Loyola University Chicago

Department of Biology

Timothy Hoellein


Associate Professor
Ph.D. 2008, University of Notre Dame
Aquatic Ecologist
Phone: 773.508.8859
Fax: 773.508.3646


Ecosystem processes and biogeochemistry. Movement and biological transformation of elements, energy, and pollution in aquatic ecosystems.


*undergraduate students, §graduate students

Drummond, J., Schneidewind, U., Li, A., Hoellein, T.J., Krause, S. and A. I. Packman. 2022. Microplastic accumulation in riverbed sediment via hyporheic exchange from headwaters to mainstems. Science Advances 8(2), eabi9305

§Hamilton, Rochman, C.M., Hoellein, T.J., Robison, B.H., Van Houtan, K.S., and C. A.  Choy. 2021. Prevalence of microplastics and anthropogenic debris within a deep-sea food web. Marine Ecology Progress Series, 675, 23-33.

§Vincent, A. and T.J. Hoellein. 2021. Microplastic Distribution and Transport in Urban Streams Follows Patterns for Fine Particulate Organic Matter. Ecological Applications. 31(8): e02429

Hoellein, T.J., Rovengo, C., Uhrin, A.V., Johnson, E., and C. Herring. 2021. Microplastics in invasive freshwater mussels (Dreissena sp.): Spatiotemporal variation and occurrence with chemical contaminantsFrontiers in Marine Science 8(690041).

Bosio, S.F., Shirey, P.A., Entrekin, S.A., Hoellein, T.J., Moerke, A.H., Rosi, E.J., Tank, J.L. and G.A. Lamberti. 2021. Dynamics of large wood added to Midwestern USA streams. River Research and Applications 37: 843–857

§Hou, L., McMahan, C.D., McNeish, R.E., Munno, K., Rochman, C.M., and T.J. Hoellein. 2021. A fish tale: A century of museum specimens reveal increasing microplastic concentrations in freshwater fish. Ecological Applications: e2320.

Kelly, J., London, M., §McCormick, A., §Rojas, M., Scott, J., and T. Hoellein. 2021. Wastewater treatment alters microbial colonization of microplastics. PLOS One 16(1): e0244443

§Piacente, J.N., Milanovich, J.R., Berg, M.B., Hoellein, T.J., Muñoz, A.G., §Cann, A.A., and I. S. Lentini. 2020. Characterizing Lentic Habitats in Golf Courses and Adjacent Green Spaces:  Water Quality, Water Chemistry, Pesticide Concentrations, and Algal Concentrations. Journal of Freshwater Ecology 35:1, 507-522

Hoellein, T.J., and C. Rochman. 2021. The plastic cycle: Pools and fluxes of plastic litter at the watershed scale. Frontiers in Ecology and the Environment: 19(3), 176-183.

Krause, S., Baranov, V., Nel, H., Drummond, J., Kukkola, A, Sambrook Smith, G. Sadler, J., Baranova, V. LewandowskiJ., Bonet., B., Packman, A., Hoellein, T., and I. Lynch. 2021. Gathering at the top? Environmental controls of microplastic uptake and biomagnification in aquatic food webs. Environmental Pollution 268:115750

Lazcano, R., Vincent, A., and T.J. Hoellein. 2020. Trash Dance: Anthropogenic litter and organic matter co-accumulation on urban beaches. Geosciences 10(9), 335

C. Rochman and T.J. Hoellein. 2020. The Global Odyssey of Plastic Pollution. Science. 368 (6496): 1184-1185

Entrekin, S. A., Rosi, E. J., Tank, J. L., Hoellein, T. J., and G.A. Lamberti. 2020. Quantitative food webs indicate modest increases in the transfer of allochthonous and autochthonous C to macroinvertebrates following a large wood addition to a temperate headwater wtream. Frontiers in Ecology and Evolution 8: 114.

Kelly, J.J., London, M., *Oforji, N., *Ogunsola, A., and T. J. Hoellein. 2020. Microplastic selects for convergent microbiomes from distinct riverine source populations. Freshwater Science. 39(2):281–291

Alldred, M., Borrelli, J.J., Hoellein, T.J., Bruesewitz, D.A., and C. B. Zarnoch. 2020. Marsh plants enhance coastal marsh resilience by changing sediment redox conditions in an urban, eutrophic estuary. Estuaries and Coasts. 43:801-813

Wisbrock, L., Reynolds, E., Mertins, J., Schultz, A., Hurt, K., Kleinschmidt, R., Cahill, S., Johnson, K., Weider, D., Hoellein, T., Smetana, L. 2020. Talking Trash: A Human Problem with Human Solutions. Science and Children. 57(8)

Zhu, J., Zarnoch, C.B., Gosnell, J.S., Alldred, M., and T. J. Hoellein. 2019. Ribbed mussels (Geukensia demissa) enhance nitrogen-removal services but not plant growth in restored eutrophic salt marshes. Marine Ecology Progress Series 631:67-80

Zarnoch, C.B., Hossain, N., Fusco, E., Alldred, M., Hoellein, T.J., and S. Perdikaris. 2020. Size and density of upside down jellyfish, Cassiopea sp., and their impact on benthic fluxes in a Caribbean lagoon. Marine Environmental Research 154: 104845.

