Home   :    Contact   :    Donations
The Shark and Coral Conservation Trust
About SCCT   :       Donations   :       The Facts   :       D.E.E.P   :       News   :       Articles   :       Videos   :       What You Can Do

articles


Algal Blooms in the Ocean
08/09/07
source : Doretha B. Foushee  Water Encyclopaedia


The ocean, that vast body of water covering 71 percent of the Earth's surface, is divided into four major basins: the Pacific, Atlantic, Indian, and Arctic Oceans. These large basins are interconnected with various shallow seas, such as the Mediterranean Sea, the Gulf of Mexico, and the South China Sea. Oceans and seas abound with life, ranging from microscopic unicellular (one-celled) organisms to multicellular (many-celled) animals.

Algae is an important life form in the ocean. Life in the ocean is maintained in balance by forces of nature and by predator–prey relationships, unless some external pressures upset the balance. When a balance upset leads to conditions more favorable for the reproduction and growth of algae, an explosive increase in the number of algal cell density occurs. Such rapid increases in the algae population are called algal blooms.

During a bloom, a liter of water may contain millions of algae. The most widely publicized type of algal bloom is associated with species that produce a toxin (chemical substance) harmful to animals that feed on the algae (and hence is known as a harmful algal bloom), and/or algae that cause a tint in the water because of the photosynthetic pigments they contain. The latter commonly is known as a "red tide," but different pigments can turn the water red, brown, purple, orange, or yellow. Depending on the circumstances and the species present, a red tide may or may not be harmful. Although not all algal blooms in the ocean produce highly visible effects nor are all blooms harmful, they nonetheless affect life in the ocean and on land in both beneficial and harmful ways.

In February 2002, the massive die-off and decay of algae from a nearshore harmful algal bloom (a "red tide") caused a rapid reduction in the water's dissolved oxygen concentration, driving tens of thousands of rock lobsters to "walk out of the sea" near the coastal town of Elands Bay in South Africa's Western Cape province. The lobsters in search of oxygen moved toward the breaking surf, but were stranded when the tide went out. Government and military staff attempted to save some of the lobsters, but others were collected for food. A similar stranding from a massive red-tide event occurred at Elands Bay in 1997

Requirements for a Bloom
Algae require warmth, sunlight, and nutrients to grow and reproduce, so they live in the upper 60 to 90 meters (200 to 300 feet) of ocean water. The upper layer of water, the epipelagic zone, is rich in oxygen, penetrated by sunlight, and warmer than water at lower levels. As algae and other organisms that live in the ocean die, they fall to the bottom of the ocean, where they decay and release the compounds from which they were made. Under certain conditions, these nutrients can deplete the oxygen in the water.

Temperature and salt concentration determine the density of water and how water moves (currents). Cold water is denser (heavier) and sinks from the surface (downwelling). Other water moves across to replace it. Eventually, water at the surface is replaced by water that has risen, or upwelled, from the bottom to the surface somewhere else in the ocean. These upwellings bring nutrient-rich waters to the top. This increase in nutrients can trigger algae blooms.

An increase in nutrients also may be caused by activities of humans, such as runoff from animal farms or fertilized croplands and lawns, or atmospheric deposition of sulfur and nitrogen compounds or oxides derived from the burning of fossil fuel. These nutrients lead to blooms in coastal waters to a greater extent than in the open ocean.

However, some of these nutrients do find their way to the open ocean far from shore, and contribute to the formation of blooms in the open ocean. Their movement is aided by the wind and by ocean currents. Algae blooms in the open ocean are not usually harmful; instead, they provide many benefits, largely deriving from the fact that the open ocean is relatively unproductive (low in nutrients).

Algae and Photosynthesis
Algae are referred to as plants because, like plants, they produce organic compounds from inorganic compounds (carbon dioxide and water) by capturing and using the energy from sunlight. Most algae are eukaryotic, an exception being the blue-green algae (cyanobacteria).

Photosynthesis takes place in organelles called chloroplasts in eukaryotic cells. Chloroplasts contain an outer and an inner membrane and pancakeshaped structures called thylakoids. Energy is captured from sunlight by pigments (chlorophylls a and b and carotenoids) stored in the thylakoids.

