An algal bloom occurs when algae grows rapidly in an aquatic system. Harmful algal blooms produce toxins that negatively impact other organisms. Blooms are caused by excess nutrients like phosphorus and nitrogen from sources like fertilizer and sewage runoff. Impacts include human health issues, environmental damage like dead zones, and economic losses. Common harmful blooms include red tides that cause shellfish poisoning and cyanobacteria that produce cyanotoxins. Control methods include physical approaches like aeration, chemical ones like algaecides, and biological options like increasing grazing organisms.

2. O Algal bloom
O Harmful algal bloom
O Effect of algal bloom
O Impact of algal bloom
O Name of some harmful algal bloom
O Control methods of algal bloom

3. Algal bloom
 An algal bloom is a rapid increase in the
population of algae in an aquatic system.
 Algal blooms may occur in freshwater as well as
marine environments.
 Result of an excess of nutrients (paricularly p and
n).
 Their growth is harmful for other plant and
organisms.

4. Harmful algal blooms
 A harmful algal blooms is an algal bloom that
causes negative impacts to aquatic organisms via
production of natural toxins, mechanical damage to
aquatic organism.
 Harmful algal blooms are often associated with
large-scale marine mortality events and have been
associated with various types of shellfish
poisonings and also fin fishes and other aquatic
organisms.

5. Causes of algal bloom
 Eutrophication
 Upwelling
 High temperature
 Presence of dead organic material
 Large mass of water
 Higher carbon dioxide levels
 Extreme storm

6. 1. Eutrophication
 Eutrophication is the process in which a water body becomes
overly enriched with nutrients( phosphorus and nitrogen),
leading to plentiful growth of simple plant life.
 The excessive growth (or bloom) of algae and plankton in a
water body are indicators of this process.
 Eutrophication is considered to be a serious environmental
concern since it often results in the deterioration of water
quality and the depletion of dissolved oxygen in water bodies.
 Eutrophic waters can eventually become “dead zones” that are
incapable of supporting life.

7. Source of nutrients
O Fertilizers runoff
O Untreated sewage
O Detergents containing phosphorus
O Industrial discharge of waste.

8. Effect of Huge Biomass of Algae in Eutrophic Waters
 The excessive growth of algae in eutrophic waters is accompanied by
the generation of a large biomass of dead algae.
 These dead algae sink to the bottom of the water body where they are
broken down by bacteria, which consume oxygen in the process.
 The overconsumption of oxygen leads to hypoxic conditions
(conditions in which the availability of oxygen is low) in the water.
 The hypoxic conditions at the lower levels of the water body lead to the
suffocation and eventual death of larger life forms such as fish.

10. 2. Upwelling
• Upwelling is a process where deeper
colder nutrient rich water comes to the
surface through the push of surface
winds.
• It is very productive water bodies for
fisheries.
• But it can be harmful when harmful algal
blooms are developed in these water
bodies due to high nutrient availability.

11. 3. High temperature
 As depletion of ozone layer is
happening due to global
warming and this reason is a
major factor behind tremendous
growth in algal bloom.
Appropriate temperature is
needed for proper growth of
algal bloom. As high
temperature leads to rapid
decompositions of the nutrients
like nitrogen, phosphorus and
these decomposed nutrients
become easy for algal bloom to
use up and grow rapidly.

12. 4. Presence of dead organic material
*There are so many varieties of
bacteria which are present in water
bodies as well as in the
atmosphere. These bacteria lead to
the growth of algae bacteria like all
other bacteria. As nutrients in water
along with dead organic matter
leads to increase in growth of algal
bloom.
5. Large mass of water
*Large mass of water is needed for
growth of algal bloom. As less
disturbance in water propagation
leads to tremendous growth of
algal bloom.

13. 6. Higher carbon dioxide
*Algae need carbon dioxide to survive.
Higher levels of carbon dioxide in the air
and water can lead to rapid growth of
algae, especially toxic blue-green algae
that can float to the surface of the water.
7. Extreme storm
*By extreme storm the various nutrients
reached into water bodies which is
helpful for algal production.

