Estuaries Semi-enclosed areas where fresh water from rivers mixes with salt water from the ocean

Estuaries

• Semi-enclosed areas where fresh water from rivers mixes with salt water from the ocean

Figure 10.22

Figure 12.01

Estuaries

• Dramatic fluctuations in salinity

• Salinity increases with depth
• Salinity decreases upstream
• Salinity varies with tides

Organisms Must Cope with Salinity Changes

• Most are euryhaline

• Can tolerate a wide range of salinity

• Or have restricted ranges

Organisms Must Cope with Salinity Changes

• Osmoconformers

• Salt concentration varies with salinity

• Osmoregulators

• Maintain constant salt concentration in their bodies

estuarine “communities”

• Open Water

• Mud (or Salt) Flats

• Salt Marsh

• Mangroves

Open Water Community

• Marine plankton comes in and out with tides

• Many fish use estuaries as nurseries

Figure 12.09

Mud Flats

• Where the bottom of estuary becomes exposed at low tide

• Many infaunal deposit feeders

Figure 12.12

Figure 12.13b

What lives In the Bottom?

• Benthic Community!

• Infaunal Organisms

• Sediment Matters!

• Can be “muddy” (like the mud flat) or “sandy” (like the sand flat)

(Bottom) “Intertidal”

• “Intertidal” zones, between high and low tide, are predominantly related to ROCKY bottoms on the NORTH SHORE (LIS)…but are made of either SAND or MUD (i.e. “soft bottom” habitats) in bays/ponds etc.

Figure 11.34

Soft Bottom Intertidal Communities

• Soft=organisms can burrow

• Sandy beaches, mud flats

Soft Bottom Intertidal Communities

• Unstable, sediments move due to currents, waves and tides

• Can’t hold on

• Not many seaweeds
• Animals must burrow = infauna
• Clams use foot
• Crustaceans dig
• Sea cucumbers eat

Figure 11.31a

Figure 11.31b

Figure 11.31c

Figure 11.31d

Figure 11.32

Soft Bottom Intertidal Communities

• Grain size of sediment is important

What else lives there?

• SMALL invertebrates

• Clams

• Sand Crabs

• Meiofauna: Tardigrades

“Water Bear” (fnft)

Grain Size of sediment

• indicates water movement

• Calm areas = muddy bottoms
• Wave and currents = coarser sediment

Grain Size of sediment

• Determines ability to stay wet

• Coarse sediments drain fast
• Fine sediments drain slower
• Mixture – blocks water drainage

Figure 11.28a

Figure 11.28b

Figure 11.28c

Problems of living in sediment

• Dessication is NOT as much of a problem

• But it is in coarse sediments

Problems of living in sediment

• Food availability

• Most infauna are deposit feeders or suspension feeders
• More organic matter (detritus) in fine sediments

Problems of living in sediment

• Oxygen availability

• Used up by animals and bacteria
• Replenished by water flowing though sediment
• Problem in muddy bottoms

Problems of living in sediment

• Oxygen availability

• Anoxic = no oxygen
• Animals may pump water from the sediment surface or adapt to low oxygen

What if??

• That “mud/sand” mixture has “GRASS” or vegetation growing in it?

• Then it gets a different name – a “Salt Marsh” (like Flax Pond)

Salt Marshes

• Common in temperate regions

• Extend landward from the mudflats

Salt Marshes

• Dominated by salt tolerant land grasses

• Spartina = cord grass (alterniflora and patens) and other grasses (spike grass, switch grass etc.)
• Bushes/Shrubs = Groundsel bush, Iva
• Some invasives too…

Figure 12.14

Figure 12.07

Local…

• Now a few slides of your “local” salt marsh, mud flat community and the species that live there…

Figure 12.08

Tropical Version

• We live in the NE, colder climate, so we have salt marshes…

• In the South, warmer climates prevail, and they get MANGROVES growing in the same “intertidal zone.”

Mangrove Forests

• Common in tropical regions

• Provide a home to many other marine animals

Figure 12.19

“BRIEF WRAP UP” Food “web” and locations

• Salt Marsh

• Open Water

• Mangrove