1. Intertidal Ecology

2. Best understood marine environment
Easy to get to
Don’t need to get wet (at least not very)
Amenable to terrestrial methods
Dominated by sessile organisms
Classic studies of Paine, Connell and others
However, poorly understood when submerged

3. The RI environment Tides Temperature- wide range
Duration, time, drastically changes environment
Temperature- wide range
Salinity-rain and evaporation
Substrate-
Rocks: Basalt and sandstone-soft ; Granites are hard
Pilings, docks, etc
Wave Action
Mechanical forces, erosion of substrate; importance of spray extension

4. Waves Waves are moving energy
Waves begin as a disturbance- some energy that is put into the system
Think of throwing a rock into a quiet pond
Wind is the cause of most of the disturbances we are concerned with to form Ocean waves

5. Teahupo'o, Tahiti

6. Wave Characteristics

7. Idealized Water Motion
Energy Flows, but not the water!
Back and forth motion

8. Swell Height Swell height is the product of 1. Wind Speed 2. Longevity
3. Fetch

9. Tides
What is a tide?
Periodic raising and lowering of average sea level
Tides are basically very long, shallow waves that wrap around the earth.
Waves are caused by a disturbance, so what is the disturbance here?
Differential Gravitational interactions of Earth, Sun and Moon.
Acts on land and water, but water can move, so it piles up on itself.
field has varying direction and strength over the volume of the earth
The stress-producing effects of a non-uniform gravitational field acting on an elastic body are called tidal forces. Tidal forces from a gravitating body have a strength that depends in the inverse cube of the distance from that body, F ~ 1/r3.

10. _ _ Center of Earth BUT… These are very small differences Water flows
Tides are a differential force, that is, they result by the difference in the force of gravity between two points. So things need to be BIG to have a difference.
change in person’s height is million times smaller than a size of atom!
Going upstairs results in a weight change that is about 5 times larger than that produced by the tidal mechanism during a spring tide.
Land can move ~14 inches at high tide, but we don’t notice.
The Day gets longer by about 2.3 milliseconds every 100 years
The Moon recedes by about 3.84 meters/century.
After a few Billion Years, this adds up until:
The Moon will be ~50% farther away from the Earth
The Lunar Sidereal Month will be about 47 days long
The Earth's rotation period (the day) will be 47 days long
The Earth & Moon will be locked together in a 1:1 Tidal Resonance, and always keep the same face towards each other.
Water flows
towards forces
___________ _ = _
___________ =
Negative net force
Positive net force

11. Tidal Forces
While gravitational forces depend on the inverse square of distance, these tidal forces, being differences in force over lengh, depend on the inverse cube of distance. That's why tidal forces on earth due to the sun are much smaller than those due to the moon, even though the sun's mass is very much greater than the moon's mass.
Water flows horizontally toward the Earth-Moon line on each side, due to the differential gravity and resulting tidal forces on each side of the globe.

12. Spring and Neap Tides
Sun is about ½ as strong an influence as the Moon
Tides are two LONG waves that the Earth rotates underneath **

13. Types of Tides
*but we are not on Waterworld

14. Types of Tides

15. The Rocky Intertidal Smallest of all ocean environments
Dominated by Algae and Inverts

16. Adaptation to Water Loss
Loss dependent on Duration and Timing
How long exposed, magnitude of tide, time of day (or night), local weather (fog, etc.)
Critical tide levels and decade lunar variations
Adaptations:
Mobility and microhabitats-Move or settle into less stressful areas (cracks, overhangs, under algae etc.)
Tolerance-many species can loose tremendous amounts of tissue water
Avoid: Shells, home scars, Mucus,
Deal: many algae-just dry out and wait.

17. Desication
Heat Balance

18. Salinity Changes Can vary from full seawater to full fresh
Evaporation can bring tide pools up to 100 ppt! Hypersaline 3x as salty as normal seawater.

19. Wave Action High energy Two Biological consequences Structural
Physical integrity
Thick shells, attachments, etc.
Functional
Behavioral integrity
Foraging patterns, Reproduction

20. An easily overlooked abiotic issue that organisms need to deal with in the intertidal:
Space
The rocky intertidal is mostly a 2-D world
Little infaunal space, organisms are epifaunal
Therefore, organisms often are in a battle for the limited available substrate

21. Zonation Stephenson 1949- based on organisms, not tide height

23. What causes zonation? Physical (probably main player in upper limits)
Tidal height, spray zone, max exposure time (and everything that goes with it)
Critical tide levels- the average is not necessarily as important as extremes
Temp, Sunlight (UV)
Biological
Competition, grazing, and larval recruitment
Many of the classic studies were trying to answer these questions…

24. Competition in the Intertidal
J. Connell, Tried to answer question: “What causes zonation”
Realized
Niches
Fundamental
Niches
High Tide ?
Zone of Competition
Low Tide

25. Keystone Species

26. Keystone Species
Keystone species have a disproportionately larger effect on the environment than expected
Presence of starfish = increased species richness and diversity

27. Other keystones

28. Impact of Grazers Regulation of algal species (lower levels)
Snails, crabs, limpets, chitons, urchins, fish…

29. Impact of cover

30. …are there any larvae?
Reproductive behaviors of species are important for larval supply
Reproductive isolation:
If numbers get too low, many species have trouble finding a “mate”
May 2001, the white abalone became the first marine invertebrate to receive federal protection as an endangered species
“Mates” need to be within about three feet of a member of the opposite sex for success!

31. Choosy Larvae- recruitment
Larval settlement is not random. The multitude of cues in a large way define the adult distribution of many species and therefore determined by larval choice and not solely by predation, competition and grazing.

32. Disturbance
Maximum species richness is found in areas with intermediate levels of disturbance
Disturbance resets the successional clock
Pioneer (few)---Intermediate (many)---climax (few)
Sousa (1979)- Intermediate Disturbance Hypothesis
Algal richness determined by boulder stability in intertidal
Small- easy overturn
Large- infrequent overturn
Disturbance must occur at some intermediate frequency or severity that allows species to accumulate within the patch, but prevents one or a few of them from monopolizing its resources, but disturbance must not occur so often or with such severity that many species are eliminated.

33. So…what causes zonation in the Intertidal?
Physical (main player in setting upper limits)
tides, waves, temp, salinity, sunlight…other abiotic factors
Biological (main player in setting lower limits)
competition, predation/grazing, symbiosis, and larval recruitment
Much time was spent trying to find the one answer to the question, but the more researchers have looked, the more apparent is the notion of the thoroughly dynamic nature of the oceans
Ecology is indeed the interaction of the abiotic and biotic worlds
So what happens to communities when the physical world changes?

34. 60 years of Change Temperature had… Species had too…
Barry et al. 1996
Same area of Hopkins Marine Station Intertidal area was compared in 1933 and in 1993; over 60 years what had changed?
Temperature had…
Water temperatures increased on average by about 1.3 °F
Peak summer temperatures in August rose nearly 4 °F !
Species had too…
Warm-adapted Southern species increased
Cold-adapted Northern species decreased
Cosmopolitan species remained the same

35. Summary
Both physical and biological interactions determine the distributions and zonation of intertidal life
Predation, competition, and larval supply are important biological determinants of distribution
Historical perspective: intertidal ecology is the best studied of all marine habitats, but it is still in its infancy (toddler?), it’s only been studied for ~50 years
The physical environment is changing in many ways due to human impact that will elicit biological changes, both in species range, health, and behavior. This makes it all the more important to understand this important system now, before it changes forever