Final Exam

• What is an estuary?

  It is a partially enclosed body of water that is subject to the flow of saltwater from the sea and freshwater from the land.
• What are some characteristics of estuaries?

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  • usually where a river meets + empties into the sea
  • it supports a large # of species, large biodiversity
  • connected to tidal flats, nearshore environments, + salt marshes
  • have constantly changing salinity
• What are the types of estuaries?

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  1. Tectonic estuary
  2. Bar Built
• What is a tectonic estuary?

  An estuary where the river meets the sea in a place that is tectonically active.
• What is a Bar Built estuary?

  It is an estuary that is partially enclosed by a barrier beach or barrier island.

  • separates ocean from mainland
  • tidal inlet connects estuary to ocean
  • salinity fluctuations w/ tides going in + out
  • organisms need to adapt to this
• What are estuaries considered to be?

  Critical transition zones
• What is a critical transition zone?

  A critical transition zone is an area where significant changes occur in the environment, such as shifts in species composition or ecosystem structure.
• How does salinity affect estuaries?

  Salinity gradient:

  • spatial: horizontal + vertical stratification
  • temporal: salinity boundaries
  • freshwater flow on top of saltwater
• What is the substrate like in estuaries?

  • soft bottom, fine grain, muddy sediment that is easily suspended
  • organic detritus
  • infauna common: crustaceans, worms, bivalves
• How does temperature affect estuaries?

  • warmer (shallower, contained compared to open ocean)
  • fluctuates
  • thermocline (only in deep estuaries)
• What are the currents and tides like in estuaries?


  • generally calm
  • river input: changes seasonally w/ rain + weather
  • flushing time: how long the water stays before it gets washed out

  Tides:

  • standing waves: up + down
  • progressive waves: back + forth
• What is the estuarine environment like?


  .

  Turbidity:

  • suspended particles, high turbidity

  Nutrient-rich:

  • humans making it richer due to eutrophication
  • excess nitrogen and phosphorous (limiting resources) leads to algal blooms

  Anoxia:

  • aerobic bacteria: bacteria decay b/c DO levels go down
  • "dead zones" where everything is dead

  Vegetation:

  • surrounding vegetation absorbs some nutrients from runoff but when destroyed, anoxia + eutrophication
• What are the two types of salinity tolerance? [estuaries]


  Euryhaline: tolerant of changes in salinity, can live in a wide salinity range

  Stenohaline: can't tolerate salinity changes, narrow salinity range
• What determines where most things in estuaries live?


  Temperature + salinity
• What are some physiological adaptations to salinity?


  Osmoregulators: can regulate their internal salt concentration if salinity changes

  Osmoconformers: if salinity changes, their internal salinity changes (NOT in estuaries)

  Osmosis: moving water across membrane
• What is the estuarine food chain like?


  • phytoplankton (diatoms, dinoflagellates)
  • detritus from salt marshes
• What are animals that live in estuaries?


  Oysters, blue crabs, horseshoe crabs, shorebirds, fish
• American Oyster - Crassostrea virginica [Estuaries]


  • structural engineers of estuarine benthic habitats
  • provides a place for other organisms to live
  • attach to/crawl within oysters
  • sanitation engineers: they are filter feeders, good at purifying water
  • consumes a lot of plankton
• Codium Fragile - "dead man's fingers" "green fleece" [Estuaries]


  • asia -> europe -> NY through ship/trade, now everywhere
• Blue Crabs - Callinectes sapidus [Estuaries]


  • dimorphic claws (crusher + cutter)
  • decapods: 10 legs
  • portunid: swimming crabs
  • have points on carapace
  • can use tides to go up + down the bay
  • overfished
• Molting + Softshell Crabs


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  • intermolt: tissue growth
  • premolt: resorb Ca + form new shell
  • ecdysis: shedding old shell
  • post-molt: harden shell
• Horseshoe crabs - Limulus polyphemus


