Exam 3

Key Concepts: Salt Marsh Intro

• Salt marshes are highly productive coastal wetlands with major ecological functions

• Their formation depends on geomorphology: sediment supply, low wave energy, and shelter

• Salt marsh plants are adapted to salinity and waterlogging through traits like salt glands, rhizomes, succulence

• Species diversity is low but functional roles are high, dominated by Sporobolus, juncus, salicornia

• Morphological strategies support resilience, driving high productivity, and persistence under stress

Salt Marsh Ecosystems

• Salt marsh ecosystems are very productive

• Ecological functions

• Nursery ground

• Habitat/production

• Food source

• Nutrient cycling

• Sediment retention

• Reduce erosion

• Storm surge protection

Salt Marsh: Intro

• 2 types of vascular plant tidal communities one earth

• Salt marshes: found where freezing air temps occur with regularity

• Mangals: limited to latitudes remain at 20C or higher

• Both restricted to low energy coastal regions

Salt Marsh: Intro

• Salt marsh:

• a halophytic grassland on alluvial sediments bordering saline water bodies where water level fluctuates either tidally or nontidally

• Salt marshes are found in areas where the accumulation of sediments is equal to or greater than the rate of land subsidence and where there is adequate protection from destructive waves and storms

Salt Marshes: Geographical Extent

• Found at mid-high latitudes along intertidal shorelines worldwide

• Range from narrow fringes on steep shorelines to open expanses several miles wide

• Found in/near

  • River mouths

  • Bays

  • Protected coastal plains

  • Protected lagoons

• Different plant associations found with different coastlines but ecological structure and function similar worldwide

Geomorphology

• Physical features determine extent of salt marshes within geographical range

• Predominately intertidal areas

• Gently sloping shorelines

• Protection from wave and storm energy

• Strong sediment supply from upland run-off

Geomorphology

• Wetlands classified as forming in either marine-dominated or deltaic areas

• Most north american salt marshes are marine dominated

• Deltaic marshes found in south atlantic and gulf of mx

• Either requires sufficient shelter to ensure sedimentation and prevent erosion

Geomorphology: Marine Dominated

• Shoreline features that allow for the development of salt marshes

• Shelter of spits, offshore bars, islands

  • Traps sediment on lee side, protects marsh from open ocean (Georgia and NC coasts)

• Protected bays

  • Large bays with shallow areas and large sediment supply allow for extensive marsh development (Chesapeake Bay, San francisco Bay)

• Estuarine zones

  • Shores of estuaries where shallow water and low gradients allow for sediment deposition, tidal action has to maintain higher salinities

Salt Marsh Plant Adaptations

• Salt marsh vegetation has 2 key features

• Adaptation of saline conditions

• Ability to grow in/be exposed to waterlogged sediments (including peat deposits)

Salt Marsh Plant Adaptations

• Flowering plants grouped into 3 classes based on adaptation to obtain and retain water

  • Xerophytes=

• plants that have morphological, anatomical, reproductive adaptations to aide in retention and uptake of water (salt marsh plants, mangroves)

• Mesophytes (glycophytic)= plants that grow in habitats where freshwater is avalible in the sediment, lack specialized adaptations to prevent water loss (wheat, beet)

• Hydrophytes= plants that live in water, partially or wholly submerged (seagrasses)

Salt Marsh Plant Adaptations

• Plants can be further divided based on salinity tolerance

  • Halophytes:

• plants that have adaptations to prevent water loss and to grow in slaine habitats

  • Facultative= halophytes that do not require saline conditions for growth (most salt marsh plants)

  • Obligate= have specific requirement for sodium and not potassium, requires salt to complete life cycle

• Most salt marsh species are facultative halophytes

• All ecotypes occur in salt marsh due to gradation of salinity b/w estuarine and upland conditions

Salt Marsh Plant Adaptations

• Species divided based on morphologies

  • Hemicryptophytes=

form of clonal growth where perennating buds are situated at or just below the soil surface (most common morphology for salt marsh plants)

Salt Marsh Plant Adaptations

• Species divided based on morphologies

• Therophytes=

• annual plants, plant that overwinters as a seed

  • Varies across latitude and salt marsh groups

  • Dominant in mediterranean and semi-arid climates 

Salt Marsh Plant Diversity

• Not extremely diverse when compared to terrestrial grasslands

• Widespread species distribution with related sp found on different continents

• Limited # of halophytic species (although more diverse than mangal communities)

