Loyola University Chicago

Department of Biology

Timothy Hoellein


  Assistant Professor
Ph.D. 2008, University of Notre Dame
Aquatic Ecologist
Phone: 773.508.8859
Fax: 773.508.3646
E-mail: thoellein@luc.edu


My research has focused on the effects of 1) restoration strategies and 2) seasonal change on ecosystem processes in aquatic environments. Both of these factors have the potential to alter rates of nutrient cycling and metabolism through changes in physical structures, light, and organic matter accumulation. However, studies rarely consider the interaction between seasonal dynamics and restoration when evaluating or monitoring their effectiveness.

My work has centered on the influence of restoration on ecosystem function across both rural and urban environments. The ecosystem pressures in rural and urban environments are different (i.e., legacy of logging vs. human population pressure and industrial pollution), but the tools and paradigms used in the analyses are very similar.

Currently I am conducting research projects related to the influence of oyster restoration on N cycling in Jamaica Bay, NYC, a study of the physiochemical controls of an invasive diatom in upstate NY, and analyses of biofilm activity on litter in urban rivers.


Hoellein, T.J, Arango, C.P., and Y. Zak. In press. Spatial variability in nutrient concentration and limitation in an urban watershed (Bronx River, New York, USA). Biogeochemistry.

Hoellein, T.J., J.L. Tank, S.A. Entrekin, E.J. Rosi-Marshall, M.L. Stephen, and G.A. Lamberti. In press. Effects of a benthic habitat restoration on nutrient uptake and ecosystem metabolism in three headwater streams. River Research and Applications.

Hoellein, T.J., J.J. Kelly, J.L. Tank, and E.J. Rosi-Marhsall. 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-Marhsall, 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.

S.A. Entrekin, J.L. Tank, E.J. Rosi-Marshall, T.J. Hoellein, and G.A. Lamberti. 2009. Responses in macroinvertebrate secondary production to 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 188:457-463.

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.

Fig. Working in the field.