Chapter 6 – Producers: Seaweeds and Plants

The Domains of Life

Introduction

• Nonplant photosynthetic organisms include photosynthetic bacteria and unicellular algae and the seaweeds.

• The seaweeds are “plant-like” because they are multicellular primary producers. A few seaweeds are actually not primary producers but instead parasite other seaweeds.

Kingdom Protista – Seaweeds (algae)

Kingdom Plantae – Plants

Introduction to Multicellular Algae

• Seaweeds= macrophytes =macroalgae– All multicellular (unicellular green and

brown algae are not seaweeds)

– Eukaryotic

– There is a large variety of seaweeds

General Structure• Seaweeds

– Lack true leaves, stem, and roots of plants

– Have the following structures:• Thallus – complete body of seaweed• Blade – leaf-like flattened portion of thallus. This

provides a large surface area for photosynthesis. They have no veins.

• Pneumatocysts – gas-filled blades used for floatation• Stipe – stem (with no vascular tissue)• Holdfast – attaches the thallus to the bottom (not

roots). No water/nutrient transport system.

Algal (macrophyte) structure

Types of Seaweeds

• There are three types of seaweed:– Green

– Brown

– Red

• It is not always easy to rely on color for identification. Sometimes chemical analysis of pigments may be needed.

Kingdom Protista – Seaweeds (algae)

Marine algae in an Oregon Intertidal Zone

Types of Seaweeds• Green Algae

Phylum Chlorophyta

• Only about 10% of 7,000 species are marine (most of them are unicellular).

• They are very common in some marine environments.

• Typically they are bright green because the chlorophyll is not masked by other pigments.

Phylum Chlorophyta – Green Algae

Types of Seaweeds• Some types of green algae:

– Filamentous – filaments may be branched or not– Enteromorpha – have a thin thallus form a hollow tube

and are found in areas of high pollution.– Sea lettuce (Ulva) – paper-thin sheets– Valonia – forms large spheres in the tropics and

subtropics– Caulerpa – single tube with multiple nuclei– Dead man’s fingers – (Codium) – multinucleated

filaments woven into a spongy branching thallus.– Halimeda – calcareous green algae – thallus contains

filaments that contain calcium carbonate, when it dies, it plays a role in the formation of coral reefs.

Chaetomorpha

Bryopsis

Green Algae

Enteromorpha

Ulva

Green Algae

Halimeda

…a calcareous reef building alga

Green Algae

Types of Seaweed

• Brown Algae

Phylum: Heterokontophyta, Class: Phaeophyta

• Anatomy:– Brown color comes from more fucoxanthin

(yellow-brown pigment) than chlorophyll.

– Almost all species are marine

Phylum Heterokontophyta: Class Phaeophyta – Brown Algae

Types of Seaweed• Brown Algae• Some examples of Phaeophyta

– Kelps (Laminaria, Agarum, Alaria, Egregia, Eisenia, Nereocystis, Macrocystis)

– Ectocarpus– Dictyota– Padina– Desmares– Fucus – Rockweed or wracks (exposed at low tide)– Sargassum – spherical air bladders that keep it

afloat

Brown Algae

Leathesia

Scytosiphon

Laminaria

Egregia

Brown Algae

Postelsia

Brown Algae

Macrocystis -- Kelp

Brown Algae

Macrocystis -- Kelp

Brown Algae

Types of Seaweeds

• Red AlgaePhylum: Rhodophyta

– Most common of the three.– Have red pigments called phycobilins which

mask chlorophyll.– Mostly marine– Not as complex as brown algae, some are

parasites, others have lost their chlorophyll and become heterotrophs

– Most are filamentous

Class Rhodophyta – Red Algae

Types of Seaweed• Red Algae• Examples:

– Gelidium and Gracilaria are found worldwide– Endocladia forms wiry clumps on rocks– Gigartina – one of the most massive red algae (blades up

to 2m long)– Porophyta – found on rocky shores – Rhodymenia – found in the Atlantic – blades can reach

1m long– Chondrus – Iris moss– Corallina – red algae that deposit calcium carbonate –

involved in the creation of coral reefs.

