4 per eco

Ecology: Living in a marine environment
Patterns, Processes, and Mechanisms
Some factors affecting Algal Ecology
Abiotic
Biotic
I. Light
Algal
g Ecology
gy
I. Herbivory
II. Temperature
p
II. Epiphytism
III. Salinity
III. Competition
IV. Nutrients
V. Water Motion
VI. TIDES
VII. Sand Burial
All act together in nature!
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Algal point of view: light is extremely variable in space and time:
I. LIGHT
- Predictable variation:
- Latitude
= Amount of radiant energy impinging on a unit of surface area
- Seasonal changes in day length
- Less predictable variation:
M
Measurement:
- At the surface = waves, white-caps, foam
Irradiance measured as: amount of energy falling on a flat
surface
- In the water = turbidity from silt, particulate matter,
phytoplankton blooms
Measured as a rate:
• Microeinsteins (= Micromole photons) per square meter
per second
• Watts per square meter
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Attenuation of Light with Increasing Depth
PAR = Photosynthetically Active Radiation
(400nm - 700nm
Attenuate: to lessen in severity, intensity, or amount
irradiance
At ~ 100 m even in clearest water, only
1% of surface radiance makes it through
depth
Different wavelengths transmitted to
different depths
Energy inversely related to wavelength
Violet = short wavelength/high energy
(blue or green goes farther)
Red = long wave length/low energy
(red drops out first)
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Clear oceanic water (I-III)
• Max transmittance in clear water occurs at ~475nm
• Blue/Green region
• 98% of surface
Light attenuation is due to:
•
Absorption (long wave length, low-energy wavelengths
absorbed first, by water itself.)
•
Scattering (high energy, short wave lengths scatter due
to water molecules and particulates)
From Jerlov 1976
Effect of Salinity?
Effect of Turbidity?
Coastal/estuarine water (1-9)
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• Max transmittance in opaque water occurs at~575nm
•Yellow/Orange region
• 56% of surface
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2
How do algae cope with attenuation?
(1) Pigments
Engelmanns Theory of Chromatic Adaptation (1884)
irradiance
depth
Across species:
Different Divisions have
different pigments, allow
potentially different depth
distributions
Chl b, lutien, neoxanthin
Green Light Only
Chl c, Fucoxanthin
Chl d, alpha carotene,Phycobilins
Appealing, but wrong (Saffo 1987)
Irradiance not spectral quality
1) produce more accessory pigments
2) produce more photosynthetic pigments
3) morphology matters- thicker fronds, arrangement of
chloroplasts
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Ecological Reality:
red, green, and brown algae mixed throughout intertidal and subtidal
zonation complexity – abiotic and biotic forcings
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How do algae cope with attenuation?
(1) Pigments
Within species
 Change ratio of accessory pigments
Up-regulation of pigments
(make more of everything)
 Change size of PSUs
antennae + reaction center
(bigger is more efficient at low light
levels)
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3
How do algae cope with attenuation?
(2) Morphology
Model for comparison of P-E curves within species:
photoacclimation
Larger PSUs
Fewer PSUs
Phottosynthesis
Photo
osynthesis
More PSUs
Smaller PSUs
Vs.
Irradiance or
light intensity
Irradiance or
light intensity
Same size, different number of
PSUs
Same number, different sizes of
PSUs
From Ramus 1981
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Comparison of P-E curves across species:
photoadaptation
Photosynthesis
Sun
adapted
Shade
adapted
Surface area: More surface to capture light, crustose
algae should do best in dim habitats, less self
shading
Thallus thickness: Thicker thalli should have a growth
disadvantage in dim habitats, also self-shading 14
II. Temperature
Pmax?
- Affects all levels of biological organization – molecules, cells,
organisms, communities. In algae – photosynthesis, enzymatic
activity
Alpha?
Too high? – Denatures proteins, damage enzymes, membranes
Too low? – Low enzymatic activity, disrupts lipids, membranes, ice
crystal formation
Irradiance or
light intensity
**Lethal temp set by tolerance of most susceptible life history
stage**
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Isotherms
All algae are single celled at some stage of life history, even the
big kelps; a species’ distribution is determined by effect of biotic
and abiotic factors across all stages of its life history
• Boundaries defined by the same surface water
temperature averaged over many years for a
particular month
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• Northern and southern limit dictated by February
and August Isotherms
Seaweed Floristic Regions
1. Artic- depauperate
2. Northern Hemisphere Cold Temperate- Laminariales
- Atlantic & Pacific have distinct communities
3. Northern Hemisphere Warm Temperate
4 Tropical
4.
