Tara and Scott SCUBA along the Wall at Runway Ten, 15 m deep, San Salvador, Bahamas.
Marine Microbes and the Fate of Red Tide
Understanding red tide requires some basic understating of marine microbes and their habitats. An operational definition of a marine microbe is a microbe that can produce offspring and develop in marine habitat. Marine Microbes are often referred to as the first life forms on earth. As these marine microbes swam in the ocean water for thousand of years they introduced the earths atmosphere to oxidizing and reducing agents, ultimately introducing molecular oxygen to the atmosphere setting the stage for the evolution of plants and animals. These microorganisms continue to shape and influence the atmosphere and chemical balance of the ocean. Therefore scientists of all backgrounds have pushed for continued research to understand these microorganisms in hopes that they will provide answers from the past and present environmental problems.
Marine microbes have a variety of habitats which results in a great amount of diversity. There are varying zones of marine microbial life. These life zones are broken into four levels: The neuston zone which is the zone where air and water mix, the pelagic zone which is considered the water column, the epibiotic zone in which attached communities can be found and the endobiotic zone (found within larger organisms, i.e. coral or fish. Figure 1, provided by a marine conservation
group, illustrates the different zones well. Habitat types
range dependant upon different criteria that the microbes
can tolerate. For example when other organisms can
reside in one place it is likely the habitat could range
from symbiotic to biofilm. When the can be dependant upon the depth of the ocean ranging from euphotic to Benthic zones. Some microbes thrive in habitats that are
high in chemical concentrations ranging from habitats called ogliotrphic to eutrophic.
Although these organisms can be restricted to certain habitats and geographical locations some can be moved by currents or natural forces such as hurricanes.
Within these zones lurks the common perpetrator of red tide, the dinoflagalette. Dinoflagalettes are a large source of plankton in the ocean and playing important role in marine life food chains. These eukaryotic protists are so named for their “spinning cells with Flagella”. They can be found in most oceanic provinces or life zones; however research does indicates they can reside in water temperatures ranging from 1 – 35 degrees Celsius. An autotrophic form of the dinoflagalette, such as Karenia brevis and Alexandrium tamarense can produce vast amount toxic neurotoxins when in bloom (Postlethwait and Hopson, 1995).
Red Tides or Harmful Alga Blooms (HABs) occur when high levels of nutrients
are present in the water. This can occur due to the
ocean and wind currents moving the plankton into
different nutrient high areas of the ocean. This can
also be seen in areas after heavy rains wash
nutrients form land into the water. Some scientists
even theorize that temperature may play a role due
to increased occurrences of the red tide in the
summer months. Harmful Algae Blooms do occur
naturally but when conditions are right the harmful algae blooms can be intensified and have many adverse effects on marine and human life. According to the Florida Fish and Wildlife Conservation Commission reports red tides or Harmful Algae Blooms have increased over the past 50 years. Figure 2 provides a national distribution of HABs pre and post 1972. The figure does not show all of the HAB events but it clearly indicates an increase in these toxic outbreaks.
Both Marine and human can be impacted by the affects of red tide. Economic and Public Safety impacts are major concerns of red tide occurrences. Since humans are at the top of the food chain often times eating shell fish, such as mussels, scallops or clams, during a red tide occurrence can be dangerous, even deadly. Consuming shellfish that collect the toxins can cause paralytic shellfish poisoning (PSP) in humans which results in death by asphyxiation. Not only eating but breathing the air filled with the toxic aresol can cause throat and eye irritations. Often time’s beaches are completely closed for public safety reasons. When beaches are closed many tourists town can be like ghost towns. Many restaurants are unable to sell products and fisherman can’t harvest their goods causing financial loss in a variety of ways.
Red tides don’t stop at with human impacts they have impacts on many ecosystems. With the bioaccumulations of
these neurotoxins sea mammals as large as
humpback whales have been found beached
after feeding during a red tide. In 1996 The
Florida State Fish and Wildlife Department
reported 150 manatees beached during a red
tide event. Thousands of fish can be killed
during a red tide event. Some scientists believe
that macro zooplankton and other marine life motor skills and physiological processes can be hindered when subjected to the HABs toxins. Figure 3 provides flow chart of how these toxins infiltrate the pathways of all ecosystems.
Due to the rising concerns related to red tide and HABs many organizations have pulled together to research and better understand these HAB’s. Research is being done by a variety of research facilities from all around the world. The Center for Disease Control (CDC) has created a HAB tracking center and present the data on a monthly basis. The CDC tracking systems indicates that July to September tended to be moths of increased HAB occurrences. This could be related to increased rain events and possibly increased hurricanes. Ecology and Oceanography of Harmful Algae Blooms (ECOHAB) is a national project designed to study HABs in the United States. Several states form the Northwest Pacific to Florida participate in research actives such classification of non affected invertebrate or determining bloom increase rates related to increase temperature. Not only The United States but European efforts also research biological control to HABs and the developing HAB monitoring systems.
Research done by these many groups can be tricky and when the challenges are many the cost of research can tend to increase. One major challenge is that the red tide events are spatial and abruptly occur. When the red tide appears it can last for only a few days making collecting some data difficult. Another challenge is that when several states collect data in different ways the results can be inconsistent. Creating recommendations from results can be difficult especially considering that water quality standards for ecosystem health are not regulated. Many changes due to development and natural weather occurrences also affect scientist’s research by effecting impact rates that could affect the red tide blooms.
Much research continues to be done and questions are being answered what happens in the future will depend on a collaborative effort by international, national and state officials. Collaborations of information between state departments may enable the development of solid management practices. Certainly there will be geographical differences between states but the management practices should remain consistent to ensure each state is approaching and responding to the problems with complete information. Federal and state interaction may be an answer to ensuring some standards are set to aid in reducing the amount of unnecessary and avoidable nutrients do not find their way to the ocean waters. Without continued funding to aid in research of red tide and HAB occurrences we will continue to see massive fish kills and great economic loss.
Frequently asked red tide questions. 2006. Aquaculture Magazine 32, (2) (03//Mar/Apr2006): 18-19.
RED ALERT ON RED TIDE. 2006. New Scientist 189, (2533) (01/07/): 4-4.
Red tide is suspected in killings of mullet. 1997. New York Times 147, (50922) (11/30/): 30.
Anderson, M, National Office for Marine Biotoxins and Harmful Algal Blooms, Woods Hole MA, National Oceanic and Atmospheric Administration Center for Sponsored Coastal Ocean Research Coastal Ocean Program (NOAA/CSCOR/COP)
Black, Jacquelyn G. 2004. Microbiology : Principles and explorations. 6th ed. Hoboken, NJ: John Wiley.
Perkins, Sid. 2006. Toxic tides. Science News 169, (23) (06/10/): 358-358.
Postlethwait, John H., and Janet L. Hopson. 1989. The nature of life. New York: McGraw-Hill Publishing Company.
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