Chapter 6
Intertidal Ecology
Intertidal Zones
Best known
Most accessible to humans
Studied intensely
Low tide observations
Greatest variations of environmental factors only cm’s away from each other
Diversity is great
Has not been invaded by terrestrial flora or fauna
Environmental Conditions
Tides
Important influencing factor
Without them, this zone does not exist
2 highs and 2 lows each day
perigee
Apogee
Bay of Fundy in Nova Scotia
Cook Inlet in Alaska
Diurnal tides
Semidiurnal tides
Mixed tides
Duration of exposure
No tides in Mediterranean, Black, Baltic
Wind action pushing water
Critical Tide Levels
Temperature
Oceans and seas so minimum ranges of temperature change because of its size
Rarely exceeds lethal limits
Intertidal do have this lethal situation
Death will occur later because of weakness from extreme temperature
Secondary causes
Marine organism – death by desiccation ( dry up )
Wave Action
Very influential or marine organisms
Directly
1. Mechanical – smashes and tears away objects
2. Wave action extends limits
Throws water higher on shore than tides
Organisms higher exposer
More chance of desiccation from high temperatures
Mixes atmospheric gases with water, higher O2
Never lacks O2
Indirectly
Salinity
Changes can effect organisms
Exposure at low tide
Flooded by heavy rains or runoff from heavy rains
Reduces salinity
Organisms limited tolerance at low salinities
Extreme reduction cause swelling by osmosis , death
Tide Pools – retain seawater at low tide
Freshwater flooding
Reduce salinity, but evaporation creates high salinity
Other Factors
ICE
Far northern of southern shores
Icebergs
Catastrophic mortality by freezing / mechanical abrasion
Different substrates have different faunas and community structure
Rocky
Sandy
Muddy
Adaptations of Intertidal Organisms
Avoiding or minimizing stresses of daily exposure to air
Major stress is wave action
Resistance to Water Loss
Maintenance of Heat Balance
Mechanical Stress
Respiration
Feeding
Salinity Stress
Reproduction
ROCKY SHORES
Composed of hard substrate
Densely inhabited with macroorganisms
Greatest diversity of animal and autotroph species
Almost barren of sand and mud surfaces
Marine biologists fascinated
Species interaction and maintain or change of community
Solitary or clonal
Atlantic and Pacific Rocky Shores
Differences Temperate Atlantic and Rocky Pacific
Atlantic lacks rocky intertidal south of Cape Code
Sedimentary dominate
Pacific dominated by rock from California up to Alaska
Sedimenatry uncommon
Range of aerial temperatures
Narrow over Pacific coast
Seasonal and daily over Atlantic
- 20 0 C winter to 40 0 C summer
Pacific, Canada, southern Alaska
rarely go below freezing in winter
Summer – cloudy and foggy
continued
Atlantic – lower diversity than Pacific
Ice age - glaciers scoured Atlantic coastline
Widespread extinction of rocky intertidal organisms
Pacific intertidal
spared, older geologically, more speciation
Puget Sound
Five common chiton
Large size
New England
3 species
All small, uncommon, primarily subtidal
Green crab species introduced from Europe
Littorine – dominate herbivore
Zonation
Horizontal banding of organisms
Succeed vertical
Mountain elevation
Km compared to meters
Vary in vertical extent
angle of slope
Gradual – zones are broad
Narrow zones
tidal range
exposure to wave action
Terms
Supralittoral fringe
Midlittoral zone
Infralittoral fringe
Infralittoral zone
Sublittoral area
Causes of Zonation
Physical and Biological factors
Physical factors
Tidal action
Exposure to air
Temperature extremes
Desiccation
Series of tidal curves
Critical Tide Levels
Doty ( 1946 )
Various places and several scientists
Gulf of Maine
Simple zonation
Barnacle
Kelp zone
Few mussels
Biological factors
Tropical Intertidal Shores
Patchiness
Succession
Horizontal Distribution Patterns
Age Structure
Interactions Among Factors: A Summary
Tidal Pools
SANDY SHORES
Environmental Conditions
Adaptations of Organisms
Types of Organisms
Feeding Biology
Community Organization on Exposed Sand Beaches
Community Organization on Protected Sand Flats
MUDDY SHORES
Physical Factors
Adaptations of Organisms
Types of Organisms
Feeding Biology and Trophic Structure
Zonation and Community Structure
INTERTIDAL FISHES
BIRDS
Low tides, they show up to feed
Sand and mudflats are the place the like to visit
Predators of infaunal invertebrates
Plenty of food available
Migratory birds in temperate zone
Infauna can recover
Tidal flats are not uniform in community
structure
Grain size
Succession patterns that follow disturbances
Depth in sediment and tidal level