14. Impact of algal bloom
Human health
 Direct exposure of toxic algae:
 By drinking water
 Accidentally swallowing of water
 Swimming in affected water bodies
 Harmful algal bloom can cause serious health problems
including:
 Rashes
 Stomach or liver illness
 Respiratory problems
 Neurological effects
 Algal blooms produce toxins harmful to humans and marine
life

15. Environmental
 Harmful algal blooms sometimes create toxins that can kill fish
and other animals. When these algal blooms are consumed by
small fishes and shellfishes then toxin move up the food chain
and largely effect the aquatic life.
 It is also block the sunlight and also cause gill chocking of
fish.
 Nutrient pollution can create dead zones area in water with
little or no oxygen where aquatic life cannot survive.
 Over 166 deads zones have been documented nationwise,
affecting water bodies like the Chesapeake Bay and the Gulf of
Mexico.
 The Gulf of Mexico dead zone is the largest in the United
States, measured to be 5840 square miles in 2013.

16. Economy
 Drinking water costs: Nitrates and algal
blooms in drinking water sources can
drastically increase treatment costs. So
cost of drinking water will increase .
 Tourism losses: The tourism industry
losses close to $ 1 billion each year, mostly
through losses in fishing and boating
activities.

17. O Commercial fishing and shellfish losses: Annual losses to
these industries from nutrient pollution are estimated to be in
the tens of millions of dollars.

18. Some HAB’s
O Redtides- Neurotoxic shellfish poisoning
O Cyanobacteria (blue-green algae)
O Ciguatera- Gambierdiscus toxicus

19. 1. Red tides
 Red tide is a phenomenon caused by algal blooms during
which algae become so numerous that they discolor coastal
waters mainly red color. (hence the name "red tide").
 The algal bloom may also deplete oxygen in the waters
and/or release toxins that may cause illness in humans and
other animals.

20.  Species in the United States that release these harmful
toxins include:
 Alexandrium fundyense - found along the Atlantic
coast from the Canadian Maritimes to southern New
England
 Alexandrium catenella - found along the Pacific coast
from California to Alaska
 Karenia brevis - found in the Gulf of Mexico along the
west coast of Florida

21. Poisoning caused by red tide
1. Paralytic Shellfish Poisoning (PSP) - This disease is caused by the
production of saxitoxin by the Alexandrium species. It is common
along the Atlantic and Pacific coasts in the US and Canada.
Poisoning occurs when one ingests shellfish contaminated with PSP
toxins causing disruption of nerve function and paralysis. Extreme
cases may result in death by asphyxiation by respiratory paralysis.
2. Diarrhetic Shellfish Poisoning (DSP) - This disease is caused by
the Dinophysis species. It generally occurs in Japan and Europe, but
it has also been found in other countries such as Canada, the US,
Chile, New Zealand, and Thailand. Symptoms of DSP include
diarrhea, nausea, vomiting, abdominal pain, and cramps. DSP is
generally not lethal.

22. 3. Amnesic Shellfish Poisoning (ASP) - This disease, which has been
found along the eastern Canadian coast, is caused by domoic acid
producing planktonic and benthic algae, including Pseudo-nitzschia
pungens forma. Pseudo-nitzschia multiseries and Amphora
coffaeformis. It can also be found in soft shell clams and blue
mussels infected by Pseudo-nitzschia delicatissima. Gastric and
neurological symptoms include dizziness, disorientation and
memory loss.

23. Cyanobacteria (blue-green algae)
 Cyanobacteria produce a toxin which is known as cyanotoxins.
 The production of cyanotoxins includes risks to human and
animal health.
 Depending on the concentration in the aquatic environment, they
can cause severe poisoning, produce chronic diseases such as
cancer, and even lead to death.
 Cyanotoxins are thus an important group of chemical
compounds, from the point of view of ecotoxicology, toxicology,
and environmental chemistry.
 Three classes of cyanotoxins are hepatotoxins, neurotoxins,
dermatotoxins.

