To keep or not to keep track of time in eternal sunshine? Diel activity patterns of Svalbard arthropods during polar day

Abstract

Organisms on Earth are exposed to cyclic changes in environmental variables due to Earth’s rotation around it’s axis. As a response, many organisms adapt their behaviour in a rhythmic manner, which is often cued by 24h light-dark cycles. However, in the Arctic, traditional 24h light- dark cycle cues do not exist for long periods at the time. Arthropods play an important role in the high latitude ecosystems, yet little is known about their diurnal cycles and the impact of these cycles in the climate change context. Presence or absence of diurnal activity patterns in arthropod- visitors on Silene acaulis cushions was investigated in Svalbard with the use of time lapse imagery. This study showed some indication of diurnal activity in Diptera and nocturnal activity patterns in Acari. Compared to similar studies from lower latitudes within the Arctic, arthropod activity did not show such a robust diurnal pattern nor strong influence by weather variables as has been described during the polar day. However, abundances showed very high variability within days, between days and between cameras. Due to lack of reference studies from the high Arctic, it is not possible to determine if observed high variance in abundance is a distinctive characteristic of this system or specific to the observed year.