Photosynthesis occurs in two stages commonly referred to as the light reactions (light is required) and the dark reactions (no light is directly required). During the light reactions, energy captured from sunlight is used to split (dissociate) water molecules. Electrons released from this reaction are passed down a series of electron carrier molecules, leading to the storage of the energy in the form of ATP (adenosine triphosphate). This is the form in which living organisms store energy to be used immediately for carrying out chemical reactions and other activities.

Oxygen is produced as a byproduct of the light reactions. During the dark reactions (Calvin cycle), six molecules of carbon dioxide are used to make sugar (glucose). Because algae use carbon dioxide and release oxygen as a product of the light reactions, these plants play an important role in maintaining the proper concentrations of carbon dioxide and oxygen in the environment, via the carbon cycle and oxygen cycle.

Algae, like green plants, produce the first organic compounds in the food chain and thus are referred to as primary producers. Other organisms cannot use inorganic molecules to make the organic compounds that they need for life, and therefore depend on algae and other plants as the initial source of organic compounds. These organisms either eat algae to obtain organic compounds, or obtain them from the water when they are released after the algae die.

Coccolithophore blooms are identifiable via space-based remote sensing because their external plates of calcium carbonate, called coccoliths, backscatter light from the water column to create a bright optical effect. This bloom (the cloudy swirl in lower lefthand corner) occurred in summer 2001 in the Celtic Sea off England's southwestern coast. When diatoms die, the frustules settle to the bottom of the ocean floor and combine with the soil to form diatomaceous earth. Diatomaceous earth is used in products such as filters for swimming pools, as temperature and sound insulators, and as an abrasive in toothpaste.

Dinoflagellates have two unequal flagella that help them direct their movement. Many of these organisms contain colored pigments that cause the water to appear colored when these organisms bloom, leading to the terms "red tide" or "brown tide," for example. Some dinoflagellates live in close association with marine animals, such as sponges, sea anemones, giant clams, and corals. The golden-brown photosynthetic cells found in these animals, called zooxanthellae, actually are dinoflagellates.

Coccolithophores.

Coccolithophores are cells covered with button-like structures called coccoliths made of calcium carbonate. The coccoliths give the ocean a milky white or turquoise appearance during intense blooms. The long-term flux of coccoliths to the ocean floor is the main process responsible for the formation of chalk and limestone.

Coccolithophores and some other algae participate in the sulfur cycle and produce the gas dimethyl sulfide. This is the primary way that sulfur is carried between ocean and land.

Dimethyl sulfide leaves the surface of the water and reacts with oxygen in the atmosphere to form tiny sulfuric acid droplets. These droplets are carried over land and fall back to land in the form of precipitation. They also aid in the formation of clouds, which partially block the transmission of harmful ultraviolet light that penetrates the surface water. Cloud formation also is thought to encourage surface winds that promote the movement of surface water, leading to upwellings that bring nutrients to the surface.

Benefits of Algal Blooms
Algal blooms provide large concentrations of algae that produce organic compounds needed by higher organisms, ranging from oysters, clams, and mussels to human beings. For this reason, productivity increases in areas where algal blooms occur. More algae in the water means that more carbon dioxide is used from the atmosphere and that more oxygen is released into the atmosphere. Oxygen is necessary for many living things, including humans. As noted previously, the production of dimethyl sulfide gas helps protect algae from harmful ultraviolet rays so they remain healthy and thus are able to continue the cycle of sustaining life on Earth.

Even in the coldest parts of the ocean, algae provide the primary source of organic material to animals at the bottom of the food chain. Organic materials are moved up the food chain as higher organisms feed on those lower down the chain. For example, algae have been found in Antarctic sea ice. As sea water freezes, algae living in the water are frozen in the ice, where they later can be released during a thaw. These algae are a vital source of food for krill, the shrimp-like organisms eaten by penguins, seals, seabirds, and whales.


