Category: Uncategorized (Page 2 of 7)

IE Student Projects Kickoff!

Today the Paerl lab kicked off a third bioassay in collaboration with the Zhao Research Group at NC A&T, which is focused on determining the water quality impacts of landfill leachates (to learn more about this project click here). IE student Meg will be building off of this bioassay for her Independent Research Project and will be determining the effects that these leachates have on algal communities and their composition over an extended period of time. We are looking forward to seeing the results of her project!

Neuse River Estuary Conditions – 24 August 2022

Hi all,

Flows on the Neuse River have increased some and have fluctuated around the seasonal norm since the beginning of August. The estuary is still really salty though. Surface water salinity at station 180 was 24.2, a 99% value for the ModMon dataset. The recent modest freshwater inputs haven’t changed that situation much but they are helping to maintain strong stratification in the upper parts of the estuary. From station 20 to 70, surface to bottom salinity differences are about 10 and the bottom waters are anoxic. The crew reported a strong sulfide smell and the water in sample bottles was bright orange from oxidation of free dissolved iron. There was a broad zone of elevated chlorophyll from station 30 to station 120. Throughout most of this zone, the chlorophyll maximum occurred at 1 to 2 m depth. At station 120, the maximum was at the surface. I examined samples from station 50 and 120. Station 120 had a typical mixed bag of cryptophytes, small diatoms, and several medium to large dinoflagellates including Scrippsiella trochoidea, Levandarina fissa (aka Gyrodinium instriatum), and Pheopolykrikos hartmannii. Station 50 was dominated by tiny, ~4 um diameter centric diatoms, but also had a few Levandarina fissa, cryptophytes, and small chlorophytes. Turbidity at the head of the estuary was about 7 NTU. At station 30 and 50 there was a zone of elevated bottom water turbidity with a subsurface turbidity maximum > 10 NTU along the pycnocline. This happens occasionally when the bottom waters are truly anoxic. I think it results from chemical precipitation of reduced iron as oxic and anoxic waters mix.

I hope everyone enjoys a safe Labor Day weekend.


Welcome Meg and Madison!


         Meg McCartney                    Madison Milotte (they/them)

The Paerl Lab welcomes two Field Site students, Madison and Meg, from UNC main campus for the 2022 Fall Semester! These students will work on independent projects in order to learn more about coastal environmental microbiology. We are very excited to work with them this semester!

Neuse River Estuary Conditions – July 12 & Aug 3, 2022

Hi all,

Prior to sampling on July 12, the Neuse basin had some substantial rain and river peaked on July 12 and 13 at about 4 times the seasonal average. On July 12, the main impact seen on the estuary was freshening of the upper estuary where low salinity water <5 extended downstream to stations 60 and 70. On the previous sampling on June 15, surface water salinity at these stations was ~10. High turbidity, 10 -15 NTU also resulted from the high flow. The estuary was stratified from New Bern to the mouth and bottom waters were hypoxic along that distance. As on June 15, there was a small subsurface maximum of chlorophyll a occurred along the pycnocline at stations 30 and 50. Microscopic examination of station 50 surface water showed the dominant organism was the same as on June 15, the dinoflagellate Levanderina fissa.

The high flows of mid July were short lived and there was hardly any rainfall in the basin in the 2 weeks prior to sampling on 3 August. Conditions on August 3 were nearly identical to those on June 15. Surface salinity at station 60 was about 10 and surface salinity at the mouth was greater 20. Bottom water salinity at the mouth exceeded 25. Stratification was strong upstream near New Bern and moderate in the mid and lower estuary. Hypoxic conditions (< 2 mg/L) occurred in the upper estuary from station 20 to 50. The only area of high chlorophyll was the subsurface patch of high biomass that has apparently persisted at stations 30 and 50 all summer.  The sample was again dominated by the dinoflagellate Levanderina fissa but it also contained a diverse mix of diatoms, cryptophytes, chlorophytes, and other dinoflagellates. None of the mixed assemblage are known to be problematic with regard to toxins and fish kills.

I hope everyone enjoys the rest of the summer and stays cool.

Best regards,



Paerl Lab Photo

The Paerl Lab took a lab photo last week in front of IMS’s brand-new mural!

