Water Quality Profiles
The NBC collects supplementary water quality profiles at six stations throughout the Upper Bay, from Phillipsdale Landing to Conimicut Point. A profile is a cross-sectional view of the water column and describes the conditions at each depth. The stations are monitored twice per month for depth, temperature, salinity, dissolved oxygen, density and PAR (photosynthetically active radiation) using a Seabird Electronics profiler. This data has been collected by the NBC at these six stations since 2006. Once on the station, the profiler is turned on and allowed to warm up for approximately 2 minutes. After the profiler is acclimated, the profiler is slowly lowered to the bottom, collecting data every quarter a second and internally logging it.
Once the sampling day is complete, the data is uploaded to a computer and backed up. On the computer, the data is separated into individual station profiles and checked for false readings. Prior to graphing the data, it is often smoothed out by averaging all the values in a given depth range to represent a single value. This assists in managing the large amount of data gathered, so it can then be plotted verse depth to show the water column conditions (as shown below). The water column profiles are important in identifying when poor water quality conditions, such as hypoxia, exist. The profile plots also indicated if stratification of the water column is present, which could lead to a hypoxic events.