Bladderwort Relationship to Zooplankton in Two Northern Michigan Lakes

Abstract

Traditionally, most of our understanding of lake zooplankton dynamics is from data collected in the pelagic, open water zone. However, the littoral and benthic zones of lakes can play a role in zooplankton community interactions and relationships. Utricularia spp., or the bladderworts, inhabit littoral and shallow waters of lakes and consume zooplankton. Limited information exists on the dietary habits of bladderworts and how diet varies across lakes and seasonally. Bladderwort dietary assemblage in two Michigan, USA, lakes was quantified during the thermally stratified period of 2020, and was compared to zooplankton in the adjacent water column. Bladderwort trap size was positively related to zooplankton prey size, but not number of prey consumed or taxa richness. Bladderworts consumed a variety of prey, the majority dominated by littoral cladoceran and ostracod taxa. Seasonal change was observed, with significantly higher ostracod dominance earlier in the season, shifting into cladoceran dominance later in the season. Ostracods were more commonly found in traps than the water column, whereas Cladocera were more commonly found in the water column than the traps. These results shed light into the dietary habits of bladderworts, which can have consequences for food web dynamics and energy transfer in small lake systems.