Greenwich Bay

Bacteria are the simplest, smallest, and most abundant organisms on earth. Most bacteria are only 1 micrometer in diameter, but they can range in size up to 10 micrometers. They are unicellular, and do not have an organized cell nucleus.

Many bacteria, like humans, require oxygen, while others are also able to live without it for some period of time. Still others are unable to live in the presence of oxygen. Bacteria that do not use oxygen are called anaerobic bacteria.

Bacteria play a critical role in both marine and terrestrial ecosystems. They break down the complex organic materials of dead plants and animals, reducing them to simpler forms that can be used by living plants. Nitrogen and phosphorous are the elements that are the key nutrients for marine plants. Bacteria who reduce organic matter to simpler chemicals are called decomposers.

If you dig up sediments from the bottom of Greenwich Bay or other estuaries, you may notice an odor like rotten eggs. This does not necessarily mean that the water is polluted, but that anaerobic bacteria are at work. Just as carbon dioxide is a byproduct of our respiration (we breathe it out), hydrogen sulfide gas is a product of theirs.

If there were no bacteria, dead organisms would simply pile up, and soon life would cease, because all the nutrients would be locked up in the organic matter.

When researchers look for bacteria in water, they are not looking for the bacteria that is naturally found in all marine sediments, but for bacteria from human sources. These sources include wastewater treatment plants, septic systems, and livestock such as cows.

Commonly, water is tested for the presence of fecal coliform bacteria, which is found in the intestines of animals, including humans. Most coliform bacteria are not harmful. However, their presence means that there are human or animal wastes in the water. Some of the other bacteria in these wastes may indeed cause disease. Examples of these pathogenic, or disease-causing bacteria include Salmonella and some types of E. coli.. Bacteria in marine waters has been known to cause diseases ranging from typhoid fever to gastroenteritis (upset stomach and diarrhea). The bacteria may get into the human body from direct contact such as swimming, or from eating shellfish such as clams and oysters that grow in contaminated waters.

Coliform levels in some parts of Narragansett Bay are measured to determine whether an area is safe for shellfishing or swimming, and some areas are closed to shellfishing because of high coliform levels. Other areas are closed conditionally: When there is a certain amount of rainfall, these areas are automatically closed because of the potential for contamination.