Factors contributing to cucumber odor in a northern USA reservoir

Abstract

Episodic occurrences of cucumber odor caused by the alga Synura petersenii in Meander Creek Reservoir (MCR), northeastern Ohio, USA, are partly attributed to increased water transparency resulting from decreased phosphorus and suspended solids loading from the watershed. The first documented occurrence of nuisance odor levels was in 1984, 52 years after the reservoir was filled. This indicates that previous environmental factors constraining the growth of S. petersenii have been relaxed, probably from changes in the physical–chemical environment in the reservoir caused by changes in land use in the catchment. Reduction in farming since 1950, and diversion of sewage around the reservoir in 1977, reduced suspended solids and total phosphorus loading into the reservoir during the time that the cucumber odors occurred. These observations support the hypothesis that increased transparency of the reservoir, resulting from decreased sediment loading and reduced productivity, has permitted the occasional occurrence of nuisance densities of S. petersenii. Based on available data, pH, iron, and silica do not appear to be key factors regulating growth of S. petersenii in MCR. The transition to lower turbidity and total phosphorus concentrations from catchment restoration actions may increases the risk of S. petersenii blooms and cucumber odor episodes. While the overall benefits of cleaner raw water for water supply may outweigh this risk, it is desirable to understand the factors that promote nuisance growths and take actions to control them.

Key words:

• diatom inferred phosphorus
• land use
• nutrient export
• odor
• reservoir
• sediment core
• Synura petersenii
• taste

Acknowledgments

Dr. Eduardo A. Morales, Curador, Herbario Criptogámico, Universidad Católica Boliviana San Pablo, Cochabamba, Bolivia and research scientist at the Philadelphia Academy of Sciences, Philadelphia, PA, helped with identification of diatoms. Dr. Gary Walker, Department of Biological Sciences, Youngstown State University (YSU), gave valuable advice on microscopy and microphotography and permitted use of his dark room and dark room facilities. Carl Leet III, YSU Media Center, provided resources and help digitizing film negatives and advice on microphotography. John Bralich, Center for Urban and Regional Studies, YSU, provided the census data and the map of MCR catchment. Ellen Wakefield-Banks at the YSU library was exceptionally helpful in tracking literature sources. Ed McCormack, Joe Paris and Martin Kielbasa of the MVSD provided access to MVSD data and logistical support for field work. We are especially appreciative to the editor of LRM and to the several reviewers for their insightful and constructive suggestions. Funding was provided by the MVSD and YSU Research Council, grant number 2004–2005 #1.