Late winter has been unusually warm and water temperatures in the estuary are about 5 C warmer than normal. High salinity conditions are still in place with salinity near 20 at the estuary mouth. The tip of the salt wedge is still upstream of New Bern. No hypoxic bottom waters were observed. Super saturated oxygen conditions were observed near the surface at station 60 where high chlorophyll (>40 ug/L) indicated a bloom. The intense surface bloom at station 60 was part of a broad region with high (~25 ug/L) subsurface chlorophyll that stretched from station 50 to 120. Microscopic examination of station 60 surface water revealed a mix of the winter/spring bloom forming dinoflagellate, Prorocentrum minimum, and a Euglena sp. These are the same two species that were found blooming in the same area in February. Neither is thought to be problematic in regards to toxins and fish kills.
Come work with the Paerl lab at UNC Chapel Hill’s Institute of Marine Sciences.
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The Neuse River basin had several significant rainfall events prior to the 7 February sampling event and salinity in the upper estuary responded strongly. Surface salinity was < 5 downstream to station 60 and the tip of the salt wedge was between stations 20 and 30. Salinity in the lower estuary dropped about 5 units since January also. The freshwater pulse also caused high turbidity (>10 NTU) at the head of the estuary. Temperature was seasonably cool (8-10 C). Dissolved oxygen was well above levels required for the health of fish and other animals. However, the bottom water dissolved oxygen at station 30 was atypically low (~ 5 mg/L) for this time of year. Strong suppression of mixing caused by the > 10 salinity difference from the surface to bottom layer led to the oxygen sag even though respiration rates were surely very slow in at such cold water temperatures. A localized surface bloom at station 60 was caused primarily by very high densities of a Euglena sp. and secondarily by the dinoflagellate, Prorocentrum minimum. Neither have been linked to fish kills or other toxicity issues in North Carolina.
The Delta Science Program would like to share that the 2022 edition of the State of Bay-Delta Science (SBDS) is now online in the latest issue of San Francisco Estuary and Watershed Science. Seven articles comprise the issue, summarizing the scientific understanding, or “the state of the science,” of plants and algae in the Bay-Delta. Individual articles explore important ecosystem services and disservices, including primary production, the ecology and management of aquatic vegetation, remote sensing methods, harmful algal blooms, and carbon sequestration and subsidence reversal.
Visit the SBDS website to learn more about this ongoing synthesis effort.
Interagency Ecological Program
IEP@wildlife.ca.gov | 2109 Arch Airport Road, Stockton, CA 95206
To learn more about the work that we are doing through ModMon and FerryMon please view our 2022 updates contained in the flyers below!
Here’s an update on the conditions during the first trip in 2023. The estuary was still extremely salty with surface salinity near the mouth well above 20. An oyster farmer friend measured a salinity of 28 in a creek near Bay River. We did have a little rain associated with a strong Christmas time cold front. The salt wedge still extends upstream of New Bern but higher flows have pushed the salt wedge downstream of Streets Ferry Bridge. The water is seasonably cold, < 10C. Dissolved oxygen conditions were normoxic throughout the estuary. Elevated turbidity (>10 NTU) at the head of the estuary likely resulted from higher flows. A subsurface chlorophyll maximum extended from station 30 to station 120 at ~1.5 m depth. Examination of station 50 surface water revealed numerous Prorocentrum minimum cells. Prorocentrum minimum is a shade adapted species that commonly forms subsurface maxima at low light levels. I bet that the observed subsurface chl-a maximum is the beginning of the nearly annual late winter/early spring bloom of Prorocentrum minimum. P. minimum isn’t known to produce toxins/ kill fish but it has been shown to cause problems with oysters. Fortunately, the area where it tends to bloom is too fresh for oysters anyway. The crew plans to be out again later this week and we’ll see how the bloom’s developed.
Join us in congratulating the Paerl Lab’s Ph.D. student, Haley Plaas on winning the UNC Graduate School’s 2023 Impact Award!
“This year’s Impact Award recipients are creating new knowledge in order to respond to our society’s greatest challenges,” said The Graduate School’s Dean Beth Mayer-Davis. “In a state where the workforce and intellectual ecosystem continues to advance, we need graduate student research to help us continue to prosper. It’s all part of how we serve our state.”
Haley’s research explores the potential threat harmful cyanobacterial blooms pose to human respiratory health and air quality and has accomplished just that. Check out more information on her website! Congratulations Haley!
Happy New Year!
Through mid-December river flow continued to be very low. The high salinity record (11.9) that was set at station 0 (Streets Ferry Bridge) in late November was smashed by a 13.4 reading at the bottom on 14 December. The rest of the estuary was really salty too with bottom waters at the mouth near 25. The upper estuary was strongly stratified based on salinity. In the upper estuary (stations 0-30) bottom waters were 3-4 degrees C warmer than surface waters and dissolved oxygen was lowest (~ 4 mg/L) in these warmer, isolated bottom waters. For the rest of the estuary, dissolved oxygen was 8 mg/L or more. Chlorophyll was 10 ug/L or less except near the surface at station 50 where chlorophyll was ~25 ug/L. Microscopic examination revealed the peak in phytoplankton biomass at this station was due to a combination of small cryptophytes and the cool-weather dinoflagellate, Heterocapsa rotundata. These phytoplankton haven’t been associated with fish kills or toxin production. We finally got some rain associated with the strong cold front before Christmas. I imagine that the high salinity upstream of New Bern has probably been pushed downstream. I think we’ll find out next week if the weather cooperates.
Overall, river flow during the fall has been very low and high salinity is still firmly in place. On 29 November, salinity still exceeded 20 in the lower parts of the estuary. The estuary was weakly stratified except in the upper estuary where the difference between surface and bottom salinity was approximately 10. At the head of the estuary at Streets Ferry Bridge (station 0), bottom water salinity set an all time ModMon record of 11.95 beating the previous record of 11.27 set in Dec. 2007. Dissolved oxygen was > 8 mg/L except in the highly stratified wates at Streets Ferry Bridge where bottom water dissolved oxygen was ~ 3 mg/L. Chlorophyll was generally less than 10 ug/L throughout the estuary with the exceptoin of a near surface maximum at station 30. Microscopic examination of station 30 surface water revealed a phytoplankton community dominated by the dinoflagellate, Prorocentrum minimum. P. minimum is the most common cool-weather, bloom-forming dinoflagellate in the Neuse. It’s not toxic and hasn’t been associated with fish kills. Turbidity was less than 5 NTU throughout the estuary. The monitoring crew is on the Neuse again today, so we’ll provide one more summary of conditions before the holiday break.
The Paerl Lab’s Ph.D. student, Haley Plaas, and Dr. Paerl received an award for the Best Critical Review of the year in 2021 in Environmental Science & Technology for their article titled Toxic Cyanobacteria: A Growing Threat to Water and Air Quality! A link to their award and the article can be found below. Join us in congratulating Hans and Haley on this fantastic achievement!
2021 Award Letter EST