Algae – diverse group of organisms
Ubiquitous distribution – algae can grow anywhere
Desmococcus grows on the fur of a sloth in warm jungle areas
This species of Chlamydomonas forms pink colonies on snow packs
Desmococcus grows the sloth’s fur and a sloth moth eats the algae which keeps it from getting too thick on the sloth fur. The moth lays eggs in the sloth feces, continuing the moth population that controls the algal growth on the sloth.
The green Desmococcus helps camouflage the sloth and make it harder for predators like eagles and harpies to spot the sloth. The alga is passed along to the offspring as they cling to the mother during the first months of their life.
Acetabularia - Mermaid’s wine glass is a macroscopic single-celled alga that has been important in early studies of molecular biology making clear the role of mRNA in protein synthesis.
Algae can grow in a desert by growing on underside of quartz. Sunlight penetrates the quartz while moisture collects on the underside and provides water for the algae.
Chara corralina
This alga was important in studying cyclosis or cytoplasmic streaming and illuminating the role of microfilaments in the biology of the cell.
Prokaryotic algae – Kingdom Monera
Blue-green algae: Cyanophyta or Cyanobacteria
Eukaryotic algae – Kingdom Protista (Protoctista)
Green algae: Chlorophyta
Red algae: Rhodophyta
Brown algae: Phaeophyta
Golden-brown algae: Chrysophyta
Dinoflagellates: Pyrrhophyta
Algae are grouped into a variety of taxonomic groupings:
Algae changed course of evolution on earth.
When photosynthetic algae evolved, they began the oxygenation of water which led to the extinction of many obligate anaerobes. Their
presence is evidenced by the banded iron formations formed from the iron oxide precipitates that formed in the oceans.
Algae produced so much oxygen that it began to enter the atmosphere, leading to the formation of the ozone layer. The ozone layer shielded the land masses from lethal doses of UV
radiation and allowed the evolution of terrestrial species.
Algae components:
Non-digestible structural carbohydrates (non-nutritional)
Up to 25% soluble carbohydrates and proteins (nutritional)
Vitamins A, B1, B12, C, D, E, riboflavin, niacin, pantothenic acid, folic acid (nutritional)
Iodine (nutritional)
Edible Algae:
Many species of algae are edible and are part of the human diet.
Why eat algae?
Porphyra
Nori - Japan
Laver – U.K, U.S.
Luche - Chile
Slack - Scotland
Sloke - Ireland
common names:
Conchospores are released and form new gametophyte fronds.
Sporophytes attach to calcareous shells
Edible fronds are haploid gametophytes
Porphyra life cycle
gametes fuse to form zygote that grows into new sporophyte
Spirulina – a cyanobacterium
Contains up to 72% protein (dw)
High productivity: 10 tons/ac
Compare to: wheat – 0.16 tons/ac
beef – 0.016 tons/ac
Dunaliella bardawil
Source of: β-carotene, glycerol
This is a commercial source of carotene that is used to dye cheeses and margarines orange.
Industrial uses of algae - Phycocolloids
Alginates
Carrageenans
Agars
Algae are the source of chemicals that have many industrial and commercial uses. These chemicals are water soluble or stay suspended in aqueous solutions. The three main classes of phycocolloids are:
Alginates
Algae Sources:
Macrocystis
Laminaria
Ascophyllum
Ecklonia
Durvillea
Composed of alginic acid and salts
Absorbs 200-300X own wt in water
Mainly mannuronic and guluronic acids
Macrocystis – harvested by ship
Reciprocating cutter (like underwater hedge clippers)
Cuts off tops of algae, which re-grow over time
Alginate uses:
Paper industry – sizings
Paint – suspend pigments, forms pseudoplastic soln., smoothes paint on surface
Charcoal briquettes – binder
Food industry – emulsifier
Cosmetics – emulsifier
Medicines – emulsifier
Ice cream – colligative binder, prevents ice formation
Beer – foam stabilizer
Alginate uses:
Fruit congealer
Artificial cherries
Fake caviar
Dental retainers – with heavy metals, forms settable plastic
High quality audio speakers – special treatment to form fibers
Synseeds – synthetic seeds for somatic embryos
Carrageenans
Chondrus crispus Irish moss
Thickening and gelling agent
Thermally reversible (solidifies as cools, can re-heat and re-melts)
Harvested in N. Atlantic
Uses:
Source:
Carrageenan uses – suspension and thickening
Milk pudding – blanc manges
Chocolate milk – keeps cocoa
particles suspended
Yogurt
Egg nog
Ice cream (ice milk)
Toothpaste
Binds well with proteins (e.g. casein – milk protein)
Clarifying wort in brew kettle
Agar
Sources:
Gelidium
Gracilaria
Pterocladia
Acanthopeltis
Ahnfeltia
Properties:
Very hygroscopic
Soluble in hot water
Used in tissue culture and microbiological research to form semi-solid nutrient media
Agar uses:
Moisturizing agent in baked goods, e.g. cakes
Clarifying agent (complexes with proteins) for wines, vinegars, juices
Binder – sushi rice (glues long-grain rice grains together, so sushi does not crumble apart)
Food-grade agar
Algal Fertilizers
1665 – King Charles II of England – allowed subjects to harvest seaweed to use as fertilizer in fields to increase yields
Chlamydomonas mexicana – has mucilaginous secretions that lead to soil flocculation – improves porosity of compacted soils improving aeration and water penetration
To improve compacted soils, can apply algae such as
Algal Fertilizers
Green manure for soil fertility
Hi in K, N; Low in P
Land reclamation - Ireland
Calcareous algae (corraline red algae) used to neutralize soil acidity
Farmers mix sand and algae on rocky land to form new soil in which potatoes are planted
These algae have calcium carbonate as part of their structure
Cyanobacteria
Carry out nitrogen fixation in specialized cells called heterocysts, thus acting as natural fertilizers
Anabaena azollae is a cyantobacterium that lives symbiotically with Azolla, an angiosperm called water fern
When grown together – increase yield in rice paddies by 18%
0.2 kg Azolla / ha is equivalent to 30 kg / ha N-fertilizer
Anabaena heterocyst
Azolla
Fossil algae - Diatoms
Diatomaceous earth (Fuller’s earth, Keiselguhr)
Siliceous frustules act as filtering agent
e.g., sugar and oil refining, pool filters, beer and wine filters
Abrasive polishing agent in toothpaste and silver polishes
Diatom shells made of silica
Make good filters and abrasives once diatom is dead leaving shell behind
Wastewater Treatment
Algae are very important in wastewater treatment for water purification and reducing biological oxygen demand (BOD) of wastewaters so they can be discharged into rivers without adverse consequences.