Salt Marsh Plant Diversity

• Distribution pattern attributed to

• Continental drift (vicariance hypthesis)

• Dispersal by birds/vegetative repro

Salt Marsh Plant Diversity

• No comprehensive list of salt marsh species

• Differing definitions of salt marsh plant

Salt Marsh Plant Diversity

• Range of species diversity

• British salt marshes (325 sp, 45 are halophytes)

• Eastern US (347 sp)

• Mississippi coast (200 sp)

Salt Marsh Plant Diversity

• Independent parallel evolution of xerophytes seen at local and continental scales

• No clear pattern for flower or seed adaptations to salt marsh enviroment

• Hard to genetically group species

Salt Marsh Plant Diversity

• Commonly occurring families include

• Poaceae, gramineae, chemopodiaceae, juncaceae, cyperaceae, plumbaginaceae, frankiaceae, asteraceae,

Salt Marsh Plant Diversity

• Commonly occuring genera include

• Spartine, sporobolus, salicornia, juncus, arthrocnemum, suaeda, plantago

 

Salt Marsh Plants

• Detail on 3 rep sepceis

• Sporobolus alterniflorus

• Juncus roemarianus

• Salicornia virginica

Sporobolus alterniflorus

• Smooth cordgrass

Monocot in family Poaceae (Gramineae)

• Species distribution:

  • Both coasts North America

  • Both coasts South America

  • Europe

  • Genus found worldwide

Sporobolus alterniflorus

• 2 main forms

• Tall: 3 m tall; found along tidal creeks

• Short: 0.2 – 0.8 m tall found in upper marsh

Sporobolus alterniflorus

• Development of different forms attributed to phenotypic expression based on edaphic (soil) factors

• Clonal species

• Subterranean rhizome with sympodial branching - primary axis that develops from a series of short lateral branches and often has a zigzag or irregular forms

• New shoots and roots produced from rhizome

Sporobolus alterniflorus

• 2 types of roots:

• Unbranched anchoring roots covered with corky material

• Ephemeral, fine, much- branched, matted absorbing roots

Sporobolus alterniflorus

• Shoots and leaves account for 1/3 to 1/10 of plant biomass – the rest is belowground

• Stems

• Hollow center (air space)

• Ring of lacunae alternating with vascular bundles on outside of stem

• Both continuous to roots

Sporobolus alterniflorus

• Leaves

• Produced by basal intercalary meristem

• Smooth flat blades with longitudinal furrows

• Contain epidermal salt glands

Juncus roemerianus

• Black Rush

• Monocot member of Juncaceae family

• 8 genera

• Most genera found in southern hemisphere

• Genus Juncus has both fresh and salt water Species

• Clonal plant

Juncus roemerianus

• Subterranean branching rhizome

• Rhizomes covered with suberized (corky tissue) scale leaves

• Lacunae in cortex

• Endodermal layer limiting cortex from pericycle

Juncus roemerianus

• Fibrous root system

• Erect stem with lacunae

• Produce long needle like leaves up to 2 m tall

• Leaves oval in cross section

• Blades develop from basal intercalary meristem

• Central portion of blade with parenchymatous mesophyll , vascular bundles, and lacunae

• Epidermis is lignified with thick cuticle

Juncus roemerianus

• Flowers occur in dense cymes –

• an inflorescence in which each floral axis terminates in a single flower

Salicornia virginica

• Pickle weed, American Glasswort

• Dicot member of the Chenopodiaceae family

• Stem and leaves are succulent

• Pickle weed, American Glasswort

  • Common name comes from glossy nature of succulent stem

• Dicot member of the Chenopodiaceae family

  • family with most halophytes

• Stem and leaves are succulent

  • plant with fleshy tissues able to conserve moisture

Salicornia virginica

• Appear swollen due to abundance of water- containing cells

• Perennial species

• Has a thick and waxy Cuticle

• Stem procumbent – produces short erect branches

• Stem produces advantageous roots to extend area

• Blades reduced to scales

• Succulent petioles wrapped around stem giving segmented appearance

Salicornia virginica

• Petioles -

• a slender stem that supports the blade of a foliage leaf

Lessons Learned (Salt Marsh Intro)

• Salt marshes are highly productive coastal wetlands with major ecological functions

• Their formation depends on geomorphology: sediment supply, low wave energy, and shelter.

