chapter 6 - seaweed
TRANSCRIPT
CHAPTER 6
SEAWEED AND PLANTS
Seaweed and Plants Most seaweeds are
considered “plants” or plant-like
Seaweed and Plants Primary Producers: Organisms that produce
organic matter from CO2 usually by photosynthesis
Seaweed and Plants Most seaweeds,
although some are parasitic to other seaweeds
Transform solar energy into chemical energy in the form of organic matter
Produce oxygen for organisms both on land and in the ocean
Multicellular Algae
The Seaweeds
Multicellular Algae Seaweed: large,
multicellular algae Most familiar type
of marine algae Some biologists
prefer the name macrophytes or macroalgae
All multicellular and eukaryotic
Multicellular Algae Takes structure, types of pigments and stored
food products into consideration Lack highly specialized structures and
reproductive mechanisms like terrestrial plants
Vary in shapes and sizes
Multicellular Algae Thallus: the complete body of a seaweed Lack true roots, stems, and leaves
Multicellular Algae Blades: The leaf-like, flattened portions of the thallus of
seaweeds have a large surface area main photosynthetic region not true leaves, no veins the upper and lower surfaces of blades are identical to
each other
Multicellular Algae Pneumatocysts: Gas-filled bladders that
sometimes keep the blades close to the sea surface
maximizing the exposure of blades to the sunlight
gases include carbon monoxide
Multicellular Algae Stipe: stem-like support structure of seaweeds
from which the blade originates long and tough in large kelps
Multicellular Algae Holdfast: root-like structure in seaweeds attaches the thallus to the bottom not involved in significant water or nutrient
absorption do not penetrate through sand or mud like
roots do water and nutrients are picked up directly
across the surface
Multicellular Algae the stipe and holdfast usually lack tissues
specialized for water and nutrient transport
Types of Seaweed
Types of Seaweed Three types: green, brown and red not always easy to recognize visually because
of pigment proportions primarily limited to areas of shallow water and
rocky shores
Green Algae Chlorophyta most live in
freshwater and terrestrial environments
the group from which embryophytes (higher plants) emerged
only 10% are marine
Green Algae most have a simple
thallus pigments and food
reserves are the same as terrestrial plants
chlorophyll is not usually masked thallus is usually a bright
green color may be branched or
unbranched
Green Algae Examples Enteromorpha
Sea Lettuce
Green Algae Examples Ulva
Valonia
Green Algae Examples Caulerpa
Halimeda
Brown Algae Phaeophyta color varies from olive green to dark brown
due to yellow-brown pigments over chlorophyll particularly fucoxanthin
Brown Algae almost all 1,500 species are marine almost always the dominant primary producers on
temperate and polar rocky coasts
Brown Algae include largest and
most complex seaweeds belong to the group
Heterokontophyta, a eukaryotic group distinguished by chloroplasts surrounded by four membranes
play an important role in food supplies and environment development
Kelps most common and
complex of all brown algae
about 30 different species
most found below the low tide level in temperate and sub-polar latitudes
provide food and shelter for many other organisms
Kelps
Some kelps consist of a single large blade
ex laminaria harvested for food in several parts of the world several blades may grow from a single holdfast in some species blade is split or branched
in some species the blade can be up to 25m long (82 ft)
some deep ocean species have a stipe up to 30m high (almost 100ft)
Kelps macrocystis
largest kelp enormous holdfast several stipes elongated blades at base of each blade
is a pneumatocyst can grow up to 50cm
per day under optimal conditions
Kelps Forests Kelp bed/forest: many individual kelps with fast-
growing and intertwining stipes colder waters of the North and South Pacific harvested by chopping off the tops for the
extraction of several natural products among the richest, most productive environments
in the marine realm
Kelp Forests
Other Brown Algae Fucus
Sargassum
Red Algae Rhodophyta more species of red than green and brown
combined have red pigments called phycobillins
mask chlorophyll most species are actually red
Red Algae very few of the
4,000 species live in freshwater or soil
inhabit most shallow-water marine environments
harvested for food and for the extraction of various products
Red Algae most filamentous,
many branches with intricate patterns increases light-
gathering surface for the seaweed
dense clumps are more common
some have lost almost all traces of chlorophyll became parasitic
Coralline Red Algae red algae that deposit calcium carbonate
within their cell walls important to several marine environments creates smooth or rough encrusting growths
on rocks actively involved in the formation and
development of coral reefs
Other Red Algae Palmaria
Chondrus
Nori
Nori Japanese name for various edible seaweed
species of red algae The term nori also commonly used to refer to
food products created from these “sea vegetables”
Nori finished products are made by a shredding
and rack-drying process that resembles paper-making
Japan, Korea and China are the current major producers valued up to $2 billion per year
Seaweed Reproduction usually asexual fragments of the thallus can usually grow
into new individuals ex. sargassum
Seaweed Reproduction some produce spores typically one-celled, reproductive unit capable of
giving rise to a new individual without sexual fusion
Sexual Reproduction
4 basic types of life histories:
diploid sporophyte alternation of
generation of three generations
animal-like reproduction
haploid thallus
Sexual Reproduction Factors affecting the number or quality of
spores/gametes amount of nutrients in the water temperature of the surrounding environment day length/amount of light received
Economic Importance mariculture: the farming of seaweed
Economic Importance phycocolloids: gelatinous chemicals produced
by seaweeds that are used in food production and product manufacturing
form viscous suspensions or gels (even at low concentrations)
Algin stabilizer and emulsifier keeps smooth used in: ice cream, shampoos, dairy
topping, cosmetics major source is giant kelp harvested in California
Carageenan obtained from red algae like Irish moss valued as an emulsifier used in: dairy products, puddings,
Agar jelly like substance used to protect canned meats, in low
calorie foods, laxatives, cosmetics used as a medium in research
especially for DNA analysis obtained from red algae
Angiosperms have true roots, stems and leaves specialized tissues only seagrasses are truly marine
Angiosperms - Seagrasses adapted to marine life horizontal stems called rhizomes pollen carried by currents Eelgrass is the most commonly distributed
Angiosperms – Salt-Marsh Plants Cordgrasses - true members of the grass
family not true marine plants, tolerant of salt live in salt marshes and other soft-bottom
environments offer protection against erosion and provide
natural water purification Halophytes - salt tolerant plants ex. pickle weed
Angiosperms - Mangroves Trees and shrubs adapted to live along tropical
and subtropical shores around the world land plants that can tolerate salt form lush forests in places like Florida can survive in both fresh and salt water
environments