Lecture #11: Intertidal Zone

Intertidal zone

The shoreline between highest high and lowest low tide

Rocky intertidal

Active margins, low sediment, organisms are epifauna (sessile & filter feeders)

Strategies for desiccation

Run and hide, close up to prevent from drying out

Wave energy

Bend or refract, move parallel to shore, influences larval settlement and food availability

Dealing with wave energy

Thicker shells, low profile, flexibility, increase density, strong attachments

Community interactions

Food is not limited but space is

Effective competition

Dispersal, attachment, rapid reproduction, remove competitors, grow over competitors

Vertical zonation

Distinct bands or zones, at characteristic heights along the shoreline

Upper intertidal

Splash zone and mostly above high tide mark

Middle intertidal

Affected by times and emersion time is important

Lower intertidal

Immersed most of the time

Subtidal zone

Never exposed at low tide

Upper limit

Set by physical factors; dessication

Lower limit

Set by biological factors; predation & competition

Ecological succession

Regular patterns of regrowth in the rocky intertidal

Soft-bottom intertidal determined by

Type of sediment, water motion

Grain size determines

Water circulation, food, amount of O2

Food web

Mostly deposit feeders feeding on detritus