Some algae blooms kill by producing toxins. Marine life such as clams may accumulate these toxins without being killed. But the toxins do poison animals that eat the clams, including humans. The bloom can also deplete oxygen in the water and kill marine life, especially caged aquaculture fish. Sabah was affected by 'red tide' last week.
A recent study found that even non-toxic marine algae can kill. In late 2007, hundreds of dead and stranded seabirds washed up on the shores of Monterey Bay, their feathers saturated with water and coated with an unknown substance. After an intensive investigation, scientists determined that a massive 'red tide' bloom of marine algae had produced a foamy soap-like substance that stripped the natural waterproofing from the birds' feathers.
Another recent study discovered more about how films of different species of microscopic algae form in the sea, forming dense layers. Besides resulting in 'red tide' this phenomenon also results in concentrations of harmless and nutritious microscopic algae that other marine life feed on.
Climate change may increase the occurrence and impact of 'red tide' events.
'Red tide' is more properly called an algal bloom as it is not related to the tides. The common name arose because the large number of tiny organisms colour the water. These colours range from green, brown and reddish orange to purple. Algal blooms can also occur in freshwater rivers, lakes and other water bodies. Red tide is a term applied to algal blooms in the sea. More on the wild facts sheets on wildsingapore.
Seabird Deaths Linked To Soap-like Foam Produced By Red-tide Algae
ScienceDaily 20 Feb 09
In late 2007, hundreds of dead and stranded seabirds washed up on the shores of Monterey Bay, their feathers saturated with water and coated with an unknown substance. After an intensive investigation, scientists determined that a massive "red tide" bloom of marine algae had produced a foamy soap-like substance that stripped the natural waterproofing from the birds' feathers.
This is the first documented case of its kind, but similar events may have gone undetected in the past, the researchers reported in a paper to be published in the online journal PLoS One on Monday, February 23.
"The problems we traditionally associate with harmful algal blooms are caused by toxins produced by the algae. In this case, it was a surfactant that removed the water-repellent properties of the feathers," said Raphael Kudela, professor of ocean sciences at the University of California, Santa Cruz, and corresponding author of the paper.
Although this red tide bloom was nontoxic, it was very harmful to the affected birds, which included grebes, loons, northern fulmars, and surf scoters. Live birds found stranded on beaches around Monterey Bay were starving and severely hypothermic, having lost the insulation normally provided by their waterproof plumage. A total of 550 birds were stranded alive and 207 were found dead during this event.
Kudela teamed up with researchers from the California Department of Fish and Game (CDFG), Monterey Bay Aquarium Research Institute (MBARI), and Moss Landing Marine Laboratories (MLML)--all members of the Central and Northern California Ocean Observing System (CeNCOOS)--to investigate the mass stranding, which occurred at the same time as the Cosco Busan oil spill in San Francisco Bay and an ongoing controversy over aerial spraying on the Central Coast to control the light brown apple moth.
"There were a lot of questions at the time about whether the stranding was related to those events, and we were able to eliminate those possibilities," Kudela said.
The dominant species in the red tide was a type of dinoflagellate known by the scientific name Akashiwo sanguinea, which has caused red tides in the past without harmful effects on wildlife. Kudela said the problems in 2007 resulted from the unusual combination of a large red tide late in the year, when large numbers of migrating birds had arrived in the area, plus big waves that churned up the water.
An algal protein produced the slimy foam that fouled the birds' feathers. Its effects were similar to those of soap and other surfactants that are used in detergents to dissolve grease. Wave action contributed to the problem by breaking up the cells of dying algae and churning the dissolved protein into the thick foam that was seen along the shoreline and floating on the surface of the water.
"We grew the algae in the lab, and when we shook it up it produced the same foam," Kudela said. "The waves act like a blender, churning up the cells and the protein."
These kinds of events may occur more often in the future, he said. The researchers noted that the frequency, size, and duration of red tides have increased substantially within Monterey Bay since 2004, and similar increases are occurring elsewhere in the world. These changes are probably due in part to the effects of climate change on surface water temperatures, Kudela said.
"Starting in 2004, we have had big red tides with greater frequency than in the past," he said. "Although 2007 was the first time we saw an impact on birds, the conditions are there for the same thing to happen the next time we have that combination of red tide, birds, and big storm waves."
The authors of the PLoS One paper include David Jessup and Melissa Miller at the CDFG Marine Wildlife Veterinary Care and Research Center in Santa Cruz; John Ryan and Heather Kerkering at MBARI; Hannah Nevins at CDFG and MLML; Abdou Mekebri and David Crane at the CDFG Water Pollution Control Laboratory; and Kudela and Tyler Johnson at UCSC.
This research was partially funded by the National Oceanic and Atmospheric Administration (NOAA) through the Monitoring and Event Response for Harmful Algal Blooms (MERHAB) program. MERHAB funds the California Program for Regional Enhanced Monitoring of Phycotoxins, which provided support for this research.
Adapted from materials provided by University of California - Santa Cruz.
Predicting Red Tide: How Thin Layers Of Tiny Organisms Form At Sea
ScienceDaily 19 Feb 09
Not far beneath the ocean's surface, tiny phytoplankton swimming upward in a daily commute toward morning light sometimes encounter the watery equivalent of Rod Serling's Twilight Zone: a sharp variation in marine currents that traps billions of these single-celled organisms and sends them tumbling until a shift in wind or tide alters the currents and sets them free.
Scientists are aware of these thin layers of single-celled creatures and their enormous ecological ramifications, but until now, they knew little about the mechanisms responsible for their formation.
