The term “red tide” is a misnomer as it does not associated with tides. It is used to described as a phenomenon microalgal species growing very fast or “bloom” and is caused by the growth and accumulation of microscopic algae (single-celled marine plants) called phytoplankton (Anton, A. et al, 1998). These algal blooms become so numerous that they can discolour coastal waters.To the scientists they prefer to call them as algal blooms or HABs These algal bloom may cause oxygen depletion in the waters and/or release toxins that may cause illness in humans and other animals.
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Red tide is a global phenomenon. Since 1980’s harmful red tide events have become more frequent and widespread. The major factors influencing red tide events include warm ocean surface temperatures, low salinity, high nutrient content, calm seas, and rain followed by sunny days during the summer months. In addition, algaerelated to red tide can spread or be carried long distances by winds, currents, storms, or ships.
Red tide has affected my countries all over the world including South East Asia and Sabah in Malaysia. The first report of HABs and shellfish toxicity in Malaysia was in 1976 when the marine dinoflagellate Pyrodinium bahamense var. Compressum bloomed in Brunei Bay on the west coast of Sabah (Roy 1977). The study by Anton, A. et al (2000) found 11 species in both the West and East Coast of Sabah and all the species densities were below 100 cells/L which is far below the densities to consider to be a bloom, which values are more than 103 cells/L. This is because too many blooms are unhealthy for coastlines because an over abundance of blooms can lead to suffocating low-oxygen conditions for fish, and increased diseases in seafood.
Below shows the distribution of PSP toxin in the world between 1970 and 2006.
Figure 1: Comparison of PSP Toxin distribution in the world between 1970 and 2006
2.0 The problem of red tide
Since there are many factors influencing the events of red tide, it has caused a lot of concern and problems to sicientists especially the marine biologists. A lot of research has been carried out such as Harmful Algal Blooms in Malaysia: Revisiting Kimanis Bay by Anton A.et al (2000); Lipid and DNA features of Gonyaulax fragilis (Dinophyceae) as potential biomarkers in mucilage genesis by M. Riccardi et al. available online on 25 January 2010; Effects of temperature, salinity and irradiance on growth of the novel red tide glagellate Chattonella 1 ovata (Raphidophyceae) by a group of scientics lead by Haruo Yamaguchi et.al. Available online on 13 February 2010 and many others has being carried out.
The presence of red tide impose a severe burden on the affected country (Gires U. et al, 2002). The problem is compounded by wide adoption of the Hazard Analysis Critical Control Point (HACCP) protocols which require that seafood is certified as safe and wholesome for consumption by monitoring the natural toxins. Red tide has also caused mass mortalities of wild and farm fish and shellfish, human illness and death from contaminated shellfish or fish, death of marine mammals, seabirds, and other animals, and alterring the marine habitats or trophic structure. In 1972, Massachusetts has declared a state of emergency because of red tide bloom. (Esterbrook, J. 2005). It has caused the shellfish industry about $3 million per week.
Although until today there are nothing much marine biologist can do to eliminate red tide problems, however, with the technological advancement such as satellite imagery have enable the scientist to better track and monitor the harmful algal booms. By tracking and monitoring these blooms has helps to reduce harmful effects of the algae by providing early warnings against eating infected shellfish and against swimming in infected water. Sophitiscated instruments to test for the presence of red tide algae in coastal waters have been developd by the Sarasota Operations Coastal Oceans Observation Laboratory. NASA Earth Observatory has develop programmes such as SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and MODIS (Moderate Resolution Imaging Spectroradiometer) instruments to detect harmful algal bloom from space.
Autonomus underwater vehicles (AUVs) equipped with temperature and salinity meters as well as a “Breve-Buster,” which is an instrument that collects water samples and determines the levels of red-tide causing algae by shining a light through the sample and noting the light absorbing characteristics within the sample (indicative of these algae) is also used in the research of red tide.
Although red tide events can be avoided, reseachers are attempting to develop an antidote to the red tide toxins. Interestingly, while developing such anti-toxins, researchers have found a possible treatment for cystic fibrosis.
3 Methods used to collect samples
Traditionally, light microscope is used to estimate the population of zooplankton in the water. An example of the equipment used is as shown in Fig.2 below.
Figure 2. A representation of the volume of water being sampled by a plankton net from a depth of 3 meters.
