You are here:
Patterns and sources of nitrogen and microbial contamination in a Pacific Northwest estuarine watershed
Citation:
Zimmer-Faust, A., C. Brown, Jim Kaldy, TChris MochonCollura, O. Shanks, W. Rugh, Pat Clinton, J. Stecher, A. Manderson, AND Y. Johnson. Patterns and sources of nitrogen and microbial contamination in a Pacific Northwest estuarine watershed. UNC Water Microbiology, Chapel Hill, North Carolina, May 22 - 24, 2018.
Impact/Purpose:
Tillamook Bay, a National Estuary Program site, is located on the northwest coast of Oregon. The Bay is one of Oregon’s leading producers of shellfish for human consumption. However, high levels of fecal indicator bacteria that exceed state water quality standards often result in shellfish harvesting area closures leading to potential public health and economic burdens. Understanding the source of the fecal contamination is important to resource management. In this study, microbial source tracking was combined with stable isotope analysis to characterize sources of watershed fecal bacteria and nutrients to receiving waters. Findings demonstrate the utility of combining microbial source tracking and stable isotope analysis to improve water quality management in agriculturally intensive watersheds.
Description:
Tillamook Bay, a National Estuary Program site, is located on the northwest coast of Oregon. The Bay is one of Oregon’s leading producers of shellfish for human consumption. However, high levels of fecal indicator bacteria that exceed state water quality standards often result in shellfish harvesting area closures leading to potential public health and economic burdens. Fecal pollution management is challenging due the presence of multiple potential sources including run-off from local dairy operations and wildlife, as well as human waste management practices such as septic systems and wastewater treatment facilities. In this study, microbial source tracking was combined with stable isotope analysis to characterize sources of watershed fecal bacteria and nutrients to receiving waters. Water samples (n = 238) were collected from 16 tributary sites, above and below potential anthropogenic pollution sources on each river system draining into the Bay, along with six sites within Tillamook Bay over a one-year period. Paired measurements were recorded for host-associated qPCR genetic markers targeting human (HF183/BacR287 and HumM2), ruminant (Rum2Bac), cattle (CowM2 and CowM3), canine (DG3), and avian (GFD) fecal pollution sources along with nitrate isotopic composition (δ15NNO3). High nitrate isotopic ratios (δ15NNO3) suggest anthropogenic sourcing of nitrate, but do not discriminate between human and other animal pollution sources. In water samples, host-associated marker detection frequencies were 24% (CowM2), 43% (CowM3), 79% (Rum2Bac), 42% (HF183/BacR287), 19% (HumM2), and 74% (GFD). Seasonal and spatial patterns were observed, with cow- and human-associated marker detection frequencies increasing along a downstream gradient. CowM3 marker levels and nitrate isotopic composition (δ15NNO3) demonstrated similar seasonal and spatial patterns (R2=0.50, p<0.01). Findings demonstrate the utility of combining microbial source tracking and stable isotope analysis to improve water quality management in agriculturally intensive watersheds.