THE EFFECTS OF SHOOT AGE ON COLONIZATION OF AN EMERGENT MACROPHYTE (TYPHA-LATIFOLIA) BY MACROINVERTEBRATES

1. The colonization and dynamics of epiphytic aquatic macroinvertebrat es are described on first-year and second-year shoots of an emergent m acrophyte (Typha latifolia) in a Swiss pond. Effects of shoot senescen ce on composition, richness, density and biomass of the macroinvertebr ates are quantified. 2. There were two phases of colonization: a short -term colonization process which corresponded with that usually observ ed on inert substrates and a longer term colonization process related to the attractiveness of the shoots for the colonizers. In this second process, the older shoots showed a higher attractiveness for most inv ertebrate taxa. 3. Taxa colonized the shoots at different rates. Rapid colonizers included the limpet Ferrissia wautieri and the mayfly Cloe on dipterum. Conversely, Oligochaeta, Chironomidae and Ceratopogonidae were particularly slow colonizers. 4. The older shoots supported a hi gher mean annual richness, abundance and biomass of invertebrates. Com pared with younger shoots, the older shoots demonstrated a higher carr ying capacity for most invertebrate taxa, as is the case for many othe r freshwater macrophytes.