Poster Session: Understanding the Ways of the Water

Phytoplankton are essential to aquatic ecosystems but can cause concern when at abnormal concentrations. The Grand Bay National Estuarine Research Reserve (GNDNERR) has occasionally experienced wide ranges in water quality parameters, elevated nutrient levels, and algal bloom events. Since exponential increases in phytoplankton can signal changes in estuary condition and lead to negative downstream impacts (e.g., hypoxia), it is important to monitor local phytoplankton assemblages and identify trends between particular phytoplankton populations and water quality metrics. From September 2023 through August 2024, monthly surface-water samples and water quality data (i.e., temperature, salinity, specific conductivity, pH, dissolved oxygen concentration, and dissolved oxygen percent saturation) were collected at fifteen sites across GNDNERR. After preserving samples with Lugol's solution, cells were identified through phase contrast microscopy and enumerated using the Sedgewick-Rafter method. More than fifty taxa have been identified, with three documented to be in bloom (>10,000,000 cells/liter) during the sampling period: Chaetoceros spp., Cryptophyceae (class), and Prorocentrum cordatum. Thirteen of the fifteen sites experienced a bloom of one or more taxa during at least one of the study months. This dataset provides a reference for the types of phytoplankton observed within the reserve and how their populations may change based on location in the estuary, time of year, and influences from the surrounding estuarine water condition. Understanding the local phytoplankton community structure will aid resource managers in detecting considerable shifts in phytoplankton abundance, illuminating environmental correlations with these shifts, and determining what ecological and economic impacts may result.

Water quality monitoring is inherently complex and resource-intensive; however, it is essential for enhancing understanding and managing coastal ecosystems. Satellite-based imagery provides an opportunity to have less resource-intensive and broader-scale assessments of water quality. PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) is the first hyperspectral satellite mission designed to monitor water quality, and the Ocean Color Instrument (OCI) onboard the PACE satellite has been continuously providing spectral data (340–890 nm) since February 2024. This capability allows for enhanced monitoring of coastal ecosystems with a spatial resolution of 1 km. Nevertheless, no investigations have assessed the comparability of PACE-based and in-situ measurements. In this study, we evaluated the hyperspectral consistency of PACE/OCI data over coastal aquatic systems in Mississippi Sound. Four PACE/OCI images were acquired at Top-of-Atmosphere (TOA) reflectance, and atmospheric effects were corrected using the 6SV radiative transfer model. In-situ remote sensing reflectance spectra were collected on the same day (n=9) and within a 1-day window (n=28) of the PACE/OCI overpass to validate the hyperspectral reflectance. The spectral bands at the green (502–598 nm), orange (600–640 nm), and red (642–699 nm) wavelengths showed high consistency with in-situ observations, with differences of less than 11% for the same-day dataset and less than 20% for the 1-day difference dataset. Blue bands (452–499 nm) had less than 40% errors for both datasets. Conversely, the red-edge (700–799 nm) and near-infrared (801–852 nm) bands showed significant discrepancies with in-situ observations, with mean errors exceeding 100%. These results suggest that PACE/OCI is highly capable of capturing watercolor features, particularly in the visible spectrum. The discrepancies in datasets around the sensor's overpass time highlight the importance of accounting for spectral dynamics in aquatic environments. 

The Grand Bay National Estuarine Research Reserve (GNDNERR) and National Wildlife Refuge in Mississippi conduct a suite of restoration activities, including prescription burning, selective cutting, and herbicide application, on over 3,000 acres to restore the degraded upland wetlands to Longleaf pine (Pinus palustris) savannas. Although there is ongoing monitoring of these restoration efforts for the upland savanna complex, the downstream effects of these efforts have only recently been investigated. Leveraging the ongoing system-wide monitoring program (SWMP), we aimed to characterize the downstream plankton communities and water quality of the GNDNERR catchment to attempt to quantify the ecological effects of upland pine-savanna restoration activities on downstream communities. Sample sites were located along transects (upper, middle, and lower) within five bayous downstream of a gradient of restoration activities and impacts, coinciding with four SWMP stations. Water column water quality parameters (temperature, salinity, dissolved oxygen, pH, nutrients, chlorophyll-a, TSS) and phytoplankton were sampled and analyzed in-house. The entire array of transects were sampled monthly (WQ and plankton) over the course of a year. We found significant differences between the bayous (Bayou Heron, Middle Bayou, Bayou Cumbest, Bangs Lake, and Alabama) and the locations (upper, middle, lower) within the bayous across the twelve months of this study. Here we present these findings in the context of the restoration activities and land use patterns within the upland watersheds of these bayous.