Calliarthron

Melobesia

Red Algae

Corallina

Palmaria

Red Algae

Microcladia

Entocladia

Red Algae

Mazzaella

Mastocarpus

Red Algae

Life History• Asexual reproduction is more important than sexual

reproduction. • Some seaweeds produce spores (that can live dormant

in unfavorable conditions)– Some have a thick wall– Zoospores have a flagella

• Sexual reproduction (with the production of gametes) is common in seaweeds. This ensures genetic variation.

• Turn your textbooks the page 107.

Algae as a Human Resource

Economic Importance

• Farming or mariculture of seaweed occurs all over the world.

• Seaweeds produce several types of gelatinous chemicals called phycocolloids.

• Algin (an important phycocolloid) has many uses (frosting, dairy products, shampoo, shaving cream, plastics, pesticides, etc.) It is found in kelp (Macrocystis).

Economic Importance• Carrageenan (another important phycocolloid)

found in red algae, it is used in dairy products as well as a variety of processed foods.

• Agar (another important phycocolloid) protects ham, fish, and meats during canning, in low calorie foods, and as a thickener. It is also used in research.

• Some other uses for seaweeds includes fertilizers, food additives, and wound dressing in hospitals.

Phycocolloids

Algin (brown algae)

Carrageenan (red algae)

Phycocolloids

Agar (red algae)

Class Rhodophyta – Red Algae

Porphyra

Algae products and harvest

Evelyn McConnaughey

OIMB

Edible Algae

Kingdom Plantae – Plants

Introduction to Flowering Plants• There are 250,000 species of flowering plants (common

name: angiosperms)/(phylum or division: Magnoliophyta)• Few live in the ocean• They have true leaves, stems, and roots (that transport

nutrients and water).• They belong to the kingdom plantae• Reproduction involves an elaborate reproductive organ, the

flower.• Most of these species are not truly marine (only the

seagrasses are). The others spend some time (at high tide submersed or just their roots are submersed).

Seagrass bed

Seagrasses• Seem to resemble grass but are not grasses. They are

most closely related to the lily family.

• Horizontal stems called rhizomes.

• Flowers are small and inconspicuous

• Pollen is carried by water currents

• Eelgrass or Zostera (50-60 species known), it is found in oxygen poor beds

• Surf grass inhabits areas on rocky coasts exposed to wave action.

Phylum AnthophytaFlowering Plants Angiosperms

Mangrove flowers

Seagrass flower

Sea grass bed at lower edge of the intertidal zone

Seagrasses

roots and rhizomes

Common Seagrass genera

Seagrass genera in Califronia waters

2 species

3 species

Zostera

Phyllospadix

Seagrasses are flowering plants

Reproductive plants

flower

Fruit with seeds

Medcalfe Marsh, near Charleston, Oregon

Salt Marsh

Salt-Marsh Plants

• Cordgrasses are true members of the grass family – they are not really marine. They just tolerate the salt air and spray.

• Tolerant plants called halophyles live in salt marshes but keep their leaves above water. Many of them have leaves that contain salt glands.

Salt marsh mudflat

Salt marsh – mudflat system

Salt Marsh plants

Salicornia (pickleweed)

Spartina (cordgrass)

Salt Marsh plants

Mangroves• Trees and shrubs adapted to living along tropical and

subtropical shores around the world.

• More than 80 different species of plants share the common name “mangrove”.

• Red mangroves are found in areas without frost. Some adaptations of red mangrove are: thick leaves, seeds germinate while still attached to the parent tree. (Like a pencil, once mature, it falls and sticks into the mud)

Mangroves

• Mangroves thrive in salty environments and are able to obtain freshwater from saltwater.

• Some spp. secrete excess salt through their leaves while other block absorption of salt at their roots.

Mangrove Impacts

• At one time, nearly 0.5 million acres of mangroves surrounded Florida’s coastal zone contributing to ecosystem health in a variety of ways.

-Trap and cycle organics, chemical elements, sediment and minerals.

-Provide shelter for marine organisms.

Mangrove

Mangrove seedling

Salt Marshes and Mangroves