Estuarine Dynamics
David Nash and Jenny McDaniel
Overview• Definition of estuary• Estuarine influences• Intertidal estuary• Subtidal estuary
• Producers• Consumers• Decomposers
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.”
Estuarine BoundariesThe 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
Estuarine BoundariesThe 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
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
Estuarine influences• oceanic tides• currents• precipitation• runoff from the land• evaporation• wind• river flow• meteorological pressure centers
Estuarine influences...cont.• salinity• size and shape of estuary • water temperature• turbidity• substrates• erosion• deposition• pollution
Intertidal EstuaryCharacteristics:
• 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
Intertidal Estuary: ProducersSpecies occurrence limited by:
• salinity• drainage• temperature• tidal influence
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.
Producers: nonvascular microphyte substrates
• mud flats• marsh pannes (unvegetated sand flats)• creek banks• soils of halophytic angiosperms• macroscopic algae• oyster shells• submerged marsh vegetation
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
Producers: nonvascular macrophyte substrates…cont.
• dead and living spartina stems• marsh periwinkle
Producers: Vascular FloraInfluenced by:• water level fluctuations• salinity• substratum type• acidity• fire• nutrient availability• aeration
Producers: Vascular Flora…cont.Influenced by:• temperature• light• plant competition• salt spray• animal activity• human activity
Subtidal EstuaryCharacteristics:
• 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.
Subtidal Estuary: Producers
• Phytoplankton• Macrophytes
Subtidal Estuary: Phytoplankton
Influenced and limited by: • salinity• temperature• light intensity at surface• light intensity below surface• nutrients• pollutants
Subtidal Estuary: MacrophytesMacroscopic algae limited by:• substrates (solid, permanent substrate often absent)• scouring action of the tides• turbidity
Subtidal EstuariesProductivity is limited by three separate, but interdependent, units of primary production• marshes and their resulting detritus• benthic micro and macrophytes• phytoplankton
Consumers• Benthic meiofauna-animals living in the sediments (0.5-.063mm in size)
- most of these animals are nematodes with copepods second in abundance
Consumers• Benthic macroinvertebrates - animals that live in the sediments and are >0.5mm 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.)
Benthic macroinvertebratesmarsh periwinkle ribbed mussel
oyster reef
Benthic macroinvertebrates
fiddler crab polychaete worm
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
Insects
Coleoptera
DipteraHemiptera
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)
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
Fishes
Striped mullet Spot
Spotted sea trout
Amphibians and Reptiles• Few species are represented in the saltmarshes of the southeast US
Amphibian examples:
Eastern narrowmouth toad
Southern leopard frogs
Reptiles
Banded water snake
Eastern glass lizard
Diamondback terrapin
Reptiles: American alligator
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
Birds
White ibis
Red-winged blackbird
long-billed marsh wren
Birds• Presence of birds helps to cycle nutrients
- dispersal of seeds- fecal material fertilizes marsh plants and has been shown to enhance growth
Birds• Wood stork- federally endangered species that relies on fish found in marshes for primary food source
Birds• Great egret- year round resident in estuarine marsh habitat. Feeds on small fish, shrimp, and crabs.
Birds• Clapper rail- permanent resident that feeds, nest, and roosts in the Spartina marsh.
Birds• Willet- shorebird that is seen seasonally in the estuarine marsh system. Feeds on crustaceans, molluscs, and annelids.
Birds• Marsh hawk- raptor that preys on clapper rails and small mammals.
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
Mammals Omnivore
• Marsh rice rat- remains persistently in the marsh. Feeds on cordgrass, crabs, and
insects.
Mammals Carnivores
• Racoons- feeds heavily on crustaceans, molluscs, and bird eggs and young
Mammals Carnivores
• River otter- depends on fishes and crabs. Has few predators, yet populations remain low.
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
Subtidal estuarine consumersZooplankton
- 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
Zooplankton...cont.
