An algal bloom is a common phenomenon occurring in waterbodies, sometimes endangering lives of fishes and other species.

1. Submitted to
Dr. Md Wahidul Alam
Associate Professor
Department of Oceanography
Faculty of Marine Science and Fisheries
University of Chittagong
Submitted by
Al Tahsin Mahamud Khan
Id no: 19902005 ; Year: 2nd B.Sc.(Hon’s)
Department of Oceanography
Faculty of Marine Science and Fisheries
University of Chittagong

2. Seasonal and Non-seasonal
Blooms of Phyto-
Plankton,Macro-algae and
Causes of Bloom

3. What is Phyto-Plankton
Phytoplankton are plantlike microscopic organisms that live in fresh,
brackish and marine water .
Some phytoplankton are bacteria, some are protists, and most are single-
celled plants. Among the common kinds are cyanobacteria, silica-
encased diatom , dinoflagellates, green algae, and coccolithophores.
They are the basic food source for small aquatic animals.
Micro-Algae are simple plants that range in size from nano to micro size.

4. Macro Algae
Macroalgae are multicellular marine plantlike organisms. They lack the
various structures that characterize higher plants, such as true leaves, root,
stem, and encased reproductive organs. They are considered as lower type
of plants.
➢Macro algae are referred as sea-weed
➢Their complete body is known as thallus
➢They are mostly found in shallow marine water, near shore , estuary and
all kind of freshwater bodies.

5. Phyto-plankton or Algal Bloom
• Dense aggregations of phytoplankton cells are termed as
phytoplankton or algal bloom
• Outbreak of algal cell well above the average for a given
region or water body.
• Considered as the peak of annual cycle of algal life.
• Growth rate of algal biomass rises quickly until checked
by resource depletion
• Concentration of chlorophyll
>2mgch/m^3 in open ocean ; >20mgch/m^3
• Occurred in the surface mixed layer ( the layer in which
vertical mixing prevails)
• The amount of macro or micro-algae is termed as total
standing stock

7. The factors that control of formation of
Phytoplankton or Algal Bloom
• Physical properties of the water body
• Chemical properties of the water body
• Type of algae that causes algal bloom
• Pathogen or Grazers

8. Physical environment regulates the magnitude, duration
and intensity of algal bloom . The important factors are :-
➢ Surface mixed layer determines algal bloom by
mixing the nutrients, dissolved and suspended matter
➢In spring , the temperature, pressure and other
properties are favorable for forming algal bloom.
Early blue–green algal blooms usually develop during
the spring when water temperature is higher and there
is increased light.
➢Water temperatures above 25°C are optimal for the
growth of Cyanobacteria. At these temperatures, blue–
green algae have a competitive advantage over other
types of algae whose optimal growth temperature is
lower (12-15°C).
Physical Factors

9. ➢In temperate regions, blue–
green algal blooms generally
do not persist through the
winter months due to low
water temperatures.
➢In tropical regions blue–green
algal blooms persist
throughout the year due to
higher temperature.

10. ➢Blue–green algae populations are diminished
when they are exposed to long periods of high
light intensity (photo-inhibition) .
➢Stable water conditions with low flows, long
retention times, light winds and minimal
turbulence are suitable for bloom.

11. ➢In stratified water, bottom waters often become depleted
with oxygen , increases nutrient release from the
sediments. Pulses of nutrient from the colder bottom
layer may fuel up the algal growth in the top layer.
➢Turbidity is caused by the presence of suspended
particles and organic matter in the water column. High
turbidity occurs due to large amount of suspended
matter in the system and it is adverse for forming a
bloom.
➢Low turbidity occurs due to small amount of suspended
matter present in the water column. Low turbidity can be
due to slow moving or stagnant water that allows
suspended particles to settle out of the water column.
More light can penetrate through the water column. This
creates optimal conditions for algal growth.

12. Chemical Factor
• Nutrients promote and support the growth of algae and
Cyanobacteria.
• Eutrification brings nutrients for bloom
• The main nutrients are phosphorus and nitrogen.
• External sources are soil erosion, river bank erosion,
sewage waste, all kind of wastages dumped in water
• Internal sources are bed of water body or reservoir
Due to hypoxia (𝑂2 depletion) cause sediments to release
phosphate into the water column.

13. • Intensive rainfall can provide nutrient that can promote algal growth
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14. Upwelling and downwelling
• The deep, nutrient-rich waters are delivered to the surface
mixed layer which triggers marine algae to multiply and
produce the biomass that drives the marine food chain.
• The world’s most potential fisheries are located on coastal
upwelling regions(especially in the eastern boundary of
subtropical gyre)
• In contrast, downwelling induces decrease of biological
productivity by transporting dissolved nutrient, heat and
oxygen rich water to greater depth .
• This occurs along the west coast of Alaska in the eastern
boundary region of the Gulf of Alaska gyre .