SCCT Editorial Comment:

This article reflects the importance of maintaining a 'marine balance'. In the context of carbon recycling, algal blooms are probably as important as the Amazon Forest in the quantity of carbon dioxide taken up and oxygen release into the atmosphere. Algal blooms are at the 'other end' of the balance spectrum with the shark at the top of the 'predator/prey' balance. The hope is that the UK government will introduce the Marine Bill into the Queen's Speech in November 2007 so that marine reserves can be introduced into UK waters as a contribution to these essential balances
.
PREVIOUS ARTICLES

2013
Sea Urchins Tolerate Acid Water
06/04/13

SHARK KILLS NUMBER 100 MILLION ANNUALLY
02/03/13

2012
A Climate Change Agreement for Children
06/12/12

Cate Change takes Centre Stage
06/12/12

Ocean acidification and warming decrease calcification in the crustose coralline alga Hydrolithon on
13/10/12

Solar Panels - Are they really clean emergy technology
07/09/12

Ocean Acidification may limit Phytoplankton
27/08/12

Acidic POceans - why should we Care?
24/08/12

Carbon Dioxide in the Earth's atmosphere
24/08/12

Jellyfish and Chips
17/05/12

The Effects of El Nino on Marine Life (2)
19/02/12

The Effects of El Nino on Marine Life
19/02/12

Protect Our Oceans
14/01/12

Decrease in shark numbers poses risk to Great Barrier Reef
11/01/12

2011
IAP STATEMENT ON OCEAN ACIDIFICATION
28/10/11

Vast Shark Sanctuary created in the Pacific
03/10/11

Cora Reef Builders Vulnerableto Ocean Acidification
02/10/11

Is Hydrogen the Future of Motoring ??
20/09/11

Marine Protection Bids Unveiled
08/09/11

Stan Ovshinsky and the Hydrogen Economy
07/07/11

Shark Fishing Banned in the Bahamas
06/07/11

Relationships between coral and fishes on the Great Barrier Reef
10/06/11

Emissions and Growth Continue their Dance
08/06/11

Acid Test for Local Action
08/06/11

2010
'Alarming' plight of coral reefs
12/10/10

Nature's Sting - The real cost of damaging Planet Earth
12/10/10

Hoga Summary
27/09/10

Great White Sharks 'Shrinking'
14/09/10

Swiss Tycoon sends patrol boat to save Serengeti of sea
14/09/10

Asia Demand spurs Brazilian shark kills
04/08/10

Plankton decline across oceans as water warms
30/07/10

Met Office Views on Climate Change (CC)
26/07/10

Ocean Acidification in 2010
23/07/10

The Great Barrier Reef is threatened by Ships and their Cargo
22/05/10

OCEAN ACIDIFICATION ACCELERATES
30/04/10

Talking Points:Japan: eating tuna to extinction
29/03/10

UK TSB INVESTS £7M IN FUEL CELLS AND HYDROGEN
07/03/10

M4 in Wales to be 'Hydrogen Highway'
12/02/10

A Boost for Clean Energy
28/01/10

Declining Coral Calcification on the Great Barrier Reef
20/01/10

Coral Can Recover From Climate Change Damage
20/01/10

Ocean Acidification
12/01/10

Impacts of Ocean Acidification
12/01/10

Chalk one up for coccolithophores
12/01/10

Coral Reefs are evolution hotspot
09/01/10

2009
Beware the "evil twin" of climate change
30/12/09

Hydrogen Power for Vehicles - COP15
20/12/09

Natural Lab shows Sea's Acid Path
22/11/09

'Coral Lab offers Acidity Insight
22/11/09

UK Funds Sea Acidification Study
22/11/09

UK Climate Targets 'Unachievable'
13/11/09

Marine Bill Enters Final Stages
12/11/09

Recovering Scotland's Marine Environment
06/11/09

An Iron-clad Partnership
06/11/09

'Freezer Plan' bid to save coral
26/10/09

Action on Shark Finning
14/10/09

Arctic Seas turn to Acid
08/10/09

Sharks pay high price as demand for fins soar
08/10/09

Diverse Fish Reduce Coral Disease
05/10/09

Pacific Nation Declares Itself Shark Haven
03/10/09

Shark Trade Limits endorsed by EU
27/09/09

Palau Pioneers Shark Sanctuary
25/09/09

China Vows Climate Change Action
22/09/09

Shark Rescue is here
21/09/09

Doctors warn on Climate Failure
16/09/09

How Global Warming sealed the fate of the World's Coral Reefs
04/09/09

A SECOND NORTH SEA BONANZA ?
04/09/09

Paradise Lost
04/09/09

Shark Tagging Mission is under way
31/08/09

The Hydrogen Cycle
19/07/09

Climate Scenarios 'being realised'.
15/07/09

Ocean Acidification - Calcifying Phytoplankton
01/07/09

Ocean Acidification on benthic biodiversity
01/07/09

In the Soup - Shark species facing extinction
25/06/09

Over fishing Threatens Shark Extinction
25/06/09

Student film highlights plight of the oceans
04/05/09

Ocean Acidification threatens underwater ecosystems
04/05/09

Drowning in Plastic
30/04/09

'Clean' Coal Plants Get Go-Ahead
23/04/09

Paving the Road to COP15: Adaptation and Outreach
21/03/09

The Road to Catastrophe
20/03/09

World's leading scientists i n desperate plea to politicians to act on climate change
14/03/09

