Ronald Hoham (Professor of Biology)

Department of Biology, Colgate University

Phone: 315.228.7342 Fax: 315.228.7997

E-Mail: RHoham@mail.colgate.edu

Research Interests: Snow microorganisms: physiological ecology, studies of life histories and mating strategies, geographical distributions, effects of temperature and acidity on their growth, and comparative studies between eastern and western North America. [Details]

Teaching Interests: Aquatic biology (phycology and macrophytes); plant evolution and diversity; introductory biology; research tutorial in snow algae; Montana Study Program in biology at the Flathead Lake Biological Station affiliated with the University of Montana, Missoula; Marine Freshwater Science topical concentration in biology and geology.  [Details]

Student Research   Publications  

Colgate Teaching & Research Directory  

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Ronald Hoham

Research Interests: 

I am one of very few scientists who studies snow microbiology. The microbes found in snow live in one of the most extreme environments, which includes high UV levels in acidic snow, temperatures near 0°C with low nutrient concentrations for growth, and the formation of resistant spores that survive conditions of extreme drought after the snowpack melts. Thus NASA has looked at snow and ice algae as one of four Earth analogs of life for the possibilities of life outside our planet. These microbes are also used as bioindicators to study increased levels of ultraviolet light and the prolonged effects of acid precipitation. The research in my lab emphasizes the study of snow algae.

Lab research over the past five years has focused on the interrelationship of light and sexual reproduction in the green snow alga, Chloromonas. The parameters of light investigated are spectral composition, irradiance level, and photoperiod, and experiments are conducted under controlled conditions using lab growth chambers. Experiments are designed to simulate light conditions in snowpacks where snow algae are found in nature. Optimal sexual reproduction is determined by counting mating pairs through microscopes and statistical analyses are done to determine the effects of the light parameters. Microscopic images are captured and stored using computer software.

We have investigated temperature optima in Chloromonas, and are now looking at pH optima. Lab isolates free of bacteria and fungi were grown at different temperatures [2.5, 5, 7.5, 10, 15, and 20°C] to determine if optimal growth is near 0°C, which are the field conditions. Experiments with pH include pH points from 3.0-8.0 at half point intervals to determine if the microbes grow optimally at the pH that is found in snowpacks at the time of growth. This research involves two species of Chloromonas, one from central NY and one from the Tughill Plateau in northern NY, and these are the same species used in the light experiments.

Under the direction of molecular biology faculty, students have examined the evolutionary position and history of the snow alga, Chloromonas, and compared it to other closely related genera of green algae. It was determined that snow algal biflagellates have invaded the snow habitat at least twice and possibly three times. In the future, students will try to isolate two transcription factors from Chloromonas and find out what genomic information might be available. 

[Image above: Cover of the book Snow Ecology, co-edited by Professor Hoham]

Teaching Interests:

I teach courses at each level in the department. I team-teach in one of the new foundation courses, biology 211, evolution, ecology, and diversity. In plant evolution 225, students learn about the evolution of photosynthetic cells, spore-producing plants, and seed plants. Topics covered include cell symbiosis, plate tectonics, plant competition and survival, plant-animal interactions, and historical geology. In phycology-macrophytes 320, students learn how to use algae and aquatic macrophytes as indicators of water quality. In this course we do a comparative research project between two lakes, and students write a research paper from the project. In my research tutorial 481 on snow algae, students work in teams of three or four to design experiments [see research section], tabulate data sets, write a research paper, and do a poster. 

I organize the Montana Study Program at the Flathead Lake Biological Station [FLBS], which is located near Glacier National Park.  FLBS is affiliated with the University of Montana-Missoula. Colgate sends about twelve students to FLBS to take field courses in the northern Rocky Mountains during the summer in even years only.  I am also a co-Director of the Marine Freshwater Science [MFWS] topical concentration along with Charlie McClennen in geology.  This program allows students to take courses in both departments, and students are required to attend a field station in either marine or freshwater sciences.  Students typically go on SEA Semester, Woods Hole, MA, or attend the summer session at FLBS in Montana.

Student Research:

In the past five years, many students have worked in my lab. The lab is a major group effort and working together is part of the lab scene. Amy Marcarelli [‘00], Mike Ragan [‘00], Haldre Rogers [‘00], Ben Petre [‘00], Joe Barnes [’01], and Mike Ungerer [‘01], along with Dave Francis [‘99] were co-authors on a research paper that examined the effects of photoperiod on sexual reproduction and mating in the snow alga, Chloromonas. This was published in December 2000 in Hydrological Processes and in the Eastern Snow Conference Proceedings. These same students completed the life cycle of this Chloromonas, and this research is ready for publication. Three of these students presented posters of this work at the Northeast Algal Society [NEAS] in April 2000 at the University of Rhode Island, and six of the students presented the same research at the Eastern Snow Conference [ESC] Meeting in May 2000 in Syracuse, NY.

Several students worked in my lab during 2001-2002 on the mating potential and temperature optima in six isolates of the same species of Chloromonas from snow used in the photoperiod and life cycle work. These students were Joe Barnes [‘01], Mike Ungerer [‘01], Noah Lipton [‘01], Joy Felio [‘02], Tom Miller [‘02], Brendan Smith [‘02], Sarah Todd [‘02] , JB Banghart [‘03], Jared Duncan [‘03], and Nick Gerken [‘03].

