Collapse of Calanus chilensis reproduction in a marine environment with high diatom concentration S.A. Poulet a, ⁎ , R. Escribano b , P. Hidalgo b , A. Cueff a , T. Wichard c , V. Aguilera b , C.A. Vargas b , G. Pohnert d a Station Biologique de Roscoff, CNRS, INSU, UPMC Paris VI, UMR 7150-Unité Mer et Santé, Roscoff 29682, France b Centerof Oceanography for the Eastern South Pacific (COPAS), Universidad de Concepcion, P.O. Box 160 C, Concepcion, Chile c Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8; D-07745 Jena, Germany d Ecole Polytechnique Fédérale de Lausanne (EPFL) Institute of Chemical Sciences and Engineering, CH-1015 Lausanne, Switzerland Received 17 July 2007; accepted 18 July 2007 Abstract Variations of egg production rate (EPR), hatching success (HS), production of abnormal larvae (AL) and histology of gonads have been investigated with Calanus chilensis females sampled weekly, from late November to December 2004, at a station located in the coastal zone off Dichato (Chile), at time diatom concentration in phytoplankton bloom was high. Weekly EPR estimate in nature did not change significantly during this period. It remained close to normal values (25–40 eggs/female/day), whereas HS was constantly low and high proportions of AL were observed. In parallel, bioassays revealed that EPR was strongly depressed by artificially enriched diets, corresponding to natural diatom assemblages (NDA) occurring in the field, while abnormal HS and AL values could not be improved. Ingestion of diatoms by females was estimated by faecal pellet production rates and SEM examination of diatom remains in pellet samples. Low HS and the high amounts of abnormal larvae were not reversible when females were offered a favourable food, the dinoflagellate P. minimum (PM). Minor cell degradations were observed in gonads of females fed NDA diets. In comparison with other environments, present results show that impairment of Calanoid copepod reproductive factors can occur at both high and low diatom concentrations, depending on maternal diets and diatom species in blooms. © 2007 Elsevier B.V. All rights reserved. Keywords: Calanus; Copepods; Diatoms; Reproduction 1. Introduction Egg production rate (EPR), egg hatching success (HS) and production of abnormal larvae (AL) are the three main factors used to describe reproduction and recruitment success of marine copepods. The reproduc- tive response determines the demography and copepod population dynamics and is strongly influenced by the maternal food. Up to now maternal diets can be characterised by food quality parameters and their content of potential adverse chemical compounds. In bioassays conduced under laboratory conditions, several authors (Ban et al., 1997; see reviews by Ianora et al., 2003; Paffenhöfer et al., 2005) found, with combinations of different copepods fed high diatom concentrations Journal of Experimental Marine Biology and Ecology 352 (2007) 187 – 199 www.elsevier.com/locate/jembe ⁎ Corresponding author. E-mail address: poulet@sb-roscoff.fr (S.A. Poulet). 0022-0981/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2007.07.019