OCR Text |
Show loading to the lake. In- lake diking greatly influences the distribution of nutrients. The Davis County Causeway restricts water exchanges between Farmington Bay and the south arm. Because natural and anthropogenic loading into Farmington Bay is high, it is extremely productive and would be classed as eutrophic ( Wurtsbaugh, 1995). Similarly, Bear River Bay receives a large portion of inflowing nutrients from the Bear and Ogden Rivers, but measurements of nutrients and biological productivity have not been made. The northern railroad causeway influences nutrient distribution in the lake in two ways. As with the conservative major ions, nutrients are transported to the north arm, depleting the more productive south arm. Although limited measurements of nutrients have been made in the north arm, the limited available data ( Sturm, 1980) found that nutrients there were often double the concentration of those in the south. However, limited bi- directional flow may also create a trap for nutrients in the south arm. When dense underflow of highly saline water occurs, this layer does not mix readily with the overlying layer as prior to 1991. Sedimentation of phytoplankton and zooplankton carries nutrients into the deep- brine layer, thus removing them for months to years from the biological cycle. Phosphate, ammonia and total nitrogen and phosphorus concentrations in the deep brine layer were 10- 100 times higher than the overlying, less- saline water ( Wurtsbaugh and Berry, 1990), but it is not clear to what extent this difference was due to sedimentation of nutrients from the overlying water, and how much was due to the bi- directional flow transporting nutrients back from the north arm. The amount of nutrient loading for the lake has not been determined. Excessive removal of nutrients would result in decreased brine shrimp and brine fly production and thus impact the bird community reliant on these food resources. Conversely, excessive nutrient loading from sewage and agricultural wastes entering the lake could produce intense and noxious blooms of algae that could be detrimental. The concentration of nutrients in Farmington Bay and the resulting biological production have produced eutrophic conditions that contribute to the odor problems in this area. Other salinity, chemistry and hydrology issues raised by the Scientific Review Committee are addressed in Appendix I. 52 |