Estuarine%20Dynamics

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Estuarine Dynamics David Nash and Jenny McDaniel
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Overview

• Definition of estuary
• Estuarine influences
• Intertidal estuary
• Subtidal estuary
• Producers
• Consumers
• Decomposers

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What is an estuary?
Cowardin et al. 1977 ...deepwater tidal
habitats and adjacent tidal wetlands which are
usually semi-enclosed by land, but have open,
partially obstructed, or sporadic access to the
open ocean and in which ocean water is at least
occasionally diluted by freshwater runoff from
the land.
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Estuarine Boundaries
The limits of an estuarine system extend 1)
upsteam and landward to the place where
ocean-derived salts measure less than 0.5
ppt during the period of average annual
low flow
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Estuarine Boundaries
The limits of an estuarine system extend 2) -
seaward to a line closing the mouth of a
river,bay, or sound - seaward to a line
enclosing an offshore area of diluted
seawater with typical estuarine flora and
fauna - seaward limit of wetland emergents,
shrubs or trees where these plants
grow seaward of the line closing the
mouth of a river, bay, or sound
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Estuaries 2 Major subdivisions

• Intertidal - those areas where the substrate is
  periodically exposed and inundated by tides
  including the associated splash zone
• Subtidal- those areas where the substrate is
  continuously submerged

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Estuarine influences

• oceanic tides
• currents
• precipitation
• runoff from the land
• evaporation
• wind
• river flow
• meteorological pressure centers

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Estuarine influences...cont.

• salinity
• size and shape of estuary
• water temperature
• turbidity
• substrates
• erosion
• deposition
• pollution

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Intertidal Estuary

• Characteristics
• high environmental stress
• low species diversity
• often dominated by salt marshes and flats
• transitional area b/w uplands and permanently
  flooded estuaries and bays
• includes both terrestrial and marine organisms

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Intertidal Estuary Producers

• Species occurrence limited by
• salinity
• drainage
• temperature
• tidal influence

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Intertidal Estuary Producers

• nonvascular flora - various micro/macrophytes
  including diatoms, blue- green algae, red and
  brown algae, etc.
• vascular flora - diversity is low, Spartina
  alterniflora tends to be the dominant
  species.

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Producers nonvascular microphyte substrates

• mud flats
• marsh pannes (unvegetated sand flats)
• creek banks
• soils of halophytic angiosperms
• macroscopic algae
• oyster shells
• submerged marsh vegetation

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Producers nonvascular macrophyte substrates

• mud flats
• marsh pannes (unvegetated sand flats)
• creek banks
• soils of halophytic angiosperms
• oyster reefs
• shell banks
• pilings and sea walls
• surface and subsurface waters

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Producers nonvascular macrophyte substratescont.

• dead and living spartina stems
• marsh periwinkle

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Producers Vascular Flora

• Influenced by
• water level fluctuations
• salinity
• substratum type
• acidity
• fire
• nutrient availability
• aeration

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Producers Vascular Floracont.

• Influenced by
• temperature
• light
• plant competition
• salt spray
• animal activity
• human activity

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Subtidal Estuary

• Characteristics
• environmental factors fluctuate more
  frequently and more widely than in either
  freshwater or seawater systems.
• Abundant nutrients supplied by sediments,
  seawater, freshwater, precipitation,
  groundwater,microbial decomposition, bacterial
  and algal nitrogen fixation, and runoff from
  intertidal salt marsh and land areas.

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Subtidal Estuary Producers

• Phytoplankton
• Macrophytes

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Subtidal Estuary Phytoplankton

• Influenced and limited by
• salinity
• temperature
• light intensity at surface
• light intensity below surface
• nutrients
• pollutants

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Subtidal Estuary Macrophytes

• Macroscopic algae limited by
• substrates (solid, permanent substrate often
  absent)
• scouring action of the tides
• turbidity

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Subtidal Estuaries

• Productivity is limited by three separate, but
  interdependent, units of primary production
• marshes and their resulting detritus
• benthic micro and macrophytes
• phytoplankton

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Consumers

• Benthic meiofauna-animals living in the
  sediments (0.5-.063mm in size)
• - most of these animals are nematodes with
  copepods second in abundance

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Consumers

• Benthic macroinvertebrates - animals that live
  in the sediments and are gt0.5mm in size
• - the number of these organisms is limited
  due to the stressful environmental
  conditions (salinity, drainage, temp, etc.)
• - inverts play an important role of reworking
  the benthic sediments (burrowers, etc.)

