Healthy Waterways: Information Sheet
6
Many of the scientific expressions in this document are defined in the glossary on page 4.
Algae and cyanobacteria – what are they?
Impacts of algal/cyanobacterial blooms
Algae and cyanobacteria are a large
and varied group of photosynthetic
organisms that are found in most
aquatic environments including rivers,
lakes, oceans, estuaries, hot springs
and glaciers. Algal and cyanobacterial
cells contain chlorophyll and other
photosynthetic pigments. They exist
in a wide variety of forms; from single
cells and strings of cells, through to
complex multicellular seaweeds. The
most familiar algae are red, brown
and green seaweeds, which are part
of a group of large multicellular algae
known as macroalgae. However, the
majority of algae and cyanobacteria
Various species of algae
are single-celled species that float
freely in the water column; they are invisible to the naked eye and
collectively form a group known as phytoplankton.
Environmental:
MARINE BOTANY, UQ
C. ROELFSEMA
What was originally known as blue-green algae is now more correctly
called ‘cyanobacteria’. Cyanobacteria are bacteria, but unlike other
bacteria they contain the same photosynthetic pigments as algae and
release oxygen from photosynthesis. Algae and cyanobacteria are
vital components of aquatic ecosystems as they are producers of
oxygen and carbohydrates. Algae and cyanobacteria undertake
photosynthesis, using the energy in sunlight to produce chemical
energy for growth and releasing oxygen as a by-product.
Phytoplankton are the primary producers in the aquatic ecosystem
and form the base of the aquatic food chain. Macroalgae play an
essential role in estuarine and marine ecosystems by providing food,
important habitat and shelter for a variety of aquatic organisms; and
creating valuable nursery areas for fish, crabs and prawns.
Printed on 100% recycled paper using a waterless printing technique
to reduce toxicants entering our waterways and minimise water use.
What are algal/cyanobacterial blooms?
The physical, chemical, and biological properties of water are altered
by algal blooms, often with negative impacts on water quality and
ecosystem health. Malformation and mortality of mangrove
seedlings can result on mudflats smothered by blooms of Lyngbya
majuscula, a toxic cyanobacterium. Seagrass death can occur when
an algal bloom prevents the penetration of sunlight to the seagrass
bed, thus depriving the seagrass of an essential source of energy –
the sun. Cyanobacteria can release toxins that cause illness or even
mortality of marine fauna. As an algal bloom decomposes it
consumes available oxygen and can cause the water to become low
in oxygen, resulting in the death of the local fish and invertebrate
communities. The input of nutrients after the ‘collapse’ and decay of
an algal bloom may also have detrimental impacts.
Economic:
Algal blooms can have a significant economic impact on the fishing
and tourism industries. Local fisheries can be adversely affected by
algal blooms as fish may actively avoid affected areas in response to
either toxins released by the algae and/or lowered oxygen levels.
Local stocks can also be affected when toxins and/or low oxygen
levels lead to the death of fish and other aquatic organisms. The
closure of oyster farms can be a response to the presence of algal
toxins in the local environment. During a bloom, masses of algae can
accumulate and decompose along the shore, emitting offensive
odours which can deter tourists from returning to holiday destinations,
having a dramatic impact on local and regional economies. Shore
clean-ups required can come at huge expense to local governments.
Human health risk:
Toxins released by some species of algae and cyanobacteria may
have adverse affects on human health. Physical contact with the
cyanobacterium Lyngbya majuscula or breathing of volatilised
Lyngbya majuscula toxins can cause skin irritations and respiratory
disorders. The consumption of fish and shellfish that have been
exposed to algal toxins may lead to diarrhoea or vomiting.
Individual algal/cyanobacterial species have specific nutrient, light,
salinity and pH requirements for growth. Algal growth can be limited
by the low availability of one of these specific factors. However, under
favourable conditions, some algal/cyanobacterial species have the
potential to ‘bloom’ as they can grow rapidly to dominate the aquatic
environment. The duration of a bloom depends on flow conditions,
weather, and the availability of nutrients and can persist for several
weeks or even months. The bloom ‘collapses’ once the algae have
consumed all available nutrients or conditions are no longer
conducive to rapid growth. As the algae decay, nutrients are recycled
back into the water or the sediments. The release of nutrients back
into the environment after the collapse and decay of an algal bloom
can in some cases stimulate the next and successive blooms.
Blooms can provide a valuable food resource for aquatic organisms,
leading to a general pulse in growth. Fisheries may benefit, as
blooms can feed a boom in local fish stocks. Algal blooms can,
however, have adverse affects on the local environment and
economy as well as human health.
CABOOLTURE SHIRE COUNCIL
Science
UISANCE ALGAL BLOOMS
NInmarine
and estuarine environments
Lyngbya majuscula accumulated on a beach at Caboolture
ALGAL BLOOMS IN THE COASTAL WATE
Hincksia sordida
Phaephyta (brown algae)
Duration:
Varies from a few days up to six weeks
T. SCHLACHER
Appearance:
Clumps of narrow branched hair-like filaments
Potential impacts:
䊏 Water scum
䊏 Offensive odour on shore
䊏 Deters swimmers
䊏 Large costs associated with shore clean-up
Increasing reports of algal blooms in
estuarine, coastal and marine waters
suggest implications not only for human
health, but also economic loss and
environmental degradation.