When bacteria and fungi grow, they have to have oxygen to support their respiration, so they create a biological oxygen demand. Algae photosynthesize and add oxygen back to the water, lowering the BOD value, keeping the water oxygenated so that it can support fish and other aquatic organisms.
Wastewater Treatment
Primary treatment – solids settle out
Secondary treatment – fungi and bacteria digest soluble organic fraction, flocculate to form sludge and fall out as solid residue. By reducing the nutrients in the water that would cause microbes to grow in the river, treatment has reduced BOD in the discharge water.
Tertiary treatment – use algal/bacterial mixture to treat sewage. Algae add oxygen, keeps bacteria growing longer, mixture reduces BOD by 90%, reduces N & P by 80%, so discharged water is even cleaner and carrying less nutrients that would cause problems in the rivers.
Algae in Medicine
Algae are a source of a chelating agent for heavy metal poisoning or radionucleotide poisoning
Iodine to treat goiter (swollen thyroid)
Vermifuge (expels parasitic worms)
Digenia simplex – kainic acid
Potential anticarcinogenics
Algae have several medicinal uses and the potential for more:
Toxins from Algae
Effects:Direct- can act directly on human physiologyIndirect – can cause fish killsIndirect – can accumulate in filter feeders and poison humans
Algal blooms – proliferations in algal populations caused by (1) upwellings of nutrient rich waters or (2) heavy rains washing phosphates into ocean
Unfortunately, there are some species of algae that are harmful to human health.
Algal fish kills:
Prymnesium parvum – releases toxin that affects gill permeability in fish
Pfisteria – causes external ulcerations and death of fish
Red tides – caused by overabundance of dinoflagellates
Paralytic Shellfish Poisoning (PSP)Nausea, vomiting, diarrhea, tingling in extremities, disorientation, paralysis and death
Neurotoxic Shellfish Poisoning (NSP)Numbness and food poisoning symptoms (usu. non-fatal)
Ciguatera PoisoningToxins accumulate in organs of coral reef fish, consumption leads to nausea, abdominal cramps, muscle weakness
Dinoflagellates can release toxins into the waters causing:
Nuisance Algae
Biofouling: attachment and colonization of underwater structures by algae.
Algal slime layer 1 mm thick results in 15% loss in ship spped, 80% increase in drag, costing marine industry over $1 billion/yr.
Nuisance Algae
Eutrophication
eutrophied
Non-eutrophied
University of Manitoba
Experimental Lakes Area
Algal “blooms” with rapid increase in population, followed by die-off and decomposition resulting in depletion of oxygen by aerobic decomposers and shading of photosynthetic autotrophs
Algal Blooms and Fish Kills
It is not the algae that kill fish. In an algal bloom, the algae populations grows rapidly because of nutrients in the waters. This population explosions by algae near the surface shades and kills the submerged aquatic vegetation from lack of sunlight. As the algae grow, they are adding oxygen to the water. When the nutrients run out, the algae die off and aerobic decomposers proliferate because of all the dead material on which to feed. These aerobic decomposers deplete the oxygen in the water, lowering the oxygen level to the point that fish cannot live. It is this oxygen depletion by the decomposers that leads to fish kills.
Important ecology concept to understand!
Salton Sea fish kill
Nutrient pollution, and warm shallow water is a deadly combination for fish – inadequate oxygen
Salton Sea
Raw sewage from Mexico drains into Salton sea
Eutrophication
High BOD
Inadequate oxygen for fish
Future Uses
Aquaculture – food for fish, shrimp, crayfish, shellfish
Cellulose production from algae with cellulosic cell walls
Oils for biofuels – grow our oil instead of mining from fossil deposits
Water detoxification – use algae to absorb toxins from water
Shrimp farm - Belize
The end
Algae not only made human life possible by altering the early earth’s atmosphere and making terrestrial life possible, algae continue to provide us with food, medicine, and many commercial products that enrich our lives, support the economy, and keep ecosystems healthy. It is when the ecology gets out of balance, that algae can be harmful to humans and other organisms and cause bad things to happen. Humans must learn to maintain healthy ecosystems if we wish to have a place in the environment and continue our species.