Sawmill Creek Sites-Taxon Richness
Mean Number of Taxa
12
10
Edge of the
Vegetation Habitat
8
6
4
2
0
Jun-99
Jul-99
Aug-99
Date
P
S
Sep-99
1000000
Organisms (#/m2)
Mean Abundance of
10000000
100000
10000
Creek Bank Habitat
1000
100
10
1
Jun-99
Jul-99
Date
Aug-99
Sep-99
Organisms (#/m2)
Mean Abundance of
Sawmill Creek Sites-Mean Abundance (#/m2)
10000000
1000000
100000
10000
1000
100
10
1
Edge of the
Vegetation Habitat
Jun-99
Jul-99
Aug-99
Date
P
S
Sep-99
HABITAT CHOICE
A. LABORATORY MICROCOSMS:
GRASS SHRIMP, FIDDLER CRABS, OR
MUMMICHOGS PUT INTO CENTER
OF TANK WITH PHRAGMITES ON
ONE SIDE AND SPARTINA ON THE
OTHER. COLLECT ANIMALS FROM
BOTH SIDES AT END OF
EXPERIMENT
?
?
HABITAT CHOICE: RESULTS
1. NO DIFFERENCE IN SELECTION
OF EITHER PLANT SPECIES BY
GRASS SHRIMP OR FIDDLER CRABS
2. MUMMICHOG CHOICE DEPENDED
ON FISH SIZE AND MICROCOSM
SIZE – NOT CONSISTENT
HABITAT REFUGE VALUE
MICROCOSMS – METHODS
• GRASS SHRIMP PUT IN MICROCOSMS
OF EITHER PHRAGMITES OR
SPARTINA
• MUMMICHOG PREDATORS ADDED
• AFTER 8 HOURS, SURVIVING GRASS
SHRIMP COUNTED
HABITAT- REFUGE VALUE
MICROCOSM RESULTS:
• EQUIVALENT SHRIMP SURVIVAL IN
PHRAGMITES AND SPARTINA
MICROCOSMS
HABITAT: REFUGE VALUE
FIELD STUDY:
TETHERED GRASS SHRIMP ON BOTH
SIDES OF SMALL TIDAL CREEK IN SAW
MILL CREEK IN HACKENSACK
MEADOWLANDS, WHICH HAS
PHRAGMITES MARSH ON ONE SIDE
AND SPARTINA MARSH ON OTHER
Results: Equivalent survival on both sides
HABITAT: NEKTON
• SAMPLE MONTHLY AT SITES WHERE
PHRAGMITES AND SPARTINA ARE
CLOSE TO EACH OTHER - FLUME
NETS AND KILLIE TRAPS
HABITAT - NEKTON
• MUMMICHOGS LESS ABUNDANT ON
PHRAGMITES; MAYBE BECAUSE THEY
ARE MOSTLY YOUNG OF THE YEAR
(KNOWN TO PREFER SPARTINA)
• ALL OTHER SPECIES EQUIVALENT
FOOD VALUE
• PUREE LEAVES TO MAKE DETRITUS
• FEED 6 TYPES OF DETRITUS TO
ANIMALS, MONITOR SURVIVAL AND
GROWTH
• FIDDLER CRABS – UCA PUGILATOR
AND U. PUGNAX, GRASS SHRIMP
PALAEMONETES PUGIO
Weight gain (mg) or % mortality
U. PUGILATOR
250
200
HM-NS
HM-RS
HM-P
AC-NS
AC-RS
AC-P
150
100
50
0
Weight gain
All types of detritus equally good
Mortality
P. PUGIO
120
HM-NS
HM-RS
HM-P
AC-NS
AC-RS
AC-P
PERCENT SURVIVAL
100
80
60
40
20
0
3
7
11
14
17
DAYS
All types of detritus equally bad
20
24
Roles of Plants in Metal Fluxes of Salt Marshes
Excretion
Litterfall
Trophic Transfer
Plant Uptake
Sediment Storage
& Porewater Flux
Field study
Leaf Tissue Concentrations
Phragmites australis
Concentration (mg/g)
0.05
0.04
Spartina alterniflora
4.00
*
*
Hg
*
3.00
Cr
0.03
2.00
*
0.02
1.00
0.01
0.00
0.00
4
6
8
Month
10
4
6
8
Month
10
Greenhouse - Pb dosing study
Low Pb
Pb concentration (ppm)
90
High Pb
d
Roots
80
Rhizomes
70
Stems
60
Lower Leaves
50
Upper Leaves
d
40
cd
30
20
10
0
c
a a
Control
Phragmites
