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Dr. Clifford A. Ochs

Department of Biology
The University of Mississippi


Office: 332 Shoemaker Hall
Telephone: (662) 915-7562
FAX: (662) 915-5144


Research Interests:

  • The Mississippi River
  • Population dynamics and ecological interactions of aquatic microorganisms.
  • Nutrient biogeochemistry in aquatic and terrestrial ecosystems.

Our lab is engaged in various studies in the areas of aquatic ecology and biogeochemistry. Broadly speaking, we are investigating connections between the abiotic environment, plankton community composition and activities, and biogeochemical cycles involving nitrogen, phosphorus, and carbon. Our research is focused mostly on aquatic habitats of northern Mississippi including oxbow lakes, various wetland types, reservoirs, the Mississippi River itself, and even flooded agricultural fields in the Mississippi Delta. Funding to support our work comes primarily from the National Science Foundation, the Environmental Protection Agency, and the Department of Agriculture.
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Ph.D. Cornell University
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Courses Taught:

Bisc 619: Ecosystems Ecology
Bisc 505: Aquatic Microbiology
Bisc 522: Microbial Ecology
Bisc 300: Research Methods in Biology
Bisc 102 & 104: Freshman Biology
Honors 101 & 102
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Selected Publications:

Ochs, C.A. and F.D. Shields, Jr. 2019. Fluxes of nutrients and biological production between the main channel and floodplain backwaters of the Lower Mississippi River – development of a simulation model. River Research and Applications. DOI: 10.1002/rra.3482

Ochs, C.A., O. Pongruktham, K.J. Killgore, and J.J. Hoover. 2019. Phytoplankton prey selection by the silver carp (Hypophthalmichthys molitrix Val.) in a Lower Mississippi River backwater. Southeastern Naturalist 18: 113-129.

Ochs, C.A. 2017. The city ecosystem—the street view of a common resident. A contribution to a Global Roundtable Discussion: Are cities ecosystems—analogous to natural ones—of nature, infrastructure and people? Does thinking about cities in this way help us think about urban design?

Payne, J.T., C.A. Ochs, C.R. Jackson, and J.J. Millar. 2017. Patterns of Variation in Diversity of the Mississippi River Microbiome over 1,300 Kilometers. Plos One (

Bussan, D.D., C.A. Ochs; C.R. Jackson; T. Anumol; S.A. Snyder; J. Cizdziel. 2017. Concentrations of select dissolved trace elements and anthropogenic organic compounds in the Mississippi River and major tributaries during the summer of 2012 and 2013. Environmental Monitoring and Assessment 189:73 (doi 10.1007/s10661-017-5785-x)

Keating, M.P., C.A. Ochs, D. Balachandran, M.M. Holland, R. Lizotte and K.Yu. 2016. Spatial variation related to hydrologic patterns and vegetation in greenhouse gas fluxes from the Mississippi Delta agricultural region. Applied Soil Ecology 98: 278-281.

Millar, J.M., J.T. Payne, C.A. Ochs, and C.R. Jackson. 2015. Particle-associated and cell-free extracellular enzyme activity in relation to nutrient status of large tributaries of the Lower Mississippi River. Biogeochemistry DOI 10.1007/s10533-015-0096-1
Pongruktham, O. and C.A. Ochs 2015. The rise and fall of the Lower Mississippi: Effects of hydrologic connection on floodplain backwaters. Hydrobiologia 742: 169-183 (DOI 10.1007/s10750-014-1983-5).

Jackson, C.R., J.J. Millar, J.T. Payne, and C.A. Ochs 2014. Biogeography of bacterioplankton in large rivers of the Mississippi River Basin: spatial patterns at microhabitat and regional scales. Applied and Environmental Microbiology 80: 7186-7195.

Ochs, C.A., O. Pongruktham, and P.V. Zimba. 2013. Darkness at the break of noon: Phytoplankton production in the Lower Mississippi River. Limnology and Oceanography 58: 555-568.

