BACTERIA AND IOWA BEACHES

Each summer we read stories in the paper and hear on the evening news how a local beach has been closed or swimming has not be recommended because of high bacteria levels.  Most people are unfamiliar with what types of bacteria the beaches are testing for or what the levels can truly mean for them.  Due to human land use in watershed areas, the nature of the agricultural industry in Iowa as well as homeowners need for lawn care, Iowa has some of the worst water quality in the United States.  Poor water quality in combination with a bacterial source have caused the Iowa Department of Natural Resources to begin monitoring its state beaches to better inform its citizens of potential health risks from certain bacteria.  The following information explains what bacteria are, the types of bacteria commonly found in Iowa as well as the potential risks related to these bacteria under ideal conditions.  Through education, we can better understand what is occurring at Iowa’s beaches and how we can all work together to help make our recreational areas safe and enjoyable. 

Bacteria

One of the earliest types of bacteria are the cyanobacteria.  Fossil evidence indicates that these bacteria existed approximately 3.3 billion years ago and were the first oxygen producing evolving phototropic organisms.  They are responsible for the initial conversion of the earth’s atmosphere from an anoxic (state without oxygen) to an oxic (with oxygen) state.  Being the first to carry out oxygenic photosynthesis, they were able to convert carbon dioxide into oxygen playing a major role in oxygenating the atmosphere. 

Bacteria are a very diverse group of microorganisms.  One property all bacteria have in common is that they are all prokaryotes.  Prokaryotes are organisms that do not have a true nucleus meaning their circular genetic material (DNA) is not surrounded by a membrane.  They also lack other membrane-bound structures known as organelles.  Prokaryotes can be divided into two groups or domains, Eubacteria or true bacteria and the Archaea or ancient organisms. 

Due to their important role in disease and the survival of organisms, Eubacteria is the most commonly known and studied group among the prokaryotes.  Even in their great diversity, bacteria do have some common characteristics to help identify the many different strains.  All bacteria are single-celled organisms most of which contain a rigid cell wall. Some are motile (through a variety of mechanisms) while others are not.  They also have a wide range of nutritional requirements and are able to fulfill those needs through nitrogen fixation and photosynthesis.  Some bacteria are able to convert the nitrogen in the atmosphere into the nitrogen of proteins and nucleic acids through nitrogen fixation while many can convert sunlight into chemical energy through photosynthesis. 

We are constantly surrounded by bacteria and are dependant upon them for our daily activities and survival.  Bacteria can be found on our skin, in our mouths and intestines, bath towels, in our foods, in the ground and water.  They can benefit us by recycling wastes, make certain types of food (such as yogurt), aid in digestion and help nitrogen-fixing plants to grow.  Most people are very aware of the negative affects of pathogenic bacteria, those that make us ill, and those that cause food spoilage.  Increasing areas of concern are the many types of coliform bacteria such as fecal coliform bacteria, a group that are found in the fecal material of humans and other animals.  These bacteria play an essential role in the intestinal tracts of animals in that they aid digestion of food.  Once these bacteria are removed from the intestines, they can enter other environments such as the soil and aquatic habitats in which they can become dangerous to humans and other animals. 

Enterobacteria

There are three common types of bacteria that normally inhabit vertebrate intestines that can sometimes be found in bodies of water, they are Escherichia coli (E. coli), Salmonella enteritides (S. enteritides), and Enterococcus faecalis (E. faecalis).  These enterobacteria (bacteria found in intestines) can end up in water through runoff of soil containing fecal matter, sewage or direct deposit of material.  Enterobacteria reside initially in the intestines of vertebrate animals but can end up in bodies of water.  There are a number of ways in which these bacteria make their way to streams and rivers.  Intestinal bacteria are found in the fecal material that is deposited by livestock, wildlife and humans and it is this material that can contaminate our bodies of water.  Direct deposit by dogs or wildlife such as geese can be a possible source as well as dumping of septic systems, sewage leaks, swimmers bodies, dirty diapers and agricultural runoff.  Runoff occurs when rain comes in contact with the soil containing the bacteria and the water then works its way to the closest body of water where it then enters and aquatic environment.  Large livestock farms can be major contributors to increased bacteria levels in streams and rivers.  This is due to the large amount of fecal material from the cattle or hogs that is deposited on the ground.  This material mixed with soil can then be washed away as runoff during a rainfall.

E. coli normally are not a harmful bacteria, especially those found in a lake or river.  Instead, E. coli are an indicator of other possible organisms.  Since they are found in the intestines of vertebrates, they are in the presence of other microorganisms, which are serious pathogens that can make us very sick.  When high numbers of E. coli are detected in a lake or river, they indicate that feces are getting into the water. The E. coli themselves are not the problem, but the potential presence of other pathogenic bacteria they may accompany could lead to health issues.  E. coli  pose little or no danger when found on skin; they are needed in our intestine to help digest food, but can make us extremely ill when ingested.

