Red tides have been an ongoing environmental problem for our ocean waters wildlife. Red tide is a phenomenon caused by harmful algal blooms that occur when colonies of algae (simple plants that live in the sea and freshwater) grow so numerous that they discolor coastal waters (resulting in the name “red tide”).
These large algal blooms of toxic producing dinoflagellates (single-celled organisms that are able to form nutritional organic substances from inorganic substances) may diminish oxygen in the waters, block sunlight that other organisms need to live and release toxins that are harmful to the health of the environment, plants, animals and humans.
Main poisoned organisms that cause these blooms in the United States are Alexandrium fundyense, along the Atlantic Northeast coast, ranging from the Canadian Maritimes to Southern New England, Alexandrium catenella, on the Pacific West Coast from California to Alaska, and Karenia brevis, in the Gulf of Mexico along the West Florida coast. Most cases of red tide occur seasonally. Even though these red tides mostly happen in the late summer and early autumn, sometimes the time of occurrence depends on the different temporal pattern in each region.
There is no single cause of red tides, but there must be an abundant amount of nutrients in the water to support the explosive growth of dinoflagellates. Coastal water pollution produced by humans, low salinity levels, and increases in sea water temperature have been contributing factors in red tides. The occurrence of red tides in some locations appear to be entirely natural like when the weather begins to get cooler, causing winds to blow, resulting in the disruption of the settled ocean floor in a process called “upwelling”. Upwellings are powerful deep currents which bring nutrients to surface waters.
These currents come from nutrient-rich bottom layers of the ocean which bring massive amounts of deep-water minerals to the surfaces. Good temperature, salinity, and light conditions at the time of the upwelling, makes it very easy for the nutrients to supply poisonous organisms, thus makes it the first step to a quickly multiplying harmful algae bloom. Climatic changes greatly affect the frequency of occurrences because it takes cool winds and a cool climatic temperature for the upwelling to occur. The waters also have to be at a higher temperature, if the waters are too cold, the developing of nutrients may not be able to take place.
Red tides can have become a problem because of their domino effect in the food chain. When these tiny plants undergo an algal bloom, they are consumed in enormous quantities, generally by clams, mussels, and oysters, which are filter-feeding animals. These animals consume large quantities of water and filter the food, often leaving behind a high concentration of the harmful algae in their system. After a shellfish consumes the algae, a human will often consume the shellfish, leading to problems. This is why humans are often warned not to consume certain seafood in an area affected by a red tide.
Cormorants (large diving birds) and pelicans died in large numbers because they were eating small fish that contained the toxic chemicals from zooplankton. Even large whales can be poisoned by algal toxins. Florida hit a new record in 2013 for 803 manatee deaths. The leading killer of these endangered mammals was the toxin in the algae bloom in the Gulf of Mexico. ( ) 803 manatee deaths were documented between January 1st, 2013 to December 13th, 2013. ( ) That is 16 percent of 5,000 manatees in the state. In 2014, thousands of fish were killed in Florida’s waters because of the algae bloom in the Gulf of Mexico. ). Red tides were officially recorded in 1844 in Florida.
Red tides in the Gulf of Mexico and Florida are a result of high concentrations of Karenia brevis, a microscopic marine algae that occurs naturally in lower concentrations. In high absorption, its toxin halts the central nervous system of fish so they cannot breathe. In result to this, dead fish wash up on Mexican gulf beaches. Red tide is also potentially harmful to human health. Karenia brevis blooms can possibly cause eye and throat irritation (coughing, sneezing, tear production, and itching) to beachgoers, boaters and coastal residents.
Irritation to the eye and throat was due to toxic particles of Karenia brevis cells airborne in sea spray. People with severe or persistent respiratory conditions (such as chronic lung disease or asthma) may experience stronger unfortunate reactions. Humans can become seriously ill from eating oysters and other shellfish polluted with red tide toxin. Diseases that may affect humans include Paralytic Shellfish Poisoning (PSP) which is caused by the production of saxitoxin by the Alexandrium species. It is mostly found along the Atlantic coasts and Pacific coasts in the United States and Canada.
Poisoning occurs when one intakes shellfish contaminated with PSP toxins causing disruption of nerve function and paralysis. In extreme cases, PSP may result in death by asphyxiation (lack of oxygen) by respiratory paralysis. Diarrhetic Shellfish Poisoning (DSP) is caused by the Dinophysis species. This has been typically found to occur in Japan and Europe, but it has also been found in other countries such as Canada, the United States, Chile, New Zealand, and Thailand. Symptoms of DSP include diarrhea, nausea, vomiting, abdominal pain, and cramps.
DSP is normally not deadly. Amnesic Shellfish Poisoning (ASP) is caused by domoic acid producing planktonic and benthic algae. This has been found along the eastern Canadian coast. This can be found in soft shell clams and blue mussels infected by Pseudo-nitzschia delicatissima. Symptoms may include gastric and neurological issues like dizziness, disorientation and memory loss. Paralytic, diarrhetic, and amnesic shellfish poisoning have the capability of making large numbers of people ill and can cause death in cases of extreme exposure or body sensitivity.
Many countries routinely monitor the toxicity of shellfish using various sorts of assays because the risk of poisoning is a very high probability. One frequently used bioassay includes the injection of laboratory mice with an extract of shellfish. If there is contaminated shellfish by a marine toxin, the mice will develop diagnostic symptoms of poisoning. However, the mouse experiment is progressively being replaced by more accurate methods of determining the presence and concentration of marine toxins using analytical biochemistry.
The analytical methods are normally more reliable and are much kinder to mice. Human activities have contributed to the contamination of the marine environment. So we need to take actions to reduce the damage of red tides for example, spread awareness among citizens and fishermen through the media, create continuous training for workers in the fish farms, stop using nitrogen based fertilizers in Florida lawns and agriculture, and spray mud over the areas that show the plankton or algae that cause red tide.
As well as health impacts, red tides have a serious economic impact. Coastal communities that mainly rely on tourism often lose millions of dollars because of dead fish washing up on beaches, tourists feeling ill, or shellfish warnings are issued because of the toxin red tides produce. Commercial fishing and shellfish businesses also lose income when have no resources of shellfish beds because they are closed due to the harmful algae toxins, which are also contaminating the fish they normally catch.
Even though water activities are safe during red tides, many people become very cautious when a bloom is reported, which causes tourism, recreation, and other businesses to be greatly affected even if they are not located directly in the area where a harmful algae bloom occurs. To calculate the actual economic cost of red tides and other harmful algae blooms is difficult. One harmful algae bloom has an estimated loss of $15 million to $25 million.