- 180 million years, 20 °C isotherm
5. Southern Hemisphere Warm Temperate
6. Southern Hemisphere Cold Temperate- Durvillaeales
-similar around the southern hemisphere
7. Antarctic- 1/3 of 100 species endemic
Best correlate for algal biogeographic patterns:
Temperature
Other correlates:
Day length
 Latitude
Confounded
f
w/ temp
p
Currents
So why temperature?
- Experimental evidence w/single spp
- Northern cold temperate southern limits set by summer high
- Warm temperate/tropical spp northern limits set by winter low
- Thermal boundaries shift with global warming/cooling events
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III. Salinity
Potential problems with invasive species?
- Increase in dispersal rates, changes in dispersal patterns
- Global warming and shifting boundaries
•Codium fragile is a pest in Japan
•Colpomenia from Japan is a serious problem in European oyster
beds
•Caulerpa spp. has become pest in the Mediterranean (San
Diego?)
Definition = Grams of salts per kilogram of solution
Measurement = Refractometer: measures light refraction
ppt or o/oo, p
parts per
p thousand.
• Unit of Measure – pp
(1kg seawater contains 34.7 g of salts ->34.7o/oo)
• Range – oceanic 32-38ppt, estuarine 1-32ppt
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III. Salinity
III. Salinity
Osmoregulation in seaweeds
Seawater is hypotonic (less saline) than most algal cells
Euryhaline: Species that can handle a wide range of salinities
• Seaweed cells lack contractile vacuoles to pump water out
• Seaweeds prevent bursting due to water diffusing in by pumping
ions both in and out
• Tolerance of hypersaline water (e.g. in tidepools) depends on
elasticity of cell wall (prevents plasmolysis = cell wall tearing away
from cell membrane due to water rushing out).
• Tolerance of freshwater (even more hypotonic) depends on ion
pumping ability and strength/elasticity of cell wall
High Salinity:
- Tidepools
• Osmotic stress (in either direction) can act synergistically with
temperature
• Gametes and spores are especially sensitive
Stenohaline: Species that can only survive in a narrow range
of salinities
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Low Salinity:
- Estuaries
- FW seeps
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IV. Nutrients
III. Salinity
The Baltic Sea: a huge estuary = brackish water
• Marine seaweeds (e.g.
Fucus) occur there but
are smaller morphologically
(smaller thalli or smaller
cells) and have different
abiotic optima
Macro-nutrients necessary for algal growth =
C H
C,
H, O
O, K,
K N,
N S,
S Ca
Ca, F,
F Mg,
Mg P
N is often limiting in coastal waters, needed for amino acids,
protein synthesis, nucleic acids
• Local adaptation
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Variation in nutrient availability in space and time:
Issues of depth stratification, role of upwelling
Seaweeds and Nitrogen:
Ammonium (NH4+) and nitrate (NO3-) are the most common and used
nitrogen sources; NH4+ is preferred because it can be utilized
directly (energy saving)
NO3- assimilation by nitrate reductase requires iron (phytoplankton
cannot exhaust high NO3- pools in Fe-limited Antarctic oceans;
famous Fe-addition experiment), more energetically costly
Cyanobacteria can fix atmospheric nitrogen = convert N2 to NH4+;
25-60% of this fixed nitrogen is released into the water
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Processes that make nutrients available to algae:
Variation in nutrient availability in space and time:
Issues of depth stratification, role of upwelling
• Chlorophyll = measure of
photosynthesis
• Irradiance higher in shallow
water
• Nutrients usually higher in
deeper
p water
• Maximum Ps happens in the
middle.
- Upwelling
- Nitrogen fixation by Cyanobacteria
- Bacterial decomposition
- Runoff in coastal areas
- Defecation by animals
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V. Water Flow
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Interaction of Water Flow and Morphology
In relatively still water (e.g protected coves), surface
area becomes really important (more surface area =
more diffusion)
- All macroalgae have a boundary
layer of water around the thallus,
affects contact with nutrients,
nutrients
gasses.
