FACTORS AFFECTING OLIGOHALINE MARSH MACROPHYTE ZONATION AND PRODUCTION AT THE PLUM ISLAND ECOSYSTEM

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FACTORS AFFECTING OLIGOHALINE MARSH MACROPHYTE
ZONATION AND PRODUCTION AT THE PLUM ISLAND
ECOSYSTEM LTER SITE
Robert J. Daoust and James T. Morris
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Plant communities within estuaries contain
striking examples of zonation
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Occurs along multiple gradients
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Upstream
Downstream
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Creekbank
Low Marsh - Spartina alterniflora
Mixed zone
Upland edge
High Marsh - Spartina patens
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Plant community structure within estuaries is
inherently complex Strong gradients of salinity
stress
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Upstream
Freshwater marsh
Decreasing salinity stress Marine
influence Freshwater influence
Oligohaline zone
Salt marsh
Downstream
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Low Marsh - Spartina alterniflora flooded with
each incoming tide
Decreasing salinity stress on plants
Mixed zone
High Marsh - Spartina patens flooded only during
extremely high tides
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These gradients of salinity stress exist in
conjunction with ecosystem wide nutrient
limitation of macrophyte production
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Competitively inferior species relegated to the
more stressful environment
Low Marsh - Spartina alterniflora
Mixed zone
High Marsh - Spartina patens
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Along the downstream-upstream gradient nutrient
limitation of macrophyte production switches
Upstream
Freshwater marsh
P-limitation
Oligohaline zone
Decreasing salinity
Salt marsh
N-limitation
Downstream
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What factors control marsh macrophyte zonation
within the estuarine oligohaline zone?
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Plum Island Ecosystem LTER, Rowley MA
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Oligohaline zone
Salt marsh
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Typha angustifolia
Upland edge
Spartina patens
Creekbank
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Porewater salinity and sulphide concentrations
Sulphide
Signficant differences between communities

S-2patensgt S-2typha
p0.0323 F4.73, F1,953.95



Salinity
Signficant differences between communities
Salpatensgt Saltypha
plt0.0001 F18.67, F1,953.95
The area dominated by T. angustifola is less
physically stressful
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NH4 and SRP concentrations
NH4

Signficant differences between communities
NH4patensgt NH4typha
p0.0240 F5.87, F1,224.30

SRP
No signficant differences between communities
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CONTROLS ON MACROPHYTE ZONATION
Utilized a common reciprocal transplant
experiment nested with an NP factorial
fertilization experiment within an oligohaline
marsh along the Parker River
Mixed Effects Complete Nested Block Design
(replicated x 2)
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Spartina patens
Tyhpa angustifolia
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Typha angustifolia
1 m2 transplant plots
Spartina patens
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Untransplanted response for both species
Net Annual Primary Production
Nutrient effect p0.01892
Species effect p0.0002
S. patens responds to N and NP suggesting
nitrogen limitation
T. angustifolia responds to P and NP suggesting
phosphorus limitation
Year effect p0.4074
SPSpartina patens TYTypha angustifolia
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Transplanted response for both species
Net Annual Primary Production
Species effect plt0.0001 Nutrient effect plt0.0001
T. angustifolia production increases dramatically
when phosphorus availability is increased,
irregardless of N availability
Transplanted S. patens production increases only
in the absence of P enrichment
S. patens production suffers when either P or NP
is added to the system
SPSpartina patens TYTypha angustifolia
Year response plt0.0001
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Response of Typha angustifolia
Net Annual Primary Production
Year effect p0.0004
Cuntransplanted plot Ttransplanted plot
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Response of Spartina patens
After the first year of fertilization it both N
and NP stimulated production even when
transplanted
S. patens does not respond the same to
fertilization when transplanted.
Net Annual Primary Production
Nutrient treatment p0.1038
Transplant effect p0.0341
Production is stimulated within its own zone when
fertilized with N or with both NP
Production is only stimulated in the absence of P
additions when transplanted
When P availability is increased S. patens is
supressed as it is out competed by T.
angustifolia (for light and space)
Year effect P0.2576
Cuntransplanted plot Ttransplanted plot
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Summary
In the oligohaline zone, macrophytes are nutrient
limited
Spartina patens and Typha angustifolia respond
differently to fertilization.
S. patens --gt Nitrogen T. angustifolia --gt
Phosphorus
Both species are able to exist within its
neighbouring zone
However, Typha angustifolia when fertilized with
phosphorus or NP in combination performs better
within its neighbouring zone than does Spartina
patens
When oligohaline marsh communities are fertilized
with phosphorus Typha angustifolia production
increases significantly and it becomes better
able to survive under more stressful physical
conditions.
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Competitively inferior species relegated to the
more stressful environment
When N is added
Low Marsh - Spartina alterniflora
Mixed zone
High Marsh - Spartina patens
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Oligohaline marshes do not follow similar patterns
Inferior stress tolerator is relegated to the
more benign physical environment
The boundary is determined solely by the ability
of T. angustifola to tolerate physical stress
Typha angustifolia
S. patens becomes more productive and is more
likely to survive if it becomes established
P
N
T. angustifolia becomes more adept at surviving
under more stressful conditions
Not likely to expand towards the upland edge of
the marsh
Spartina patens
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In the past, emphasis has been placed on nitrogen
when considering the impacts of cultural
eutrophication on coastal wetlands. These data
suggest that the importance of phosphorus should
not be overlooked as it may also lead to shifts
in the ecological structure of these ecosystems.
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YUMM!!!
AHHH!!! NO!!!!
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Response of Spartina patens to fertilization
FNgtPC
plt0.001
2000
2001
2002
2003
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Response of Typha angustifolia to fertilization
FPgtNgtC
plt0.001
2000
2001
2002
2003