CORRELATION OF SEDIMENT P CONCENTRATIONS WITH SEDIMENT AND HYDROLOGIC PROPERTIES IN IRONDEQUOIT BAY, NEW YORK

The impact of P on aquatic ecosystems is well recognized, and has been the subject of intensive studies. The primary focus of many of these studies has been to develop best management practices (BMP) that reduce loading of soluble reactive P (SRP) to surface waters. Recently, the role of sediment P has become more prominent as the recovery of surface waters bodies has not met predictions based on the decreased loading from surface water runoff inputs. Irondequoit Bay is a dimictic lake that typically stratifies in early May to June. The bay has a length of 6.44 km and a maximum width of 0.97 km, giving a surface area of 6.68 km2. It has a maximum depth of approximately 23 meters which occurs in the northern portion of the basin. The primary input into the bay is Irondequoit Creek and the outlet is into Lake Ontario. Severe eutrophication was common from the early 1900's until the mid 1980's when external P loading was reduced from 286 kg/day to approximately 60 kg/day and an alum treatment was completed. Continued management of the bay includes hypolimnetic oxygenation to prevent P solubilization from deep sediments. Previous studies have focused on only the deep basin sediments. In this study we investigate the relationships between sediment P concentrations and various sediment and hydrologic properties of the system, including particle size, water depth, proximity to stream discharge point and the overall structure of Irondequoit Bay. Results indicate that P concentration in the sediment is most closely correlated to Al and Fe content of the sediment with r2 values of 0.71 and 0.68 respectively. Conversely, sediment P concentration was not closely correlated to sediment particle size or proximity to stream mouths. This likely indicates that suspended sediment bound and organic bound P are being preferentially added by Irondequoit Creek and accumulated in the deep basin. The current management practice which focuses on the deep basin sediments will likely to remain successful.