Algae in these environments tend to have high SA:V =
maximize uptake of nutrients
-Algae depend on water motion to
deliver gasses, nutrients, and
remove O2 from their surfaces
-e.g, Macrocystis, nitrate uptake
increases by 500%, and Ps by
300% if flow goes from zero to 4
cm/second
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Relationship between SA/V
(morphology) and photosynthetic
rate
From Stewart and Carpenter,
Ecology (2003)
A B C D E
Costs of high SA:V? In high flow environment = leafy,
foliose shapes are a drag 
- Variation in species composition on wave exposed vs. wave
protected shores = particular morphotypes consistently found in
particular flow environments
- Variation within species =
phenotypic plasticity in
traits that affect water
flow around the algal thallus
e.g. Nereocystis “ruffles”
and wide blades in protected
areas
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VI. Tides
Complicated effects of water flow
Positive effects:
Negative effects:
Reduce shading by rearranging thalli
Damage, destruction
Mixing of nutrients
Reduce boundary layer
Dispersal of spores,
gametes, zygotes
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Loss of settling
zygotes/germlings
Energetic expense of
structure
Littoral zone = intertidal zone
Inhibits external
fertilization in some spp
Supralittoral = above mean high water, rarely submerged
Sublittoral = below mean low water, permanently submerged
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MOON
• Sun and moon pull in the same plane at full and new moon (=
spring tides, big changes in tide ht), and compete at half moon
(= neap tides, smaller change).
SUN
Tide
Level
Semi-diurnal (twice daily) tides
X
X
gravitational pull
12:00
Noon
X
X
6:00 PM
X
X
X
12:00
Midnight
X
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Sun and moon have different gravitational strengths
(previous slide) and topography of ocean basin
modifies tidal current so that high (and low) tides
are not same height. This is referred to as mixed
semi-diurnal tides
Spring tide sequence
6:00 AM
Tides = Periodic “waves” that result in a change in water level
generated by the attraction of the moon and the sun
Diurnal
Semidiurnal
(equal)
Semidiurnal
(unequal = mixed)
mean sea level
http://tbone.biol.sc.edu/tide/
0 ft mark at MLLW (mean lower low water)
= mean lowest tides over the year at that location
• Frequency and amplitude of tides affected by the tilt of the
earth and morphology of the ocean basin
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• Diurnal, mixed, and semidiural in different locations
spring tides
neap tides
spring tides
neap tides
• Frequency and amplitude of tides affected by the tilt of the
earth and morphology of the ocean basin
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Tides help to determine zonation patterns in intertidal
spring tides
neap tides
spring tides
neap tides
spring tides
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Tides are sinusoidal. Appearance of the sine wave tidal
function might lead one to believe that the relationship
between immersion time (time underwater) and tidal
height decreases smoothly (and linearly or gently
curvilinear) with increasing tidal height:
Mean no. hr of
immersion
(= submergence)
low
high
tidal level (= height in intertidal)
Does this correspond intuitively to sharp breaks in zonation patterns?
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Doty (1946, Ecology 27:315-328)
Pattern: sampled distributions of species of macroalgae along CA and
Oregon coasts and found (at all sites):
Six distinct zones
high
crustose coralline reds (cc)
Mastocarpus(M)
Endocladia ((En))
elevation
in
intertidal
Egregia (Eg)
MLLW
fleshy reds (fr)
Laminaria – kelp (L)
low
General hypothesis: tidal fluctuation and differential tolerance to
immersion causes zonation of species in intertidal
Specific hypothesis: species zones will correlate with discrete zones of
immersion (“critical tide levels”)
Harsh environment: temp, desiccation, wave stress, salinity, light
Doty (1946, Ecology 27:315-328)
Test: Calculated the actual immersion times over the tidal range:
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Literally cut and weighed tide tables!
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Mean no. hr of
12
immersion
((= submergence)
g
) 8
4
0
low
L
fr
Eg
En
M
CC
high
tidal level (= height in intertidal)
Results: dramatic non-linear steps in immersion that correlated with
algal zonation!