• Salt marsh plants are adapted to salinity and waterlogging through traits like salt glands, rhizomes, and succulence.

• Species diversity is low but functional roles are high, dominated by Sporobolus, Juncus, and Salicornia.

• Morphological strategies support resilience, driving high productivity and persistence under stress.

 

Key Concepts: Salt Marsh Enviroment

• Salt marshes are harsh but productive ecosystems shaped by flooding, salinity, sediment supply

• Plants persist through morphological and anatomical adaptations rhizomes, aerenchyma, xerophytic traits)

• Ecophysiological strategies regulate salt and water: ion exclusion, succulence, salt glands, osmotic adjustments.

• Photosynthetic pathways differ (C3 vs. C4), but all support high productivity under stress.

• Diversity extends beyond grasses - algae, seagrass, ferns, and bryophytes add to function

Salt Marsh Enviroment

• Plants have to be adapted to live in harsh environments:

• Variable salinity

• Flooding

• Low oxygen

• Edaphic changes

• Strong gradients over small spatial scales

Morphological Adaptations: Flooding

• High tide results in:

• edaphic changes (lower soil aeration and redox potential)

• Lower photosynthesis

• Damage or uprooting of plants due to water movement

• Anaerobic sediments

Morphological Adaptations: Flooding

• Anaerobic soils BIG problem

• If oxygen cut off from roots and rhizomes toxic compounds (e.g. sulfides, reduced metal ions) can accumulate

• Rely on oxygen produced in leaves to diffuse to belowground material

Morphological Adaptations: Flooding

• Thickness of oxidized layer directly related to:

• Rate of O2 transport across the atmosphere-surface water interface

• Population of oxygen-consuming organisms present

• Photosynthetic oxygen production by algae within the water column

• Surface mixing by convection currents and wind action

Morphological Adaptations: Flooding

• Due to harsh salt marsh environment rhizomes very important

• Few cm to 1 m below surface

• Storage organs during periods of dormancy

• Vegetative expansion

• Reduce erosion due to anchoring and absorbing roots

Morphological Adaptations: Flooding

• Rhizosphere -

• narrow region of soil that is directly influenced by root secretions and associated soil Microorganisms

Morphological Adaptations: Flooding

• Lacunae/aerenchyma =

• up to 60% of total plant body

• 50% of root volume

• Effective a moving O2 to roots

• Level of air system development directly related to level of water- logging

Salt Marsh Enviroments: Anatomical Adaptations

•  Xerophytic adaptations to maximize water retention in stems, leaves, and roots:

• Increased lignification

• Complex epidermal development

• Well-developed bundle sheaths

• Leaves and stems also develop lacunae and aerenchyma

Salt Marsh Enviroments: Anatomical Adaptations

• 3 types of xeric leaves found in salt marsh plants:

• 1. Succulent – store water and dilute internal salt concentrations

• 2. Thick – increase vascular, water-storage and photosynthetic tissue

• 3. Dry-type (thin) – have enhanced cuticular resistance to water loss, produce epidermal hairs, and can curl to reduce water loss

Salt Marsh Enviroments: Anatomical Adaptations

• S. alterniflorus has dry-type leaves

• Upper (adaxial) side of leaf

  • higher concentration of stomates

  • Groves with specialized cells, collapse when dry conditions persist

• Lower (abaxial) epidermis

  • thicker, lignified walls and cuticles

• Causes leaf to roll up in a tube and the thicker cell wall is exposed reducing water loss

Salt Marsh Enviroments: Anatomical Adaptations

• Succulence is an adaptation for

• Water storage

• Dilution of inorganic salts

• Reduction in surface area (reduces water loss)

• Occurs when petiole wraps around stem replacing leaf blade as photosynthetic organ

Ecophysiology of Salt Marsh Plants

• Cope well with less than optimum habitat

• Edaphic factors:

• High sodium and chloride concentration

• Limited essential nutrients

• Anaerobic conditions

Ecophysiology of Salt Marsh Plants

• Cope well with less than optimum habitat

• Tidal immersion:

