Seasonal and diel patterns of mayfly (Ephemeroptera) drift in Korge stream, Latvia

Abstract

A complex set of biotic and abiotic factors affects a drift. Mayfly drift has been extensively studied worldwide, but the manner in which the environmental factors interact is not completely clear. The aim of the present study was to characterise mayfly seasonal and diel drift patterns in relation to abiotic factors in a medium-sized lowland stream in Latvia. Drift samples were collected at three-hour intervals in a riffle section in May, August and September 2007. Distinct seasonal and diel patterns of the mayfly drift were observed in the Korge stream. These were not directly infuenced by primary hydraulic factors e.g. current velocity and discharge, but depended on the active growth period of the mayfly species.

Keywords:

• mayflies
• drift
• abiotic factors
• lowland stream

Acknowledgements

The authors express their gratitude to the staff of the National Research Programme “Climate Change Impact on Water Environment in Latvia” (KALME) and the Laboratory of Hydrobiology, Institute of Biology of University of Latvia. The investigation was also supported by the European Social Fund. Many cordial thanks to all assistants for their help in this exciting diurnal fieldwork undertaking and to Assoc. Prof. Voldemars Spungis for his valuable advice in writing this manuscript. We are also grateful to Prof. John Brittain, Natural History Museum, Oslo, for valuable suggestions and significant linguistic improvement of the manuscript.