Srinivas, R. and C.A. Ochs. 2012. Effect of UV-A Irradiance on Lipid Accumulation in Nannochloropsis oculata. Photochemistry and Photobiology 88(3): 684-689.

Pongruktham, O., C.A. Ochs and J.J. Hoover. 2010. Observations of Silver Carp (Hypophthalmichthys molitrix) Planktivory in a Floodplain Lake of the Lower Mississippi River Basin. Journal of Freshwater Ecology 25: 85-93.

Ochs, C.A., H.E. Capello, and O. Pongruktham. 2010. Heterotrophic bacterial production in the Lower Mississippi River – Temporal and spatial patterns. Hydrobiologia 637: 19-31.

Koh, H-S, C.A. Ochs and K. Yu. 2009. Hydrologic gradient and vegetation controls on CH4 and CO2 fluxes in a spring-fed forested wetland. Hydrobiologia 630: 271

Ogbebo, F.E. and C.A. Ochs. 2008. Bacterioplankton and phytoplankton production rates compared at different levels of solar ultraviolet radiation and limiting nutrient ratios J. Plank. Res. 30: 1271-1284.

Ochs, C.A. and H.E. Capello 2008. Bacterioplankton production in the Lower Mississippi River. Verh. Internat. Verein. Limnol. 30(1): 57-59.

Sthapit, E., C.A. Ochs, and P.V. Zimba. 2008. Spatial and temporal variation in phytoplankton structure in a southeastern U.S. reservoir determined by HPLC and light microscopy. Hydrobiologia. 600: 215-228.

Ochs, C.A. and H.E. Capello. 2007. Aquatic Life: Freshwater. In: The New Encyclopedia of Southern Culture. The University of North Carolina Press.

Canion, A.K. and C. Ochs. 2005. The population dynamics of freshwater armored dinoflagellates in a small lake in Mississippi. J. Freshwater Ecology 20: 617-626.

Ochs, C.A. 2002. Planktonic microorganisms: bacterioplankton, p. 2519-2539. In G. Bitton [ed.], Encyclopedia of Environmental Microbiology, John Wiley, N.Y.

Pezeshki, S.R., R.D. DeLaune, W.J. Catallo, J.A. Nyman, C.A. Ochs, S.A. Milburn, J. Melack, L. Mertes, L. Hess, and B. Forsberg. 2003. Wetland biogeochemistry, p. 125-156 In: M. Holland and L. Shaffer, Proceedings from the Center for Water and Wetlands Research Conference, Oxford, MS.,Island Press.

Rhew, K., and C.A. Ochs. 2000. Spatial patterns in autotrophic picoplankton abundance in a reservoir examined using microcosm experiments. Internat. Rev. Hydrobiol. 85 (4): 395-412 .

Rhew, K., R.M. Baca, C.A. Ochs, and S.T. Threlkeld. 1999. Interaction effects of fish, nutrients, mixing and sediments on autotrophic picoplankton and algal composition. Freshwater Biology. 42:99-109.

Ochs, C.A. and L. Eddy 1998. Effects of UVA on grazing pressure of a marine heterotrophic nanoflagellate on the unicellular cyanobacterium Synechococcus spp. Appl. Environ. Microbiol. 64: 287-293.

Ochs, C.A. and K. Rhew. 1997. Population dynamics of autotrophic picoplankton in a southeastern U.S. reservoir. Internationale Revue der gesamten Hydrobiologie 82: 293-313.

Ochs, C.A. 1997. Effects of UV radiation on feeding by two marine heterotrophic nanoflagellates on autotrophic picoplankton. Journal of Plankton Research 19(10): 1517-1536.

Ochs, C.A. J.J. Cole, and G.E. Likens. 1995. Population dynamics of bacterioplankton in an oligotrophic lake. Journal of Plankton Research 17(2): 365-391.
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