• Temperature shock

• Changes in photoperiod

• Mechanical effects of tidal currents

• Siltation of leaves by sediment (blocks stomates)

Ecophysiology: Salinity

• Soil salinities vary across the salt marsh

• Highest middle to upper marshes (depending on FW input)

• High elevation within marshes limits tidal flushing

• Combined with high evaporation salinity levels can become toxic

• To take up groundwater there has to be a gradient in osmotic potential within the plant

• Seawater at 35 PSU has a water potential of -2.5 mPa

Ecophysiology: Salinity

• Roots of a halophyte has to be BELOW that osmotic potential to take up water

• Most halophytes considered to be either:

• Roots of a halophyte has to be BELOW that osmotic potential to take up water

  • Glycophytes cell osmotic potential of -0.5 to -1 mPa

• Most halophytes considered to be either:

  • Osmoconformers – shows a gradient in osmotic potential between soil and plant

  • Osmoregulators – lacking a gradient and exhibiting sharp changes in internal ion concentration when subjected to changes in external salinity concern

Ecophysiology: Salinity

• Regulation of shoot salt content accomplished by:

• Ion exclusion in roots

• Growth and Succulence

• Shedding – concentrating ions then shedding material

• Secretion – salt glands

• Root discharge – move salt from growth areas to roots; then discharged into rhizosphere

• Controlling water loss – reducing transpiration; lowers water needed and reduces subsequent salt uptake

Ecophysiology: Salinity

• Enzymes of halophytes adapted to tolerate higher salinity without adjustments

• Above threshold values salt becomes toxic

• Production of organic solutes effective method at reducing salt stress

• Cells with a 20 – 40% sugar concentration can acclimated up to 100 M m-3 of NaCl

Ecophysiology: Salinity

• Salt Accumulation

• Most commonly accumulated ions:

• Na +, Cl -, SO4-2, NO3-

• Tolerate Na + and Cl- at 10 – 13 psu

• Above threshold = ribosomal breakdown

Ecophysiology: Salinity

• Dehydration

• Loss of water increases cellular ionic strength

• Also results in loss of turgor pressure

  • Photosynthetic and metabolic shutdown

  • Curling

  • Wilting

• Can be lethal

Ecophysiology: Salinity

• Salinity also affects depth of rooting

• Shallow-rooted plants subject to greater changes in salinity

• Deeper-rooted plants do not deal with wide ranging salinities

• Current research investigating changes in root morphology and depth with zonation and type of salt regulation

Ecophysiology: Photosynthesis

• Advantages of C4 fixation:

• High affinity of PEP carboxylase for CO2

• Efficient use of N for growth and organic solute production

• C4 photosynthesis is less efficient at colder temps

Ecophysiology: Costs

• Halophytes have high energy costs and high anatomical requirements (specialized cell development)

• Lower growth rates

• Lower nutrient uptake (higher costs due to anaerobic soils)

• Reduced photosynthesis

Other Salt Marsh Plants

• Variety of types of plants found in salt marshes

• Ferns, bryophytes, algae (micro and macro), seagrasses, epiphytes

 

Other Salt Marsh Plants: Ferns

• Acrosticum most common genus found in warm temperate climates

• Fringing understory in mangal systems

• Overtop marsh plants in some areas (Florida west coast; African marshes)

 

Other Salt Marsh Plants: Bryophytes

• > 50 moss species and 1 liverwort found in British marshes

• Also found in arctic and Scandinavian areas

• Understory in the upper elevations of tidal marshes

• Few species found in lower latitudes

Other Salt Marsh Plants: Algae

• Significant source of production

• 4 main communities:

• Sediment microalgae

• Macroalgal turf

• Epiphytic algae on marsh plants

• Subtidal drift or attached macroalgae

Other Salt Marsh Plants: Algae

• Significant source of production

• Microalgae found on lower slopes below salt marsh and on sediment below plants

• Mostly blue-green algae and diatoms

• Species composition is dynamic, seasonal, and localized

• Generally limited by nutrients

Other Salt Marsh Plants: Algae

• Significant source of production

• Epiphytes are important source of primary production in salt marshes

• Colonize area around dead stems

• Provide food source for benthic and pelagic organisms

Other Salt Marsh Plants: Seagrass

• May dominate shallow marsh basins

• Most common species

  • Ruppia maritima

  • Zostera noltii

  • Zostera marina

  • Change in species composition due to climate

 

Take Home Messages (Salt Marsh Enviroment)

• Adaptation enables survival in extreme environments.

