Transcript Mar 5 - University of San Diego

I.
Coral Reefs
C.
Components & Dynamics
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Corals important components of reefs
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Other organisms also contribute
Coralline red algae cement debris together
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More important in Pacific than Atlantic
Part of bioerosion process
Fig. 15-8
I.
Coral Reefs
D.
Structure
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Coral abundance & diversity decrease with depth
Competition for light affects growth forms
Upper slope - doming corals
Mid slope - branching corals
Lower slope - plate-like corals (Why?)
Fig. 15-12
I.
Coral Reefs
D.
Structure
Fig. 15-12
I.
Coral Reefs
E.
Types
1.
Fringing
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Simplest, most common type of reef
Occur near shore throughout tropics
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Form narrow band (fringe) along shoreline
Proximity to land  vulnerability to sedimentation,
freshwater runoff, human influence
Fig. 15-10
I.
Coral Reefs
E.
Types
2.
Barrier
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Not always obviously distinct from fringing reefs
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Often occur farther from shore (up to 100+ km)
May be sand cays on back reef slope
Fig.
15-10
I.
Coral Reefs
E.
Types
3.
Atoll
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Fig. 15-10
Most common in Indo-West Pacific
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Rare in Caribbean, tropical Atlantic
Usually far from land
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Little influence from freshwater runoff,
sedimentation
Range in size from <1 to 20+ miles in diameter
Often influenced by trade winds
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Differences between windward and leeward sides
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Windward: Spur-and-groove, distinct algal ridge
I.
Coral Reefs
E.
Types
3.
Atolls
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How do atolls form?
Why do they occur in rings?
Fig. 15-11
II.
Coral Reef Ecology
Among most productive communities in
ocean
Generally occur in areas with low nutrient
concentrations, low primary production
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A.
How can coral reefs be so productive?
Trophic Structure
1.
Nutrient cycling
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Within corals, tight relationship between polyps and
zooxanthellae
II.
Coral Reef Ecology
A.
Trophic Structure
1.
Nutrient cycling
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“Nutrient traps”
Other reef animals also contain symbionts and recycle
nutrients within their tissues
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Sponges
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Nudibranchs
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Giant clams
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Sea squirts
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Waste products also recycled
Some inputs still required
II.
Coral Reef Ecology
A.
Trophic Structure
2.
Nitrogen fixation
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3.
Primarily by cyanobacteria
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Some free living, some symbiotic in sponges
Nitrogen may not limit productivity in coral reefs
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Different from most other marine communities
Nitrogen also acquired by
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Absorption of dissolved organic matter (DOM)
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Predation on zooplankton
Food webs
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Base formed by corals and algae (esp. turf algae)
Complex feeding interactions
Diversity from extensive resource partitioning
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More niches  More species
II.
Coral Reef Ecology
B.
Competition
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Limited resources include space and light
1)
Fast-growing corals may overgrow or shade slowergrowing species
II.
Coral Reef Ecology
B.
Competition
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Limited resources include space and light
2)
More aggressive corals may attack other corals
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Mesenterial filaments used to digest away tissue
from competitor/neighbor (video)
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Special sweeper tentacles sting adjacent colonies
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Slower growers tend to be most aggressive
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Faster growers tend to be less aggressive
II.
Coral Reef Ecology
B.
Competition
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Limited resources include space and light
3)
Soft corals may release toxins that harm hard corals
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Ecological role filled by sponges on Caribbean
reefs (fewer species of corals than in Pacific)
II.
Coral Reef Ecology
C.
Predation
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Most coral predators eat portion of coral
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Ex: Butterflyfishes, parrotfishes
Doesn’t kill coral; permits regrowth
Predation may limit growth rates of certain fastgrowing species
Other coral predators eat entire corals
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Ex: Crown-of-Thorns Sea Star
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Extrudes stomach, digests coral tissue
II.
Coral Reef Ecology
D.
Grazing
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Many fishes are herbivorous
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Ex: Surgeonfishes, parrotfishes, damselfishes
Invertebrate grazers and microherbivores also
important
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Ex: Sea urchins, gastropods, crustaceans
Grazing controls populations of seaweeds
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Could overgrow corals if not grazed by herbivores
Ex: Seaweeds protected from grazers grew much
faster than unprotected seaweeds
Removal of grazers  proliferation of algae
II.
Coral Reef Ecology
E.
Mutualism
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Numerous mutualistic interactions in reef
community
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Ex: Corals & zooxanthellae
Ex: Giant clams & zooxanthellae
Ex: Anemones & anemone fishes, crabs, shrimps
Fig. 9-1
III. Annelida
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Mostly segmented worms
Body composed of repeated segments
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Gut runs through body cavity (coelom)
Coelom filled with fluid – hydrostatic skeleton
Longitudinal and radial muscles
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Efficient locomotion and burrowing
More than 15,000 species
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Cosmopolitan
III. Annelida
A.
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Polychaeta (class)
10,000+ species (mostly marine)
Body segments bear pairs of parapodia
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Parapodia used for locomotion, feeding
Often tipped with setae
Closed circulatory system**
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Efficient transport of blood, gases
Gas exchange
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Small species exchange gases across body
wall
Large species have gills for gas exchange
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Highly vascularized with capillaries and thin body walls
Fig. 9-21
III.
Annelida
A.
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Polychaeta
Larva = Trochophore
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Band of cilia around body; tuft on apex
Same larval stage in Mollusca
Diverse lifestyles
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Errant vs. Sedentary
Free-living predators
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Often well-developed eyes, sense organs, jaws
Deposit feeders
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Nonselective
Selective
Suspension feeders
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Active
Passive
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Solitary
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Colonial
Reproduction
Fig. 9-10
Pomatoceros
lamarckii
Haliotis asinina
Wikipedia
III.
Annelida
A.
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Polychaeta
Larva = Trochophore
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Band of cilia around body; tuft on apex
Same larval stage in Mollusca
Diverse lifestyles
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Errant vs. Sedentary
Errant: Free-living predators
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Fig. 9-23
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Deposit feeders
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Nonselective
Selective
Suspension feeders
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Often well-developed eyes and sense organs, jaws
Active
Passive
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Solitary
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Colonial
Reproduction
niwa.co.nz
tolweb.org
IV.
Nematoda
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Free living and parasitic forms
Cosmopolitan/Ubiquitous
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Mostly in sediments (free living) or hosts (parasitic)
Common in fine muds
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Organic rich areas
Described species: 28,000+ (>55% parasitic)
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May be up to 500,000 species total!
Extremely abundant!!
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Up to hundreds of individuals per ml of sediment
90,000 in one rotting apple (not marine)
Hydrostatic skeleton
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Longitudinal muscles only
Move by whipping back and forth