Human impacts:Effluent discharges- indirect effectsChannel 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
Zooplankton...cont.
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
Benthic macroinvertebrates• Species diversity depends on 2 factors:
Substratesilt, sand, or clay - high
diversitymedium to fine grain sand-
low diversityclay and either silt or fine
grain sand- low diversity
Benthic macroinvertebrates• Species diversity depends on 2 factors:
Salinity< 5 ppt (oligohaline waters) 5-18 ppt (mesohaline
waters)
> 18 ppt (polyhaline/euhaline waters) * Species diversity tends to increase with an increase in salinity
Benthic macroinvertebrates amphipods, polychaetes, bivalves
Benthic macroinvertebrates
Sand dollar Green Jacknife Clam
Commercially important macroinvertebrates
White shrimp
Brown shrimp
Blue crab
Fishes• Species composition is abundant and diverse
Atlantic croaker
Spot
Trophic relationships
Primary Producers
HerbivoresMullet and Menhaden
1° Carnivores
Bay Anchovy
Top CarnShark
Reptiles • One of the only reptiles truly found in the
subtidal estuarine system is the:Diamondback terrapin
Birds• Birds use the subtidal region for:
resting and feeding•Species include:
Herring gull- scavengerRing-billed gull- scavengerLaughing gull-scavengerBrown pelicans- piscivoreRoyal terns- piscivoreect….
Birds
Herring gull
Ring-billed gull
Laughing gull
Birds
Brown pelican
Royal Tern
Mammals• Only 2 consistent components of the subtidal estuarine system:
River otter
Mammals• Only 2 consistent components of the subtidal estuarine system:
Atlantic bottlenosed dolphin
References http://www-staff.lboro.ac.uk/~cvcfs/simulations/estuarinedynamics/frame.htmlhttp://www.tulane.edu/~eeob/Courses/Ecology_Materials/estuary_biome.htmlhttp://inlet.geol.sc.edu/nerrsintro/nerrsintro.htmlhttp://riceinfo.rice.edu/armadillo/Galveston/Chap8/ch8.estuarine.food.htmlhttp://www.geog.ucl.ac.uk/~jfrench/EEI.htmlhttp://www.nwrc.gov/about/web/nutrient.htmlhttp://www.ucc.uconn.edu/~skoog/Michaelb.htmhttp://www.environment.gov.au/portfolio/anca/mpa/c_ray.htmlhttp://www.epa.gov/nep/http://www.estuarylive.org/http://www.epa.gov/ceisweb1/ceishome/atlas/maiaatlas/maia__condition_of_the_mid.htmlhttp://pelotes.jea.com/fidcrab.htmhttp://oak.conncoll.edu/~dmwhi/milfordpaper.htmlhttp://www.tpwd.state.tx.us/expltx/eft/gulf/cspecies/wildlife.htmhttp://www.st-and.ac.uk/~seeb/pheromone/pcWorms.html
References…cont http://ag.arizona.edu/tree/eukaryotes/animals/arthropoda/hexapoda/hemiptera/hemiptera.htmlhttp://www.mdarchives.state.md.us/msa/mdmanual/01glance/html/symbols/reptile.htmlhttp://www.mbr-pwrc.usgs.gov/id/framlst/i1840id.htmlhttp://www.kwic.com/~pagodavista/harrier.htmhttp://www.cviog.uga.edu/Projects/gainfo/wildlife/marshrabbit.htmhttp://employeeweb.myxa.com/rrb/Audubon/VolV/00541.htmlhttp://donb.furfly.net/malheur/birds/willet.htmlhttp://www.otternet.com/galleries/naotter/http://www.csc.noaa.gov/otter/htmls/ecosys/ecology/estuary.htm#tophttp://www.bio.swt.edu/Lavalli/guides/phylum_arthropoda.htmhttp://endangered.fws.gov/i/B2S.htmlhttp://www.camacdonald.com/birding/DesJardin/LaughingGull.html
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