15. Pathogens or Grazers
• Pathogens can affect the production of
phytoplankton
• The presence of grazers can limit the growth of
algae.
• Important grazers are copepod, protists, krill ,
fish , whale and other marine invertebrate
• If the amount grazers is outnumbered by
phytoplankton , then a bloom can be formed.
• To avoid predator, some phytoplankton release
toxic chemicals

16. Types of algae that cause bloom
1. Green algae :
➢Green algae are both found in freshwater and
marine environment
➢They are not involved in toxin production
➢Cause localized hypoxia ( stress for fish)
➢Example are chlorophyte , cladophora
➢Cladophora forms foul smelling nuisance that
are deposited in the beach , can log inlake and
potentially harbor pathogen , such as : E coli

17. 2. Basillariophyceae :
• Diatom are unicellular and cell wall are composed
of silica
• Domoic acid (ASP) is caused by diatom
• The diatom is widely distributed in both north and
south hemisphere
3. Euglenids:
• Euglenidophytes can be found in marine, fresh and eusturine water
• Euglena produce ichthyotoxin which can kill fish
• Bloom are most likely to occur in summer in freshwater ponds
• Most common in stagnant , high nutrient concentration water
• Indication of organic water pollution
• Euglena bloom can have reddish , green , brown or red

18. 4. Golden brown algae
• It is small(10um) generally halophilic organisms
• Prymnesium parvum is called golden algae due its yellow-golden accessory pigment
• Blooms of golden algae produces an Ichthyotoxin
• Aquatic insects, birds and mammals are not infected by this toxin
• Blooms of P parvum are responsible for killing fish in backrish and inlands water
5. Dinoflagellates:
• Most dinoflagellates are marine plankton but they are common in freshwater
habitat
• The blooms turn the ocean into various shades of red tide
• They can produce toxins that can kill fish and accumulating filter-feeder such as
shellfish
• Some dinoflagellates aren’t dangerous at all
• Bluish flicker are visible at night often comes from the bioluminescent
dinoflagellates, which emits short flashes of light when disturbed

19. 6. Blue green algae :
• Cyanobacteria are major harmful algal group in freshwater
environment
• These are recognized as rapidly expanding global problem
that threaten human and ecosystem health
• In marine environment, only a few species of blue green algae
causes HAB
• Form bloom of different color
The most common species of
cyanobacteria
• Anabaena , Oscillatoria, Nostoc and microcystic – fresh water
• Trichodesmium and Nodularia are marine species but these
have not been associated with human syndrom so far .
• Nodularia also found in brackrish water

20. Bloom species can be classified into
three different groups
These groups are :
1. Species that produce harmless water discoloration, but the dense bloom
decomposition can cause anoxia and lead to indiscriminate mortality of
a marine life .
2. Species which produce potent toxins causing a variety of gastrointestinal
and neurological illness to humans and animals.
3. Species which are not toxic to humans but are harmful to fish and
invertebrate by damaging or clogging their fish gills

21. Types of Algal Bloom
1. Fresh water algal bloom : In fresh water, blue-green algae, green algae and
filamentous algae are responsible for algal bloom. Ex: cyanobacteria
Fresh water algal bloom are of two types:
• Green algal bloom: This kind of bloom is caused by phytoplankton or micro-
algae
• Filamentous algal bloom: This kind of algal bloom is caused by multicellular
algae

22. • Green algal bloom : Euglena ,
anabaena and microcystic cause
green algal bloom.
• Filamentous bloom : Spyrogyra,
Oscillatoria, chlorella, Nostoc,
Odogonium, Chara cause algal
bloom

24. 2. Marine Algal bloom : Marine algal bloom can appear as red water
discoloration commonly referred to as ‘ red tide ‘ or a range of other
discolored water, from green, yellow and brownish to an oily or milky
appearance.
• BACILLARIOPHYCEAE ( Diatom)
• DINOPHYCEAE ( Dinoflagellates )
• PRYMNESIOPHYCEAE ( Golden-brown flagellates )
• CHRYSOPHYCEAE (Golden-brown algae)
• RAPHIDOPHYCEAE (Chloromonads)
• DICTOCHOPYCEAE ( Silicoflagellates )
• CYANOPHYCEAE ( Marine blue green algae)

25. On the basis of color
1. Red tide :
red tides are caused by phytoplankton that have a reddish
pigment called peridinin. Most dinoflagellates such as Alexnadrium,
catenella, have this pigment. As a result, when there is a bloom of
dinoflaggellates the ocean will easily turn into red. This type of tide is very
common on both the east and west coast as well as Florida and the Gulf of
Mexico.

