Between the Tides

http://video.google.com/videosearch?q=Grunion%20run%20at%20la%20jolla&rls=com.microsoft:en-us&oe=UTF-8&startIndex=&startPage=1&um=1&hl=en&ie=UTF-8&sa=N&tab=iv#

La Jolla Grunion Run

Where?• Shoreline between high

and low tide marks

Organismal adaptations?• Community has to be

adapted to exposure to air

• Communities differ greatly depending on structure– Rocky or sandy

bottoms

What is the greatest concern to the intertidal organisms?• Water loss or desiccation• Take advantage of crevices, clustering, shade,

tidepools, other organisms, etc.

Fig. 11.2

• Move to moisture & clamp their ventral surface to the substrate to conserve water (chitons)

• Closed mussel shells• Contracted anemone• Resilient tissues that can

withstand 75-90% water loss…tidal exposure limits activities…can be harsh conditions

Fig. 11.3Fig. 11.4

Fig. 11.5

Wave exposure and wave shock

• Adaptations to cope? – Seaweeds?– Mussels?– Intertidal fishes?

• Wave energy varies– Sheltered coastlines– Angled wave approach– Varied impact to organisms– Gradient of impact (shock)

and exposure

Fig. 11.7

Fig. 11.8

• Distribution, diversity, & abundance partially defined by exposure

• Why the differences?

Fig. 11.11

• Sheltered– Less wave force– Higher profile

• Heavier wave action– Lower profile to reduce drag

Fig. 11.12

• Flexibility to deal with wave action

Fig. 11.13

• Safety in numbers– (a) Wave force can detach higher profile individuals– Clustering can protect from wave shock (as well as preventing

excessive desiccation).– (b) Wave force is indirect – reduced or dissipated some– (c) Too dense can be a problem sometimes

Fig. 11.14

• Shaping the intertidal zones so far…– Effects of wave exposure

• Temp, salinity, desiccation– Effects of wave shock

• What else effects organismal distribution?

• Food / nutrients• Trophic interactions

– Many suspension feeders– Grazers– Scavengers– Predators– Detritus is central

• typically most important food source

Fig. 11.15

• Space is typically most limiting resource

• Most organisms are attached to substrate– Mussel species– Barnacle species– Anemones, seaweed

• Much competition for any freed-up space

Fig. 11.16

What is happening here?• Juvenile sea palm settled

on mussels– Increased profile and drag

increases vulnerability of wave shock

• Mussel clumps detach

• Makes space for juvenile sea palms on substrate

Fig. 11.17

Trophic interactions & environmental adaptations define zones

• Vertical zonation– Patterns or banding of

distribution– Upper limit set by physical

factors• Space often defines upper end

of range – zones• Exposure

– Lower limit set by biotic factors

• Predation• Competition

Fig. 11.19

Fig. 11.18

Fig. 11.20

Fig. 11.21

Diversity and abundance• At Scripps intertidal, organismal diversity was high.• Species abundance varies with diversity

– Mussels in mod. abundance; Barnacles – mod.; Sea stars – mod.• Keystone predators

– A predatory species that significantly affects the community beyond their abundance

– Can maintain diversity

Fig. 11.22

Fig. 11.23

Page 252

Predation on dominant competitors = disturbance• ↓ predation = ↓ disturbance = competitive

exclusion• ↑ disturbance = ↓ establishment = ↓ diversity• Moderate disturbance = provides a balance

between abiotic and biotic factors; a chance for diverse species

Fig. 11.23 & 11.24

What about sandy intertidal areas? Beaches?• Still get zonation patterns…

– However, here many organisms are adapted for sand/sediments rather than rocks and tidepools

Fig. 11.33 & 11.34