Smetana, L., §Wisbrock, L., *Zaker, M., and T.J. Hoellein. 2019. Let’s Be Litter Free: Investigating Anthropogenic Litter in Local Ecosystems. Science Scope. 43(3): 42-52.

Hoellein, T.J., §Shogren, A.J., Tank, J.L., *Risteca, P., and J.J. Kelly. 2019. Microplastic deposition velocity in streams follows patterns for naturally occurring allochthonous particles. Scientific Reports. 9(1): 3740

Panno, S.P., Kelly, W.R., Scott, J., Zheng, W., McNeish, R.E., Holm, N., Hoellein, T.J. and E.L Baranski. 2019. Microplastic contamination in Karst Groundwater Systems. Groundwater 57(2):189-196.

Qasem, K., Vitousek, S., O’Connor, B. and T. Hoellein. 2019. The effect of floods on ecosystem metabolism in suburban streams. Freshwater Science 38(2): 412-424

Barrows, A., Christiansen, K.S., Bode, E.T., and T.J. Hoellein. 2018. A watershed-scale, citizen science approach to quantifying microplastic concentration in a mixed land-use river. Water Research 147:382-392. 

McNeish, R.E., §Kim, L., §Barret, H., Mason, S.A., Kelly, J.J., and T.J. Hoellein.  2018. Microplastic in riverine fish is connected to species traits. Scientific Reports 8:11639.

C. Vaughn and T.J. Hoellein. 2018. Bivalve impacts in marine and freshwater ecosystems. Annual Review of Ecology, Evolution, and Systematics 49:183-208.

Hoellein, T.J., Zarnoch, C.B, Bruesewitz, D.A., and J. DeMartini. 2017. Contributions of freshwater mussels (Unionidae) to nutrient cycling in an urban river: filtration, recycling, storage, and removal. Biogeochemistry 135(3): 307-324

Zarnoch, C.B., Hoellein, T.J., Furman, B.T., and B.J. Peterson. 2017. Eelgrass meadows, Zostera marina (L.), facilitate the ecosystem service of nitrogen removal during simulated nutrient pulses in Shinnecock Bay, New York, USA. Marine Pollution Bulletin 124(1): 376-387

Hoellein, T.J., §McCormick, A., London, M., *Hittie, J., Scott, J.W., and J.J. Kelly. 2017. Longitudinal patterns of microplastic concentration and bacterial assemblages in surface and benthic habitats of an urban river. Freshwater Science. 36(3):491-507

Denise A. Bruesewitz, Hoellein, T.J., Mooney, R.F., Gardner, W.S., and E. J. Buskey. 2017. Wastewater influences nitrogen dynamics along in a coastal catchment during a prolonged drought. Limnology and Oceanography 62:S1: S239–S257

*Vincent, A., and T.J. Hoellein. 2017. Anthropogenic litter abundance and accumulation rates point to seasonal litter sources on a Great Lakes beach. Journal of Contemporary Water Research and Education 160 (1): 72-84

*Vincent, A., Hoellein, T.J., Drag, N., Lyandres, O., and S. Neville. 2017. Citizen science datasets reveal drivers of spatial and temporal variation for anthropogenic litter on Great Lakes beaches. Science of the Total Environment 577: 105-112.

McCormick, A., Hoellein, T.J., London, M., *Hittie, J., Scott, J.W., and J.J. Kelly. 2016. Microplastic in surface waters of urban rivers: Concentration, sources, and associated bacterial assemblages. Ecosphere 7(11): e01556.

McCormick, A. and T.J. Hoellein. 2016. Anthropogenic litter is abundant, diverse, and mobile in urban rivers: Insights from cross-ecosystem analyses using ecosystem and community ecology tools. Limnology and Oceanography 61(5):1718-1734

Reisinger, A., Tank, J.L., Hoellein, T.J., and R.O. Hall. 2016. Midwestern river sediment, water column, and open-channel denitrification measured using membrane-inlet mass spectrometry. Journal of Geophysical Research, Biogeosciences 121(5): 1258-1274.

Cook, A.R. and T.J. Hoellein. 2016. Environmental drivers of leaf breakdown in an urban watershed. Freshwater Science 35(1): 311-323

Lindeman, S., Castignetti, D., Zarnoch, C.B., and T.J. Hoellein. 2016. Effect of eastern oysters (Crassostrea virginica) and seasonality on nitrite reductase gene abundance (nirS, nirK, nrfA) in an urban estuary. Estuaries and Coasts 39:218-232.

Turek, K.A., and T.J. Hoellein. 2015. The invasive Asian clam (Corbicula fluminea) increases sediment denitrification and ammonium flux in 2 streams in the Midwestern USA. Freshwater Science 34(2): 472-484

Hoellein, T.J., *Westhoven, M., Lyandres, O., and J. Cross. 2015. Abundance and environmental drivers of anthropogenic litter on 5 Lake Michigan beaches: A study facilitated by citizen science data collection. Journal of Great Lakes Research. 41:78-86

Hoellein, T.J., Zarnoch, C.B., and R. Grizzle.  2015. Water quality influences on eastern oyster (Crassostrea virginia) feeding, biodeposition, and sediment N cycling in Great Bay, NH. Biogeochemistry 122(1): 113-129

McCormick, A., Hoellein, T.J., Mason, S., Schluep, J., and J.J. Kelly. 2014. Microplastic in an abundant and district microbial habitat in an urban river. Environmental Science and Technology. 48(20):11863-71.

