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Gregory O'Mullan

Associate Professor, Graduate Advisor
Environmental Microbiology

Science Building, Room D206
Phone: 718-997-3452

View Resume

Research Interests:


Environmental Microbiology. My research focuses upon the microbial ecology of aquatic environments. The microbial communities are studied in order to:

  • understand the variation and regulation of biogeochemical functioning in aquatic environments; 
  • understand the interaction between human activities and pathogen dynamics in the environment.

Specific Interests:

Include studies of:

  • Factors regulating the variability in coastal water quality, including the persistence of pathogens in estuaries and water-sediment interactions.
  • nitrogen cycling in the coastal ocean, especially nitrification and denitrification.
  • bioaerosols and the connection of water quality and air quality at the scale of the urban waterfront.
  • changes in microbial diversity and activity in response to: a) hypoxia; b) aquifer acidification.
  • the role of subsurface microbial communities in altering carbon sequestration activities.

View data from my Hudson River water quality study

Sources of Current and Prior Research Support Include:
Hudson River Foundation, Riverkeeper, US Environmental Protection Agency, National Science Foundation, Eppley Foundation, and Sloan Foundation
Departmental Service Includes:


  • Graduate Program Advisor for:
    MS in Applied Environmental Geosciences
    -     MA in Geological and Environmental Sciences
  • Departmental Personnel and Budget Committee
  • Environmental Studies Undergraduate Major Advisory Committee



Courses taught:

  • EnSci 203 Environmental Microbiology
  • EnSci 100 Our planet in the 21st Century
  • GEOL 009 Environmental Issues and Answers
  • GEOL 766 Analytical Approaches in Environmental Geosciences
  • GEOL 788.6 Cooperative Education Placement
  • GEOL 799.3 Environmental Microbiology
  • GEOL 799.3 Special Topics Aquatic Geomicrobiology

Representative Publications (see resume linked above for complete list):

O’Mullan, G.D., M.E. Dueker, K. Clauson, Q. Yang, K. Umemoto, N. Zakharova, J. Matter, M. Stute, T. Takahashi, and D. Goldberg.  2015. Microbial succession and stimulation following a test well injection simulating CO2 leakage into a shallow Newark Basin aquifer.  PLoS ONE 10(1): e0117812. doi:10.1371/journal.pone.0117812

Yang, Q., J. Matter, T. Takahashi, M. Stute, G.D. O’Mullan, K. Clauson, K. Umemoto, D. Goldberg.  2015.   Groundwater geochemistry in bench experiments simulating CO2 leakage from geological storage in the Newark Basin. International Journal of Greenhouse Gas Control 42:98-108.

Afshinnekoo, E., et al.  2015. Geospatial Resolution of Human and Bacterial Diversity with City-Scale Metagenomics, Cell Systems, ISSN 2405-4712,

Yang, Q., J. Matter, M. Stute, K. Umemoto, K. Clauson, M.E. Dueker, G.D. O’Mullan, T. Takahashi, N. Zakharova, D. Goldberg.  2014.  Groundwater hydrogeochemistry in injection experiments simulating CO2 leakage from a geological storage reservoir. International Journal of Greenhouse Gas Control. 26:193-203. 

 Dueker, M.E. and G.D. O’Mullan. 2014. Aeration remediation of a polluted waterway increases near-surface coarse and culturable microbial aerosols. Science of the Total Environment. 478:184-189.

Young, S., A. Juhl, and G. O’Mullan. 2013. Antibiotic resistant bacteria in the Hudson River Estuary linked to wet weather sewage contamination. Journal of Water and Health. 11(2):297-310.

Francis, C.A., G.D. O’Mullan, J.C. Cornwell, B.B. Ward. 2013. Transitions in nirS-type denitrifier diversity, community composition, and biogeochemical activity along the Chesapeake Bay Estuary. Frontiers in Aquatic Microbiology. 4(237):1-12.

Dueker, M.E., G. O’Mullan, A. Juhl, K. Weathers,. and M. Uriarte. 2012. Local environmental pollution strongly influences culturable bacterial aerosols at an urban aquatic superfund site. Environmental Science and Technology 46(20):10926-10933.

Bouskill, N., D. Eveillard, G. O’Mullan, J. Jackson, and B. B. Ward. 2011. Seasonal and annual reoccurrence patterns in ammonia-oxidizing bacterial population structure. Environmental Microbiology 13(4):872-886.
Jayakumar, A., G.D. O’Mullan, S.W.A. Naqvi, and B.B. Ward. 2009. Denitrifying bacterial community composition associated with the stages of denitrification in oxygen minimium zones. Microbial Ecology 58(2):350-362.
Foster, R. and G. D. O’Mullan. 2008. Chapter 27-Nitrogen fixing and nitrifying symbioses in the marine environment. Pages 1197-1218. In: Nitrogen in the Marine Environment, 2nd edition. Edited by D. G. Capone, D. A. Bronk, M. R. Mulholland, and E. J. Carpenter. (2008)
O’Mullan, G.D., and B.B. Ward. 2005. Comparison of temporal and spatial variation of ammonia oxidizing bacteria and nitrification rates in Monterey Bay, CA. Applied and Environmental Microbiology 71(2): 697-705.
Ward B. B. and G. D. O’Mullan. 2005. Community-level analysis: aerobic ammonia oxidation activity measurements and gene analysis. Methods in Enzymology 397: 395-413.
Giller, P., H. Hillebrand, U.K. Berninger, M.O. Gessner, S. Hawkins, P. Inchausti, C. Inglis, H. Leslie, B. Malmqvist, M. Monaghan, P J. Morin, and G.D. O’Mullan. 2004. Biodiversity effects on ecosystem functioning: emerging issues and their experimental test in aquatic environments. Oikos 104: 423-436.




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