• Trade-offs matter: tolerance costs reduce growth but increase resilience.

• Biodiversity underpins resilience and ecosystem services.

• Big picture: Salt marsh physiology connects to coastal protection, nutrient cycling, and habitat provision

Key Concepts: Salt Marsh management

• Salt marshes are structured, dynamic ecosystems shaped by abiotic and biotic interactions.

• Zonation reflects adaptations to gradients in elevation, salinity, and inundation.

• Human activity has drastically altered salt marsh extent and function.

• Restoration and management rely on balancing ecological processes with human use.

 

Ecology of Salt Marshes: Key Drivers

• Driving abiotic/biotic factors

• Edaphic factors

• Tides

• Elevation

• Climate

• Zonation

• Competition

• Facilitation

Zonation

• Zonation n salt marshes due to differing vertical ranges of species

• Not just marsh vegetation (microalgal, seaweed, faunal components also zoned)

• Mechanisms controlling zonation patterns not well understood

  • May be related to competition

Zonation

• Number of zones depends on latitude, physical factors, criteria used to develop zones

• • NC= 4 veg zones

  • NW FL= 8 zones

  • Gulf of MX= 3 zones

Zonation

• S of Chesapeake along atlantic coast see shift in marsh sp and zonation

• Tall S. alterniflora only found in narrow bands around creek

• Short form S. alterniflora found more commonly in middle zones

• Juncus roemerianus replaces J. gerardi in high marsh

Zonation

• Dominant species shifts to S. patens in Gulf of Mexico salt marshes

• Dominates > 200,000 acres in Louisiana coastal marshes

Salt Marsh Succession & Stability

• Succession in salt marsh systems complicated

• Multiple stable states (subclimax)

• Elevation drives community transitions

• Disturbance= predictable recovery sequence

Salt Marsh Dynamics

• Disturbance common in salt marsh communities

• Storms, fires, ice rafting, wrack deposition

Antropogenic Considerations: Human Uses of Salt Marshes (Historical)

• Farming

• Strip or open cast mining

• Salt and chemical production

• Land reclamation

• Industrial and urban sites

• Insect control

• Wildlife management

• Waste disposal

• Recreation

• Scientific studies

Antropogenic Considerations: Modern Impacts

• Estuarine marshes exposed to industrial, agricultural, domestic runoff

• Nutrients, metals, toxins stored in plants and sediments

• Metals binds to sulfides or organic matter in porewater

• Released back to food web through decomposition and grazing

Antropogenic Considerations: Uses & Impacts

• Channelization for flood protection and insect treatment causes

• Increased salinity

• Sediment starvation downstream

• Nutrient limitations

Antropogenic Considerations: Uses & Impacts

• Lack of sediment can lead to large scale loss of salt marsh

• Rising salinity reduces seed banks and plant recruitment

• Marsh loss decreases filtration and water clarity

• Industrial activity adds head and other stressors

Antropogenic Considerations: Uses & Impacts

• Largest present-day impact due to urban expansion

• Construction, dredging, filling

Antropogenic Considerations: Uses & Impacts

• Building harbors and ports

• Present global loss of salt marsh estimated at 60%

• Exotic spartina species spreading in europe and CA

• Hybrid forms outcompete native marsh plants

• Disrupt ecosystem balance and migratory bird habitats

Antropogenic Considerations: Management Restoration

• Until early 1950s tidal wetlands were treated as a commons

• Quickly became example for tragedy of the commons

• British public trust doctrine (PTD) 1st attempt to manage tidal resources

Antropogenic Considerations: Management Restoration

• PTD not prefect solution problems with

• Enforcement, liability issues, jurisdiction of regulators

Antropogenic Considerations: Management Restoration

• Big ?-

• where does intertidal beach begin and marsh end

• Clean water act- protected wetland areas

• Plans must be approved by USACE

Antropogenic Considerations: Management Restoration

• Developed detailed management plans

• Restrict inflow of pollutants

• Stop dredge and filling

• Restore coastal wetlands

Supreme Court Ruling on Wetland Definition (Sackett v. EPA, 2023)