Caulerpa
Caulerpa taxifolia
NOOSA
CATCHMENT
Chlorophyta (green algae)
Duration:
Continuous; it was first reported in 1946
C. ROELFSEMA
Appearance:
Frond-like seaweed growing in the sediment
with root-like structures for attachment
Potential impacts:
䊏 Occupies the same niche as seagrass;
competes with seagrass for substrate
and light availability
䊏 Reduces seagrass density
䊏 Reduces seagrass availability for dugong
and turtle consumption
䊏 Does not provide the sediment stability
that seagrass does (little to no root system)
Caloundra
Various red and brown macroalgae (summer)
䊏 Beaches
䊏 Estuaries
Trichodesmium (August to January)
䊏 Coastal waters
Lyngbya majuscula (summer)
䊏 Northern tip of Bribie Island
䊏 Bells Creek
‘Red Tide’ dinoflagellate –
Karenia (winter)
䊏 Currimundi lakes
䊏 Canal areas
MAROOCHY
CATCHMENT
MOOLOOL
CATCHME
PUMICESTO
REGION
CATCHMEN
PUMI
PA
Sea sawdust/whale food/
whale sperm/sea scum
Trichodesmium
Cyanophyta (cyanobacteria)
Duration:
Four to ten days
MARINE BOTANY, UQ
Appearance:
Similar to sawdust floating on the water
surface; filaments in the water column
Potential impacts:
䊏 Water scum
䊏 Offensive odour
䊏 Releases low concentrations of toxins
䊏 Potential respiratory irritation
Caboolture
Lyngbya majuscula (summer)
䊏 Deception Bay
䊏 Bribie Island and
Deception Bay beaches
C A B O O LT U R E R I V E R
C A T C H M E N T DE
PINE
CATCHMENTS
Redcliffe
Trichodesmium
䊏 Redcliffe foreshores
LOWER
BRISBANE
CATCHMENT
Brisbane
Ulva lactuca (winter)
䊏 Bramble Bay
LOGAN –
CATCH
Redlands
QPWS
Caulerpa taxifolia (year round)
䊏 Waterloo Bay seagrass meadows
䊏 Amity Banks seagrass meadows
The removal of Lyngbya majuscula from mangroves using a vacuum pump
ERWAYS OF SOUTH EAST QUEENSLAND
Mermaids hair/blanket weed
Lyngbya majuscula
This map identifies the occurrences
Cyanophyta (cyanobacteria)
of various types of algal blooms that
Duration:
Varies from one week up to a few months
have been reported by the relevant
Appearance:
Dark black-brown colour; resembles
clusters of fine matted hair; attached to
seagrass or floating as rafts on the surface
South East Queensland local
C. ROELFSEMA
government authorities.
Potential impacts:
䊏 Releases toxins
䊏 Causes skin irritation and respiratory
problems in humans
䊏 Reduces fish catches
䊏 Smothers seagrass beds
䊏 Large costs associated with shore clean-up
Sea Lettuce
Ulva lactuca
Noosa
Chlorophyta (green algae)
Hincksia sordida (spring/summer)
䊏 Noosa beaches
䊏 Lower estuary of the Noosa River
Lyngbya majuscula (small amounts
associated with Hincksia blooms)
䊏 Noosa coastal waters
Duration:
Varies from weeks to months
Appearance:
Bright green, small to large flat sheets; blooms
form large mats covering the intertidal zone
Potential impacts:
AH
NT
Various brown, green
and red macroalgae
(spring, summer, autumn)
䊏 Beaches (most often
Alexandra Headland Beach)
䊏 Lower estuary of the
Maroochy River
ONE
NTS
ICESTONE
ASSAGE
CPTION
BAY
C. ROELFSEMA
Maroochy
Anaulus australis
Duration:
One week
CENTRAL
BAY
Appearance:
Dark patches in the surf zone;
oily appearance and texture
REDLANDS
CATCHMENTS
SOUTHERN
BAY
P I M PA M A
CAT C H M E N T
BROADWATER
NERANG –
MUDGEERABA
CAT C H M E N T
TA L L E BU D G E R A
CAT C H M E N T
CURRUMBIN
CAT C H M E N T
Trichodesmium (summer)
䊏 Broadwater
䊏 Estuaries
䊏 Gold Coast beaches
Anaulus australis
(single occurrence in May 2000)
䊏 From Byron Bay to
Point Lookout
䊏 Surf zone
Cornflake weed –
Colpomenia sinuosa
䊏 Broadwater
䊏 Mouth of the estuary
䊏 Beaches
Various brown macroalgae
(associated with northerly winds)
䊏 Surf beaches
Lyngbya majuscula (summer)
䊏 Jumpinpin area
Potential impacts:
䊏 Brown colour deters swimmers
䊏 Generally harmless
G. PARK, COURIER MAIL
EASTERN
BANKS
N. WALTHAM
Gold Coast
COOMERA –
COOMBABAH
CAT C H M E N T
concentration
Chrysophyta (diatom)
BRAMBLE
BAY
– ALBERT
MENTS
䊏 Localised reduction in oxygen
Surf zone diatom
EASTERN
BAY
WATERLOO
BAY
䊏 Offensive odour on shore
Earth moving machines remove brown algae accumulated on a Queensland beach
WHAT CAUSES ALGAL BLOOMS ?
