Zooplankton seasonal dynamics in a recently filled mine pit lake: the effect of non-indigenous Daphnia establishment Sheree F. Balvert Æ Ian C. Duggan Æ Ian D. Hogg Received: 1 July 2007 / Accepted: 4 January 2008 / Published online: 25 January 2008 Ó Springer Science+Business Media B.V. 2008 Abstract We examined the temporal and vertical dynamics of zooplankton in Weavers Lake, New Zealand, between October 2004 and October 2005, at a time when it was colonised by a non-indigenous Daphnia species. Zooplankton community composi- tion changed during the study from one of rotifer dominance (e.g. Asplanchna, Polyarthra, Brachionus and Keratella species) to cladoceran (Daphnia den- tifera) dominance. Temporal changes in zooplankton community composition were strongly associated with a gradual increase in lake water clarity, and were attributable to the highly efficient filter feeding of D. dentifera. The corresponding reduction in rotifer densities may have resulted from the superior competitive abilities of the newly established Daph- nia. As Daphnia were rare inhabitants of New Zealand lakes before 1990, the arrival and rapid spread of the non-indigenous D. dentifera has lead to widespread changes in both water clarity and zoo- plankton community composition. An apparent lack of mixing in the lake was facilitated by the lake’s extremely small surface area:depth ratio. However, we conclude that physical features of the lake had minimal influence on water clarity relative to the invasion of D. dentifera. Keywords Daphnia dentifera invasion Á Succession Á Lake morphology Á Rotifera Introduction New Zealand lakes have fairly predictable zooplank- ton assemblages. For rotifers, compositional variation among lakes is largely determined by trophic state, while calanoid copepod distributions are determined by geological history (Jamieson 1998; Duggan et al. 2001). Cladoceran and cyclopoid copepod species, in contrast, are seemingly ubiquitous, with Bosmina and Ceriodaphnia the typical cladoceran inhabitants of any lake (Chapman and Green 1987). Daphnia have traditionally been an uncommon component in New Zealand lakes (Chapman and Green 1987), although the North American Daphnia dentifera has recently become widespread and abundant throughout North Island lakes (Duggan et al. 2006). A high efficiency of filter feeding has been observed for daphnids relative to other zooplankton species, and these species are generally considered responsible for initiating the spring ‘‘clear water phase’’ in many lakes elsewhere (e.g. Lampert et al. 1986; Leibold 1989). Additionally, Daphnia species are commonly found to have superior competitive abilities relative to other zooplankton, and their presence can have profound effects on zooplankton community compo- sition (e.g. Gilbert 1988; MacIsaac and Gilbert 1989). S. F. Balvert Á I. C. Duggan (&) Á I. D. Hogg Department of Biological Sciences, Centre for Biodiversity and Ecology Research, University of Waikato, Private Bag 3105, Hamilton, New Zealand e-mail: i.duggan@waikato.ac.nz 123 Aquat Ecol (2009) 43:403–413 DOI 10.1007/s10452-008-9165-z