Agar: a complex gelling compound found in the cell walls of some red algae. It has commercial applications.

Alga (plural algae): a collective term for photosynthetic organisms lacking distinct cellular differentiation and elaborate protected reproduction systems. In addition to seaweeds, includes some plankton, bacteria, plants and other species.

Algin: a complex emulsifying compound found associated with the cell walls of brown algae. It has commercial applications.

Amorphic: without defined form.

Anaerobic: lacking oxygen.

Annual: living for one year (cf. Ephemeral, Perennial).

Anoxic: in the absence of oxygen.

Anthropocene: a proposed epoch that defines the geological period of humanity’s influence.

Apical growth: growth resulting from cells located at the apex or along the margins of the plant (cf. Intercalary growth).

Arachidonic acid (AA): an omega-6 essential fatty acid.

Asexual: a form of reproduction that does not involve sexual fusion, e.g., spores, fragments (cf. Sexual).

Axil: the upper angle created by a leaf coming off a stem (or a blade coming off a stipe).


Basal: at the base.

Binomial: the two names for a species (e.g. Saccharina latissima).

Bioavailability: an expression of the availability of substance to the living system. Usually applied to heavy metals and other toxic substances.

Biofuel: substances derived from plants that are used in combustion. This process is considered sustainable in contrast to fossil fuels.

Biogas: usually methane that is produced by the anaerobic digestion of plant material. A biofuel.

Biota: all of the inhabitants of an area, usually the combined fauna and flora.

Bq: A unit of radiation. One Bq equals one nuclear disintegration per second.


Calcareous: containing magnesium and/or calcium carbonate (lime) to the point of being brittle, bone-like.

Canopy: layers of foliage held above the ocean bottom, most significantly produced by the kelp Macrocystis and Nereocystis, but may be produced by lower-lying forms as well.

Carbonic acid: an inorganic form of carbon associated with ocean acidification.

Carrageenan: a complex gelling compound found in the cell walls of some red algae. It has industrial uses.

Chlorophyll: the photosynthetic pigment found in all photosynthetic organisms.

Chloroplast: the cell structure responsible for photosynthesis.

Chloroplast DNA: unique DNA associated with the chloroplast.

Coenocytic cells: long cells, usually with many nuclei, that are incompletely isolated by cell end walls from adjoining cells.

Collenchyma: a type of plant cell that has minimal secondary thickening of the cell wall and gives the plant physical support until sclerenchyma has been produced.

Crust: a growth form in which the plant adheres tightly to the substrate (crustose).


Diatom: a simple photosynthetic organism, usually a solitary cell that is encased in a silicon housing. Diatoms are common phytoplankton.

Diffuse growth: growth resulting from cell divisions more or less evenly spread over the plant and not concentrated in particular areas (cf. Meristem).

Digitate: shaped like the fingers on a hand (refers to the shape of a seaweed blade).

Dioecious: (describing an individual plant) bearing either a male or female reproductive structure but not both (cf. Monoecious).

Diploid: (describing a cell) containing two sets of chromosomes (cf. Haploid).

DNA barcode: a species-identification technique that uses short DNA sequences from a standardized region of the genome to identify unknown organisms.

Dorsal-ventral: having a differentiated front and back.


Eicosapentaenic acid (EPA): ): an omega-3 essential fatty acid.

Electron microscope: a microscope capable of resolving very small structures, such as details of the chloroplast structure.

Emulsifier: a chemical compound that suspends other compounds.

Ephemeral: short-lived, usually much less than one year (cf. Annual, Perennial).

Epiphyte: an organism that grows on another organism without harming it.

Exfoliate: to remove dead or damaged skin.


Fatty acids: complex organic compounds found in dietary fats (e.g., lard), usually classsified as saturated or unsaturated.

Filamentous: thread-like (describing plants usually one cell or a few cells wide).

Flagella: whip-like cellular appendages used to move a cell.

Fucoid: a member of the order Fucales. Includes Fucus, Sargassum and related forms.

Fucoidan: a sulfated carbohydrate, the slime of kelp, a dietary fibre.

Fucoxanthin: a photosynthetic pigment found in brown seaweeds, which gives the seaweeds their brown colour.


Gamete: a cell capable of sexual fusion, usually eggs and sperm.

Gametophyte: the plant phase that bears one set of chromosomes (haploid) and produces eggs and sperm (gametes) (cf. Sporophyte).

Geniculate: jointed. In calcareous red algae, the term refers to alternating calcified and uncalcified segments.


Habit: the physical appearance of a seaweed or other organism.

Haploid: (describing a cell) containing one set of chromosomes (cf. Diploid).

Hapteron (plural haptera): finger-like projections of the holdfast that attach a seaweed to its substrate.

Herbivory: eating vegetative matter.

Heteromorphic: (describing a seaweed) having two plant phases with different morphologies (cf. Isomorphic).

High intertidal: the upper third of the intertidal zone, an area that is exposed to air more than water.

Holdfast: the organ of a seaweed by which it attaches.


Intercalary growth: growth that takes place between two parts of a plant. Growth that is concentrated in the middle of a filament, or between the stipe and blade, is referred to as an intercalary meristem (cf. Apical growth).

Intertidal: the region of beach extending between the highest and lowest levels reached by the tide. This region is exposed to air at least occasionally (cf. Subtidal).

Invasive species: an organisim introduced to a foreign biota that is aggressive.

Isomorphic: (describing a seaweed) having two plant phases with the same morphology (cf. Heteromorphic).


