Hurricane Harvey made landfall near Rockport, TX (USA) as a Category 4 storm then stalled out over southeast Texas. While the moving eastward the storm released ~21 trillion gallons of precipitation over the Houston-Gulf coast region. A subsequent freshwater flushing event occurred as runoff and river discharge flowed into the Bay and then the Gulf of Mexico. Within one week of the storms passing we began a series of 5 sampling campaigns (over 24 days) along a transect extending from the mouth of the San Jacinto River to the Gulf of Mexico (10 stations). Our research goal was to monitor the changes in water quality parameters and microbial community to determine the effects of storm water runoff (polluted from sewage, pesticides, oil etc) on Bay ecology. Parameters analyzed include: 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), caffeine, 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).
Results/Conclusions
During the first sampling cruise, 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 decreased to just above or below detection level for remaining cruises. The removal of terrigenous DOC during the first cruise was negligible suggesting the Bay acted as a pipe and delivered tDOC to the coastal shelf without much alteration. The Bay system responded after a lag time of about 10-12 days (from peak discharge) with a substantial removal of tDOC (42%). The generally dominant bacteria of the marine coastal community, (Acidimicrobiia, Cyanobacteria, Betaproteobacteria SAR11, and Gammaproteobacteria, Oceanospirillales) were replaced by microorganisms of terrestrial (Actinobacteria, OBP45 Soil Group, Opitutae), sedimentary (Actinobacteria), and freshwater (Betaproteobacteria Burkholderiales) origin. Pre-Harvey the phytoplankton community was predominantly estuarine/marine bacillariophytes and dinophytes which transitioned to freshwater cyanophytes and chlorophytes following the flooding event. Following the storm, phytoplankton began to transition back to the estuarine/marine bacillariophytes and dinophytes. This collaborative effort will allow for improved understanding of the physicochemical and biological changes following a large storm event within subtropical estuaries.