Gull Microbial Source Tracking Case Studies

Detect General Gull Fecal Load, Quantify % Gull Contamination, Multiple Samples Recommended

Gull MST Case Studies 2017-06-28T18:26:14+00:00

1. Gulls Are Big Polluters at Topanga Lagoon and State Beach in California 

Gulls are one of the main causes of fecal pollution at Topanga Lagoon and State Beach in California, according to a microbial source tracking (MST) study conducted by the University of California Los Angeles in collaboration with the Resource Conservation District of the Santa Monica Mountains and the Southern California Coastal Water Research Project Authority.

Topanga State Beach, located between Santa Monica and Malibu in California, was ranked one of the dirtiest beaches in the state of California based on fecal indicating bacteria (FIB) levels in the 2005-2006, 2010-2011, and 2011-2012 seasons. Researchers wanted to know the origin of the bacteria impairing water quality at the beach.

The study involved long-term molecular marker monitoring at 10 sampling locations in the Topanga Creek watershed. Monitoring was done over a 21-month period between October 2011 and June 1, 2013. Samples were collected twice monthly at five creek sites, three lagoon sites, and two marine sites. Monitoring was done over a 21-month period between October 2011 and June 1, 2013. Samples were collected twice monthly at five creek sites, three lagoon sites, and two marine sites.

Four host-associated markers were deployed to identify sources of fecal pollution present within the watershed ? the human-associated Bacteroidales HF183 TaqMan assay, the BacHum TaqMan assay, the Catellicoccus gull-associated Gull2 TaqMan assay, and the dog-associated Bacteroidales DogBact TaqMan markers. The markers were analyzed using quantitative polymerase chain reaction (qPCR).

Both Gull and Dog-associated markers were present at high frequency and were identified as important sources to Topanga Lagoon and State Beach. Seasonal variability was seen for both markers, with highest levels occurring in winter. Some gulls exhibit migrating behaviors, and it has been documented that larger shorebird populations are present in Southern California beaches in winter months. There are also many dogs belonging to owners who live along the beach and lifeguard presence on the beach decrease in winter months.

Human markers were also found frequently in the upper watershed and their levels appear to consistently decrease downstream. Researchers point to transient populations and faulty septic systems possible culprits.

2. Seagulls Are a Major Contributor to Pollution at Tower Road Bayside Beach in Delaware 

Seagulls are a major contributor to the fecal contamination at the Tower Road Bayside Beach in Delaware based on a 2011 study funded by the Delaware Department of Natural Resources and Environmental Control (DNREC).

Tower Road Bayside Beach waters are historically monitored weekly for bacterial load using the indicator bacteria Enterococcus. For the study, sampling analysis frequency expanded to three times weekly at three different locations along the active beach shoreline from May 9 through September 1, 2011. Water samples were collected in knee deep water.

Bacterial DNA analysis, specifically quantitative polymerase chain reaction (qPCR), was conducted by two laboratories. The Seagull Gull-2 biomarker (Catellicococcus marimammalium) was the primary target in this study but the Bird Bacteroidetes marker, Human Polyomavirus biomarker, Human Bacteroidetes HF183 marker, and Dog Bacteroidetes biomarker were also tested.

Seagull DNA was detected by both laboratories in all but one sample, that of June 29, 2011, making it undoubtedly a major contributor to fecal contamination at the Tower Road Bayside Beach.

Source Molecular detected the Human-Associated Bacteroidetes HF183 Biomarker in 4 out of 49 samples with a maximum concentration of 112 gene copies per 100 ml. The Human Polyomavirus biomarker was not detected leading researchers to believe that fecal contamination by human sources has not been confirmed, but may be occurring sporadically.

The Bird Bacteroidetes marker was not detected either. The Dog Bacteroidetes Biomarker was only identified in two samples and at low concentrations.

3. Gulls Found to be Contaminating Lake Water Samples Taken in Cleveland 

Scientists with the U.S. Geological Survey and the Northeast Ohio Regional Sewer District found evidence that gull feces contributed to the water pollution at certain places and at certain times during the 2007 recreational season at Villa Angela Beach in Cleveland, Ohio.

Scientists had observed an increased number of exceedances of recreational water-quality standards, with a greater average concentration of E. coli, in 2007 compared to 2006 data. In order to understand the sources behind these elevated E. coli concentrations, researchers used quantitative polymerase chain reaction (qPCR) to analyze water samples to determine relative quantities of certain DNA markers.

Sample collection of potential sources was done in August 2007 while spatial sampling of the study area was done in July and August 2007. Samples were collected over a range of weather conditions and E. coli concentrations. All samples were analyzed for E. coli and for three Bacteroides DNA markers AllBac, a general fecal marker that is expected to be present in all sources; and two human fecal markers. The study also analyzed source and beach samples for a gull-specific DNA marker.

The gull marker was present in more than half of the lake water samples collected in July and August 2007, but it had a weak presence in 3 sand samples out of 10 collected from Villa Angela Beach.

The human markers were absent in most of the samples collected. In cases where they were present, they were generally in low concentrations, with the exception of two samples collected from Euclid Creek following recent rainfall. The human marker was present in both those samples at the two highest concentrations found during the study.