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Marine Biology Chapter 4 Review: Seaweed

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Lydia G

on 10 December 2013

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Transcript of Marine Biology Chapter 4 Review: Seaweed

Marine Biology Chapter 4 Review: Seaweed
Kelp Forests
Canopy-includes long stipes
Understory- shorter stipes
Substrate- encrusting, clumping or filamentous algae
Seaweed includes divisions:
Chlorophyta (green), Phaeophyta(brown) and Rhodophyta(red)
Found in intertidial zones
most common between 30-40 m
some can survive in 200m
Can survive/thrive in extreme surf
Structural Features
Reproduction and Growth
Seaweed reproduction can be sexual, asexual or both
Patterns of sexual reproduction create large structural variety
Larger seaweeds often alternate between sporophyte and gametophyte generations
in some species, one generation is suppressed by another. This results in a large sporophyte or gametophyte generation while the other generation only creates small organisms
generally the male reproductive cells are flagellated, but if not, cells are dependent upon water currents for fertilization

West Coast vs. East Coast
similar species in same trophic levels
maintain delicate balance with major grazers
mixed red and brown algae understories
massive brown algae
large diversity
complex trophic interactions
dominated by
Large kelp growth limited by light
Low species diversity
Simpler trophic interactions
Dominated by
Large kelp growth limited by grazers (sea urchins)
West Coast
East Coast
Shape: flat, often broad
Site of photosynthesis
While similar in appearance to leaves, blades are structurally different
Highly active photosynthetic cells concentrated on
sides of blade (no distinct top or bottom)
not present in all species
filled with gases most abundant in air (N, O and CO)
Purpose is to buoy blades towards the surface
shape: stem-like
Purpose is to anchor blades to holdfast
Visible distinction between stipe and blade varies
Site of photosynthesis
In large seaweeds, the stipe may also provide method of internal transportation
Shape: resembles roots of terrestrial plants
Purpose: to attatch seaweed to substrate
Contrary to roots, holdfasts rarely absorb nutrients
Photosynthetic Pigments
Special combinations of pigments characterize each seaweed division
Green Algae
chlorphyll dominates accessory pigments
fewest marine species
Brown Algae
green color often masked by gold xanthophyll
includes species larger in size
also called kelp
thrive in temperate water
Red Algae
red and blue phycobilin pigment
can range in color from green to brown to various red-toned colors
small in size
Though green algae can adapt to low light, brown/red algae have an advantage with accessory pigments.
Basic Reproductive Cycle
Threats to Kelp Forests
Kelp forests closely depend on the steady control of grazers; inverse relationship
In the past, excess sewage indirectly and severely damaged kelp forest populations by reducing the number of grazers' predators
the flattened, usually broad, leaf-like structure of seaweeds
the flexible, stem-like structure found in the large seaweeds
a structure that attatches seaweeds to the sea bottom or to other substrates
short, sturdy, root-like structures that form the holdfast of seaweeds
: gas-filled float used by some siphonophores to maintain buoyancy in the water
a spore-producing diploid plant
a gamete-producing haploid generation of a plant
special plant cells or structures that produce spores
diploid spores produced by the carposporophyte
a generation of plants, unique to red algae, that produce caropspores
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