River bacteria time series analysis: a field and laboratory study which demonstrates aquatic ecosystem health

Abstract

Time series analysis of heterotrophic bacterial viable counts on agar plates incubated at 20 ° and 4°C from weekly river water samples for 1 year has revealed a periodicity of 6 to 7 weeks in the total numbers. A cycle of increase and decrease in the counts which could not be attributed to season, river water temperature, pH, and flow rate has been observed in the heterotrophic bacteria which were isolated from river water samples. Spectral analysis has demonstrated a hidden periodicity in population increase and decrease which could not be detected by examination of the raw count data. Fluctuations with periodicity could imply that this is the expected behaviour in a well-balanced ecosystem.Pseudomonas fluorescens, the predominant species isolated from a river water sample which was at 0°C at the time of sampling, utilized two different pathways at 5 ° and 30°C. In addition, 2-ketogluconate, a product of the utilization of glucose, was utilized by the same organism. Fluctuations in enzymic responses could contribute to the overall periodicity in bacterial numbers. The flexibility in bacterial metabolism would serve to maintain P. fluorescens in the predominant flora. A feature which sustains health in this ecosystem, P. fluorescens, is one of the most successful of all biodegraders in the aquatic system.

A bacterium with close genetic identity to Pseudomonas mandelii associated with spring fish kills in wild bluegill Lepomis macrochirus Rafinesque and pumpkinseed sunfish Lepomis gibbosus (Linnaeus)

“…Pseudomonads, including Pseudomonas fluorescens , are highly diverse and ubiquitous in nature, commonly found in aquatic environments and known to be important in biodegradation in aquatic ecosystems (Holder‐Franklin & Franklin, ). Several species of pseudomonads have also been found to be pathogenic in fish (Austin & Austin, ).…”