The amount of water sampled and how to properly enumerate the organisms in the sample is important. This is because the amount of water sampled can be considered equalto the amount of water that passes through the plankton net. Since the opening of the plankton net is circular, the amount of water that passes through the net from a specific depth to the surface would be similar in shape to the cylinder. Therefore, the formula for the volume of a cylinder is, V=°R2 x H. By applying this formula the amount of water sampled through the plankton net can be calculated. Once the plankton has been captured in the filter canister at the bottom of the plankton net, small volume (1ml) sub-samples can be placed under the microscope so that each plankton organism can be counted. Finally, the total number of plankton within the sampled water can be calculated by extrapolation. This number can then be extrapolated so that the total number of plankton in the seawater can be estimated.
Figure 3. Custom-fabricated pucks for the 2G ESP shown L to R as sample
collection and filtration, array processing, and FISH archival. Quarter
shown for size.
However, recently there is a shift from using traditional ligh microscopy to molecular approaches for identifying and quantifying marine harmful algal bloom (HAB) species has been driven by the need to expedite sample processing for both research and monitoring purposes (Anderson 1995; Scholin et al. 1996). In addition, light microscopy has limitation to sufficient resolution to discern species when compared to electron microscopy. Some methods used to accurately identify HABs in a fast manner are fluorescent in situ hybridization (FISH) (Lim et al. 1993), fluorescently labeled antibodies and lectins (Sako et al. 1996), sandwich hybridization (Scholin et al. 1996), probe arrays (Loy et al. 2002), environmental sample processor (ESP) (Scholin et al. 2001) and a variety of nucleic acid amplification methods that target specific signature sequences. However, most of these techniques require ccess to shore-based laboratories for sample processing and analysis, which can be both time and labour intensive. Most of the methods mentioned above are very technical and require researchers who are well verse in handling the equipment and also thoroughly understand the methods used. It takes time to prepare, process and image analysing of the samples collected, and interpreting the results. An example of the equipment used in ESP is the ‘puck’ as shown below.
4. Application and implications of biology
Implications of red tide
There are many species of red tide that release harmful toxins. Among the harmful species found in the United States are:
Alexandrium fundyense – found along the Atlantic coast from the
Canadian maritimes to southern New England
Alexandrium catenella – found along the Pacific coast from California to Alaska
Karenia brevis – found in the Gulf of Mexico along the west coast of Florida
Figure 4: Different species of red tide
Although red tide algae make potent natural toxins but it is unknown why these toxin are created, but some can be hazadous to larger organisms through the processess of biomagnification and bioaccumulation. Grazers such as fish and krill are unaffected by the toxins, so when they eat the algae to toxins are concentrated and accumulated to a level that is poisonous to other aquatic lives such as bigger fish that feed on them. Then when mammals such as birds, man, etc. consume these fish they will either contracted diseases or they can cause death.
Diseases that may affect humans include:
1. Paralytic Shellfish Poisoning (PSP)
This disease is caused by the production of saxitoxin by the Alexandrium species and they are common along the Atlantic and Pacific Coast in the US and Canada (Monica Bruckner, Montana State University). Poisoning occurs when on ingests shellfish contaminated with PSP toxins causing disruption of nerve function and paralysis. In extreme cases it may result in death due to asphyxiation.
2. Diarrhetic Shellfish Poisoning (DSP)
This disease is caused by the Dinophysis species. It generally occurs in Japan and Europe, but it has been found in other countries such as Canada, the US, Chile, New Zealand, and Thailand. Symptoms of DSP include diarrhea, nausea, vomiting, abdominal pain, and cramps. However, DSP is generally not fatal.
3. Amnesic Shellfish Poisoning (ASP)
Amnesic shellfish poisoning has been found along the eastern Canadian coast. It is caused by domoic acid producing planktonic and benthic algae, including Pseudo-nitzschia multiseries and Amphora coffaeformis. It can also found in soft shell clams and blue mussels infected by Pseudo-nitzschia delicatissima. It causes gastricand neurological symptoms including dizziness, disorientation and memory loss.
Domoic Acid and Amnesic Shellfish Poisoning
Diarrhetic Shellfish Poisoning
Saxitoxin and Paralytic Shellfish Poisoning
Figure 5: Different types of poisoning caused by red tide
Red tide has also caused substantial impact to the ecosystem that include a reduction in light penetration, a reduction in the extent of seagrass beds and a reduction in the growth rates of hard clams. Further, red tide caused mass mortalities of mussel populations in Rhode Island and in Long Island waters, Recurrent blooms have had severe impact on bay scallops, affecting more than 80% of New York’s commercially valuable harvest. Acute or chronic exposure to red tide and their toxins either directly or through the food web, puts the affected population at increased risk (Anderson, D. 2007).