24. • Main toxins from cyanobacteria
Cyanotoxins Genera of main producers
1. Hepatotoxins
Microcystins Anabaena, Planktothrix, Nostoc, Anabaenops
is
Nodularins Nodularia
Cylindrospermopsins Cylindrospermopsis
raciborskii, Aphanizomenon
ovalisporum, Aphanizomenon zflos-aquae
2. Neurotoxins
Anatoxin-a Anabaena, Aphanizomenon, Planktothrix
Anatoxin-a(s) Anabaena
Saxitoxins Dinoflagellates: Alexandrium, Pyrodinium,
Gymnodinium
Cyanobacteria: Anabaena
circinalis, Aphanizomenon
sp., Aphanizomenon
gracile, Cylindrospermopsis
raciborskii, Lyngbya wollei

25. 3. Dermatotoxins
Lyngbyatoxin-a Lyngbya
Aplysiatoxin
Lyngbya, Schizothrix, Planktothrix
(Oscillatoria)
Lipopolysaccharides (LPS) Cyanobacteria in general

26. Ciguatera- Gambierdiscus toxicus
 Ciguatera fish poisoning (or ciguatera) is an illness caused by eating
fish that contain toxins produced by a marine microalgae
called Gambierdiscus toxicus.
 People who have ciguatera may experience nausea, vomiting, and
neurologic symptoms such as tingling fingers or toes.
 They also may find that cold things feel hot and hot things feel cold.
 Ciguatera has no cure.
 Symptoms usually go away in days or weeks but can last for years.
People who have ciguatera can be treated for their symptoms.

27. Control method
 Physical controls
 Chemical controls
 Biological controls

28. Physical controls
 Aeration
 Mechanical mixing
 Surface skimming
 Ultrasound

29. Aeration
 Aeration Air is pumped into a pond or lake from an
aeration device placed on the bottom.
 This forms plumes of air that disrupt the stratification of
the body of water and limit the nutrients the algae can
get.
 Drawback - Proximity limit of mechanical devices

30. Mechanical mixing
 This mixes the water, disrupting the stratification and
limiting nutrients to the algae.
 Drawback - Proximity limit of mechanical devices

31. Surface skimming
 By using oil skimmers, the algae can be
removed.
 Drawback - High labor cost

32. Ultrasound
 Ultrasound Ultrasonic waves of a particular frequency are
used to kill the algae by destroying their cellular structure.
 Drawback - Transmitter could be blocked; Need
reprogramming for different types of algae

33. Chemicals controls
 Algaecides
 Barley straw
 Coagulation

34. Algaecides
 Copper sulfate, copper citrate,
and other copper based
products
 Potassium permanganate
 Chlorine
 Drawback - Harmful to the
environment

35. Barley straw
 Barley Straw Bales of barley straw are placed in the water.
 When exposed to sunlight and oxygen, the straw produces a
chemical that stops algae growth.
 Drawback - Cannot produce chemical without sunlight;
Occupy space

36. Coagulation
 Coagulation Chemicals are introduced into the water that makes
the algae coagulate and fall to the bottom of the pond or lake.
 At the bottom, the algae has no access to light, oxygen, or other
critical resources, eventually dies.
 Drawback - Current ways of applying the solution are not
efficient and effective

37. Biological controls
 Increasing grazing organisms
 Floating artificial wetland

38. Floating artificial wetlands
 Plants are placed on floating
mats and placed in the water.
 As the plants grow, they filter
excess nutrients from the
water, helping to prevent an
algae bloom.
 When the plants mature, they
need to be switched out with
young plants in order for the
process to continue.
 Drawback - Occupy space;
Need effort for planting and
switching to young plants

39. Increasing grazing pressure
 By increasing the growth of zooplankton, plants, and other
organisms that feed on algae, it will be less likely for algae to
experience a bloom.
 This can be done by removing fish that feed on these organisms.
 Drawback - May introduce new risks