- cont. shelf btwn. high and low tides

-regularly exposed to air

-usually at active cont. margins

- earth, moon and sun aligned

- highest high/ low tides

- sun and moon form 90 degree angle with Earth

- intermediate highs and lows

1. diurnal vs. 2. mixed semidiurnal

vs. 3. semi diurnal

1. 1 high and 1 low

2. 2 unequal highs, 2 unequal lows

3. 2=highs and 2=lows

- MLLW= 0 tide level

-avg. of 2 daily Low tides, averaged over many years

positive: high MLLW

negative: low MLLW

-emmersion: exposed to air

-immersion: covered by water

- high in intertidal = more time emersed each month

- daily emersion = high T and salinity

- air T varies more than water T

(high heat capacity for water)

- low tide at midday = very high T and salinity + low O2

-food not limited in intertidal, but

time to feed may be limited

(most animals feed when immersed)

-higher in intertidal=lower immersion

=less feeding time

- major, daily factor

-high variability (space and time)

1. clamp down, close shells, clump

(barnacles, mussels, limpets)

2. slimy coating that turns into dry protective coating

(anemones, rockweeds)

3. live in tidepools

(fishes, anemones, worms)

1. clamp down, close shells, clump

2. live in tide pools

3. live in crevices/ overhangs

4. physiological tolerance

(sculpins, periwinkle snails)

5. live in/ move to cool, moist places

6. close up or have light color

1. hang on (barnacles)

2. keep a low profile (anemones)

3. go with the flow (seaweeds)

4. avoid it (crabs, urchins)

- #1 limiting resource in intertidal

- many orgs. attach 

- space is limiting leading orgs. to compete= all space occupied

1. overgrow other orgs.

(colonial seasquirts, mussles, barnacles)

2. dislodge competition

(giant owl limpet)

3. stinging wars

(fighting tentacles)

- each org. lives in specific vertical range

- high intertidal, mid intertidal and low intertidal

-seldom completely submerged

-common orgs: lichens, copepods, periwinkle snails, acorn barnacles

-regularly submerged and uncovered

-upper mid zone- acorn barnacles

-lower mid zone- mussles

- mostly submerged

- predators abundant

- high diversity: invertebrates, algae, fishes, plants

- upper limit set by abiotic factors

(wave action, salinity, space, temp.)

- lower limit set by biotic factors

(predation, competition)

- keystone species

- feeds on mussels in intertidal

-remove star and the mussels move from above low mid tide to below it =

change in community and less biodiversity