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.

Green Algae Chaetomorpha Bryopsis

Green Algae Ulva Enteromorpha

Green Algae Halimeda …a calcareous reef building alga

Phylum: Heterokontophyta, Class: Phaeophyta 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

Brown Algae Egregia Laminaria

Brown Algae Postelsia

Brown Algae Macrocystis -- Kelp

Brown Algae Macrocystis -- Kelp

Types of Seaweeds Red Algae Phylum: 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.

Red Algae Calliarthron Melobesia

Red Algae Corallina Palmaria

Red Algae Microcladia Entocladia

Red Algae Mazzaella Mastocarpus

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

Edible Algae Evelyn McConnaughey OIMB

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 Anthophyta Flowering 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

Salt Marsh Medcalfe Marsh, near Charleston, Oregon

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 system

Salt Marsh plants Salicornia (pickleweed)

Salt Marsh plants Spartina (cordgrass)

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