Pictured from left to right:

Back Row

Maxfield Palmer, Hans Paerl, Jeremy Braddy, Haley Plaas, Nathan Hall, Mingying Chuo

Front Row

Madison Sholes, Alex Sabo, Karen Rossignol, Leah Nelson, Randy Sloup 

The Hall Lab, who we often collaborate on projects with, also got a lab photo.

Pictured from left to right: Maxfield Palmer, Nathan Hall, Mingying Chuo

Investigating Associations between Air and Water Quality in Eastern North Carolina

This past week PhD student Haley Plaas and intern Madison Sholes deployed PurpleAir Sensors at pre-established sites along the Chowan River, where Cyanobacterial Harmful Algal Blooms (CHABs) are known to occur. In recent years, communities in northeastern North Carolina surrounding the Chowan River and Albemarle Sound have faced degraded water and air quality tied to a suite of environmental issues, including increased incidences of toxin-producing harmful algal blooms. Previous work done by Plaas et al. found that several aquatic cyanobacterial genera were detected in sampled particulate matter (PM), including two toxin-producing strains, Dolichospermum and Microcystis. These findings suggested a need for further research on the link between HABs and HAPs, i.e., the presence of Harmful Air Pollutants, in this region. The goal of this project is to investigate the association between indicators of CHABs and corresponding PM mass concentrations via the deployment of several PurpleAir sensors throughout the Chowan River and Albemarle Sound basin.

Haley and Madison deploying sensors in the field:


Photos taken by: Tom Brennan

Research in the Bay Delta, CA

The Paerl Lab was in the Bay Delta, California last week to kick off Haley Plaas’ PhD thesis research, which focuses on assessing the linkage between nutrient enrichment, phytoplankton community composition, cyanobacterial harmful algal bloom toxin production, and aerosol formation in the Sacramento-San Joaquin River/Bay Delta estuarine ecosystem. Research Technician, Leah Nelson, accompanied Haley to California where they met up with Seyong, who is one of the Paerl Lab’s summer interns. The bioassay went off without a hitch! We saw surface scums of cyanos at both of our sample locations, Discovery Bay and Stockton. Upon filtering toward the end of the week it appeared as if the P and N+P treatments responded the most, suggesting P limitation at both sites. Early aerosol findings showed Microcystis and other cyanobacterial cells collected from the air. The data will tell us soon, so stay tuned! We want to thank our collaborators at CA-DWR, USGS, and Restore the Delta (and more)!


Neuse River Estuary Conditions 15 June, 2022

Hi all,

As I’m sure you’re all aware, it’s still really dry. The Neuse River flow is less than half its seasonal norm. Salinity is still high along the estuary and salinity is >20 in the surface waters near the mouth. The tip of the salt wedge is still upstream of New Bern. The estuary is moderately stratified with surface to bottom salinity differences of ~8 at station 30 to ~ 2 at station 180. Warm bottom water temperatures (> 25 C) and stratification promoted hypoxia (< 2 mg/L) from stations 30 to 120 and even the lower stations had bottom water DO < 4 mg/L. A small subsurface maximum of chlorophyll a occurred along the pycnocline at ~ 1.5 m depth at stations 30 and 50. Microscopic examination of station 50 surface water revealed a phytoplankton community dominated by the summer bloom forming dinoflagellate, Levandarina fissa (formerly known as Gyrodinium instriatum). Its not known to produce toxins and hasn’t been associated with fish kills.


Neuse River Estuary conditions 31 May, 2022

Hi all,

We finally got some rain in the basin on 26 May that sent river flows to nearly twice their seasonal norm. On May 31, the estuary was still really salty though. The salt wedge was upstream of New Bern and bottom water at New Bern (station 30) was ~ 10. Surface salinity at the mouth of the estuary was ~20. Water temperatures ranged from low 20s C in the bottom waters to nearly 30 C at the surface. The strong temperature gradient reinforced the vertical density gradient caused by salinity. Surface to bottom salinity differences ranged from about 10 upstream to 2 at the mouth. Hypoxic bottom water conditions were observed from the tip of the salt wedge at station 30 downstream to station 160. A subsurface zone of elevated chlorophyll (~40 ug/L) occurred at ~ 1 m depth at station 50. Microscopic observation of station 50 surface water indicated the phytoplankton community was dominated by small centric diatoms and cryptophytes. Generally, both small centric diatoms and cryptophytes are highly edible fuel for the estuarine food web. Elevated turbidity (15-20 NTU) at the freshwater head of the estuary is indicative of the elevated discharge conditions.


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