Dana Nieuwkerk: University of North Florida (Jacksonville)

Dana Nieuwkerk: University of North Florida (Jacksonville)

Two days in and we have already been to the beach and on the boat! We spent Memorial Day at multiple beaches, studying inlets, sand dunes, and the effects shifting inlets have on dynamic beaches. At St. Augustine Beach, we saw the longshore current and how its wave action causes the beach to be steep in the winter and flat in the summer. 

Example of a drop dune, caused by wave action

The St. Augustine Inlet is barricaded with jetties, so that it will not shift, making it an ideal habitat for barnacles. It was bizarre to see the shifting of the inlets, drastically increased by the dredging of St Augustine Inlet (which displaces sediment), and the shifting inlets effect on development. At the Ponte Vedra beach, a bridge was built to be over the water but because the inlet shifted, the bridge is mostly over beach with a 30-ft stretch being over water. When construction started, it was thought the inlet would shift in the opposite direction. 

An extensive section of the bridge that was supposed to be over water; due to inlet migration, it exists over sand.

Small portion of the bridge that is actually over water.

There were also beachfront houses affected by the shifting inlet; the inlet closed off a waterway which eventually dried, causing boat ramps to turn into porches on the sand. 

A boat lift and dock that used to be on/over the water. Closing-off and drying of the inlet turned the dock into a detached porch. 

The dried sand allowed other habitats to form, including sand dune building plants and fiddler crabs. 

Fiddler crab holes!

Female fiddler crab, notice it does not have the large claw that is a signature of males.

A storm even wiped out the road that used to exist on the beach, which was then covered by sand from the inlet, forcing A1A to be pushed further back. The road ends at the houses and is barricaded by riprap rocks, which act as an armor to stabilize the sediment. 

Riprap rocks stabilizing sediment to prevent erosion.

We noticed the sand was mostly calcium carbonate from the coquina. The coquina compresses and dehydrates as it is pushed further up the beach, which we were able to witness at the beach of Marineland, FL. 

Lunch on the coquina rocks!

Tide pools are formed in the coquina colonies, in which we found starfish, snails, barnacles, algae, crabs, sergeant majors, gobe, and shrimp. The diversity was incredible within the confined spaces.

 

One small tidepool in the coquina rock formation.

During our boat day we were able to test water quality throughout the St. John’s River, from the river basin to the delta! 

Dana and Cara ready for a day of sampling!

We used the YSI to measure conductivity in the water, allowing us to retrieve measurements of salinity, temperature, and D.O. concentration as a percentage and in mg/L. We did a preliminary turbidity test using the secchi disc and took top and bottom water samples, collecting the bottom with a Vandorin bottle. 

Dr. Smith explaining the YSI

Layna and Heather using the YSI

Our teammates taking water samples near downtown Jacksonville.

Once we got back to the lab, we were able to run tests on our collected samples using a vacuum pump to filter out chlorophyll, and a colorimeter to determine color (in platinum units) and turbidity, and we used the fluorometer to determine chlorophyll a. 

Danielle learning how to operate the colorimeter.

I really enjoyed observing zooplankton (captured during plankton pulls) in the microscopes. 

Zooplankton (fish larvae) found in one of the phytoplankton pulls.

We saw the importance of uniformity in sampling when we saw several discrepancies between the water samples collected from both boats; we later realized it was because one boat was taking surface water samples while the other was taking bottom water samples. It is interesting how much the data changes from the top to the bottom of the water column; the turbidity and chlorophyll a measurements were higher at the surface of the Buckman Bridge collection, however both were lower at the surface (than the bottom sample) in the Mayport samples. This may have been caused by a discrepancy in sampling technique, as sediment may have been stirred while collecting the sample. Jesse was our boat driver for the day and her research is in dolphin socialization of the St. John’s River, it was really fun and exciting to see so many dolphins swimming among us in the river and to have someone so knowledgeable providing us information!