Wira Natanael

RED TIDE

Background: Algae are vitally important to marine ecosystems, and most species of algae are not harmful. However, under certain environmental conditions, microscopic marine algae called Karenia brevis (K. brevis) grow quickly, creating blooms that can make the ocean appear red or brown. People often call these blooms “red tide.”

K. brevis produces powerful toxins called brevetoxins, which have killed millions of fish and other marine organisms. Red tides have damaged the fishing industry, shoreline quality, and local economies in states such as Texas and Florida. Because K. brevis blooms move based on winds and tides, pinpointing a red tide at any given moment is difficult.

Red tides occur throughout the world, affecting marine ecosystems in Scandinavia, Japan, the Caribbean, and the South Pacific. Scientists first documented a red tide along Florida’s Gulf Coast in fall 1947, when residents of Venice, Florida, reported thousands of dead fish and a “stinging gas” in the air, according to Mote Marine Laboratory. However, Florida residents have reported similar events since the mid-1800s.

Red Tide

Karenia brevisK. brevis is a microscopic, single-celled, photosynthetic organism that can "bloom" (see algal bloom) frequently along Florida coastal waters. Each cell has two flagella that allow it to move through the water in a spinning motion. K. brevis naturally produces a suite of potent neurotoxins collectively called brevetoxins, which cause gastrointestinal and neurological problems in other organisms and are responsible for large die-offs of marine organisms and seabirds. K. brevis is unarmored, and does not contain peridinin. Cells are between 20 and 40 μm in diameter.

Ecology and distribution

In its normal environment, K. brevis will move in the direction of greater light and against the direction of gravity, which will tend to keep the organism at the surface of whatever body of water it is suspend within. Cells are thought to require photosynthesis to obtain nutrition. Its swimming speed is about one metre per hour.K. brevis is the causative agent of Red Tide, when K. brevis has grown to very high concentrations and the water can take on a reddish or pinkish coloration. The region around southwest Florida is one of the major hotspots for red tide blooms. Red Tide outbreaks have been known to occur since the Spanish explorers of the 15th century, although not nearly as common, or for as lengthy a duration as now. Some sources say Florida red tide blooms are about 10- to 15-fold more abundant than they were 50 years ago. Algal species that have harmful effects on either the environment or human health are commonly known as Harmful Algal Blooms (HABs). HABs are harmful to organisms that share the same habitat as them, though only when in high concentrations.

Detection

Traditional methods for the detection of K. brevis are based on microscopy or pigment analysis. They are time-consuming and typically require a skilled microscopist for identification. Cultivation based identification is extremely difficult and can take several months. A molecular, real-time PCR-based approach for sensitive and accurate detection of K. brevis cells in marine environments has therefore been developed. Another upcoming technique for the detection of K. brevis is multiwavelength spectroscopy, which uses a model-based examination of UV-vis spectra. This particular protist is known to be harmful to humans, large fish, and other marine mammals. It has been found that the survival of scleractinian coral is negatively affected by brevetoxin. Scleractinian coral exhibits decreased rates of respiration when there is a high concentration of K. brevis.

Karenia Brevis

Harmul Algal Blooms (HABs)

Harmful algal blooms, or HABs, occur when colonies of algae—simple plants that live in the sea and freshwater—grow out of control while producing toxic or harmful effects on people, fish, shellfish, marine mammals, and birds. The human illnesses caused by HABs, though rare, can be debilitating or even fatal.
While many people call these blooms 'red tides,' scientists prefer the term harmful algal bloom. One of the best known HABs in the nation occurs nearly every summer along Florida’s Gulf Coast. This bloom, like many HABs, is caused by microscopic algae that produce toxins that kill fish and make shellfish dangerous to eat. The toxins may also make the surrounding air difficult to breathe. As the name suggests, the bloom of algae often turns the water red.
HABs have been reported in every U.S. coastal state, and their occurrence may be on the rise. HABs are a national concern because they affect not only the health of people and marine ecosystems, but also the 'health' of local and regional economies.
But not all algal blooms are harmful. Most blooms, in fact, are beneficial because the tiny plants are food for animals in the ocean. In fact, they are the major source of energy that fuels the ocean food web.
A small percentage of algae, however, produce powerful toxins that can kill fish, shellfish, mammals, and birds, and may directly or indirectly cause illness in people. HABs also include blooms of non-toxic species that have harmful effects on marine ecosystems. For example, when masses of algae die and decompose, the decaying process can deplete oxygen in the water, causing the water to become so low in oxygen that animals either leave the area or die.
Scientists at the National Ocean Service have been monitoring and studying this phenomenon for a number of years to determine how to detect and forecast the location of the blooms. The goal is to give communities advance warnings so they can adequately plan for and deal with the adverse environmental and health effects associated with these 'red-tide' events.

HABs or Scientific name of "Red Tide"

Assessing the Impact on Public Health

In addition to killing fish, brevetoxins can become concentrated in the tissues of shellfish that feed on K. brevis. People who eat these shellfish may suffer from neurotoxic shellfish poisoning, a food poisoning that can cause severe gastrointestinal and neurologic symptoms, such as tingling fingers or toes.

The human health effects associated with eating brevetoxin-tainted shellfish are well documented. However, scientists know little about how other types of environmental exposures to brevetoxin—such as breathing the air near red tides or swimming in red tides—may affect humans. Anecdotal evidence suggests that people who swim among brevetoxins or inhale brevetoxins dispersed in the air may experience irritation of the eyes, nose, and throat, as well as coughing, wheezing, and shortness of breath. Additional evidence suggests that people with existing respiratory illness, such as asthma, may experience these symptoms more severely.