Phase 2- Water Quality Monitoring

The primary goal of this research project is to determine how much water quality is improved by the salt marsh. We plan to do this by calculating a mass balance of nitrogen entering the marsh and leaving the marsh. The difference in the two masses is the amount removed or retained by the salt marsh. To find the mass of nitrogen passing each station requires continuous flow and nitrogen concentration measurements. Continuous flow measurements have been possible for many years now, but long term continuous concentration measurements have not been possible.

Past research has used one of two methods to estimate the amount of nitrogen removed in salt marsh systems. The first method is intensive short term studies, where the flow and nitrogen concentrations are measured continuously for a few days. This gives a good estimate for a few days, but does not take into account how nitrogen input and processes vary throughout the year. Long term intensive monitoring was not practical due to the large costs and labor requirements. The water quality samples had to be collected regularly and carried to a lab for analysis. The other method that has been used is taking daily or weekly samples for multiple years. This method is more likely to show the variation in nitrogen concentrations due to seasonality, but does not show the daily variation due to tidal and storm flow.

Figure 1 (left). Picture of a water quality sampler. These samplers were used to collect water samplers that had to be transported to the lab for analysis.

Using newly available water quality probes, we plan to combine these two methods and intensively monitor the nitrogen concentrations in a salt marsh for at least one year. The new water quality probes allow the water to be analyzed at the site instead of having to be carried to a lab. This will provide a better estimate of the water quality benefits provided by the salt marsh.