But that's very tenuous because for a long time we didn't take those readings. To combat this problem, the harbor contains a pump-out facility where the sewage from boats can be emptied. No exact amounts of nitrogen pollution that reach harbor waters from individual home septic tanks is known. It is estimated that they could contribute as much as 31,128 kilograms per year. Nitrogen pollution to Bay waters and other rivers and creeks that run into the Bay causes an increase in algal blooms.
Algal blooms prevent light from reaching submerged vegetation, causing it to die off.
Other nitrogen sources come from boat discharges, golf course runoff, pasture field runoff and commercial runoff. Algae concentrations for 1997 were the fifth lowest recorded in the harbor since the study began. Based on this study , the CBL analysts recommended that the County continue to encourage the use of pump-out facilities in the harbor by resident and transient boats. They noted that development of areas within the watershed can diminish its nutrient retaining capacity, and thereby increase the nutrient load to harbor waters. Calvert County commissioners agreed to fund the study next year.