Algae

Why are seaweeds assigned to the Protista rather than Plantae?

Seaweed has many plantlike features but it is not a plant, it is algae. Algae is assigned to Protista causing seaweed to fall under Protista as well.

Four basic parts of seaweed

Holdfast, Stipe, Blades, and Pneumatocyst/Floats

Thallus

Whole body of the seaweed which is photosynthetic

Holdfast

Serves as an anchor and attaches the seaweed or algae to the sea floor. (Not the same as roots because it is not used for water and nutrient uptake)

Stipe

The "stem" of a seaweed is called the stipe, which carries sugars from the blades to wherever they're needed. The stipe also supports the rest of the plant.

Blades

Blades, the leaves, are used for photosynthesis by providing a large surface for the absorption of sunlight

Pneumatocyst/Floats

Pneumatocysts, also known as Floats, are the gas filled balls on the seaweed. They help to keep the blades (and stipe) of the seaweed afloat or on the water's surface so that they can absorb energy from the sun

Important ecological roles of seaweed

They create a physical structure that provides animals with food and shelter, by acting as underwater nurseries where the blades form a dense forest canopy (Kelp Forests).

Kelp Forests

Dense underwater forests formed by large seaweeds.

Physical Characteristics of Environment

Because seaweeds absorb gases and nutrients from the surrounding water, they rely on the continual movement of water past them to avoid nutrient depletion.

Rocky Intertidal Communities

(area that is covered and uncovered by the advance and retreat of the tides) To survive in the intertidal, seaweeds must be able to tolerate or minimize the effects of evaporative water loss and temperature and salinity changes.

Environmental stress seaweeds encounter

1. The constant motion of ocean water is sometimes strong enough to rip seaweeds right off the rocks.

2. Exposure to air and weather conditions- when exposed to air seaweeds lose water through evaporation and can sometimes dry out and on cold days, seaweeds can be damaged by freezing.

Asexual reproduction in seaweed

Through Fragmentation or Spore Formation

Asexual

reproductive process that does not involve gametes

Fragmentation

thallus breaks up into smaller pieces which then grows into new algae

Spore Formation

Haploid spores are the result of meiosis from sporangium. Diploid spores are produced by sporophytes.

Sporangium

the enclosure in which spores are formed

Sporophytes

produce and release spores (diploid)

Haploid

contains only one complete set of chromosomes

Diploid

contain two complete sets of chromosomes

Sexual reproduction in seaweed

After released from the sporophyte, the haploid spores settle and grow into gametophytes. The gametophytes produce gametes which then fuse together to form a diploid cell

Gametes

specialized male and female reproductive cells

Meiosis

cell division process that halves the number of chromosomes and forms new haploid cells

Gametophytes

male and female plants that are haploid and produce gametes

Brown Algae - Phylum/Division

Heterokontophyta

Brown Algae - Example

Bull Kelp- some can grow up to 30 cm a day (feather boa kelp, winged kelp, stipe-less kelp, and strap kelp)

Brown Algae - Forms

crusts, filaments, and large elaborate kelps

Brown Algae - Pigments

fucoxanthin- reflects yellow light that masks the green coloring from chlorophyll

Brown Algae - Habitat

found in temperate waters (not too hot or too cold)

Brown Algae - Useful Substances/Human Uses

Algin- an emulsifier used in food products

Fucans- have potential medicinal uses

Brown algae- collected, treated, and sold as a fertilizer for agriculture.

Red Algae - Phylum/Division

Rhodophyta

Red Algae - Example

Turkish Towel- surfaces of the blades have a towel-like appearance and texture

Red Algae - Forms

simple and branched filaments, fleshy plants, and sheets

Red Algae - Pigments

phycocyanin (absorbs blue light) and phycoerythrin which gives red algae its red coloration

Red Algae - Habitat

Bottom algae (benthic), they grow in deeper waters due to blue light absorption

Red Algae - Useful Substances/Human Uses

Gelling compounds...

Carrageenan- important ingredient in toothpaste and milk products

Agar- many scientific applications and is used in the packaging of canned meats

Green Algae - Phylum/Division

Chlorophyta

Green Algae - Example

Sea Lettuce (and Dead Man's Fingers)

Green Algae - Forms

single-celled forms, multi-cellular sheets, and branched filaments

Green Algae - Pigments

chlorophyll a and b (absorbs red light) which gives green algae its green color and is used for photosynthesis

Green Algae - Habitat

most live in shallow freshwater areas (only 10% marine)

Green Algae - Useful Substances/Human Uses

can be used as food products

Brown Algae

least diverse and contains the largest/biggest algaes

Red Algae

most diverse, over 8,000 species, and 98% is found in marine environments

Green Algae

most are unicellular (diatoms)

Lilies

the common land plant that seagrasses are most closely related to

Seagrass Environment

shallow coastal waters

Importance of Seagrasses

Seagrass provides food and shelter for many marine organisms. primary food source for manatees and turtles and lobsters,shrimp, and crabs use seagrass as nurseries. Fish forage in seagrass habitats and some spend their juvenile stage there.

Seagrasses

-hydrophytes

-vegetative growth

-have aerenchyme

-secrete tannins

-have roots

-release gametes in water for reproduction

Hydrophytes

plants that only grow in or beneath water

Vegetative Growth

vertical stems and leaves that arise from rhizomes

Rhizomes

horizontal stems

Aerenchyme

gas filled spaces that allow for floatation

Tannins Secretion

protects the aerenchyme

Seagrass Classification

12 genera (genus), 5 families, 3 clades

clades

groups with a common ancestor

3 Seagrass Clades

1. eelgrasses and surf grasses

2. paddle grasses, turtle grasses, and Enhalus

3. paddle grass, manatee grass, and shoal grass

Mangroves

Includes 54 species of partly submerged trees, shrubs, palms, and ferns that can be divided into 4 categories: Red, Black, White, and Buttonwood. Associated with salt lagoons and estuaries and create mangals.

Red and Black Mangroves

half of all mangroves belong under these categories

White Mangroves

other half of mangroves belong under this (and Buttonwood) category

Buttonwood Mangroves

roots are near the shore

Mangrove Distribution

along tropical shores with limited wave action, a subtle slope (for sediment build up), high rate of sedimentation, and soil that's waterlogged, anoxic (no oxygen), and a high salt content.

Mangals

mangrove swamp communities

Complex root systems

many aerial root systems above ground that have prop, drop, and stilt roots

Lenticels

scar-like openings that expose aerenchyme to the atmosphere (stilt roots have lenticels)

Pneumatophores

a type of ventilation system (black mangroves)

Mangrove Leaves

simple, leathery, thick, and never submerged in water. Their stomata allow for gas exchange and water loss

Salt elimination through leaves (mangroves)

salt is concentrated in old leaves that are shed in others

Mangrove Reproduction

mangroves release buoyant seeds that can drift in the water (these seeds can stay buoyant for up to 100 days) and produce propagules

Propagules

an embryonic plant that grows on the parent plant and then falls from the parent tree and drifts in currents