Salmonella enteritides as well as Salmonella typhimurium are both pathogenic bacteria that can be found in bodies of water.  Illness can be caused by exposure to these microorganisms.  If consumed, Salmonella can cause diarrhea, fever and abdominal cramps.  It is rare that a person will be exposed to Salmonella in an aquatic environment and become infected.

Another enterobacteria that may be found in water samples is Enterococcus faecalis.  Not much is known as to the function of E. faecalis in the intestine but we are more aware of what it can do once it enters a host.  It has the unique ability to attack the weakened immune system with incredible resistance to antibiotics.  Once it invades it can cause a variety of illnesses such as heart disease infective endocarditis and urinary tract infections.

Aquatic environments are not the natural habitat of the enterobacteria, therefore most are not able to survive for great lengths of time.  A continuous source such as several days of rain, sewage leaks or dumping can create high levels of bacteria posing risk for animals that come in contact with the water.  With several days of rain and runoff, the water not only can contain high bacteria levels but can also become saturated with sediment making the water cloudy and decreasing the amount of sunlight that penetrates the water.

Cyanobacteria

Initially, cyanobacteria were not recognized as bacteria.  For many years they were mistakenly identified as blue-green algae.  Since cyanobacteria do not have their genetic material contained within a membrane bound nucleus they are not classified as algae.  What does set these bacteria apart from others already discussed is that they contain chlorophyll or other pigments to use the sun as an energy source.  They actually range in colors, depending on the photosynthetic pigments, from red (phycoerythrin) to blue-green (phycocyanin) to green (chlorophyll), the first to be identified were blue-green in color hence their initial classification.  Still others are capable of nitrogen fixation to produce ammonia.  Although there are many species of cyanobacteria, three of the more common types founding Iowa include Anabaena, Microcystis and Oscillatoria. 

The cells of Anabaena are barrel shaped, giving the filaments the appearance of a string of beads.  These filaments are called trichomes, which contain specialized cells called heterocysts.  These cells are responsible for fixing nitrogen, and arise from the differentiation of vegetative cells.  Heterocysts interact with the vegetative cells of the trichomes in that they exchange materials.  Heterocysts move products of nitrogen fixation into vegetative cells and vegetative cells move products of photosynthesis into the heterocysts.  Sometimes these cells can differentiate into akinetes, thick walled resting cells that can survive in sediment during extreme conditions for years.  Like certain types of cyanobacteria, Anabaena can cause toxic blooms in freshwaters.  Certain strains produce anatoxins, or neuromuscular poisons that constitute serious danger to animals and can even be fatal.  The risk of human consumption is unlikely since Anabaena also add a taste and smell to the water. 

Microcystis, a colonial, round-celled bacterium or cocci, are generally not a potential health risk to animals unless they are found in great quantities such as during a bloom.  The toxins are produced and contained within the cells of Microcystis and are released when the cells die.  If exposed to the hepatoxin of these cells the primary effect is on the liver.  At very high doses, liver cells begin to die and blood vessels are destroyed.  Although the long-term effects are known, these toxins can cause chronic liver

Oscillatoria, like Anabaena, form trichomes that are unbranched and often have rounded apical cells.  What does make them stand out from the others is that they do not contain heterocysts.  They are known for the motility, being able to glide by wave movements of microfibrils aided by mucilage secreted through pores in the cell walls.    Oscillatoria can survive in a variety of conditions including shaded areas in which some have been found beneath blooms of green algae.  Animals that come in contact with the toxins of Oscillatoria can develop irritation of the skin and mucous membranes.

When conditions are ideal, cyanobacteria can reproduce rapidly producing a bloom.  For heavy blooms of cyanobacteria to occur, conditions need to be ideal, meaning there needs to be an abundant nutritional source as well as adequate sunlight, water and temperature ranges.  Cyanobacteria rely upon nitrogen and phosphorous for their nutrients much of which can enter water through runoff from agricultural fields as well as urban fertilized lawns.  These blooms tend to be found in the littoral zones (shore) where runoff first enters the body of water, is shallow and warms quickly.  Heavy blooms can overtake bodies of water and potentially choke out portions of streams or rivers. 

When blooms occur, their dense growth can make the water so cloudy that it shades other organisms beneath so that they do not have enough light for photosynthesis.  These organisms also cause depletion of oxygen as they die because other bacteria that use oxygen decompose the cyanobacteria. They also release harmful toxins (toxic chemicals) that can cause severe illness and even death in organisms.  The depletion of oxygen in water when large blooms of cyanobacteria die, create an anaerobic environment.  This environment is ideal for coliform bacteria.  Coliform bacteria cannot survive well in an environment that contains oxygen (aerobic condition) and therefore can increase in numbers when in a body of water that is lacking oxygen (anaerobic condition).  This explains the correlation between cyanobacterial blooms and high coliform numbers that has been seen in some cases.