Conclusion: physical factors - immersion - control species distribution and
determine zonation of species in intertidal
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Zonation Patterns
Intertidal organisms show striking patterns of
zonation
physical
factors
biotic
interactions
Dave Lohse
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Zonation Patterns- physical factors and biotic interactions
Zonation Patterns
high
zone
low
zone
mid
zone
Dave Lohse
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VII. Sand Burial
Adaptations to living intertidally:
- Wicked holdfasts for attachment
- Morphology that minimizes drag, shear stress
- Tolerant of high temps (H2O temperature typically 10-17
degrees C along Central Coast; in tide pools
pools, up to 30 degrees C)
- Desiccation tolerance (some algae can survive 60-90% water
loss), some require low tide for survival
- Synchrony in gamete release (e.g. intertidal Fucoids, like
Silvetia compressa)
- Photoprotective pigments
How do algae deal with this?
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Ecology: Living in a marine environment
Two basic strategies: recover or resist
Patterns, Processes, and Mechanisms
Opportunistic spp:
Chaetomorpha, Ectocarpus, Ulva
Some factors affecting Algal Ecology
Abiotic
I. Light
II. Temperature
p
III. Salinity
Stress “tolerators”:
Gymnogongrus, Laminaria sinclairii, Neorhodomela
IV. Nutrients
Biotic
I. Herbivory
II. Epiphytism
III. Competition
V. Water Motion
VI. TIDES
VII. Sand Burial
All act together in nature!
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I. HERBIVORY
(i.e. “predation” on algae)
I. HERBIVORY
• Damage caused by herbivores varies a lot
Macrocystis and sea urchins
…versus certain crustose corallines and limpets
How do algae deal with herbivory?
recover, avoid, or resist
“Recover”
Chiton example = minimal cost of
grazing of algal fitness
R id growth
Rapid
th
How do algae deal with herbivory?
recover, avoid, or resist
“Avoid”
Spatial escape
 Low herbivory habitats
 Associational defenses
Temporal escape
 Life history
 Size
Opportunistic recruitment
Hypnea
Sargassum
Mastocarpus spp.
sporophyte (2N)
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How do algae deal with herbivory?
recover, avoid, or resist
“Resist”
- Geographic variation in levels of algal chemical defense
Endocladia
tough, spiny
- Within-INDIVIDUAL variation in defense
Structural defenses
Turbinaria
So… why aren’t all algae defended?
Life history variation is all about trade-offs
(limited energy, how do you spend it?)
calcified
Chemical warfare:
Secondary metabolites
•
Polyphenolics and pholorotannins in
browns
•
Terpenes in tropical spp
Inducible defenses versus Constitutive defenses
-Inducible defense: Can turn on and off
- Constitutive: Always on
$$$
Interaction of grazing and morphology
Padina example
Increased Grazing
Ascophyllum
Toth and Pavia 2000
When do you want one versus the other?
Cues?
Predictability?
Cost of Defense?
Typical Fanliose Fan-Shaped thallusShaped thallus
Prostrate,
Branching thallus
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Some common, local intertidal herbivores
Snails
Herbivory- determine the lower limit of species (Harley 2003)
Limpets
Littorines
Tegula
Urchins
Chitons
Herbivory- determine the lower limit of species (Harley 2003)
Haven Livingston
II. EPIPHYTISM
Benefits to epiphyte?
- Access to resources (nutrients, sunlight, etc…)
- Place to live
Costs to basiphyte?
- Extra drag
- Depleted resources
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How do algae deal with epiphytes?
- Outrun them (rapid growth, blade turnover)
- Ditch them by sloughing off outer layer of cells
(e.g. Ascophyllum, Silvetia, other fucoids)
Laminaria blade but not stipe
Membranipora on Macrocystis
- Resist with chemical defenses
III. COMPETITION in Algae
Allelochemicals. E.g. phenolics and polyphenolic
compounds originate in plastids,produced by browns,
active as antifouling agents and herbivore deterrents
pH. rapid growing spp often have increased pH at
thallus surface. e.g. Ulva, Enteromorpha
Exploitative: scramble for a limiting resource (no direct
antagonism)
Interference: interactions between organisms (limiting
resource not necessary)
Chondrus crispus inhibits diatoms
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Explotive Competitionpassive, consumptive
Interference Competitionovergrowth
Exploitative Competitionpassive, pre-emptive
Interference Competitionchemical
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