The explanation by researchers in MIT's Department of Civil and Environmental Engineering of how these common, startlingly dense layers of photosynthetic phytoplankton form, moves the scientific community a step closer to being able to predict harmful algal blooms, a well-known example of which is red tide. The work also opens new perspectives on other phenomena, like predatory feeding by larger organisms at these ecological hotspots.
"Phytoplankton are incredibly small. You would have to stack about 10 back to back to equal the width of a single human hair," said PhD student William Durham, co-author on a paper appearing in the Feb. 20 issue of Science. "But despite their small size, they play an outsized role in the environment: they form the base of the marine food web and cumulatively produce half the world's oxygen. Many species can swim, but this fact is often neglected by researchers because phytoplankton are slow compared to ocean currents. However, we have shown that their motility can play a crucial role by concentrating them into dense assemblages, known as thin layers."
In the Science paper, Durham, Professor Roman Stocker and University of Arizona physics Professor John Kessler explain how adjacent layers of water moving at different speeds produce a "shear" flow that traps the phytoplankton as they swim into it. These layers form in the top 50 meters of the ocean and can be anywhere from a few centimeters to a couple of meters thick, span several kilometers horizontally and last hours, days or weeks.
"Our research pinpoints a mechanism for the formation of these thin layers of phytoplankton, which are analogous to watering holes in a savanna — localized areas of concentrated resources that draw a wide range of organisms and thus play a disproportionate role in the ecological landscape," said Stocker, the Doherty Assistant Professor of Ocean Utilization at MIT.
Because motile phytoplankton have different morphologies and swimming abilities, one species may be able to swim through a layer of shear that will capture another. This means that each species could be trapped in a different level of shear, creating a sort of oceanic layered-cake effect, a boon for zooplankton or young fish that feed on specific species.
And when a toxic species of phytoplankton gets trapped in a thin layer, that layer can spawn a harmful algal bloom — an explosion in the population of toxic phytoplankton that sickens or kills the larger animals that ingest the cells. Harmful algal blooms are a major source of social and economic concern, particularly near coastal areas, because they are becoming more frequent and cause billions of dollars in annual losses to fishing and recreational industries worldwide.
In a perspective piece accompanying the paper in Science, scientist Daniel Grünbaum of the University of Washington writes: "The authors demonstrate a sort of Peter Principle for algae migrating in shear: cells swim up until they reach their level of instability. At this critical shear level, cells can swim in, but they cannot swim out. The resulting aggregation, in what is arguably an unfavorable microenvironment, may have widespread consequences, as harmful blooms of toxic algae often take the form of thin layers."
Using video-microscopy, Durham and Stocker were able to track the movements of individual cells as they become trapped in the layers of shear. They also modeled the movements of the swimming cells mathematically and proved that they cannot escape these layers. Once trapped, they're at the mercy of the flow, and must wait for the shear to decrease before they can swim out and exit the Twilight Zone.
This research was supported by grants from the National Science Foundation and the MIT Earth Systems Initiative.
Adapted from materials provided by Massachusetts Institute of Technology.
Red Tide: Study on whether fish, marine life are contaminated
Daily Express 19 Feb 09
Kota Kinabalu: The State Fisheries Department said it is conducting tests on fish and other marine life in other districts in Sabah to determine whether they are contaminated by the Red Tide.
Confirming the advisory by the State's Health Department, Fisheries Director, Rayner Stuel Galid said the department has detected the presence of Paralytic Shell Fish Poisoning (PSP) toxins in sample of bivalves (kerang-kerangan) in the Kuala Penyu (particulary Sitompok Lake area), Papar, Gaya Island, Sepanggar Bay (including Kuala Menggatal) and Tuaran.
In a statement, Wednesday, he said that there was a high possibility that adjoining districts will be affected in the future, adding that it has also detected high densities of PSP-causative organisms in sea water samples taken from these areas.
He said 400 MU (Mouse Unit) is considered the lowest limit in the danger level for humans, adding that some samples taken to date have shown levels to be as high as 5000 MU, which is very dangerous.
Rayner advised the public to refrain from consuming any types of shellfish including oysters, mussels and cockles but said that all types of prawns and crabs, coral fishes, stingrays and deep sea fish are safe for consumption.
"However, consumers are advised to throw away the guts and gills of these fish and have them washed properly," he said, adding that any type of dried, canned, bottled or salted fish products are safe to consume.
He also advised fish cage operators to be on the lookout for 'algal blooms' as it can suffocate the fish.
The department, will continue to update the public on the Red Tide situation, he said, adding that further information can be obtained at the nearest Fisheries office or via the department's website at www. fishdept. Sabah. gov/ download/redtideinfo. Doc.
He said that Red Tide is an occasional natural phenomenon in Sabah where micro-organisms (dinoflagellates) in the sea undergo a population explosion that sometimes imparts a brownish-red colour to the sea surface.
"These micro-organisms usually do not represent a health threat. It is only when they become many and eaten in large numbers by filter feeding sealife such as shellfish that render these shellfish toxic because of the accumulation in their guts. Some fish, which eat these organisms or other sea life that eat the dinoflagellates, can also become toxic.
"In addition, these dinoflagellated organisms become so many, that it depletes oxygen in the water causing fish to die because of suffocation.
In Sabah the cycle seems to be connected with the alternating rainy and hot days that occur at the end or beginning of the year, thus the rainy seasons of December, January and February can be expected to coincide with the Red Tide season."
Rayner said it could also be caused by the increase in nutrients in the sea because of the more than usual churning of the sea bed, adding that another cause may be because of the extended lower temperatures brought about by the rainy season.
