Download Microbial Source Tracking in Murrells Inlet, Horry County Volunteer Monitoring Luncheon

Microbial Source Tracking
in Murrells Inlet,
Horry County
Volunteer Monitoring Luncheon
April 30, 2013
Inlet Affairs
Tiered Approach
Weight
of Evidence
Microbial Source
Tracking
Cost
Intensive sampling using
standard FIB measurements;
Infrared thermography
Sanitary Survey
Identification of impaired areas based on long-term
monitoring
Effort
Weight of Evidence
Source Tracking Strategies
• Space and Time
– Targeted wet and dry weather sampling
• Tracers
– Fecal bacteria concentrations
• Enterococcus
• E. coli
– Chemical concentrations
• Water mass indicators
• Optical brighteners
• Caffeine
– Host animals
• Multiple antibiotic resistance of fecal bacteria
• Genetic markers of fecal bacteria
Sample Sites
Fecal Indicator Bacteria (FIB) Summary
• All sites have at
least one
contravention of
WQS’s for FIBs
• Sites 1 & 6 have
the highest FIB
concentrations
• Some sites are
relatively clean,
i.e. some of the
samples <WQS
• No consistent
pattern with
rainfall
Genetic Marker Overview
• Warm-blooded signal generally shows the
same pattern of concentrations as FIB
concentrations
• Canine signal concentrations appear high at
many sites. Detections are most common and
concentrations highest after rain.
• Only 2 of 27 samples were positive for human
signal (sites #1 and 5).
• The bird assay is not ready but samples are
archived for future analysis.
Canine sources
• High concentrations
of canine-sourced
fecal bacteria suggest
that dogs are an
important contributor
to FIB loading at sites
2, 3, 4, 5, 7, & 8
– These sites are all in
residential areas
where residents
likely walk pets
– Sites 3, 4, & 8 are
downstream of a
pond
– Sites 2, 5, & 7 are
adjacent to grassy
areas on the inlet.
Human Sources
• Site 1 (Woodland Dr. Pond) has high E. coli
concentrations in volunteer monitoring data
– High FIB levels may reflect human sources concurrent detections of OB, caffeine and BacHum
• Site 5 is a SC DHEC shellfish monitoring site
(04-01) that has exhibited high and continual
contraventions of the shellfish FC WQS.
– Site 5 exhibits signs of human influences elevated FIB, OB, and a low level detection for
BacHum
Human Sources (cont)
• Site 6 drains a
medium density
modular and
multi-family home
community
– Results suggest
strong human
influence –
high levels of FIB,
caffeine, and OB
– However, no
BacHum signal
was detected
Sample Sites
Moving Forward
• One dry and wet event still to be sampled
– May confirm preliminary conclusions
– May detect tracers that went undetected due to
dilution from flushing (compared to Withers)
• Bird assay to be measured on all samples
• Iterative process? May warrant further testing
• Georgetown County intends to undertake
similar approach in next fiscal year (budget
pending)