c
bc
c
a a
bcd
ab
ab b
a a a
Control
Spartina
b
a
Pb-added
Phragmites
Treatment
Pb-added
Spartina
Field - Excretion of metals from leaves
150
Phragmites
Spartina
-1
-1
Mercury Release (ng g d )
Seasonal Mercury (Hg) Release
100
50
*
*
*
0
5
6
Month
7
Excretion of Hg from leaves correlates with leaf Hg concentration
300
-1
-1
Mercury Release (ng g d )
Mercury Release vs. Leaf Concentration
Phragmites
Spartina
Linear (Spartina)
Linear (Phragmites)
200
100
0
0
20
40
60
80
Mercury Concentration in Leaves (ng g-1)
100
Findings
• Phragmites provides equivalent habitat for
most fishes and marsh invertebrates (but
not killifish)
• Phragmites detritus gets into food webs
the same as Spartina detritus and is
equally nutritious (or non-nutritious)
• Phragmites sequesters metal pollutants
more efficiently than Spartina by keeping
more belowground in roots rather than
moving into leaves where it can cycle in
the ecosystem
Marsh Restoration
• Many efforts--but still in early stages, not
yet a science
• Mitigation for “no net loss”—newly created
marsh may not be equivalent to old one
• What are endpoints for success?
– Species composition?
– Vegetation?
– Canopy architecture?
– Fish?
– Diversity?
– Productivity?
Restoration Issues
providing proper tidal flushing and
topography – tidal creeks
elevation is critical to desired plants
substrate - soil texture/amount of organic
matter
salinity-if too low, converts to different
vegetation
eutrophication and contaminants
disturbance - trampling by people
invasive exotics
RESTORATION BY INCREASING TIDAL
FLOW
Bridges and culverts often too small for tidal flow. Original 12-inch
culvert under a road provided inadequate tidal exchange. New culvert of
four 24-inch pipes allows better tidal exchange.
OTHER TECHNIQUES INVOLVE HERBICIDES TO KILL
PHRAGMITES, BULLDOZERS TO LOWER THE MARSH
LEVEL, AND REPLANTING SPARTINA
prior to restoration
Saltmarsh planting
IMPROVEMENT OVER TIME
• PLANTS RETURN QUICKLY, BUT MAY HAVE
LOWER STEM DENSITY & HEIGHT
• SOIL ORGANIC MATTER SLOW INCREASE
• GRADUAL INCREASE IN INVERTEBRATE
DENSITY, AND DIVERSITY
• TAXA WITH DISPERSED LARVAL STAGES
SLOWER TO RETURN
• ~15-20 YEARS FOR IT TO APPROACH
“NORMAL” LEVELS OF BIODIVERSITY AND
ECOSYSTEM FUNCTION
TAKE-HOME MESSAGES
IF YOU WANT TO RESTORE A MARSH BY
REPLACING PHRAGMITES WITH SPARTINA,
YOU SHOULD EITHER:
• 1. CHOOSE SITES WITH LOW LEVELS OF
CONTAMINATION, OR
• 2. CLEAN UP THE SITE BEFORE OR
WHILE RESTORING IT
• REMEMBER: PHRAG MARSHES ARE NOT
ECOLOGICALLY USELESS BUT ARE
FUNCTIONING ECOSYSTEMS THAT CAN BE
MANAGED, RATHER THAN ALWAYS
DESTROYED AND REMOVED
AND REMEMBER
• Plan for Sea Level Rise lest your marsh
turn into a coastal pond in 10 or 20 years