• Key Change

• Wetlands must have a “continuous surface connection” to navigable waters to be federally protected

• Excludes many isolated or intermittently connected salt marshes

Supreme Court Ruling on Wetland Definition (Sackett v. EPA, 2023)

• Immediate Effects

• Loss of federal Clean Water Act protection for many coastal wetlands

• Increased vulnerability to filling, dredging, and pollution

• Regulatory gaps where state protections are weak or absent

• Greater uncertainty in permitting and project approvals

Supreme Court Ruling on Wetland Definition (Sackett v. EPA, 2023)

• Management Challenges

• Reduced funding and oversight for restoration on delisted wetlands

• State and local agencies must take on more monitoring and enforcement

• Fragmented protection across jurisdictions increases planning complexity

Supreme Court Ruling on Wetland Definition (Sackett v. EPA, 2023)

• Ecological Consequences

• Potential decline in filtration, flood protection, and habitat continuity

• Loss of buffer zones critical to shoreline resilience and biodiversity

• Long-term degradation of marsh ecosystems already under stress

Key Concepts: Salt Marsh Management

 

• Salt marshes are structured, dynamic ecosystems shaped by abiotic and biotic interactions.

• Zonation reflects adaptations to gradients in elevation, salinity, and inundation.

• Human activity has drastically altered salt marsh extent and function.

• Restoration and management rely on balancing ecological processes with human use.

 

What Are Seagrasses?

• Marine flowering plants (angiosperms) that live fully submerged in salt water

• Form extensive meadows in shallow, protected coastal zones

• Belong to multiple monocot families, not one taxonomic group

• Defined by ecological function and habitat, not ancestry

Seagrass Common Characteristics

• What defines a seagrass

• The plants must be adapted to life in a saline medium

• The plants must be able to grow when fully submerged

• The plants must have a secure anchoring system

• The plants must have a hydrophilous pollination mechanism

• The plants must be able to compete successfully with other organisms in the marine enviroment

Seagrass Common Characteristics

• What defines a seagrass

• The plants must have a hydrophilous pollination mechanism

  • Hydrophilous=

• water mediated, abiotic pollination

Why So Few Marine Angiosperms

• Known species vs 300,000+ terrestrial and freshwater angiosperms

• Marine life presents

  • High salinity, wave energy, low light

• Few plants evolved full submersion tolerance and hydrophilous pollination

Seagrass Vs Algae

• Seagrass

• Complex root structure to anchor plant in the sediment, and extract nutrients and minerals

• Photosynthesis restricted to cells in leaves

• Transport minerals and nutrients in aerenchyma and the lacunae (veins)

• Sexual reproduction via flower, fruits, seeds

Seagrass Vs Algae

• Marine algae

• Simple holdfast to anchor to hard substrate such as rocks or shells

• Photosynthesis undertaken by all cells

• Uptake of minerals and nutrients from water column via diffusion

• Sexual reproduction via spores

Seagrass Distribution

• 18% of earths shallow coasts could support seagrass habitat

Seagrass Evolution

• Returned to marine life 100 million years ago (Cretaceous)

• Independent adaptations among several lineages

• All within Order Alismatales (monocots)

  • Families: Zosteraceae, Cymodoceaceae, Posidoniaceae, Hydrocharitaceae

• Not true grasses (Poaceae)= more closely related to lilies and pondweeds

• 70 sp globally, mostly in Zosteraceae and Cymodoceacea

 

Common Seagrass genera

• Temperate: Zostera, Phyllospadix, Ruppia, Amphibolis

• Tropical: Thalassia, Halodule, Syringodium, Halophila, Cymodocea, Enhalus, Posidonia

 

Seagrass Succession

• Succession shifts from small fast colonizing pioneer species to larger slow growing species

• Climate community can be monospecific or multi-species (mixed)

• Maximum biomass shifts from above-grown to below ground as community matures

Seagrass Morphology

• Leaves:

• Rhizomes:

• Roots:

• Shoots:

• strap-like or petiolate, with parallel veins and no cuticle

• horizontal stems connecting shoots, store carbohydrates

• adventitious, arise from rhizome nodes, anchor ins sediments

• contain multiple leaves at different growth stages

• Size range: few cm (Halophile) to several m (enhalus)