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Benthic macroinvertebrates
marsh periwinkle ribbed mussel
oyster reef
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Benthic macroinvertebrates

fiddler crab
polychaete worm
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Insects

• Insects are significant pathways of energy
  flow within the marsh ecosystem
• Insect fauna is varied and abundant in almost
  all salt marsh habitats
• Diptera (flies, mosquitoes, and midges),
  Coleoptera (beetles), and Hemiptera (true
  bugs) comprise about 75 of the species in
  marshes

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Insects
Diptera
Coleoptera
Hemiptera
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Insects

• Most non-aquatic species tend to avoid areas
  subject to tidal inundation
• Carnivrous insects- most common are spiders,
  beetles, and mosquitoes
• Low plant diversity limits food sources for
  herbivorous insects examples grasshoppers,
  ants
• Insects are also important prey items for
  predators such as birds (marsh wren)

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Fishes

• Most resident species move in and out with the
  tide or remain in standing pools of water -
  example mummichog, sheepshead minnow
• Other species use the marsh for different life
  stages
• - example mullets, spotted seatrout, spot

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Fishes

Spot
Striped mullet
Spotted sea trout
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Amphibians and Reptiles

• Few species are represented in the saltmarshes
  of the southeast US
• Amphibian examples

Eastern narrowmouth toad
Southern leopard frogs
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Reptiles

Eastern glass lizard
Banded water snake
Diamondback terrapin
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Reptiles American alligator

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Birds

• Salt marsh vegetation serves as a base for
  reproduction, feeding, and roosting activites
• - examples
• long-billed marsh wren- defends its feeding
  and breeding territory individually
• white ibis- colonial nesters remove large
  amounts of marsh grasses to build nests
• red-winged blackbirds- roost in marsh

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Birds

long-billed marsh wren
White ibis
Red-winged blackbird
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Birds

• Presence of birds helps to cycle nutrients
• - dispersal of seeds
• - fecal material fertilizes marsh plants and
  has been shown to enhance growth

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Birds

• Wood stork- federally endangered species that
  relies on fish found in marshes for primary
  food source

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Birds

• Great egret- year round resident in estuarine
  marsh habitat. Feeds on small fish, shrimp, and
  crabs.

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Birds

• Clapper rail- permanent resident that feeds,
  nest, and roosts in the Spartina marsh.

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Birds

• Willet- shorebird that is seen seasonally in
  the estuarine marsh system. Feeds on
  crustaceans, molluscs, and annelids.

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Birds

• Marsh hawk- raptor that preys on clapper rails
  and small mammals.

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Mammals

• Herbivores
• Marsh rabbit-feeds on cordgrass, but
  populations are limited due to predation by
  marsh hawks
• White-tailed deer-tends to graze in the
  higher marsh regions

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Mammals

• Omnivore
• Marsh rice rat- remains persistently in the
  marsh. Feeds on cordgrass, crabs, and insects.

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Mammals

• Carnivores
• Racoons- feeds heavily on crustaceans,
  molluscs, and bird eggs and young

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Mammals

• Carnivores
• River otter- depends on fishes and crabs. Has
  few predators, yet populations remain low.

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Decomposers bacteria and fungi

• 3 primary roles
• decomposition of dead organic matter
• conversion of indigestible plant material
  (cellulose) to a form that is readily used by
  detritivores and deposit feeders
• conversion of dissolved organic and inorganic
  materials into consumable particulate matter

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Subtidal estuarine consumers
Zooplankton - animals that live in the water
column and are at the mercy of the
currents - able to tolerate salinity
fluctuations up to 12ppt during a single
tidal cycle - zoo. biomass is greatest in
estuaries - serve important role in estuarine
food web - food for many larval and
juvenile fish
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Zooplankton...cont.
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Zooplankton...cont.
Human impacts Effluent discharges- indirect
effects Channel dredging- decrease primary
production which in turn lowers zoo.
populations Pesticides and heavy metals- not
only effect zoo.populations, but also
impact larval fish and invertebrates by
causing developmental delays,
abnormalities, and death
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Benthic meiofauna

• Benthic meiofauna-animals living in the
  sediments (0.5-.063mm in size)
• - most of these animals are copepods,
  including both interstitial and burrowing
  species
• - these animals are highly sensitive to both
  temperature and oxygen fluctuations

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Benthic macroinvertebrates

• Species diversity depends on 2 factors
• Substrate
• silt, sand, or clay - high diversity
• medium to fine grain sand- low diversity
• clay and either silt or fine grain sand- low
  diversity

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Benthic macroinvertebrates

• Species diversity depends on 2 factors
• Salinity
• lt 5 ppt (oligohaline waters)
• 5-18 ppt (mesohaline waters)
• gt 18 ppt (polyhaline/euhaline waters)
• Species diversity tends to increase with an
  increase in salinity

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Benthic macroinvertebrates
amphipods, polychaetes, bivalves
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Benthic macroinvertebrates

Sand dollar
Green Jacknife Clam
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Commercially important macroinvertebrates


Brown shrimp
White shrimp
Blue crab
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Fishes

• Species composition is abundant and diverse

Spot
Atlantic croaker
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Trophic relationships

Top CarnShark
1 CarnivoresBay Anchovy
HerbivoresMullet and Menhaden
Primary Producers
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Reptiles

• One of the only reptiles truly found in the
  subtidal estuarine system is the
• Diamondback terrapin

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Birds

• Birds use the subtidal region for
• resting and feeding
• Species include
• Herring gull- scavenger
• Ring-billed gull- scavenger
• Laughing gull-scavenger
• Brown pelicans- piscivore
• Royal terns- piscivore
• ect.

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Birds


Herring gull
Ring-billed gull
Laughing gull
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Birds


Brown pelican
Royal Tern
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Mammals

• Only 2 consistent components of the subtidal
  estuarine system
• River otter

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Mammals

• Only 2 consistent components of the subtidal
  estuarine system
• Atlantic bottlenosed dolphin

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References
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Referencescont
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