| Popis: |
Sulfate, nitrate, and phosphate are the primary contaminants that contribute to harmful algae blooms (HABs) in Lake Erie. Combined with sunlight, and the warm, shallow waters of Lake Erie’s western basin, photosynthetic blue-green algae (cyanobacteria) can flourish. Previous work has established Lake Erie’s western basin as a point of origin for HABs due to its bathymetric properties and its proximity to the mouth of the 220 kilometer long Maumee River. The Maumee originates in Ft. Wayne Indiana and flows northeast through agriculture dominated counties and numerous urban areas until it drains directly into the western basin. Along its flow path, the Maumee accumulates large amounts of contaminants from agricultural fertilizers, urban runoff, and bedrock geology. This research quantifies the contaminants present in the water and sediment of the lower ~60 miles of the Maumee River from June to December, 2018, through water quality monitoring at seven sampling points. Each contaminant studied exhibited unique concentration patterns over time and appeared to respond differently to precipitation events providing some indication of their sources. In the case of nitrate and phosphate, there was high variability in their concentrations and they seemed to respond to precipitation events. Concentrations of sulfate, on the other hand, were less variable, which suggest sulfate mineral deposits in Silurian sedimentary units are contributing sulfate into the system. The results of this study have shown relationships between many of the measured parameters in the water such as the correlations between dissolved oxygen (DO) in the water, organic matter (OM) in the sediments, pH, and phosphate concentration in the water. The data have shown that as OM increases, DO and pH decrease due to OM decomposition which releases CO2. With regard to phosphate, it is more soluble in lower pH waters and is one of the fundamental nutrients that fuel HAB development. The low solubility of phosphate minerals and their accumulation in the river sediments suggests that changing pH and redox conditions can put phosphate in solution even during periods where there is not considerable input from the tributaries. The input of contaminants into the western basin is not the only factor to consider with regard to HAB’s. Wind, water temperature, and currents combined with contaminant concentrations determine the presence and severity of HAB’s in Lake Erie each year. |
