Algae
Michael Renfroe
Algae – diverse group of organisms
Ubiquitous distribution –
algae can grow anywhere
This species of
Chlamydomonas forms pink
colonies on snow packs
Desmococcus grows
on the fur of a sloth in
warm jungle areas
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.
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.
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.
Acetabularia has very large cells. Each of these is a single cell.
Chara corralina
This alga was
important in studying
cyclosis or
cytoplasmic
streaming and
illuminating the role
of microfilaments in
the biology of the
cell.
Algae are grouped into a variety of taxonomic groupings:
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 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.
Edible Algae:
Many species of algae are edible and
are part of the human diet.
Why eat algae?
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)
Of 160 spp. of algae used for food, 3 genera are most important
Porphyra
Laminaria
Undaria
Porphyra
common names:
Nori - Japan
Laver – U.K, U.S.
Luche - Chile
Slack - Scotland
Sloke - Ireland
Porphyra life cycle
Edible fronds
are haploid
gametophytes
gametes fuse to
form zygote that
grows into new
sporophyte
Sporophytes attach
to calcareous shells
Conchospores are released and form
new gametophyte fronds.
Nori is harvested, washed,
chopped, dried into sheets,
and used for making sushi
rolls
Nori
sushi prepared in traditional bamboo roller
Laminaria
kelp
kombu
kelp is used in
soups and stews
Kombu harvest in Japan
Kombu harvest in Japan
Kombu harvest in Japan
Kombu harvest off Maine
Kombu harvest off Maine
Undaria
Wakame
Increases instestinal absorbtion of Ca,
aids bone formation and maintenance
Undaria life cycle
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
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
Carrageenans
Agars
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
Other species are
harvested by
smaller boat:
Ascophyllum
Durvillea
Laminaria
Ecklonia
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
Source:
Chondrus crispus
Irish moss
Uses:
Thickening and gelling agent
Thermally reversible
(solidifies as cools, can re-heat
and re-melts)
Harvested in
N. Atlantic
Source:
Euchema
Carrageenans
Harvested in Phillipines
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:
Properties:
Gelidium
Very hygroscopic
Gracilaria
Soluble in hot water
Pterocladia
Acanthopeltis
Ahnfeltia
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
To improve compacted soils, can apply algae such as
Chlamydomonas mexicana – has mucilaginous secretions
that lead to soil flocculation – improves porosity of
compacted soils improving aeration and water penetration
Algal Fertilizers
Green manure for soil fertility
Hi in K, N; Low in P
Land reclamation - Ireland
Farmers mix sand and algae on
rocky land to form new soil in
which potatoes are planted
Calcareous algae (corraline red
algae) used to neutralize soil acidity
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 have several medicinal uses and the potential for more:
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
Toxins from Algae
Unfortunately, there are some species of algae that are
harmful to human health.
Effects:
Direct- can act directly on human physiology
Indirect – can cause fish kills
Indirect – 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
Dermatitis – caused by exposure to high numbers of:
Anabaena
Oscillatoria
Lyngbya
Schizothrix
Silicosis – chronic lung infection – silica dust from diatoms
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
Dinoflagellates can release toxins into the waters causing:
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 Poisoning
Toxins accumulate in organs of coral reef fish,
consumption leads to nausea, abdominal cramps, muscle
weakness
Red tide organisms - dinoflagellates
Red tide outbreak as seen from airplane
Red tide and other coastal algal blooms
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
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
Non-eutrophied
University of Manitoba
eutrophied
Experimental Lakes Area
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
Eutrophication of Black Sea
Eutrophication is a problem world-wide
Eutrophication of Australian lake
Future Uses
Aquaculture – food for fish, shrimp, crayfish, shellfish
Cellulose production from algae with cellulosic cell walls
Water detoxification –
use algae to absorb
toxins from water
Oils for biofuels – grow
our oil instead of mining
from fossil deposits
Shrimp farm - Belize
Biofuel
reactors for
growing oilproducing
algae
Algae for biofuels
biological oil production
Biofuel algae farms
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.
The end