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  • congregate on protected beaches in june/july
  • lays eggs on beach b/c of fish predators
  • lays withing first 2 inches of sand
  • grind food (bivalves) w/ legs
  • book gills: flap around + extract oxygen out of the water
• Migratory Shorebirds [estuaries]


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  • sanderlings, ruddy turnstones, semipalmated sandpiper, red knot
  • red knot: nest in arctic, migrate from patagonia (endangered species now)
• Fish in Estuaries:


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  • most are migratory / visitors
  • estuarine spawners: lay eggs in estuary
  • offshore spawners: spawn offshore, tide takes eggs in
  • permanent residents
• Why are estuaries important?


  They are nursery grounds.

  • food is abundant
  • large predators are scarce
• Migratory fish in estuaries:


  Anadromous: live in ocean, swim up the river into estuaries to spawn

  • feed on plankton/little invertebrates
  • shad, herring, salmon, alewife, striped bass

  Catadromous: live in freshwater estuaries, migrate to the sea to spawn

  • eels (spawn in sargasso sea)

  Estuarine Spawners: adults live offshore, migrate to estuaries to spawn, young develop in estuaries

  • ex. winter flounder, tautog

  Offshore Spawners: adults live + spawn offshore

  • eggs + larvae use tides to migrate into estuaries + develop there
  • ex. menhaden, mullets, scup, flounder
• Where are fish-permanent residents abundant?


  In marsh creeks.

  • sticklebacks, killifish mumichs, silversides
• What is a salt marsh?


  An intertidal ecosystem inhabited by flowering plants (mostly grasses).

  • occurs in protected shores + where the land meets the sea
  • muddy + unconsolidated substrate
  • peat: semi-decomposed plant parts
  • anoxic + salty causing very few plants to live in that env.
  • stressful due to flooding and salinity
• Where do salt marshes line?


  They typically line estuaries and are behind barrier beaches.
• How does clonal growth happen in salt marshes?


  Genet: single genetic individual (product of a single seed)

  Ramet: units of clonal growth

  • connected by horizontal rhizome
  • has upright shoots
  • ex. corals + polyps, hydroids + zooids

  Aerenchyma Tissue: airspace in tissue that allows the diffusion of oxygen to the plants through the rhizomes and roots
• What is aerenchyma tissue?


  Airspace in tissue that allows the diffusion of oxygen to the plants through the rhizomes and roots.
• What is the ecology of salt marshes like?


  ,

  • detritus-based ecosystem
  • plants die, decay carried out by bacteria + fungi
  • things eat bacteria + fungi, poop it out
  • tide carries it out of salt marshes, influencing the food chain by moving nutrients
• What zonation patterns do salt marshes have?


  Low marsh: gets covered by low + high tides

  High marsh: may or may not get covered by low + high tides
• Spartina alterniflora - Salt Marsh Cordgrass?


  • by the edge of creeks
  • low marsh zone (gets flooded 2x day)
  • soil conditions affect how tall it grows (due to amount of oxygen)
• Spartina patens - Salt Marsh Hay / Salt Meadow Grass?


  • high marsh zone
  • stems are fine, no energy to hold themselves up
  • neighbors hold them up
• Juncus gerardi - Black Rush


  • flower, makes fruits
  • high marsh zone
  • remets closely spaced together
• Disticulus specata - Spike Grass?


  • waits for a disturbance to kill off other plants (like s.patens + juncus gerardi), then moves in
  • ramets widely spaced along rhizome -> fast-moving/spreading
• Iva frutescens - Marsh Elder?

  • gets to 1-2m in height
• Fugitives:


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  • Glasswort (salicomia): must grow from seed
  • Sea Lavender (limonium)
  • Salt Marsh Aster (aster)
  • Goosefoot (atriplex)
• Phragmites [salt marsh]?


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  • upper end of high marsh
  • native non-native
  • clonal invasion