Last Friday, the Paerl Lab gathered together to carve some pumpkins and taste some yummy fall foods such as smoked pecans, apple cake, apple cider donuts, and candy corn!
Our crew was out Tuesday, 13 October 2020. The estuary was stratified with pockets of hypoxic water observed near New Bern at station 30 and near the bend at stations 100 and 120. The fluorescence probe that measures chl-a failed mid-cast at station 140 and all chl-a data upstream of 140 was removed due to meaningless, negative values. A bloom at station 70, however, was indicated by the high near surface DO, observation of brown water color, and clogging of filters back in the lab. The crew observed fish actively dying south of Fairfield Harbor (our station 70) and fish dead on the surface from there to mid-channel north of Slocum Cr. (our station 100). The dominant species in the bloom, the dinoflagellate Gyrodinium instriatum aka Levanderina fissa) is not known to be toxic. G. instriatum is the most common bloom former in the Neuse during the summer and early fall and hasn’t previously been associated with a fish kill. This fish kill appears to have been ongoing since 30 September.
I’m playing catch up again.
Conditions on 18 August were about as stratified as they get in the Neuse. From New Bern to the mouth bottom water salinities were more than 10 ppt greater than at the surface. The pycnocline increased in depth from about 2 meters at New Bern to 5 m at the mouth, and waters below the pycnocline were hypoxic/anoxic along that whole stretch. Overall, chl-a levels were low but there was a broad zone of moderate 10-20 ug/L at the surface that extended from station 60 to station 140. A subsurface, thin layer of chl-a > 40 ug/L was observed at station 70. (image below)
After ~20 kt winds from 14-15 Sep. and continued ~15 kt winds on 16 Sep, the estuary was much more mixed on 16 Sep. There were pockets of stratification and hypoxia near New Bern and near the bend at stations 100 and 120. These pockets of hypoxia were associated with waters that were warmer than surface waters and saltier than downstream bottom waters. It’s not unusual for bottom waters to be warmer than surface waters during the fall as the surface loses heat to a cooling atmosphere. It is weird to see higher salinity upstream, and may reflect cross channel variability that isn’t being captured by our down-channel transect. Chl-a was moderate (10-20 ug/L) from New Bern to the mouth. (image below)
On Monday 28 Sep, the estuary was highly stratified again. Bottom waters were 2 mg/L or less from New Bern to about station 70 and were ~4 or less from station 70 to the mouth. A broad zone of elevated surface chl-a was observed from station 60 to station 140, with a surface maximum of ~40 ug/L at station 100. Downstream of station 100, maximum biomass occurred as a subsurface maximum at 1 to 2 m depth. Two days later on 30 Sep., a fish kill was reported on Flanners Beach. Water from the location of the kill contained high concentrations of the potentially harmful raphidophyte species, Heterosigma akashiwo. Microscopic observation of surface water from station 100 contained very few Heterosigma akashiwo cells. The community was primarily cryptophytes, dinoflagellates, and small diatoms that are typical for this time of year and not known to harm fish. During an unrelated sampling trip on 2 Oct., I observed an ongoing fish kill near the mouth of Slocum Cr. There was a mix of actively dying and menhaden that had been dead for a day or two. I microscopically examined water samples collected from the fish kill area and from the Neuse outside the fish kill area. Low concentrations of Heterosigma akashiwo were present but the low observed concentrations have not been previously related to fish kills. (image below)
The Paerl lab recently conducted another bioassay for IE student Kelly Puente’s research this fall 2020 semester. Even during challenging times, the Paerl lab is conducting exciting research and results about the local area!
Dr. Paerl spoke with Spectrum News about how major storm events are not only becoming more frequent, but precipitation is also increasing. Lasting impacts are observed in waterways as they receive nutrients washed away from the land causing increased and fast algal growth.
Dr. Paerl suggests to “make sure your septic system is working really well. Not over fertilizing your lawns, especially not ahead of a major storm event” to prevent excessive nutrient run-off and algal growth in waters we drink, play in, and enjoy.
The Fall 2020 issue of Coastwatch (NC Sea Grant magazine) features some of the long-term water quality research performed in the Paerl lab. The article, titled “Science Needs You“, highlights the necessity for research of the second largest estuarine complex in the United States and how you can help accomplish the goal of continued research to track the health of the Neuse River Estuary. Whether you live locally or visit the area’s beaches or protected forests, you can make an impact to improve the land and water we enjoy!
This article features a chapter from Dr. Paerl’s water quality monitoring book, North Carolina Science Adventures for the Everyday Explorer: Thirty Great Places to Learn About Environmental Science in Our State. Check it out for other fascinating information about the Neuse River Estuary region!
Big THANKS to NC Sea Grant for highlighting our important work!
The Paerl lab conducted a bioassay from the Chowan area this week headed by graduate student Malcolm Barnard (front left)!
Exciting results to come! Stay tuned to Malcolm’s website for updates and future publications!
Welcome UNC-IE student Kelly Puente! Kelly will be working in the Paerl lab during the Fall 2020 semester conducting exciting research. Stay tuned!
Good-bye Wei Jin! The Paerl lab has had the pleasure of having visiting Phd Student, Wei Jin, from China for the past two years. We are sad to see you go and wish you the best as you finish your degree back home. Safe travels!