Chitin is the second most abundant polysaccharide in nature with an estimated 1 billion tons of chitin produced annually, much of it in marine environments. It is a linear polymer of N-acetylglucosamine. Chitin is found in the cell walls of fungi, the exoskeletons of arthropods, the radulae, cephalopod beaks and gladii of mollusks, as well as in some nematodes and diatoms. Significant amounts of chitin are produced in marine environments by crab, shrimp, and squid. Chitin and chitinase enzymes have potential medicinal, industrial and biotechnological applications. For example, chitinases are used to synthesize low molecular weight chitooligomers which are proven bioactive compounds with activities such as anti-tumor, antimicrobial, and immunity modulation. Chitinases and chitin-degrading bacteria can be used as anti-fungal agents by attacking the fungal cell walls which contain chitin. Our goal was to isolate chitin degrading bacteria and characterize their chitinae enzymes. We collected sea water and soil samples from coastal Alabama sites and used them to establish chitin enrichment cultures. Chitin degrading bacteria were isolated on agar plates containing chitin and identified by the formation of clear zones in the agar. Once pure cultures were obtained, we identified the bacteria by PCR amplifying and sequencing the 16S rRNA gene. The chitin degraders belonged to the following genera: Rheinheimera, Enterobacter, Achromobacter, Flavobacterium, Pseudomonas, Acinetobacter, and Stenotrophomonas. Growth assays were performed to quantify growth on chitin. Lastly, the isolates were screened for the presence of chitinase genes by PCR with five isolates testing positive to date. Future work will focus on cloning and characterizing the chitinases from the best chitin degrading bacteria.

The Mississippi Sound is a very productive brackish environment that has historic, cultural, and economic importance for the region. Over the past decades, natural and anthropogenic sources have negatively impacted the Mississippi Sound through hurricanes, oil spills, and influxes of sediment-rich freshwater from various watersheds. Lake Pontchartrain and Mobile Bay, fresh to brackish bodies of water, feed into the Sound, which can additionally contribute to the variability of different water quality parameters. Understanding where and when these parameters vary within the Sound will allow for informed water quality management. This study performed data collection in 25 locations in the Mississippi Sound from Bay St. Louis to Biloxi Bay in different period of 2023/2024 to characterize the seasonal variability of water quality parameters. Surface water sampling and radiometric measurements were performed from 9:00 AM to 1:00 PM during clear-sky days. TriOS sensors recorded water-leaving radiance, sky radiance, and solar downwelling irradiance to estimate water surface reflectance. Other in-situ data (turbidity, pH, dissolved oxygen, conductivity, water temperature) were collected using a YSI 4-probe sonde. Additionally, date, time, GPS location, sky and water surface conditions, Secchi depth, water depth, air temperature, and wind speed were collected utilizing various devices. Eight liters of water from each point are collected, filtered, and analyzed in the lab for colored dissolved organic matter, total suspended solids, transmittance and reflectance, chlorophyll-a, and phycocyanin using spectroscopy. As a result, concentration maps were produced to visualize the spatial and temporal distribution of water quality parameters on the in-situ data. These results demonstrated that the peak turbidity and total suspended sediment concentration occur during summer, while chlorophyll-a and phycocyanin concentrations remained low or insignificant over time. Secchi disk depth showed an increasing trend from the coastline to offshore points. Colored dissolved organic matter values were homogenous and low among the samples. Collection of such data sets can be utilized by other researchers, agencies, and water quality managers to train remote sensing or hydrologic models, identify critical areas for monitoring stations, or target specific watersheds for enhanced management practices.

