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Cook Inletkeeper
Salmon Stream
Monitoring Program
Phosphorus
BACKGROUND
In the past 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.
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