Phosphorous

During five years of monitoring, thirty percent of total phosphorus measurements on the lower Kenai Peninsula salmon streams have exceeded EPA’s recommended level (0.1 mg/L).  Phosphorus is a nutrient that is important to aquatic life, but at high levels it is considered a contaminant.  High levels of nutrients can cause increased algal growth beyond what is normal and impact the quality of the water, particularly by removing dissolved oxygen.

Inletkeeper Strategies

Intensive phosphorus, turbidity, and discharge sampling took place in September 2005 and May 2006 from headwaters to river mouth in the Anchor and Ninilchik Rivers to determine if there are sampling locations that suggest a major tributary is contributing a disproportionate amount of phosphorus and to determine if phosphorus levels are related to geology or land use.

Since phosphorus binds easily to sediments, data analysis in 2005/2006 focused on the relationship between phosphorus values and turbidity levels. Total phosphorus increased consistently with higher turbidity levels.  Total phosphorus increased above EPA’s recommended levels with turbidity levels above 5 NTUs. These results suggest that elevated phosphorus levels may be due to the volcanic origin and sedimentary geology of the region.

A comparison of the total nitrogen to total phosphorus molar concentrations (TN:TP) indicates that primary productivity in Ninilchik and Anchor Rivers is limited by nitrogen availability due to the high ambient phosphorus concentrations.  Anthropogenic sources of nitrogen therefore have a greater likelihood of increasing primary productivity to levels that could be detrimental to stream health. Potential sources of nitrogen additions are sewage, wastewater effluent, logging and lawn debris, and deposition from the atmosphere.

Future Work

Monitoring will continue to track nutrient levels in these salmon streams.