LAKE RESTORATION Does sediment capping have post-application effects on zooplankton and phytoplankton? Deniz O ¨ zkundakci • Ian C. Duggan • David P. Hamilton Received: 18 May 2009 / Accepted: 8 September 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Although in situ sediment capping is frequently used to reduce internal loading of con- taminants and nutrients, post-application assessment rarely includes the potential undesirable short-term effects on plankton species composition. We hypoth- esised that a modified zeolite (Z2G1) application as a sediment capping agent in Lake Okaro, New Zealand, could cause significant undesirable shifts in species composition of both zooplankton and phytoplankton due to burial of resting stages or interference with feeding for the zooplankton. Alternatively, we pre- dicted that the capping agent might have no effect due to, for example, the coarse grain size of the material (1–3 mm). We used multidimensional scal- ing (MDS) and analysis of similarity (ANOSIM) to identify any adverse effects of Z2G1 on zooplankton and phytoplankton species composition (i.e. shifts in community structure, including species loss) by comparing the community structure before and after the Z2G1 application. We found no significant differences in species composition before and after the Z2G1 application at the depths investigated (surface and 9 m). However, all of the analyses showed statistically significant differences among seasons, indicating seasonal variations in plankton composition far outweigh those that may have resulted from the Z2G1 application. Coarse particle size, low dose rate and a restricted area where the sediment capping agent was applied were considered to be the factors limiting potential adverse effects on plankton species. Considerations of finer-grained material to increase coverage and efficacy of phos- phorus adsorption require assessment for their effects on zooplankton, however, and a direct mode of application into the hypolimnion is recommended to minimise effects on zooplankton and phytoplankton communities. Keywords Eutrophication Á Lake Okaro Á Modified zeolite Á Turbidity Introduction Internal loading of phosphorus (P) and nitrogen (N) can contribute significantly to nutrient loads entering the water column of lakes (Søndergaard et al., 2003). Such inputs can delay the improvement of water quality following restoration measures (Jeppesen et al., 2005). Several methods have therefore been developed to reduce P in both the water column and bottom sediments of lakes (Klapper, 2003). Floccu- lation or P precipitation with iron or aluminium salts Guest editors: D. P. Hamilton, M. J. Landman / Lake Restoration: An Experimental Ecosystem Approach for Eutrophication Control D. O ¨ zkundakci (&) Á I. C. Duggan Á D. P. Hamilton Centre for Ecology and Biodiversity Research, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand e-mail: do12@waikato.ac.nz 123 Hydrobiologia DOI 10.1007/s10750-009-9938-y