Intertidal Ecology

What is the Intertidal Zone?

• Zone between highest and lowest tide lines

• Immersed and Emersed

• Rocky and soft intertidal zones

Review: TidesReview: Tides

• What causes tidal movements?• What does it mean to be:

• Diurnal• Semidiurnal• Mixed

• How do tidal movements vary by area?

• What causes tidal movements?• What does it mean to be:

• Diurnal• Semidiurnal• Mixed

• How do tidal movements vary by area?

Pattern: Vertical Zonation

Processes: What causes the pattern?

Upper limit determined by physical factorsExposureWave shock

Lower limit determined by biological factorsCompetitionPredationRecruitment

Varies by location and often not totally clear cut

Exposure

Problems due to emersion: Physical:

DessicationTemperature and salinity fluctuationO2 availabilityUV radiationWave shock

Biological:Feeding restrictionsInability to hide from predators

Dessication

Water loss to the airStrategies:

“Run and Hide” - crevices, tide pools, moist algae, subtidal, burrowing (soft only)

“Clam up” - protective cover seals in moisture (mussels, periwinkles, barnacles)

Allow drying out - massive water loss until next tide (seaweed, limpets)

Temperature Variation

Air vs. Water Adaptations:

Higher tolerance Seek shade and

moisture Morphology Clumping (ex.

Mussels)

Other Issues

Salinity variation due to rain, evaporation

Respiration Gills reduced and/or protected to reduce

drying Organisms slow down metabolism

Feeding Active when tide is high (reduces risk of

exposure)

Wave ActionVaries based

on shorelineF=ma (Where

does the force go?)

Wave shock and shearing

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Dealing with Wave Action

Shelter Permanent

anchorage Holding on Morphology

Compact and streamlined

Hardened bodies Flexibility

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Competition - The Battle for Space

Open space quickly colonized

Strategies: Fast dispersal

and settlement Evict competitors Grow on or over

competitors

Connell experiment

Very little difference at settlement Chthamalus range reduced by competition Transplant/Exclusion experiment results:

Balanus high = dies Chthamalus low = thrives

Eating and Not Being Eaten

How are limits set?

How are limits set?

Rocky Upper Intertidal

“Splash zone” Lichens,

cyanobacteria, and some algae

Periwinkles and limpets

Terrestrial predators

Rocky Mid-Intertidal

Upper areas - gray and rock barnacles Lower limit set by competition and

predationLower areas - mussels and brown algae

Lower limit set by predation from sea stars and spiny lobsters

Ecological Succession

Ecological Succession

Rocky Lower Intertidal

Mostly immersedDominated by seaweeds

Food for grazers, protection from predators

Compete with each otherSea urchins, stars, anemones,

nudibranchs, fishes

Soft-Bottom Intertidal

Sediment accumulationUnstable bottom - what kinds

of organisms cannot live here?

Sediment composition based on wave mixing

Gravel, sand, mud

Importance of Grain Size

Burrowing (Infauna) or living between grains (Meiofauna)

Water circulationLess dessicationNeeded for O2 (no photosynth)

Amount and type of detritus (coarser has less)

Dual problem with mud: Less water + more detritus to decay = less O2

Feeding