Excess nitrogen is an ongoing problem in aquatic ecosystems. This nitrogen intensifies hypoxic dead zones and causes increased algae blooms. Current methods of nitrate removal from wastewater require either large scale biological processes or ion exchange resins. Biological systems take up a lot of space and still manage to leave nitrate behind. Ion exchange resins can work for removing nitrate but suffer from affinity and specificity problems that can limit their nitrate adsorption. The use of bacterial nitrate binding proteins offers a new approach to remove excess nitrogen from our wastewater. Additionally, it can offer the possibility of recovering the nitrate once it has been removed. This is not an option with biological systems as they utilize denitrification which removes nitrate from the system in the form of N2. With Ion exchange resins, some can be washed and regenerated, but this requires large amounts of brine to be run through the system. Previous research into phosphate binding proteins showed minimal loss of function after repeated use. This will be done by identifying nrtA genes in Pseudomonas, cloning the Pseudomonas NrtA proteins, and running tests on the protein isolate. In this study we identified nitrate binding proteins in the genomes of 5 Pseudomonas isolates. Two nrtA genes were cloned into an expression vector in order to characterize their nitrate binding capacity. After verifying production of the NrtA protein we will characterize the nitrate binding affinity and specificity of NrtA when exposed to other competitive ions that commonly interfere with nitrate binding by ion exchange resins. Based on previous research into a cyanobacterial NrtA, we expect to see proteins with binding affinities greater than many commercially available resins and almost no competitive interference from other anions.

The objectives of this study are to measure water column and sediment respiration rates as well as benthic nutrient fluxes during different seasons at sites along the Mississippi coast. Sediment pore water nutrient concentrations were also measured to inform nutrient flux models. Respiration rates were measured in recirculating incubation chambers outfitted with Firesting optical dissolved oxygen sensors. Nutrient samples were collected at the beginning and end of each experiment, which lasted until the sediment incubations became hypoxic (10 to 26 hours). Summertime water column respiration rates ranged from 1.5 to 2.8 µmol O₂ L⁻¹ hr⁻¹. The presence of sediments lowered oxygen concentration in the overlying water much more than in incubations with water alone. When normalized to sediment surface area, respiration rates ranged from 220 to 1,700 µmol O₂ m⁻² hr⁻¹. Ammonium (NH4+) and soluble reactive phosphate (SRP) concentrations were low in surface waters and changes in water column incubations were minimal. Conversely, nutrient fluxes from the sediment incubations increased overlying water nutrient concentrations significantly. Benthic NH4+ flux ranged from 9.4 to 530 µmol N m⁻² hr⁻¹, while SRP flux ranged from 1.8 to 46 µmol P m⁻² hr⁻¹. Pore water NH4+ concentrations were as high as 580 µM while soluble reactive PO₄ concentrations peaked at 64 µM. The concentrations of additional parameters (nitrate + nitrite, dissolved organic carbon and total dissolved nitrogen) are currently being analyzed and will also be presented. Spatial variations in respiration rates, nutrient fluxes and correlations with temperature, salinity, organic matter content, will also be examined.

Grand Bay National Estuarine Research Reserve (GNDNERR) was established in 1999 and contains ~18,000 acres of protected estuarine habitat. The reserve is in southeast Mississippi, approximately 10 miles east of the Pascagoula River and 18 miles west of Mobile Bay. This estuarine system has no riverine input and has been cut off from land-overflow by Interstate 10 and the railway that is south and parallel to Interstate 10. The reserve is bordered to the west by Chevron Oil Refinery and the MS Phosphate plant (decommissioned superfund site), to the east by the Grand Bay NWR in Alabama, and to the south the reserve is open to the Mississippi Sound. As a retrograding delta with minimal upland development, GNDNERR offers a unique opportunity to compare long-term trends between the less impacted eastern portion of the reserve, more heavily impacted western portion of the reserve, and more saltwater influenced southern portion of the reserve. In 2005 the reserve began collecting continuous water quality parameters and monthly nutrient samples at four different sites, each representing distinct zones within the reserve. The goal of this study is to quantify spatial patterns and temporal trends of chlorophyll a using 17 years (2006-2023) of water quality data (e.g., pH, dissolved oxygen, salinity, temperature, turbidity) and monthly nutrient samples (e.g., chlorophyll-a, orthophosphate, ammonia) on 4 distinct zones within the estuary: Upper (Bayou Heron), Middle (Bayou Cumbest), Lower (Bangs Lake), and Bay (Point Aux Chenes).