A decade-long study on mayfly emergence patterns

Abstract

Mayfly assemblage structure, microhabitat preference and emergence patterns were studied over a decade in two types of karst freshwater habitats, namely, a spring and two tufa barriers. Mayfly adults were collected using pyramidal emergence traps. A total of nine species was recorded. Tufa barriers had a higher species richness but a lower abundance than did the spring. All sites were dominated by species typical of the rhithral zone. The spring had the highest share of grazers, whereas gatherers (collectors and filter feeders) dominated at tufa barriers, with minimal changes through the years. Mayfly abundance at the spring was higher in years with a higher discharge. The opposite was recorded for tufa barriers, which could be related to drift and food availability. Mayflies emerged from the spring between March and November, most probably being triggered by the photoperiod. Emergence from tufa barriers was seasonal and related to changes in water temperature. Some species exhibited typical central European emergence patterns, whereas, in some others, certain discrepancies were recorded. Several taxa showed preference towards emergence from a particular microhabitat. The present study showed that for fine ecological data on aquatic insects, long-term studies are essential.