The occurrence of PAHs and faecal sterols in Dublin Bay and their influence on sedimentary microbial communities

1. The occurrence of PAHs and Faecal Sterols in
Dublin Bay and their influence on
sedimentary microbial communities
Dr. Brian Murphy
Brian.murphy1986@gmail.com

2. Dublin Bay
• Special areas of conservation (SAC) such as Dollymount (pictured)
• Dublin Bay named as a UNESCO biosphere reserve in 2015
Organic Compounds of interest in The marine sediment:
Polyaromatic hydrocarbons (PAHs)
• persistent organic pollutants (POP)
• Carcinogenic and mutagenic potential
• Sources: Petroleum spills, fossil fuel combustion, smoking.
Faecal Sterols Biomarkers
• Used as sewage pollution indicators
• Persist in the sediment
Phospholipid Fatty Acids (PLFAs)
• Biomarkers for living micro-organisms
• Bacterial Taxonomy
• Indicate Microbial response to pollution?

3. Reasons for conducting this Research
INFOMAR funded Cruise CV10_28
• Gas seepage structures, mapping and ground truthing.
• Adding value to samples taken aboard the R.V Celtic Voyager (pictured)
How is Human activity such as sewage discharge and fossil fuel
use impacting the Ecosystem of the Bay?
Can PLFAs be used as a
bio-monitoring tool for pollution
impact on marine sediments?
What are the sources of
organic pollutants
to the bay?

4. Sampling and Analysis
30 sediment samples in the Bay + 2 controls
Organic Pollutant and Biomarker analysis
1.Sediments Solvent extracted 2.SPE fractionation for PAHs, Sterols and PLFAs
3. Identification and quantified by GCMS
-Particle size analysis -Elemental analysis (C,H,N, TOC)

5. PAH Sources/Distribution
Dominance of 4-5 Ring
PAH’s(75%)
pyrogenic/combustion source
PAH isomer pair ratios used to
identify possible sources:
• Low contribution from
unburned petroleum
• Combusted petroleum is a
dominant source
• Coal combustion (Historic)
URGE Report 2009 from the GSI,
PAHs studied in 196 soil
samples around Dublin.
(Urban Geochemistry in
Europe)
Similar sources and/or urban
run-off

6. Results:Polyaromatic Hydrocarbons
Table 1:PAHs Dublin Bay
Warning Levels for Biological effects:
(Long et al., 1995) Effect Range Low/Medium
ERL = 552ng/g ERM=3160ng/g
Dublin Bay
10 stations exceed the ERL
No Stations exceed the ERM
Previous Studies of PAH’s in
Dublin Bay (Scarce):
•V.Choiseul, J.G.Wilson and E.Nixon
(1998) studied Hydrocarbon’s in
the Liffey estuary
•Macken et al (2009) PAH levels of
5575ng/g in marine sediment of
Dublin Port

7. Faecal Sterols

8. Coprostanol Distribution
Marker for Human faecal
matter: Concentrations
0.005 to 0.25 ug/g
Dublin Wastewater
treatment report 2012:
History:
Sewage discharged with
only rudimental screening
along the Dun Laoghaire
coast line until 1993
Sewage discharge off
Howth Head until 2001
virtually untreated.

9. Epicoprostanol Distribution
Coprostanol is converted to
Epicoprostanol by:
1.activated sludge digesters
in sewage treatment
2. slowly by bacteria in the
environment.
Suggests older sewage
input near Dun Laoghaire

10. Sterol ratio cross plot to indicate level of sewage contamination

11. PLFA Distribution
Living Microbial
Biomarkers
Total PLFA’s used as
measure of microbial
biomass
56 different PLFA
biomarkers identified
Long chained >C20
polyunsaturated = marine
algae input
Short chain <C20 Branched
Bacterial input
E.g
G030 and G035 similar
bacterial input but G030
much higher in Marine
algae

12. Principle component analysis
PAH’s
%Clay
%Silt
%Mud
Algae Biomarkers
Natural/ubiquitious
Sterols
Sewage biomarkers
Bacterial PLFA’s
%TOC
%TN

13. Correlation Analysis Outcomes
No significant correlation between PAH’s and Faecal sterols
suggesting different sources:
PAH’s : strong correlation with %clay and to a lesser extent %silt. Negative
correlation with sand:
 Accumulating in areas of deposition e.g. deeper areas of the bay
Diffuse sources – urban run-off, atmospheric dry/wet deposition.
Faecal Sterols: no correlation with %clay, %silt or %sand.
Significant correlation with %Total organic carbon and %Total nitrogen
Not accumulating in depositional areas
Point sources – Former discharge points at nose of Howth, and Dun Laoghaire
%TOC and %TN, unusual lack of association with areas of clay and silt (deposition)
Strong correlation between faecal sterols and %TOC

14. Microbial Communities (PLFA’s)
PLFA’s with significant correlation to faecal sterols
 16:1ω9, 16:1ω7c gram negative bacteria
 Cy17:0 gram negative bacteria also environmental stress indicator
 18:1ω6 reported in methane oxidising bacteria
 i16:0 and 15:0 non specific
•Significant correlation between algae and ubiquitous sterols i.e. cholesterol
and cholestanol.
Certain PLFA’s display significant correlation to PAH’s concentration :
10Me16:0 reported in sulphate reducing bacteria
i17:0 and a17:0 reported in hydrocarbon degrading bacteria
18:1ω9 gram positive bacteria also reported in hydrocarbon degraders

15. Conclusions
Polyaromatic Hydrocarbons:
• 10 sites exceed the ERL
• Mainly from petroleum combustion
• Source – urban run off, atmospheric deposition, River Liffey.
Faecal Sterols:
• Point source former Howth Head (2001) and Dun Laoghaire (1993) outfalls
• Sewage input has a significant impact on %total organic carbon
Microbial community:
• Impacted by organic matter input
• Algae correlates with sewage input
• Certain Bacterial biomarkers appear to vary depending on PAH or sewage
input, this may be indicating different strategies employed by microbial
communities in response to environmental pollutants
• These specific PLFA’s may be a useful bio-monitoring tools

16. Output/Future work
Of interest to:
EPA, Dublin Waste Water Treatment, Fisheries and other scientists
Building a Database of pollutants in Urban Bays
Understanding pollution impact on marine environments
Possible bio-monitoring tools
Informed planning Decisions for WWT
OGRe group are already involved in another similar
study of the Inner Bay/Bull island in collaboration with
the GSI......Poster 4

17. Thank You
Brian T.Murphya
, Shane S.O’Reillya
, Xavier Monteysb
, Barry F.Reida
, Michal T.Szpaka
,
Margaret V.McCaula
, Sean F.Jordana
, Christopher C. R. Allenc
, Brian P.Kellehera*
.
a.
School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
b.
Geological Survey of Ireland, Beggars Bush, Haddington Rd, Dublin 4, Ireland.
c.
School of Biological Sciences, Queens University Belfast, Medical Biology Centre,
Lisburn Rd, Belfast, N.Ireland.
Available in Marine Pollution Bulletin (2016) @OGRe_Lab