Hurricane Harvey made landfall near Rockport, TX (USA) as a Category 4 storm then stalled out over southeast Texas. The storm released ~21 trillion gallons of precipitation over the Houston-Gulf coast region resulting in an extreme flooding event causing increased runoff and river discharge into Galveston Bay. Over the 24 days following Hurricane Harvey, 5 sampling campaigns were conducted in Galveston Bay from the San Jacinto River to the Gulf of Mexico (10 stations). Samples were collected to characterize fluctuations in water quality and microbial communities to determine the effects of storm water runoff on the ecology of the Bay. Parameters analyzed included: water quality (temperature, salinity, pH, dissolved oxygen), nutrients (NO3-, NO2-, NH4+, HPO43-, SiO32-), oil (PAHs, PCBs), pesticides, pharmaceuticals (cotinine, imidacloprid, carbamazepine and carbamazepine-epoxide, prednisone), organic carbon (dissolved and total), enzymatic activity (laccase, lipase, leucine amino-peptidase, alkaline phosphatase, Β-glucosidase), viruses, bacteria (16S) and phytoplankton community (18S, Imaging FlowCytobot). Following the flooding event, salinities in Galveston Bay decreased to 0-5 psu relative to pre-Harvey salinities of 20-30 psu. Pharmaceuticals (except Prednisone) were present in lower concentrations immediately following Harvey and steadily increased over successive weeks. Prednisone was detected at highest levels immediately following Harvey and then rapidly decreased in subsequent sampling events. The microbial community responded after a lag time of about 10-12 days (from peak discharge) with a substantial removal of tDOC (42%). The marine coastal microbial community dominated when samples were collected before this flooding event and then were replaced by microorganisms of terrestrial sedimentary and freshwater origin. This collaborative effort will allow for improved understanding of the physicochemical and biological changes following a large storm event within subtropical estuaries.

Estuaries in south Texas, such as the Mission-Aransas Estuary (MAE), receive very low base freshwater inflow for much of the year, interspersed with sporadic pulses of precipitation and resulting freshwater inflow events. These episodic storm events and variable freshwater inflow are critical contributors to the MAE’s dynamic salinity, nutrient availability, and particulate organic matter (POM) composition, including phytoplankton community composition. Estuarine food webs are largely fueled by POM, which includes both living and non-living organic material. Hurricane Harvey, a category 4 hurricane, passed directly over the MAE in late August, 2017, impacting the entire estuary and lower portion of the Mission and Aransas river watersheds with heavy rain and winds up to 130 mph. Previous work demonstrates that POM sources and composition change dramatically from drought to flood conditions, but the impact of a category 4 storm on the MAE’s POM composition and phytoplankton community structure was unknown. We analyzed suspended particulates from four sites across the MAE taken monthly from 2011-2018, using stable carbon isotopes and accessory pigments as biomarkers for POM sources, and total particulate amino acids (TPAAs) as proxies for POM lability. We found that bulk particulate organic carbon and chlorophyll a increased significantly during non-drought conditions in the MAE, especially following periodic storm events. Overall increases of TPAAs following storm events indicated enhanced lability of available POM. Phytoplankton community composition also shifted in response to freshwater inflow events, favoring cyanobacterial species at river-influenced sites in Copano Bay. Hurricane Harvey, which caused tremendous physical mixing in the MAE, did not appear to significantly alter phytoplankton community composition. The “flood or famine” paradigm of the MAE during typical drought/flood conditions causes dynamic responses in POM sources and quantity, and the resilience of the phytoplankton community post-hurricane may be an indication of overall system resilience to major storm disturbances.

Riverine dissolved organic matter (DOM) is a major source of reduced carbon from land to marine environments, and the inflow of terrestrial riverine organic matter highly affect biogeochemical cycling in estuaries and bays. Thus, any change in DOM composition, such as changes caused by flood waters as a result of hurricanes, could subsequently change estuarine environments. To investigate the impact of category 4 Hurricane Harvey on riverine DOM, multidimensional structural molecular level information of DOM from four south Texas Rivers (Aransas, Lavaca, Mission, and Nueces) was acquired using a high-resolution analytical technique, Ion Mobility Quadrupole Time of Flight Liquid Chromatography Mass Spectrometry (IM QTOF LC/MS). Pre-hurricane samples were collected in May, July and October of 2016, while post-hurricane samples were collected in September of 2017. The LC data showed that under ESI+ mode, pre-hurricane DOM share very similar chromatograms despite different seasons, but the chromatograms of post-hurricane DOM possess multiple unique peaks, suggesting the influence of flood waters. The MS data further showed that H/C ratios of the DOM molecules significantly decreased, while the O/C ratios increased. The change in elemental composition in post-hurricane DOM may indicate an increase of recalcitrance of the riverine DOM, which might be result of mobilization of refractory DOM from the watersheds by the flooding after hurricane. Principal coordinates analysis (PCoA) of DOM composition supported this conclusion as the May-2016 samples, which were collected after a storm event, were similar to the post-Harvey samples. Currently the analysis is still on going, and more results, including geometric and isomeric information of DOM, will be presented.

