Multicellular Primary Producers Chapter 7 Multicellular Primary Producers

Plankton Phytoplankton – Plants Zooplankton – Animals Most are microscopic Can not swim against currents and waves Meroplankton – Live part of their lives as plankton Holoplankton – Remain plankton their entire lives

Multicellular Algae Major groups: Red algae (phylum Rhodophyta) Brown algae (phylum Phaeophyta) Green algae (phylum Chlorophyta)

Multicellular Algae Economy of coastal seas: Produce 3 habitat for other marine organisms Consumed by an array of animals

Distribution of Seaweeds Most are Benthic: Growing on rock, sand, mud, corals and other hard substrata Distribution is governed by Light and Temperature

Distribution of Seaweeds Effects of Temperature Diversity greatest in Tropical waters Many colder-water algae are perennials (living more than 2 years) Only part of the alga survives colder seasons Freezing and ice scouring can eliminate seaweeds in high latitudes Intertidal algae can be killed if temperatures become too hot or cold

Structure of Seaweeds Thallus: Body When flattened, called a frond or blade Holdfast: Attaching the thallus to a surface Stipe: A stem-like region between the holdfast and blade Lack vascular tissue, roots, stems, leaves and flowers

Biochemistry of Seaweeds Photosynthetic pigments Chlorophylls absorb blue/red wavelengths of light Accessory pigments absorb various colors

Biochemistry of Seaweeds Cell walls Primarily cellulose Maybe with calcium carbonate Many secrete slimy mucilage as a protective covering Holds moisture, and may prevent desiccation Can be sloughed off to remove organisms Some have a protective cuticle - a multi-layered protein covering

Biochemistry of Seaweeds Nature of food reserves Unique sugars and alcohols may be used as antifreeze during cold weather

Reproduction in Seaweeds Fragmentation: Asexual reproduction Drift algae: huge accumulations of seaweeds formed by fragmentation, e.g., some sargassum weeds Asexual reproduction through Spore formation

Reproduction in Seaweeds Sexual reproduction Alteration of generations: The possession of 2 or more separate multicellular stages in succession

Green Algae (Phylum: Chlorophyta) Most are unicellular or small multicellular filaments, tubes or sheets There is a large diversity of forms among green algae

Green Algae Herbivory Tolerance: Rapid growth and release of huge numbers of spores and zygotes Avoidance: Small size allows them to occupy out-of-reach crevices Deterrence: Calcium carbonate deposits require herbivores with strong jaws and fill stomachs with non-nutrient minerals Many produce repulsive toxins

Red Algae (Phylum: Rhodophyta) Primarily marine and mostly benthic Highest diversity among seaweeds Red color comes from phycoerythrins Thalli can be many colors, yellow to black Structure - Almost all are multicellular

Red Algae Seasonal food for sea urchins, fish, molluscs and crustaceans Herbivory Less edible by calcium carbonate Avoiding by growing in crevices

Red Algae Human uses Phycocolloids are valued for stiffening properties e.g. agar, carrageenan Irish moss is eaten in a pudding Porphyra are used in oriental cuisines e.g. sushi, soups, seasonings Cultivated for animal feed or fertilizer in parts of Asia

Brown Algae (Phylum: Phaeophyta) Familiar examples: Rockweeds Kelps Sargassum weed 99.7% of species are marine, mostly benthic (sargassum – not benthic) Olive-brown color

Brown Algae Distribution More diverse and abundant along the coastlines of high latitudes Most are temperate Sargassum weeds are tropical

Brown Algae Structure Most have thalli that are well differentiated into holdfast, stipe and blade Bladders - gas-filled structures used to help buoy the blade and maximize light

Brown Algae Kelp house many marine animals Habitat Kelp house many marine animals Sargassum weeds of the Sargasso Sea provide a home for unique organisms Human uses: Thickening agents Once used as an iodine source Food (especially in Asia) Cattle feed in some coastal countries

Marine Flowering Plants Seagrasses, Marsh Plants, Mangroves Halophytes, meaning they are salt-tolerant

Seagrasses Generally beneath the water Structure 3 basic parts: stems, roots and leaves

Seagrasses (Structure) Stems Rhizomes—horizontal stems usually lying in sand or mud Vertical stems - grow upward toward the sediment surface Roots From nodes of stems and anchor plants Usually bear root hairs Absorb mineral nutrients

Seagrasses Reproduction some use fragmentation, drifting and re-rooting and do not flower

Seagrasses Primary producers Depositing and stabilizing sediments contribute to food webs through fragmentation and loss of leaves Depositing and stabilizing sediments blades reduce water velocity decay of plant parts contributes organic matter help stabilize the bottom reduce turbidity—cloudiness of the water

Seagrasses (Ecological Roles) Habitat other organisms can settle, hide, graze or crawl Nursery for commercial species of fish and shellfish Human uses: Indirect – fisheries Direct – for food, medicine and industrial application

Salt Marsh Plants Must be exposed to air by ebbing tide well developed along the low slopes of river deltas and shores of lagoons and bays in temperate regions

Salt Marsh Plants Structure flowers are pollinated by the wind seeds drop to sediment or are dispersed by water currents

Salt Marsh Plants Adaptations Facultative halophytes—tolerate salty as well as fresh water Leaves covered by a thick cuticle to retard water loss Well-developed vascular tissues Spartina alterniflora have salt glands

Salt Marsh Plants Ecological roles of Contribute to detrital food chains Stabilize coastal sediments and prevent shoreline erosion Serve as refuge, feeding ground and nursery Remove excess nutrients from runoff Consumed by crabs and terrestrial animals (e.g. insects)

Mangroves Classification Red mangrove (Rhizophora mangle) Black mangrove (Avicennia germinans) White mangroves and Buttonwood

Mangroves (Distribution) Tropical shores with limited wave action, low slope, high rates of sedimentation, and soils that are waterlogged, anoxic, and high in salts

Mangroves Structure Trees with simple leaves, complex root systems Roots: many are aerial (above ground) Prop roots of the red mangrove arise high on the trunk

Mangroves (Structure) Pneumatophores: grow out of sediments and into water or air Act as ventilation system for black mangrove

Mangroves (Structure) Leaves Simple, oval, leathery and thick, succulent like marsh plants, never submerged Salt is eliminated through salt glands (black mangroves) or by concentrating salt in old leaves that shed

Mangroves Reproduction Propagule: grows an elongated cigar-shaped stem Falls from parent tree and may drift in currents for as long as 100 days

Mangroves Ecological roles Root systems stabilize sediments Epiphytes live on aerial roots Canopy is a home for insects and birds Nursery and refuge Mangrove leaves, fruit and propagules are consumed by animals Contribute to detrital food chains