Chapter 7 Multicellular Primary Producers

Primary producers – those organisms that photosynthesize Previously, we talked about phytoplankton: Cyanobacteria We also talked about unicellular protists that are phytoplankton (for example: dinoflagellates, diatoms, etc) Now we will talk about the macro algae (“seaweeds”) and marine plants

Multicellular Algae Most primary production in marine ecosystems takes place by phytoplankton but seaweed and flowering plants contribute especially in coastal areas Seaweeds are multicellular algae that inhabit the oceans Major groups of marine macroalgae: red algae (phylum Rhodophyta) brown algae (phylum Phaeophyta) green algae (phylum Chlorophyta)

Algae – not “plants” Red algae Green algae Brown algae

Multicellular Algae Scientists who study seaweeds and phytoplankton are called phycologists or algologists Seaweeds contribute to the economy of coastal seas Produce 3 dimensional structural habitat for other marine organisms Consumed by an array of animals, e.g., sea urchins, snails, fish

Distribution of Seaweeds Most species are benthic, attaching and growing on rock, sand, mud, corals and other hard substrata in the marine environment as part of the fouling community Benthic seaweeds define the inner continental shelf, where they provide food and shelter to the community compensation depth: the depth at which the daily or seasonal amount of light is sufficient for photosynthesis to supply algal metabolic needs without growth Distribution is governed primarily by light and temperature

Figure 7-1b ZONATION OF SEAWEEDS

Structure of Seaweeds Thallus: the seaweed body, usually composed of photosynthetic cells when flattened, called a frond or blade Holdfast: the structure attaching the thallus to a surface Stipe: a stem-like region between the holdfast and blade of some seaweeds Seaweeds are not plants Lack vascular (conductive) tissue, roots, stems, leaves and flowers

Figure 7-2a VARIABLE SHAPES OF SEAWEEDS.

Figure 7-2c VARIABLE SHAPES OF SEAWEEDS.

Figure 7-2d VARIABLE SHAPES OF SEAWEEDS.

Biochemistry of Seaweeds Composition of cell walls Primarily cellulose, like plants May be impregnated with calcium carbonate in calcareous algae Many seaweeds secrete slimy mucilage (polymers of several sugars) 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

Green Algae Diverse group of microbes and multicellular organisms that contain some pigments found in vascular land plants Structure of green algae Most are unicellular Unicellular ones are part of the phytoplankton There is a large diversity of forms among green algae Multicellular ones are seaweed

Figure 7-4 (c) COENOCYTIC GREEN ALGAE.

Red Algae Primarily marine and mostly benthic Highest diversity among seaweeds Red color comes from special protein-pigment complex Thalli can be many colors, yellow to black Structure of red algae Almost all are multicellular Thallus may be blade-like or composed of branching filaments or heavily calcified (may be hard)

Red Algae Annual red algae are seasonal food for sea urchins, fish, molluscs and crustaceans

Red Algae Ecological relationships of red algae a few smaller species are: epiphytes—organisms that grow on algae or plants epizoics—organisms that grow on animals red coralline algae precipitate calcium carbonate from water and aid in consolidation of coral reefs

Red Algae Human uses of red algae Ice cream yogurt 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 Familiar examples: rockweeds kelps sargassum weed 99.7% of species are marine, mostly benthic (sargassum – not benthic) Olive-brown color comes form a carotenoid pigment that masks the chlorophylls

Figure 7-8 KELP.

Figure 7-9 SARGASSUM WEED.

Brown Algae Distribution of brown algae more diverse and abundant along the coastlines of high latitudes most are temperate sargassum weeds are tropical

Brown Algae Structure of brown algae most species have thalli that are well differentiated into holdfast, stipe and blade bladders—gas-filled structures found on larger blades of brown algae, and used to help buoy the blade and maximize light

Figure 7-10a DIVERSITY OF SHAPE IN THE BROWN ALGAE.

Figure 7-10 (b) DIVERSITY OF SHAPE IN THE BROWN ALGAE.

