Chapter 6 - Seaweed

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

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

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

Flowering Plants

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