Casey Peck, Gallaudet University

Class Year:

2018

Mentor:

Caroline Solomon Ph.D.

Abstract:

The Anacostia River, “the forgotten river,” has an overall poor quality caused by several anthropogenic sources including sewage, excess nutrients from runoff, and combined sewer overflows (CSOs). To assess the impact of changing nutrient concentrations and forms on the bacterial and phytoplankton community composition and productivity, samples were collected from the Anacostia River into fifteen cubitainers with different nutrient additions (different combinations of +N, +P, +Si). Our project focused on one aspect: the influence of different nutrient additions on urease activity, an enzyme responsible for the breakdown of urea to ammonium. We hypothesized that there would be more urease activity in the +NO₃^- and +urea additions because NH₄⁺ suppresses urease activity and there will be no difference in +P treatments because urease activity does not require ATP. Urease activity increased in the NH₄⁺ treatments once NH₄⁺ was exhausted and the microbes were physiologically stressed. Urease activity and NO₃^- concentrations remained mostly steady throughout the experiment for the other treatments, with the exception of in +P treatments where urease activity varied even though PO₄ concentrations decreased on specific days. Based on these results, changing nutrient dynamics in the Anacostia River will have an influence on urease activity if ammonium levels are reduced due to the new storage tunnel that went on-line in March 2018. 

Location:

Gallaudet University