In 2005, the massive red tide outbreak in New England has caused the shellfish industry to lose $3 million per week and forcing the Massachusetts to declare a state of emergency. This has lead to the shellfisherman to raise their prices especially for the shellfish industry.
The 2009 paralytic shellfish poisoning (red tide) occuring in Maine, Portsmouth, New England has caused devastating economic impact where Maine authority estimates that there were 89,000 acres of productive shellfish in the state waters and at that time more than 97% of these resources were closed due to red tide (Anderson, D. (2007). Further, there had been unusual reports of mortality events of both short-nose sturgeon and eider ducks which were suspected to be caused by the transfer of red tide toxicity through the food web to these larger animals.
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The first paralytic shellfish poisoning (PSP) case recorded in Sabah in 1976 where 202 victims were reported to be suffering from PSP and 7 deaths. (Roy 1977). This event has caused significant economic losses to fishermen because the public are afraid to consume all types of seafood during the bloom event which lasted two to three weeks. Then in 1991, three people were taken ill after consuming green mussel (Perna viridis) cultured at a newly established mussel form in Sebatu Malacca (Gires, U. et al 2002). Symptoms suggested that of intoxication due to algal toxins were confirmed by testing the extracts from mussles collected during the event confirmed the presence of toxins caused by dinoflagellate Alexandrium tamiyavanichi. Further, in September 2001, six people were taken ill after consuming ‘lokan’ (Polymesoda sp.) collected from a coastal lagoon (Sungai Ubi) in Tumpat Kelantan and one of the victim died with symptom suggested intoxication due to algal toxins (Usup et al. 2000).
Picture 4: A spectacular “red tide” bloom (non-toxic) of Noctiluca scintillans in New Zealand
Brevetoxins and Neurotoxic Shellfish Poisoning
Saxitoxin and Paralytic Shellfish Poisoning
Figure 6: The economic loss due to the effect of red tide
Although the impact of red tide (algal blooms) events are more associated to the environmental impact as well as economic impact, however, the presence to these events have also affected the recreation, tourism and local aesthetics by diminishing the qualities of the environment (Anderson, A. 2007). This can manifest in a variety of ways in different regions of the country. Some examples are:
Massive fish mortalities that result in fish accumulating on beaches
Clossure of receational fisheries
Respiratory ailments experienced by beachgoers from aerosolized toxins
Unsightly and noxious piles of macroalgae that accumulate and decompose on beaches
Discolouration of water
Mortalities of protected species and modification of their habitats
Working patterns can also be disrupted when fisherman seek alternative occupations or sources of income and restaurants seek alternate suppliers for their seafood. Boat charter reservations and pier attendance for recreational activities will be disrupted, vacations ruined and some may never visit an impacted region again. In addition to that, people who have retired to coastal or lake shore homes may find their property values adversely affected when red tide or harmful algal blooms (HABs) frequently occur.
Division of Environmental Hazards and Health Effects from the National Centre for Environmental Health, Communicable Disease Control (CDC), Atlanta is also very concern with the frequent occurrence of red tide (HABs) events all over the world. This has lead them to work with investigators from local, state, and federal health agencies of the country concerned to assess the respiratory effects of:
Recreational exposure to red tide toxins dispersed in the air. For example, in 2003, CDC completed and reported a pilot study oftwo separate red tide events in Florida.
Occupational exposure to red tide toxins dispersed in the air. For example, CDC has collected respiratory-function data from Flrida lifeguards who worked during a red tide event.
Red algae bloom at Leigh, near Cape Rodney.
This massive “red tide” of the dinoflagellate Noctiluca stretched for more than 20 miles along the southern California coast. Non-toxic blooms such as these can cause extensive mortalities of plants and animals in shallow waters when the bloom biomass decays, stripping oxygen from the water.