Pollution to devastate shellfish by turning seas acidic
14/03/09

THREATS FROM OCEAN ACIDIFICATION
11/03/09

CO2 HIGHEST FOR 650,000 YEARS
01/03/09

SLOW PROGRESS ON OCEAN PROTECTION
28/02/09

Jellyfish and Chips
18/02/09

London Marathon Motivation
07/02/09

EU Gives Shark Protection Teeth
06/02/09

ACID OCEANS 'NEED URGENT ATTENTION'
31/01/09

OCEAN ACIDIFICATION - The other CO2 problem
28/01/09

Panel Warns on Great Barrier Reef
03/01/09

Coral Reef Growth is Slowest Ever
03/01/09

2008
Changes amplify Arctic Warming
17/12/08

Rise in CO2 affrects Jumbo Squid
16/12/08

Jellyfish Invasion
21/11/08

The Rate of Ocean Acidification
18/11/08

Ocean Acidification Impacts
18/11/08

Impact of Ocean Acidification on Coral Reefs and Other Calcifiers
20/10/08

Nature Loss Dwarfs Bank Crisis
10/10/08

The Creation of Artificial Reefs
23/09/08

Iceland - Fossil fuels to Hydrogen-based Economy
17/09/08

The world's oceans at risk from rising acidity
25/07/08

Coral reefs under threat from humans
11/07/08

Ocean Acidification - Plankton hold surprise for Climate Research
28/06/08

Anthropogenic Ocean Acidification over the 21st Century and its Impact on Calcifying Organisms
13/06/08

Mileage from Megawatts
12/06/08

Could US scientists 'CO2 Catcher' help slow warming ?
09/06/08

Sharks Swim Closer to Extinction
22/05/08

Wildlife Populations Plummeting
16/05/08

Introducing Hydrogen Power
30/04/08

Ocean Acidification - Technical Information
28/04/08

Carbon Capture and Storage - UKCCSC Project
28/04/08

Lemon Sharks and Dogfish - Hyperbaric Sensitivity ??
29/03/08

The GAIA Theory
26/03/08

Status of the World's Coral Reefs
24/03/08

Krill, Fishing Threatens the Antarctic
23/03/08

Marine Altruistic Behaviour - - 4 stories
22/03/08

Global Sea Level Changes
22/03/08

Climate Change Controversies - A Simple Guide
21/03/08

Sharks and Coral Reefs (One year on)
10/03/08

Shark Species face extinction amid overfishing and appetite for fins
28/02/08

SCCT Presentation Uptake
11/02/08

Coral Reefs Under Rapid Climate Change and Ocean Acidification
27/01/08

An exchange of views on Marine Reserves and Trophic Cascades
25/01/08

2007
The Effects of Global Warming on the Great Barrier Reef
21/12/07

Microbial Ecology and Evolution:A Discussion at Metagenomics 2006
15/12/07

Habitat Conservation
28/11/07

Marine Balances and Climate Engineering
27/11/07

Oceans are 'soaking up' less CO2
20/10/07

Algal Blooms in the Ocean
08/09/07

UK Marine Bill
15/08/07

Tourism Vs Traditional Fishing
10/08/07

US National Plan of Action for the Conservation and Management of Sharks
29/07/07

Shark Depredation and unwanted Bycatch in Pelagic Longline Fisheries
17/07/07

Ecosystems: Coral Reefs
28/06/07

Shell-shocked
20/06/07

Ongoing Collapse of Coral Reef Shark Population
12/06/07

Shark trade restriction bid fails
12/06/07

Be nicer to sharks
26/05/07

Cascading Effects of the loss of Apex Predatory Sharks from a Coastal Ocean
25/05/07

Sharks are vital for Coral Reef Health
25/05/07

Sharkless Seas
21/05/07