Cedarville Bay water quality survey

TitleCedarville Bay water quality survey
Publication TypeReport
Year of Publication1995
AuthorsGrant M
Pagination28 pp.

The water quality monitoring project conducted in Cedarville Bay during the fall of 1994 had three primary objectives: 1) to determine the actual amount of phosphorus reaching Cedarville Bay following discharge from the Clark Township wastewater treatment plant; 2) to follow the movement of the discharge plume in the bay and determine its residence time; 3) to measure the effects of increased nutrient load on the biota found in the bay. The study revealed that prior to any discharge from the wastewater treatment plant, the phosphorus level in Cedarville Bay was approximately twice that of Hessel Bay or Marquette Bay. This suggests that Cedarville Bay has been receiving phosphorus from sources other than the treatment plant, and that poor exchange of water with Lake Huron has allowed phosphorus levels to increase to the point where dense stands of aquatic weeds and higher concentrations of phytoplankton (algae) can be supported. There are distinct chemical and biological differences between the bays in the study area, particularly in the types and distributions of benthic invertebrates. Cedarville Bay is dominated by Isopods, a species that is very tolerant of organic pollutants. During one discharge period, from November 3-5, the treatment plant released 92 kg (202 pounds) of phosphorus into Pearson Creek; of this amount, 64% or 59 kg (130 pounds) reached Cedarville Bay. The resulting increase in phosphorus triggered a small algal bloom, the intensity of which was probably attenuated by the lower water temperature and reduced light level in the bay during the fall. Marked increases in the species Dinobryon and Synura were observed. Plume location in the bay was monitored for approximately 10 days. Its movement showed close correlation with prevailing winds. Actual residence time in the bay could not be accurately calculated but is estimated at 2-3 weeks.