Ecosystem health index (EHI) and electron transport system (ETS) activity of plankton and sediment in two lakes differing in trophic status

Abstract

Ecosystem health index (EHI) and respiratory electron transport system (ETS) activity were measured in plankton and sediment communities from two Slovenian lakes differing in their trophic status. The EHIs for Lake Bled and Lake Bohinj corresponded to a health status Middle and Good, respectively. The negative correlations that were found between EHI on the one hand and ETS activities of zooplankton and sediment and total ETS activity on the other indicated a higher ETS activity of zooplankton, sediment and total ETS activity at higher trophic status. The low seasonal variation of respiratory potential in the sediment, and its importance in degradation of organic matter and recycling of nutrients in the lakes, makes the measurement of the biological oxidation capacity of sediment appropriate for monitoring changes in ecosystem functioning in comparison to plankton communities. Thus, sediment ETS activity is a valuable source of information on the lake ecosystem, its functioning and its health, in combination with other indicators or information about the system. However, the interpretation of measured ETS activities of sediments needs knowledge on the specific characteristics of the lakes under investigation.