Indian River Lagoon Experiments-IRLEX 2012

During the week of July 23-July 27, 2012, Dr. Robert J. Weaver, a faculty member with FIT Ocean Engineering and his friend and colleague from the University of South Alabama (USA), Dr. Bret Webb, conducted a field experiment in the Indian River Lagoon (IRL), IRLEX 2012.  The experiment consisted of three days on the water using Dr. Webb’s surveying instrument, the Jag Sk, named for the USA mascot.  On the first day Dr. Weaver was getting familiarized with the Personal Watercraft Platform.  The two took turns sampling the surface water quality in the lagoon along a zig-zag transect from Sebastian up through the Haulover Canal and into the Mosquito Lagoon, a total trip length of 166.7 km.  Sampling the surface water every twelve seconds, measurements of Oil, Fuel, Dissolved Oxygen (DO), Chlorophyll a (Chl a), Salinity (S), Temperature (T), pH, and Colored Dissolved Organic Matter (CDOM) the 7 hour duration of the trip.  Along the way the path included water quality stations that are regularly sampled by the Saint John’s River Water Management District (SJRWMD).  The researchers were able to see signs of the algae bloom in the northern IRL that extended into  Mosquito Lagoon.

On Day 2, the researchers conducted an ADCP survey of Sebastian Inlet.  The inlet is a relatively narrow inlet with high velocities at both ebb and flood.  In the image to the right, Dr. Weaver is getting started on his first 3 hour shift in Sebastian Inlet. The researchers would like to thank the friendly folks at the Sebastian Inlet State Park for allowing us to use their park as the survey base, and set up our RTK GPS system beside the South Jetty.

In Sebastian Inlet the current was very high at times greater than 2.5 m/s.  Between the current speed and the many boaters making their way in and out of the inlet, the day was filled with some tense moments.

The RTK base station was set-up close to the survey area to provide the most accurate positioning possible.  In the image to the left Dr. Weaver is preparing to start the first transect in the series of three.  This is the farthest point from the base station, and the closest to the mouth of the inlet.

Below the transects have been added to a Google Earth image of the Sebastian Inlet region.  The green arrows indicate the transects where ADCP data was collected. The orange squares indicate locations where CTD casts were to be made using the YSI Castaway CDT profiler.  Unfortunately due to the high boat traffic and high current velocities, CTD casts were more often than not deemed too dangerous and fewer casts were made than originally planned.

On Day 3, an ADCP survey of the inlet at Port Canaveral was performed.  The friendly folks at the Port Canaveral Jetty Park, allowed us to stage our survey from their jetty pier.  It was very convenient with facilities and snacks right there on site.  Again we surveyed along three transects across the inlet.  The nearly non-existent current at this site was a very interesting contrast to  the previous days survey; however we did have to stop a couple of times to let some very large ship pass through the channel.

In the image to the left, Dr. Weaver is collecting data along on of the transects in Port Canaveral Inlet.  The absence of a strong current at this location is evident.  The surveying on this day was a much more relaxed than the experience in the high flow conditions of Sebastian.  The presence of the lock separating Port Canaveral from the IRL play a big part in the  flow at the inlet at the port.

Below is a Google Earth image of Port Canaveral Inlet with the transects indicated.  Again the green arrows indicate the transects where ADCP profiles were recorded.  The orange squares indicate locations were CDT casts were to be taken.  Unlike Sebastian Inlet, there was far less boat traffic here, and the current was negligible.  Both operators were able to obtain frequent CTD casts.  Just as within Sebastian Inlet, the PSK was in continuous operation, collecting WQ data for the entire duration of the survey.  High Chlorophyll levels were indicated around the South Jetty beginning just after ebb and for the duration of the flood cycle.


 On Friday it was time for Dr. Webb to head back to Alabama.  We have begun the post-processing of the data collected over the three days in the field.  We will be posting more as the data processing progresses.

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