Tomas Bonome [‘00], Jesse Chandler [‘00], and Chris Martin [‘01] worked in conjunction with another professor, Jim Leebens-Mack, and they used gene sequences to determine the evolutionary position of Chloromonas from snow in relationship to other green algae that were found in cold and temperate habitats. This work emphasized the rbcL plastid gene and the nuclear 18S rDNA gene and its adjacent ITS1 and 2 regions. Tomas Bonome presented this work in 2000 at the NEAS and ESC poster sessions, and it was later published in the Journal of Phycology in October 2002.

Between 2002-2004, students have been looking at how spectral composition, irradiance level, and photoperiod affect mating and reproduction in another species of Chloromonas isolated from central NY, and the results of this research are being compared to the Tughill Plateau species already investigated.  These two species of Chloromonas have different mating strategies and appear not to be responding to light in the same way.  This research has involved JB Banghart [‘03], Jared Duncan [‘03], Andrew Forbes [‘03], Nick Gerken [‘03], Blair Goodridge [‘03], Jesse Berman [‘04], Paris Miller [‘04], and Jeff Ryba [‘05].  Jesse Berman, Paris Miller, and Jeff Ryba presented some of this research in April 2003 at the NEAS Conference at Skidmore College.

Several undergraduates are employed by the Colgate Research Council to assist with the lab research done by students in the research tutorial, biology 481. These students, Jesse Berman [‘04], Ben Blom [‘06], Jane Hornickel [‘06], Tim Pusack [‘05], Dave Rozolsky [‘06], and Jeff Ryba [‘05] maintain all lab cultures used in the research. This includes making media, streaking agar plates, preparing cultures for experiments, organizing microscopic images, and general lab maintenance. Without this assistance, the research would not happen!  These students have also conducted two pH optima experiments, one for each of the two species of Chloromonas mentioned above.

Recent Publications:

Hoham, R.W., Kang, J.Y.*, Hasselwander, A.J.*, Behrstock, A.F.*, Blackburn, I.R.*, Johnson, R.C.* and Schlag, E.M*. 1997. The effects of light intensity and blue, green, and red wavelengths on mating strategies in the snow alga, Chloromonas sp.-D, from the Tughill Plateau in New York State. In Albert, M. & Taylor, S. [Eds.], Proceedings of the Fifty-fourth Annual Eastern Snow Conference and Sixty-fifth Annual Western Snow Conference, Banff, Alberta, Canada, pp. 80-90.

Hoham, R.W., Schlag E.M.*, Kang, J.Y.*, Hasselwander, A.J.*, Behrstock, A.F.*, Blackburn, I.R.*, Johnson, R.C.* and Roemer, S.C.* 1998. The effects of irradiance levels and spectral composition on mating strategies in the snow alga, Chloromonas sp.-D, from the Tughill Plateau, New York State. Hydrological Processes 12: 1627-1639.

Duval, B. Duval, E. and Hoham, R.W. 1999. Snow algae of the Sierra Nevada, Spain, and High Atlas mountains of Morocco. International Microbiology 2: 39-42. .

Hoham, R.W. and Ling, H.U. 2000. Snow algae: the effects of chemical and physical factors on their life cycles and populations. In Seckbach, J. [Ed.], Journey to Diverse Microbial Worlds: Adaptation to Exotic Environments, (In the book series, Cellular Origin and Life in Extreme Environments), Kluwer Press: The Netherlands, pp. 131-145.

Duval, B. and Hoham, R.W. 2000. Snow algae in the northeastern U.S.: photomicrographs, observations and distribution of Chloromonas spp. (Chlorophyta). Rhodora, 102:365-372.

Hoham, R. W., Ragan, M.D.*, Marcarelli, A.M.*, Petre, B. M.*, Barnes, J.M.*, Rogers, H.S.* and Ungerer, M.D.* 2000. The effects of Vita-Lite and blue light pre-acclimation on sexual reproduction in the green snow alga, Chloromonas sp.-D (Chlorophyceae, Volvocales), using different photoperiods. In Hardy, J (Ed.), Proceedings of the Fifty-seventh Annual Eastern Snow Conference, Syracuse, NY, pp. 207-220.

Hoham, R.W., Marcarelli, A.M.*, Rogers, H.S.*, Ragan, M.D.*, Petre, B.M.*, Ungerer, M.D.* and Francis, D.O.* 2000. The importance of light and photoperiod in sexual reproduction and geographical distribution in the green snow alga, Chloromonas sp.-D (Chlorophyceae, Volvocales). Hydrological Processes 14:3309-3321.

Hoham, R.W. and Duval, B. 2001. Microbial ecology of snow and freshwater ice with emphasis on snow algae. In Jones, H.G., Pomeroy, J.W., Walker, D.A. and Hoham, R.W. [Eds.], Snow Ecology: An Interdisciplinary Examination of Snow-covered Ecosystems, Cambridge University Press, Cambridge, UK, pp. 168-228.

Hoham, R.W., Bonome, T.A.*, Martin, C.W.*, and Leebens-Mack, J.H. 2002. A combined 18S rDNA and rbcL phylogenetic analysis of Chloromonas and Chlamydomonas (Chlorophyceae, Volvocales) emphasizing snow and other cold-temperature habitats.  Journal of  Phycology 38:1051-1064.

Hoham, R. W. 2004. Snow algae: A unique world in a cold environment. Wildflower Magazine: in press.

*indicates student co-author