Nutrients:
Elevated nutrient concentrations (particularly nitrogen and
phosphorus) in an aquatic environment can lead to algal blooms. Eutrophication
is the accumulation of organic matter in an ecosystem leading to increased
growth of aquatic plants (some growing much faster than others). Nutrients
enter our waterways through natural processes but also as a result of human
activity. Major sources of nutrients include sewage effluent, urban runoff, and
erosion and runoff from fertilised agricultural areas.
Light: Exposure to increased light can lead to algal blooms. However, under
low light conditions, blooms can still occur in response to inputs of high nutrient
concentrations. In highly turbid waters, large amounts of suspended sediment
and organic matter limit light availability; however, the concurrent input of nutrients
can, in some cases, enhance algal growth. As such, in our coastal waters, algal
growth is often restricted by a combination of limited light and nutrient availability.
Water flow and circulation: Blooms are less likely
to occur in well-flushed waterways or in coastal systems with a high
tidal range. In well flushed areas there is a shorter residence time
of algae and nutrients within the system. Flushing can also affect the
amount of light available to the algae by increasing turbidity (as tidal
mixing can cause the resuspension of fine sediments).
Trace elements (e.g. iron):
The growth of some algal
species can depend on the availability of essential trace elements
such as iron, molybdenum and zinc. Iron has been shown to influence
the growth of Lyngyba majuscula in Moreton Bay. In other places iron
has also been found to influence Trichodesmium blooms. Typically the
level of ‘bioavailable’ iron in seawater is very low and not enough
to support a bloom, however, additional iron entering the waterway
via groundwater or surface run-off may lead to an algal bloom.
Temperature:
Algae respond to increasing
water temperatures, with warmer waters often causing
accelerated growth leading to algal blooms. The temperature
of coastal waters varies with daily and seasonal cycles
caused by variations in solar radiation, air temperature and
local hydrodynamic processes (e.g. currents).
Season: Algae tend to bloom in the warmer
months, when water temperatures are higher and when
there is increased light. Under stable weather conditions,
there are low levels of mixing in coastal waters, creating
prime environmental conditions for algal growth.
Higher frequency of algal blooms
Lower frequency of algal blooms
Bank erosion
Phytoplankton bloom/crash
Caulerpa taxifolia
Nutrient inputs
Seagrass loss
Flushing
Light limitation
Macroalgae bloom
Upgraded sewage treatment plant and industrial discharges
Mixing
Increased iron concentration
Trichodesmium bloom
Stormwater quality improvement device (SQID)
Temperature
Iron limited
Lyngbya majuscula
Sediment resuspension and deposition
Glossary
Bioavailable – A particular chemical form necessary for an
element to be taken up by an organism
Organic matter – Any material originating from a living
organism
Cyanobacteria – Primitive, photosynthetic bacteria occurring as
a single cell or in filaments, some of which are often capable
of nitrogen fixing; often referred to as blue-green algae
Photosynthesis – Process carried out by plants and some
bacteria, in which light energy is harvested by pigments
(mostly chlorophyll) and utilised to convert carbon dioxide
and water into organic molecules and oxygen
Eutrophication – Over-enrichment of a waterway with nutrients
Hydrodynamics – The movement of water and the
interactions of the body of water with its boundaries
Intertidal – Area along the coast below the high tide and
above the low tide
Macroalgae – Large multicellular plants that include green
algae, red algae, and brown algae
Phytoplankton – Microscopic algae and cyanobacteria (may
be either single-celled or strings of cells) that live floating in
the water column
Residence time – Average length of time that water, or
compounds dissolved or suspended in the water, remains
in a certain location
This factsheet is produced by
the Moreton Bay Waterways
and Catchments Partnership.
July 2005
Resuspension – Process in which sediment particles are
brought back into suspension in the water column by
waves, tide or wind
Tidal mixing – When strong tidal currents mix the water column
Tidal range – The difference in height between low tide and
high tide
Trace elements – Minerals that generally occur at very low
levels in the natural environment
Turbidity – Reduced water clarity resulting from the presence
of suspended matter
Water column – The area between the surface and the
bottom of a body of water
For further information contact Dr Eva Abal
Tel: (07) 3403 4206 Fax: (07) 3403 6879
Email: [email protected]
This factsheet is available via: www.healthywaterways.org
Newsletter compiled by: Emily Saeck and
Dr Eva Abal. Conceptual diagram by: Emily
Saeck. Thanks to: contributions by Dr Thorsten
Mosisch, Dr Judy O’Neil and Dr Julie Phillips.
Healthy Waterways offers a service for the identification of algal bloom samples. Please contact our office for further information.