26. 1. Green Tide :
Green tide can be caused by Phaeocystis, which is a unicellular ,
photosynthetic algae found throughout the world. Green tides can also be caused by
macro algae such as Enteromorpha sp. Damage to many coastal regions. When in
bloom, macro algae often outcomplete sea grass and coral reefs. This results in
habitat loss for marine fish , less oxygen and sunlight for other organisms and an
ecosystem more vulnerable to extinction and invasion

27. 1. Brown Tide :
It is caused by the pelagophytes ( another type of micro-
algae such as Aurococcus , Anophagefferens.
Aurococcus is a spherical non-motile species that has caused
noticeable damage to the coastal ecosystems in which it occcus. Brown tides
are commonly seen in the northeast and mid-Atlantic US countries.

28. Effect of algal bloom
❑Effect on water : the quality of the water degrade make it difficult for other
organisms to survive .
❑Effect on aquatic organisms : Many aquatic organisms die off due to change in
ph, oxygen depletion and absence of light
❑Effect on human health : Water become toxic due to harmful algal bloom and
make it totally impossible for man to consume or utilize the water for other uses
❑Effect on commerce and other human activities :
The fishing industry is a victim of harmful algal bloom causes a rapid die-off of fish and
fisherman cannot fish properly
❑Nitrogen fixation:
Phytoplankton bloom helps to fix nitrogen in the physical environment

29. Annual cycle of algal bloom
Algal blooms can be broadly differentiated into two stages in the annual
cycles of plankton of a given water body or region. These stages are :
1. Seasonal or regular bloom
2. Non-seasonal or unusual bloom
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30. In Lake
https://blog.limnology.wisc.edu/2014/10/29/algae-blooms-in-fall-mean-lake-menodta-is-mixed-up/

31. Seasonal recurrent
The seasonal bloom initiated by seasonal change of physical regime.
Seasonal bloom occurs due to warming and shallowing of the (Surface mixed layer ) by
thermal stratification in the spring. This process improves the light supply of the cells
trapped in the SML
In the autumn, vertical mixing reintroduces nutrients lost by sinking from it and
seasonal bloom is formed.
Spring and autumn blooms, respectively, are the result of these physical processes.
Blooms are also a regular feature of the upwelling region of lower latitude.

32. Spring Bloom
• Spring bloom is caused by the termination of winter vertical mixing
and advent of stratification in spring in both fresh and marine water
bodies
• Latitude influences the timing of spring bloom (light intensity).
• Thus, spring blooms along the melting ice edge off Greenland occur
well before the bloom on the Norwegian shelf 1000 km (10 latitude)
further south.
• Similarly, blooms start about a month earlier in protected bays and
fjords than in the adjacent, open shelf.
• Turbidity also plays an important role in forming the spring bloom
• If bloom forms in prolonged calm, sunny weather,the bloom peak is
reached within 2–3 weeks and is often dominated by only one or two
diatom species. In this case, bloom is terminated by mass sinking of
ungrazed cell
• On the contrary, bloom can be dominated by different species across a
succession of smaller peaks if waterbody is dynamic. In this case ,
bloom will be terminated by nutrient exhaustion and establishment of
recycle community

33. • Diatom dominate the spring bloom as a result of high growth and well defense
mechanism.
• (Skeletonema, Thalassiosira, Chaetoceros ) These three morphologically dissimilar
genera dominate spring blooms worldwide, from the coasts to the open ocean.

34. Autumn bloom
• Enhanced vertical mixing due to dynamic weather(wind, cooling) cause autumn bloom by
introducing new nutrients from the deep.
• The biomass and species composition vary regionally more than spring bloom
• Do not occur in all high- and midlatitude oceans.
• In many regions, the autumn bloom is dominated by diatoms that, in the Kiel Bight, can reach
their peak as late as mid-November.
• Diversity of species is present
• Most prominent dinoflagellates are species of the armored genus Ceratium, in particular the
cosmopolitan species C. tripos, C. fusus, and C. furca.
• Ceratium blooms regularly occur in many, but not all, coastal environments from the tropics
to the Arctic but they are absent around Antarctica.

