Lecture 10: Salt Marsh Ecology

Ecosystem Engineer

Species whose activities strongly affect the physical

structure of the environment.

_________ ________ functions as an “ecosystem engineer” in the salt marsh.

Spartina sp.

What ecosystem was a saltmarsh before?

• Marsh

• When Spartina moves in becomes saltmarsh

Newley established seedlings reproduce ___________ through lateral extension of rhizomes.

asexually

Salt marsh formation:

1. Bare intertidal sediment (sand/mud flat)

2. Early colonization by patches of Spartina

3. Clonal growth and trapping of sediment

4. Gradual rise of sediment surface and accumulation of peat

5. Development of a higher marsh, dominated by terrestrial plants

What makes heterogenity in an environment?

• Tidal Heights

• Thickness of peat

• Presence of creeks

Why is a heterogenous environment important

for species diversity?

• Allows more niches to be held within the environment

• Creates biodiversity

• Allow for interspecific competition

• Competition allows them to not outcompete each other

Heterogenieity

When an ecosystem has more variables that create more niches for organisms.

Salt marshes typically have _______ _______, with each dominated by a different grass species.

distint zones

What factors cause zonation patterns in a salt marsh?

• Dessication

• Competition

• Predation

• Coorperation

• Salinity

• Access to water

• Flooding can create anoxic conditions

Transplant expiriments show that:

• Spartina alterniflora can grow within the Spartina patens (upper) zone.

• S. patens does NOT grow well in the S. alterniflora (lower) zone.

• S. patens can outcompete S. alterniflora within the upper zone.

Spartina alterniflora has ____________ __________ for transport of oxygen.

aerenchymal tissue

How does aerenchymal tissue make S.alterniflora well-adapted to the lower marsh?

• Acting as an internal ventilation system, allowing the plant to transport oxygen from the atmosphere down to its roots and rhizomes submerged in anaerobic (oxygen-deficient), waterlogged soils.

Homogenous environments result in a multitude of issues

• Interspecific competition

• Principle of exclusion (winner takes all)

Heterogeneity allows for ______________.

coexistence

Spartina alterniflora and Distichlis spicata have “_______ ____________”.

runner morphologies

Spartina patens and Juncus gerardi have “____ _________”.

turf morphologies

How do root morphologies correlate with competitive ability?

Dominance of a zone is a combination of physiological tolerance of ______ _______ and __________ ________.

abiotic conditions, competitive ability

How can we determine which factors of zonation patterns are most important?

Through field expiriments and transplant studies

What is the theoretical niche of Spartina alteriniflora?

Lower zone

What is the realized niche of Spartina alteriniflora?

• Lower zone

• Upper zone

What is the theoretical niche of Spartina patens?

• Upper zone

What is the realized niche of Spartina patens?

• Upper zone

Runner Morphology:

• Rhizomes: A specialized, slender horizontal stem that grows above ground, rooting at nodes to produce new clones

Turf Morphology

• A dense, functional ground cover of grass

• Turf morphology focuses on the collective, dense growth that provides stability and resilience

Why doesn’t Spartina patens, the superior competitor, exclude

Distichlis spicata and Salicornia from the high marsh?

Physiological seperation via a heterpgenious environment.

Mats of dead Spartina are rafted onto the high marsh during early spring, creating _______ ______.

bare patches

Cooperative interactions play a role in the ______ ______.

Lower marsh

S. alterniflora grows better in dense stands due to ________ ________.

intraspecific cooperation

How do Uca pugnax (fiddler crab) and Geukensia demissa (mussels) contribute to the growth of Spartina alterniflora?

• Fiddler crab aerates soil and increase drainages

  • Feces helps provide nutreints

  • Boost cordgrass productivity

• Mussels attached to Spartina with their byssel threads to their roots and stabilize the marsh against erosion

How do these disturbances increase species diversity in the upper marsh?

Hypersaline due to evaporation create an inhospitable environment for new succession.

Spartina alterniflora is considered an _______ _______ species on the west coast.

invasive species

Impacts of Spartina alteriflora on the west coast:

• Displacement of native grasses and Salicornia species

  • Local animal species threatened

  • Loss of habitat diversity, as S. alterniflora outcompetes other species.

• Conversion of tidal mud flats to meadows

  • Loss of feeding grounds for migratory shorebirds

  • Loss of viable oyster habitat (WA State)