Brown Algae Brown algae as habitat kelp forests house many marine animals sargassum weeds of the Sragasso Sea form floating masses that provide a home for unique organisms There are species of animals that have coevolved with the sargassum and blend in (sargassum fish, sargassum seahorse) Human uses of brown algae thickening agents are made from alginates once used as an iodine source used as food (especially in Asia) used as cattle feed in some coastal countries

Now we will talk about the plants of the marine environments Most terrestrial plants are not tolerant of the marine environment, not that many plants that grow successfully in the ocean when compared to land

Marine Flowering Plants Seagrasses, Marsh Plants, Mangroves General characteristics of marine flowering plants vascular plants are distinguished by: phloem: vessels that carry water, minerals, and nutrients xylem: vessels that give structural support seed plants reproduce using seeds, structures containing dormant embryos and nutrients surrounded by a protective outer layer

Marine Plants 2 types of seed bearing plants: conifers (bear seeds in cones) flowering plants (bear seeds in fruits) all conifers are terrestrial marine flowering plants are called halophytes, meaning they are salt-tolerant Examples are sea grasses, mangroves, dune plants

Invasion of the Sea by Plants Flowering plants evolved on land and then adapted to estuarine and marine environments Flowering plants compete with seaweeds for light and with other benthic organisms for space

Seagrasses Seagrasses are hydrophytes (generally live and flower beneath the water) Classification includes: Eelgrasses Turtle grass Manatee grass Shoal grass

Seagrasses Structure of seagrasses vegetative growth—growth by extension and branching of horizontal stems (rhizomes) from which vertical stems and leaves arise 3 basic parts: stems, roots and leaves

Seagrasses Ecological roles of seagrasses highly productive on local sale role of seagrasses in depositing and stabilizing sediments blades act as baffles to reduce water velocity decay of plant parts contributes organic matter rhizomes and roots help stabilize the bottom reduce turbidity—cloudiness of the water

Seagrasses (Ecological Roles) role of seagrasses as habitat create 3-dimensional space with greatly increased area on which other organisms can settle, hide, graze or crawl rhizosphere—the system of roots and rhizomes also increases complexity in surrounding sediment the young of many commercial species of fish and shellfish live in seagrass beds human uses of seagrass indirect – fisheries depend on coastal seagrass meadows direct – extracted material used for food, medicine and industrial application

Salt Marsh Plants Much less adapted to marine life than seagrasses; must be exposed to air by ebbing tide Classification and distribution of salt marsh plants salt marshes are well developed along the low slopes of river deltas and shores of lagoons and bays in temperate regions salt marsh plants include: cordgrasses (true grasses) needlerushes various shrubs and herbs, e.g., saltwort, glassworts

Figure 7-17 SALT MARSH

Figure 7-18 PLANTS OF THE SALT MARSH.

Salt Marsh Plants Structure of salt marsh plants smooth cordgrass, initiates salt marsh formation, grows in tufts of vertical stems connected by rhizomes, dominates lower marsh flowers are pollinated by the wind seeds drop to sediment or are dispersed by water currents

Salt Marsh Plants Adaptations of salt marsh plants to a saline environment facultative halophytes—tolerate salty as well as fresh water leaves covered by a thick cuticle to retard water loss well-developed vascular tissues for efficient water transport Spartina alterniflora have salt glands, secrete salt to outside shrubs and herbs have succulent parts

Salt Marsh Plants Ecological roles of salt marsh plants contribute heavily to detrital food chains stabilize coastal sediments and prevent shoreline erosion serve as refuge, feeding ground and nursery for other marine organisms rhizomes of cordgrass help recycle phosphorus through transport from bottom sediments to leaves remove excess nutrients from runoff are consumed by (at least in part) by crabs and terrestrial animals (e.g. insects)

Mangroves Classification and distribution of mangroves red mangrove black mangrove white mangroves

Figure 7-20a MANGROVES.

Mangroves (Distribution) thrive along tropical shores with limited wave action, low slope, high rates of sedimentation, and soils that are waterlogged, anoxic, and high in salts low latitudes of the Caribbean Sea, Atlantic Ocean, Indian Ocean, and western and eastern Pacific Ocean associated with saline lagoons and tropical/subtropical estuaries

Mangroves Structure of mangroves trees with simple leaves, complex root systems plant parts help tree conserve water, supply oxygen to roots and stabilize tree in shallow, soft sediment roots: many are aerial (above ground) stilt roots of the red mangrove arise high on the trunk (prop roots) or from the underside of branches (drop roots)

Mangroves (Structure) leaves mangrove leaves are simple, oval, leathery and thick, succulent like marsh plants, never submerged stomata: openings in the leaves for gas exchange and water loss salt is eliminated through salt glands (black mangroves) or by concentrating salt in old leaves that shed

Mangroves Ecological roles of mangroves root systems stabilize sediments aerial roots aid deposition of particles in sediments epiphytes live on aerial roots canopy is a home for insects and birds mangals are a nursery and refuge mangrove leaves, fruit and propagules are consumed by animals contribute to detrital food chains