Bacteria

Background

The presence of bacteria is another way to measure the health of an ecosystem. The presence of certain bacteria, such as E. Coli, Cyanobacteria and vibrio species can have negative impacts on water quality and aquatic ecosystems. These bacteria can harm human health and disrupt nutrient cycles in the ecosystem. In the case of the East River, it is possible that there is a presence of E. Coli or other harmful bacteria due to combined sewage overflows. 

Maps of water sample collection sites 

Methodology

Three samples were collected for E. Coli testing, two were taken from the Bridge Park Dr site and one was taken from Pier Five. It is important to note that the Bridge Park Dr site is located at a combined sewage outfall. One of the samples from Bridge Park Dr was taken before heavy rainfall and the other was taken after heavy rainfall. All three samples underwent a test using EMB agar1 with one sample from Bridge Park Dr (post rainfall) also being tested using regular agar as well.  

1. A specific type of medium that selectively grows gram negative bacteria.

Results and Discussion 

Bacteria Growth of Sample from Bridge Park Dr (post rainfall) using normal agar 

All samples tested using EMB agar did not produce any growth, indicating that there was not a presence of E. Coli or other gram negative bacteria. It is possible that due to the tidal nature and sheer volume of water, bacteria such as E. Coli could have flowed away relatively soon after it entered the river. It is also possible that there was not enough rainfall to cause a CSO at the time of sample collection. The plain agar on the other hand, did produce gram positive bacteria growth. There was also growth of an unidentified presence of microgranisms that possibly may be fungus. Bacterial colonies tend to form in small round formations (see middle right of image above), while the larger growth is significantly larger and seems to spread from one central point. The species of organism is unknown, and would likely require significant further research to identity it.