Author: lacrocem (Page 1 of 3)

Hi all,

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.

Best regards,

Nathan

Hi all,

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.

Best regards,

Nathan

Hi all,

The estuary is fresher now due to all the rain from Arthur and Bertha but the tip of the salt wedge still extends almost to New Bern. A strong pycnocline occurred at about 4 m depth at stations upstream of station 120 and at about 5 m at the lower stations. Bottom waters were hypoxic (< 2 mg/L) at station 50 -120, and were <4 mg/L at the lower stations. There was a zone of high surface chlorophyll from stations 70 to 120. Microscopic examination of station 120 surface water where chlorophyll was greatest showed that the bloom was dominated by the dinoflagellate, Gyrodinium instriatum (more correctly known as Lavanderina fissa). This dinoflagellate is our most common summer-time bloom former in the Neuse and is not known to produce toxins. The other phytoplankton in the sample were a mix of cryptophytes, small diatoms, and smaller dinoflagellates.

Nathan

Hi all,

Since I’ve last reported on conditions in the Neuse River Estuary our world has changed a lot more than it has. Nothing exceptional to report water quality-wise. The high chl-a at stations 120 and 140 during March were likely remnants of the dinoflagellate bloom noticed in February. I’ll find out once I’m able to get back to the lab. Y’all stay safe and well.

Best,

Nathan