35. • Terminated by mass cell death and disintegration in the water column
• Recurrent large Ceratium blooms regularly lead to anoxic events in the Laholm Bay of
southern Sweden.
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36. Blooms in Upwelling Regions of Low
Latitudes
• Water with high concentration of nutrients is brought up to the surface
• Regional and variation affect the intensity of upwelling also
• Intensity may change over the interval of several years
• Bloom span is short due to high sunlight angle warming the ocean making bloom
to reach peak earlier
• Skeletonema, Thalassiosira,Chaetoceros are prominent genera that dominate
bloom although Phaeocystis blooms have only been reported from the Arabian
Sea.
• In certain upwelling region, local Sardin like fish has developed special gills for
grazing micro-algae
• Upwelling regions harbor large stocks of pelagic fishes indicating that a
significant proportion of primary production is retained in the surface pelagic
system.
• If upwelling is prolonged over many months, subotoxic conditions can develop
in deeper layers due to excess dead cells

37. Continious upwelling zone (light algal bloom)

38. Non-seasonal algal bloom
Bloom that do not fall under the categories of traditional bloom are called non-
seasonal bloom.
These blooms are influenced by unexpected events in the waterbody.
For instance, the passage of storms over stratified, nutrient-poor waters of
summer months causes deep mixing and upward transport of nutrients, often
resulting in a bloom.
Generally the standing stock of these blooms is lower than in seasonal ones. Red
tide is a example of non-seasonal bloom clearly visible spatially ranges from
meters to quite a few km. Harmful algal bloom are often result of non-seasonal
bloom

40. Harmful Algal Bloom
➢A harmful algal bloom is a boom of certain type of algal species
that produce toxic chemical.
➢According to International council for the exploration of seas
(1984) ,exceptional bloom have been defined as those which are
noticeable, particularly to the general public, directly or
indirectly through their effects such as visible discoloration of
the water, foam production ,fish or invertebrate mortality or
toxicity to humans

41. Allelopathy
➢the ability of certain harmful algal species or micro-
organisms to produce and release chemicals
(allelochemicals) or compounds that inhibit their
potential co-occurring competitors for similar
resources.
➢Toxic substances produced by allelopathic
organism gives it a competitive advantages ,
moreover these toxic substances act like secondary
metabolites with harmful capacity and their
production has been enhanced by enhanced factor
N and Ph . It is shown by bacteria, cyanobacteria
and dinoflagellates
➢Some species can even produce toxic substance
during eutrophication where nutrient ratios is
altered and nutrient are limited

42. Favorable conditions for HAB
• Sunlight
• Increase in nutrients
• Low flow conditions
• Still water
• Release of nutrients from sediments
• Reduced grazing by predators
• High temperature
• Low salinity

43. Toxin
• Only a few HAB species actually produce toxins
• Poisonous to people and marine animals
• The most well known toxins are generically referred to as
1. Ciguatera fish poisoning
2. Neurotoxic shellfish poisoning
3. Paralytic shellfish poisoning
4. Diarrhic shellfish poisoning
5. Amnesic shellfish poisoning

44. Effect on people and wildlife
HAB can cause illness and death towards human , pet and
wildlife . Symptoms include:
• Skin rash
• Muscle cramp
• Paralysis
• Twitching

45. • Nausea
• Vomiting
• Respiratory failure
• Acute liver failure

46. • Human , wild-life and domestic animals can be exposed to algal toxins
through contaminated food , water and aerosol depending on the toxins
• Other degrade eco-system by forming such large blooms that they alter
habitat quality through overgrowth , shading and oxygen depletion (
hypoxia )
• Adversely affecting coral, seagrass and bottom dwelling creatures
• High biomass of certain non-toxic harmful algae can also harm fish and
other invertebrate by :
❑Damaging gills
❑Causing starvation
❑Low reproduction due to poor food quality

47. REFERENCE :
• Marine Algal Bloom: Characteristics, Causes and Climate Change Impacts by Santosh Kumar Sarkar
• P Assmy. Algal Blooms. Encyclopedia of Microbiology.(MoseliSchaechter, Editor), pp. 27-41 Oxford:
Elsevier.
• Anderson GM, Gilbert PM , Burkholder JM (2002) Harmful algal bloom and eutrophication : nutrient
sources , composition and consequences
• Satopathy KK, Nair KVK (1996) Occurrence of phytoplankton bloom and its effect on coastal water
quality . Indian J Mar
• Global ecology and oceanography of Harmful algal bloom by Patriciea M. Gilbert , Elisa Berdalet ,
Michele A Burford, Grant C. Pitcher , Mingjiang Zhou
• https://www.noaa.gov/what-is-harmful-algal-bloom
• http://www.fao.org/fishery/topic/14759/en

48. Thank You