Figure 7: Red Tide occurrence
5.0 Benefits and risk to humans, other organisms and environment
The site of seeing red tide at the beach indicate that there is something unusual has occurred in the sea especially at the site of the event. As discussed in details above, red tide occurrence has been widespread all over the world. They have caused many implications to the environment, ecosystem and the living organisms that depended on the equatic lives to live. Among the risk to humans are not only man are not able swim in the beaches, lost in tourism but by the exposure to these events can cause harmful effect to the health of the population living nearby. Besides, the toxins produced by the harmful algal blooms have caused extensive mortalities to plants and animals when the bloom biomass decays, stripping oxygen from the water. It has also cause shellfish fisherman to loose million of dollars in income because of the fear to consume shellfish during red tide seasons.
However, with many research being carried out from time to time on red tides or harmful algal blooms (HABs), man has learn a lot about the causes to the occurrence of these events. Sophisticated instruments have been designed and built such as SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and MODIS (Moderate Resolution Imaging Spectroradiometer) instruments to detect harmful algal bloom from space. Autonomus underwater vehicles (AUVs) equipped with temperature and salinity meters as well as a “Breve-Buster,” which is an instrument that collects water samples and determines the levels of red-tide causing algae by shining a light through the sample and noting the light absorbing characteristics within the sample (indicative of these algae) is also used in the research of red tide. All these instruments are used to track and monitor these blooms and have help to reduce harmful effects of the algae by providing early warnings against eating infected shellfish and against swimming in infected water.
Research carried out by Peterson, J. 2004 with red tide toxin yields potential therapies for cystic firbosis. In the research, experiments conducted with both the compounds; Î²-Naphthoyl-bevetoxin and brevenal (a natural compound produced by red tide) in sheep revealed that both the compounds were able to block the effects of the red tide toxin on the respiratory system. While conducting the experiments an even more important discovery prevailed – the anti-toxins behaved much like drugs used to treat cystic fibrosis because these compounds helps to speed up the clearance of mucus from the lungs. According to Danial Baden, Ph.D., director of University of North Carolina in Wilmington’s Centre of Marine Science and director of the project, mucociliary clearance is one of the most important defense systems in the lungs, protecting the airways from bacteria and pollutants. Tests conducted in sheeps also showed that these compounds to be effective at doses 1 million times lower than the current medications used in the treatment of cystic fibrosis and they have no side effects.
6.0 Alternatives views or solutions for implications of biology encountered
One of the ways to control red tide or harmful algal blooms (HABs) is to reduce excess pollutants and key nutrients from being released into coastal ocean areas. From the environmental perspective, taking steps to reduce pollution would also reduce HAB occurrences. For HABs, reducing nitrogen release is especially important; however, this is also one of the most difficult pollutants to control as it comes from a wide range of widely used agriculture chemicals such as fertilizers and fossil fuels. Therefore, efficient and effective dissemination of useful information about HABs to the populations that live in the coastal areas is important.
Subsequently, controlling harmful algal blooms (HABs) using chemicals, fine clay particles or biological agents should be studied further. Although the potential dangers of chemical or biological agents should be known, they also hold great promise in controlling unwanted toxic phytoplankton populations. Under some circumstances, dispersal of fine clay particles over a bloom has seen some sucess, as the clay aggregates with itself and with other particles in the water (including HAB cells) and pulls the harmful algae to bottom sediments. Control techniques in the context of risk assessments, similar to those applied in evaluating land-based agriculture, should be purseued with HABs.
Better monitoring systems and detection methods on HABs need to be further developed. Government and multinational companies and philantrophies such be encouraged to fund monitoring programs and research. In addition, the medical community should be better informed and prepared to treat individuals suffering from HAB toxicity. Individuals visiting or living on the shore or consume seafood also need to be better informed about the risks.
Overall, scientiests need to be encourage to investigate HAB controland mitigation strategies. This is because it is easier to pursue basic or fundamental science, rather than taking on the challenging and highly visible practical research that tries to control blooms. There are surely technologies that we have not even considered or explore yet that will be effective if scientists and engineers are given the resources and encouragement to pursue control and mitigation research.
Red tides and harmful algal blooms is one of the important areas where the biologist can seriously undertake in their research. This is because there are many factors that can cause HABs or red tides. Once it occur, it will cause much harm to the environment, aquatic ecosystem, lost of income to the shellfish and fishery industries and the health of the populations exposed and staying in the coastal areas will be affected.
Therefore, it needs a concerted multi-prong effort from not only the biologists but also the agencies involved; be it governmental or public, and last but not the least the affected populations and individuals at large to help find effective mitigation solutions to the problems at stake.
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