Cyanobacteria have important symbiotic (intimate association) relationships with other organisms.  It has been found that heterotrophic bacteria often cover cyanobacteria and attempts to grow the cyanobacteria without the symbiotic bacteria have not been successful.  Other symbiotic relationships have been found with liverworts, ferns and cycads.

Health Implications

Exposure to pathogenic bacteria and cyanobacteria can cause potential health risks to humans and other animals.  Although there have been no reported cases of illness to the Department of Natural Resources (DNR), exposure to pathogenic bacteria can lead to rashes, diarrhea and infections of the ears, eyes, and nose ad well as cuts found in the skin.  Neurotoxins can affect the nervous systems of animals and continued exposure can be fatal.  Due to the wide variety of symptoms and few cases that may occur, it is possible that people have become ill after coming in contact with water containing high bacteria levels.  Since there are a number of ways in which people can develop these symptoms, it has been difficult to pinpoint the source; therefore no reported cases have been documented by the DNR.

To reduce potential health risks associated with swimming, it is recommended that people should avoid swallowing lake water and avoid swimming within 24-48 hours after a heavy rainfall and if the water is still murky.  If you have stomach problems or have had diarrhea within the past week, please stay out of the water as well as keep clean diapers, or swim diapers on children that are not toilet-trained to reduce the possibility of releasing bacteria into the water.

Testing

Currently, many of Iowa’s beaches are being tested by the DNR to check the level of fecal coliforms.  Thirty-five of Iowa’s state beaches are being tested weekly to monitor levels.  Many other beaches throughout the state are not being tested such as those that are run by city, county and federal organizations.  It is easier to test for coliform bacteria rather than the pathogenic bacteria because they are found in greater numbers.  Coliforms are good indicators of pathogenic bacteria due to the origin of both types of microorganisms being the intestinal tract of vertebrate animals.  It is very expensive to test for pathogenic bacteria and they can go undetected, as they will be in small quantities, if they are even present.  If indicator bacteria such as E. coli are found in a body of water, the potential exists for contamination by pathogenic bacteria such as Salmonella. 

The Iowa DNR currently tests a body of water by taking nine samples of water are taken at the beach and various depths, ankle, knee and chest deep.  The water is then filtered and the filtered material is then placed on a culture medium and incubated.  The samples of water are taken on Monday or Tuesday of each week and results are not returned until approximately three days later. The USEPA sets standards for levels of coliform colonies found in water; these levels differ depending upon the uses of the body of water. The current recommendation for body contact recreational water bacterial counts is 200 colonies per 100 ml of water or lower; for fishing and boating, fewer than 1000 colonies/100 ml; for domestic water supply for treatment, fewer than 2000 colonies/100ml; and drinking water is less than 1 colony/100 ml.  These tests are run from mid-April to the end of October to ensure the safety of those who come in contact with the body of water. 

High levels of bacteria have lead to the posting of some beaches where swimming is not recommended.  The source of the high bacteria levels has been difficult to identify.  Bacteria could be coming from a number of sources such as geese, livestock fields, or sewage and once a beach can identify the major source, steps can be taken to reduce the level of bacteria.  Some beaches are having difficulty in identifying the source; but there could be help on the way, in a few years.  Tests are being developed to help identify between the different types of bacteria that are found at beaches and their sources.  Samples of fecal material from different animal species such as goose, cattle, hog and human are being tested to identify possible differences between the different strains.  Each of these animals contain within their intestines, bacteria that are very similar in function but require different types of carbohydrate material in which to survive.  If patterns of nutritional requirements can be identified it may be easier to pin point which animal is the source of bacteria causing high levels. 

Iowa Beaches

Currently in Iowa, 35 state park and recreation areas and beaches are being tested in 2003.  Water samples will be collected on Monday or Tuesday during the test period.  If beaches exceed the standard levels they will not be closed, this is a change from previous years.  Rather the beaches will have signs posted that state that swimming is not recommended.  The signs will be removed when the bacterial counts return to levels below the standard set by the USEPA.  Two beaches in eastern Iowa, Backbone and George Wyth, have had times earlier this spring when bacteria levels were high and swimming was not recommended.  State investigators are trying to determine the sources and are continuing to monitor the tributaries to these beach areas.

Photomicrographs by Kerry Bohl under the supervision of Dr. Maureen Clayton.

This page was designed by Melissa James, a High School Science Teacher at Center Point-Urbana, as a graduate project for credit in 830:285 Readings in Environmental Science under the supervision of Dr. Leslie S. Jones, as part of the Masters Degree Program in Science Education.