T.J., Bruesewitz, D.A., and D.P. Hamilton. 2012. Are geothermal streams important sites of nutrient uptake in an agricultural and urbanizing landscape (Rotorua, New Zealand)? Freshwater Biology 57: 129–142

Richardson, D.C., *Oleksy, I.A., Hoellein, T.J., Arscott, D. B., Gibson, C.A., and S.M. *Root.  2014. Spatial distribution and macroinvertebrate community effects of a nuisance, bloom-forming diatom (Didymosphenia geminata) in Catskill Mountain streams, New York.  Aquatic Sciences 76(4):553-564

Hoellein, T.J., §Rojas, M., *Pink, A. *Gasior, J., and J. J. Kelly. 2014. Anthropogenic litter in urban freshwater ecosystems: Distribution and microbial interactions.  PLoS One 9(6): e98485

Hoellein, T.J., and C.B. Zarnoch. 2014. Effect of eastern oysters (Crassostrea virginica) on sediment carbon and nitrogen dynamics in an urban estuary. Ecological Applications 24(2):271-286

Hoellein, T.J., Bruesewitz, D.A., and D. Richardson.  2013. Revisiting Odum (1956): A synthesis of aquatic ecosystem metabolism.  Limnology and Oceanography.  58(6), 2013, 2089–2100.

Hoellein, T.J., J.L. Tank, S.A. Entrekin, E.J. Rosi-Marshall, M.L. Stephen, and G.A. Lamberti. 2012. Effects of a benthic habitat restoration on nutrient uptake and ecosystem metabolism in three headwater streams.  River Research and Applications. 28 (9): 1451-1461

Hoellein, T.J, Arango, C.P., and Y. Zak*. 2011. Spatial variability in nutrient concentration and limitation in an urban watershed (Bronx River, New York, USA). Biogeochemistry 106:265–280

Hoellein, T.J.,  J.L. Tank, J.J. Kelly, and E.J. Rosi-Marshall. 2010. Seasonal variation in nutrient limitation of microbial biofilms colonizing organic and inorganic substrata in streams. Hydrobiologia 649:331-345

Kominoski, J.S., T.J. Hoellein, C.J. Leroy, C.M. Pringle, and C.M. Swan.  2010.  Beyond species richness: expanding biodiversity-ecosystem functioning theory in detritus-based streams. River Research and Applications. 26: 67-75.

Hoellein, T.J., J.L. Tank, E.J. Rosi-Marshall, and S.A. Entrekin. 2009. Temporal variation in substratum-specific rates of N uptake and metabolism and their relative contribution at the reach scale.  Journal of the North American Benthological Society. 28(2): 305-318.

Entrekin, S.A., J.L. Tank, E.J. Rosi-Marshall, T.J. Hoellein, and G.A. Lamberti. 2009. Responses in macroinvertebrate secondary production to large wood addition in three Michigan streams.  Freshwater Biology 54 (8): 1741-1758.

Kominoski, J.S., T.J. Hoellein, J.J. Kelly, and C. M. Pringle. 2009. Does mixing litter of different qualities alter stream microbial diversity and functioning on individual litter species? Oikos. 118:457-463.

Entrekin, S.A., J.L. Tank, E.J. Rosi-Marshall, T.J. Hoellein, and G.A. Lamberti. 2008. Responses in organic matter accumulation and processing to an experimental wood addition in three headwater streams. Freshwater Biology 53:1642–1657.

Hoellein, T.J., J.L. Tank, E.J. Rosi-Marshall, S.A. Entrekin, and G.A. Lamberti. 2007. Controls on spatial and temporal variation of nutrient uptake in three Michigan headwater streams.  Limnology and Oceanography 52 (5) 1964-1977. 

Entrekin, S.A., E.J. Rosi-Marshall, J.L. Tank, T.J. Hoellein, and G.A. Lamberti. 2007. Macroinvertebrate secondary production in forested sand-bottom streams of the Upper Midwest.  Journal of the North American Benthological Society. 26 (3): 472-490.


Harrison, J.P., Hoellein, T.J., Sapp, M., Tagg, A., Ju-Nam, Y., and J.J. Ojeda. 2017. Microplastic-associated biofilms: A comparison of freshwater and marine environments. Pgs 181-201 In: Wagner, M, and S. Lambert (Eds). Freshwater Microplastics: Emerging Environmental Contaminants? Series: The Handbook of Environmental Chemistry, Vol. 58. Springer International Publishing. ISBN 978-3-319-61614-8


With [re]Purpose – 9th Annual Juried Exhibition. 9/15/18– 11/3/18. South Haven Center for Arts. South Haven, MI. Work invited for the exhibition “North Branch Chicago River 8” by T. Hoellein.