The recent dry conditions have allowed salinity to creep up to New Bern in the bottom waters. The estuary is still highly stratified from New Bern downstream to station 120. True anoxic conditions occurred from New Bern to station 100, just upstream of the bend at Minnesott/ Cherry Branch. Bottom waters in this area smelled strongly of sulfur indicating that there was essentially no oxygen present. Elevated chlorophyll a occurred at the surface at station 50, and as a subsurface chlorophyll maximum downstream to station 120. Microscopic observation of surface water from station 50 indicated the bloom was a mix of small centric diatoms and nanoflagellates. The nanoflagellates were hard to identify but their morphology wasn’t consistent with any types of particular concern, e.g. toxin producing dinoflagellates.
Check out the UNC “In Pursuit” article titled “Algal Blooms Pose Possible Respiratory Threat” featuring our own Haley Plaas, PhD student in the Paerl Lab! We are so proud of Haley for coordinating this as the bloom activity in eastern NC begins to heat up and for rocking her first public interview!
The estuary is extremely well stratified from New Bern to the mouth. The salinity difference is the major driver of the stratification, but a temperature difference of ~4 degrees C is playing an unusually strong role in reinforcing the stratification. Bottom waters were hypoxic from New Bern to the mouth. There were no reports of rotten egg smell from the bottom waters. So the bottom waters were probably hypoxic rather than anoxic. A zone of high surface chlorophyll occurred from New Bern (station 30) to where the estuary widens at stations 60 and 70. From there downstream there was also a subsurface chlorophyll maximum along the pycnocline. I haven’t looked to see what was blooming.
PhD student Haley Plaas worked with Chowan-Edenton Environmental Group to sample a recent bloom on the Chowan River. Big thanks to this local community science group!
Haley sampling the Chowan River during her fellowship work with @seagrantNC. Notice the coloring of the water sample! (Twitter: @HABhaley)
Aerial image of the Chowan River sampling site. I am seeing a lot of green!
Photo credit: Abe Loven
PhD student Malcolm Barnard was sampling a bloom on the Chowan River this morning. Check out his photos as well as the latest LANDSAT image of the bloom.
Photo credit: CyanoTRACKER
Take a few minutes to watch, PhD student Haley Plaas (ESE) totally nailed her first tv interview!
Algal Blooms in ENC
The estuary looks almost exactly like it did two weeks ago. The upper region above New Bern is very turbid as flows are still much higher than normal for this time of year. Surface waters are basically fresh to near the bend at Cherry Branch. The tip of the salt wedge is at station 50 just downstream of the HWY 17 bridge and the estuary is highly stratified ,and bottom waters were hypoxic from station 50 to the mouth. A broad zone of elevated chlorophyll a occurred from stations 100 to 160. Depth-wise the high phytoplankton biomass was maximum at about 1 m depth. This vertical patchiness is a tell-tale sign that the phytoplankton producing the peak is likely a flagellate seeking optimum light levels for photosynthesis. Our surface sample is collected at 0.2 m and missed the peak. I suspect it’s probably still an ongoing bloom of Gyrodinium instriatum.
The estuary continues to freshen with the 2020 spring deluge. Surface water salinity at station 140 near Oriental is only about 5. The tip of the salt wedge is still just below New Bern at station 50, and the estuary is highly stratified from there to the mouth. Bottom waters were hypoxic from station 50 to 140. A broad surface bloom extended from station 60 to 120. This is likely the same dinoflagellate bloom of Gyrodinium instriatum from two weeks ago. I’ll take a look when I’m in the lab next and will post a correction with the next report if I’m wrong. With the rain still falling, the estuary will likely stay very fresh, and the hypoxic zone may expand without some serious wind mixing.
Dr. Paerl and PhD student Malcolm Barnard have collaborated on a paper that was published in Harmful Algae! Click the link to read their paper.
Paerl and Barnard 2020