Kelpanol: a term appied to ethanol derived from the fermentation or other manipulation of kelp


Life cycle: the events (meiosis, sexual fusion) and phases (gametophyte, sporophyte) through which an organism passes to enable it to reproduce sexually.

Lignin: a complex cell wall material that strengthens advanced plants.

Low intertidal: the lower third of the intertidal zone, an area that is exposed to water more than air.


Macroscopic: being large enough to see with the unaided eye (cf. Microscopic).

Mariculture: the farming of plants and animals in the sea.

Meiosis: a type of cell division that reduces the sets of chromosomes from two (diploid) to one (haploid) (cf. Mitosis).

Meristem: a region on a plant where cell division and growth are prevalent, apical or intercalary meristems (cf. Diffuse growth).

Methane: a gas derived from the anaerobic digestion of seaweeds, a sustainable fuel alternative.

Micronutrients: elements such as zinc and manganese essential to good health.

Microscopic: being too small to see with the unaided eye (cf. Macroscopic).

Mid-intertidal: the middle third of the intertidal zone, an area that is exposed to air and water for approximately the same duration.

Midrib: a regular thickening along the middle of a seaweed blade.

Mitochondrion (plural mitochondria): the cellular structure responsible for the release of chemically bound energy.

Mitosis: a type of cell division that maintains the number of chromosome sets at their original level while increasing the number of cells (cf. Meiosis).

Motile: capable of movement. In describing seaweeds, the term refers to movement resulting from flagellar activity on spores or gametes.

Monoecious: (describing an individual plant) bearing both male and female structures (cf. Dioecious).

Monosodium glutamate (MSG): an organic compound found naturally in kelp that is a flavour enhancer.

Morphology: the study of the structures and forms of organisms.

Mutigen: a substance that induces mutation.


Ocean acidification: the changing acidity of the ocean, primarily a response to increased levels of carbon dioxide and associated carbon forms.


Parasite: an organism that lives on another organism, causing harm to the host. In the red algae, parasitism involves the host providing nutrition to its parasite.

Parenchyma: a type of plant cell lacking secondary cell walls and retaining the ability to undergo cell division.

Peltate blade: a blade whose stipe is attached near its centre and not to its margin.

Penultimate branches: those branches next to the outermost branches or the most recently produced branches.

Perennial: living for more than one year (cf. Ephemeral, Annual).

Phenotypic plasticity: the ability to change form or function in response to environmental change.

Pheromone: a chemical attractant produced by the female that directs the sperm to the egg.

Photoperiod: the duration of light relative to darkness over a 24-hour period that affects a plant, e.g., long- and short-day plants.

Photosynthesis: the use of energy from light and the process of converting it into organic compounds necessary to growth and maintenance.

Phycobilins: water-soluble photosynthetic pigments found in red algae and some photosynthetic bacteria.

Phycologist: one who studies algae.

Phycology: the study of algae, including seaweeds.

Phyllotaxy: the arrangement of leaves down a stem (or blades down a stipe).

Phytoplankton: microscopic photosynthetic organisms, usually suspended in the water, that drift with the water.

Plant gums: complex carbohydrates with many industrial uses. Seaweed examples are agar and algin.

Polysiphonous: composed of tiers of elongated cells, stacked as bundles of straws. Found in some red algae.


Refugium (plural refugia): an area in which a population of organisms can survive through a period of unfavourable conditions, especially glaciation.


Sclerenchyma: a type of plant cell with considerable secondary thickening of the cell wall that gives the plant its major physical support.

Sessile: can refer to an organism being either fixed in one place, i.e., immobile, or having no stipe.

Sexual: a form of reproduction that involves the fusion of gametes, e.g., egg and sperm (cf. Asexual).

Sorus (plural sori): a patch of cells that have undergone meiosis, producing spores.

Splash zone: the region just above the highest tide level that receives seawater spray.

Spores: small, usually single-celled structures that are produced by an organism for reproduction. Spores produced by meiosis participate in the organism’s life cycle and spores produced by mitosis are usually a form of asexual reproduction. Many spores are motile.

Sporophyll: a specialized blade bearing spore patches (cf. Vegetative blade).

Sporophyte: the plant phase that bears two sets of chromosomes (diploid) and usually produces spores by meiosis (fucoids are an exception) (cf. Gametophyte).

Spray pool: a pool of water located above the highest tidelevel but influenced by seawater spray.

Stipe: a stem-like structure that bears the blades of seaweeds.

Storage products: energy-rich compounds produced and stored by seaweeds for later use in supporting plant maintenance, growth and/or reproduction. Starches, sugars, oils and fats may be stored.

Subtidal: the region of beach below the lowest tide level, never exposed to air (cf. Intertidal).

Symbiont: either of two organisms living in symbiosis, i.e., a relationship between two different organisms of different species living in close association.


Tetrasporophyte: a diploid plant that produces spores in clusters of four by meiosis. Usually refers to a free-living sporophyte in the life cycle of many red algae.

Translocation: the active conducting of compounds through special cells at rates that cannot be accounted for by diffusion alone.


Vegetative blade: a blade that is primarily responsible for photosynthesis and growth of an organism. It may also be the site of spore production (cf. Sporophyll).


Xylem: specialized cells found in advanced plants that conduct water and nutrients from the roots to the aboveground plant tissues.


Zooplankton: small animals, usually suspended in water, that drift with the water.

Zygote: the fertilized egg cell, the first cell of the new diploid generation.



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