Estuarine properties associated with a salinity intrusion:

1. Estuarine properties associated with a salinity intrusion: An investigation of Chocolate Bayou, TX Dabbs, Z.1, Langston, L.1, Nunez, M.1, Rogers, R. 1 1Dept. of Marine Sciences, Texas A&M University at Galveston , Galveston, 77553 Texas, USA RESULTS RESULTS ABSTRACT Chocolate Bayou, a tidally influenced tributary to Galveston Bay, was used to investigate the influence of a salinity intrusion on estuarine properties. This research focuses on the entire length of the bayou from the bay end member to an upstream dam. The study measured water column properties using a CTD, sediment properties, and chemical contaminants, and phytoplankton parameters using Fluorescence Induction and Emission (FIRe). Sediments are predominately silts and clay with small amounts of sand, but along the bayou trends revealed spatial variability in sediment distributions that distinguished bay sediments from bayou sediments. Copper, chromium, iron, and manganese showed moderate contamination along portions of the bayou. Upon evaluating the photosynthetic performance, higher levels of productivity were observed in bottom waters and lower levels at the surface. Overall, salinity increased with water depth, but decreased with distance up bayou, and a strong halocline developed closer to the dam. Results from photosynthetic performance suggest increased nutrients in bottom waters indicative of slow moving waters. Furthermore, chemical contaminants observed resulted from chemical plants located near the bay end member. The dam had no effect on phytoplankton, but a large effect on preventing further intrusion of the salinity and potential contamination by chemical plants. (B) (A) (D) (C) (A) (B) Figure 2: Salinity (A) Salinity gradient- Bay to Bayou (B) Salinity cross-section (B) (A) (E) (F) (C) Figure 1: Sample collection of grab samples • Objective • To determine if the salinity intrusion affects the distribution of sediment. • How it impacts biology via phytoplankton communities. • How it influences contaminant transport. • This study will assess potential future effects that may result from rising sea level. (A) (B) (H) (G) Figure 3: (A) Low level dam, (B) Salinity Profile, (C) Sand distribution Figure 2: Sand distribution • Hypothesis • The location of the salinity intrusion is dependent on terrestrial runoff or ground water seepage. • The dam defines the landward extent of the salinity intrusion. • Increases in suspended sediment concentration (SSC) at the salinity front will inhibit photosynthetic performance (health). • Phytoplankton communities will be varied depending on salinity intrusion. 1.00 0.05 (C) (D) MATERIALS AND METHODS Figure 8: Gravity Cores (A) Core 17, (B) Core 15, (C) Core 11, (D) Core 9, (E) Core 7, (F) Core 5, (G) Core 3, (H) Core 1 (C) 0.05 0.3 BAY CONCLUSIONS • The salt intrusion in the bayou was significantly hindered by the low level dam. Salinity levels decreased as distance to the dam decreased. • Contaminants found in the area included copper, iron, manganese, and chromium. Toxic levels, especially in copper, revealed a pattern consistent with the location of chemical plants located on the bayou. • Phytoplankton communities were dominated by diatoms at surface levels and bottom water showed an increase in cyanobacteria. • Sediment distribution showed that primary silts and clays dominated the region. In addition, a higher energy allows for further transport of sand into the bayou, and a higher concentration near the dam. Figure 5: Toxicity (A) Copper, (B) Manganese, (C )Iron, (D) Chromium *Anything above dash line is considered toxic. (A) (B) ACKNOWLEDGEMENTS We would like to thank the Coastal Geology Laboratory at Texas A&M University at Galveston for allowing us to use their facilities and equipment throughout our research. We would especially like to thank Joe Carlin and Ryan Gay for all of their support and guidance in completing these findings. Additionally, we would also like to thank the Geographic Information Systems Laboratory for assistance with map generation. BAY BAYOU BAY BAYOU Figure 6: (A) Photosynthetic Activity (B) Phyto-Pam Phytoplankton Communities- Diatoms vs Cyanobacteria .