Hurricane Harvey made landfall in Texas as a category 4 storm on August 25, 2017. The eyewall passed directly over the Mission Aransas Estuary (MAE), part of the Mission-Aransas National Estuarine Research Reserve, bringing sustained winds >130 mph, storm surge, and rainfall. These disturbances had profound impacts on the biogeochemistry of the MAE, which is a shallow (<1 m) system characterized by limited exchange with the open Gulf. We collected sediments (0-5 cm) at 19 stations within the MAE pre-Harvey (June 2017) and post-Harvey (October 2017 to June 2018) to characterize the effects of the storm on sediment properties, including grain size, organic content, pigments, and nitrate reduction rates (denitrification, anammox, DNRA). Continuous turbidity data from the NERR system wide monitoring program show extremely high turbidity levels (>1300 NTU) for two days following the storm, the highest recorded level since the sensors were installed in 2007. Sediment grain size also changed dramatically post-storm, with sediments becoming coarser on average, at some stations by up to 100 um. Turbidity and grain size results reflect resuspension of fine material from wave action and surge, indicating major movement of sediment within the MAE. Sediment organic matter concentrations were mostly unchanged from June to October 2017, but the quality of that organic matter changed post- storm. Benthic chlorophyll a decreased at most stations by an average of 40% from June to October 2017. Chla values at most stations were returning to pre-Harvey levels by March 2018. Rates of benthic denitrification, anammox, and DNRA were spatially variable pre-Harvey, with denitrification dominating NO3- reduction. These rates decreased substantially from June to October 2017 at most stations, indicating reduced biogeochemical activity estuary-wide. Analyses are ongoing, but preliminary data suggest that redistribution of sediments may have impacted sediment organic content and related sediment nitrogen cycling processes post-Harvey.

Hurricane Harvey delivered 100-135 cm of rain to the Galveston Bay watershed in 5 days. The highest of this rainfall was delivered across the heavily urbanized and industrialized bayous that drain into the upper reaches of Galveston Bay, within the San Jacinto River and the Houston Ship Channel (SJR/HSC). The SJR/HSC has experienced up to 3 m of subsidence in the past century and with at least half of this new accommodation space filled with contaminated sediment, with average sedimentation rates of 2.2-2.8 cm y-1. The sediment deficit within the SJR/HSC is likely, at least in part due to the number of dams and reservoirs within the lower drainage basins of the SJR. These reservoirs include Lake Houston, which is 12 km up stream from our upstream most sampling station and the Barker and Addicks Reservoirs (BAR). The BAR are 50 km to the west of the confluence of Buffalo Bayou and the SJR/HSC, and this stretch of the Buffalo Bayou extends across center of Metro Houston. Controlled releases from the Barker and Addicks Reservoirs resulted in continual high discharges across Buffalo Bayou for weeks after the storm, resulting in the delivery of a prolong pulse of flood water into the SJR/HSC. Newly collected cores coupled with comparisons of archived cores will be used to determine the inventory of contaminants within the SJR/HSC as well as other parts of Galveston Bay pre-Hurricane Harvey and post-Hurricane Harvey to assess the delivery and dispersal of the flood pulse sediment as well as the inventory of contaminants within this flood pulse and to assess the contribution towards filling the sediment deficit within the SJR/HSC.

Hurricane Harvey, one of the worst hurricanes that hit the United States in recent history, poured record-breaking rainfall in Houston area. This extreme precipitation event caused dramatic changes in estuarine dynamics. Freshwater load into Galveston Bay during Harvey and the following month was estimated to be 8.98±2.62×109 m^3, 1.7 to 3 times the volume of the entire Galveston Bay. Such amount of freshwater water had completely renewed the entire Galveston Bay. Harvey also delivered 9.86×10^7 metric tons of flood deposit to the bay, equivalent to 21 years of average sediment load to the bay. Acute sea-bed erosion (as large as 0.5 m) followed by significant flood deposition was observed. Slow salinity recovery (~2 month), thick flood deposit (~10.5 cm average over entire bay), and spilling of large amount of toxic chemical pollutants had likely degraded the ecosystem over the bay and the adjacent shelf.