Influence of salinity on fertilization and larval development toxicity tests with two species of sea urchin C. Carballeira a, * , L. Martín-Díaz a, b , T.A. DelValls a a UNITWIN/UNESCO/WiCoP. Physical Chemistry Department, University of Cádiz,11510 Puerto Real, Cádiz, Spain b Andalusian Center of Marine Science and Technology (CACYTMAR), Campus Universitario de Puerto Real,11510 Puerto Real, Cádiz, Spain article info Article history: Received 10 June 2011 Received in revised form 6 August 2011 Accepted 19 August 2011 Keywords: Standardized tests Paracentrotus lividus Arbacia lixula Confounding factor Bioassay Fertilization membrane abstract Sea urchin embryo-larval development (ELD) and fertilization tests have been widely used in ecotoxicity studies and are included in regulatory frameworks. Biological processes occur naturally within a range of salinity that depends on the species considered. In an attempt to determine the optimum range of salinity, ELD and fertilization bioassays were performed at different salinities (15e40.5&) with two species of Atlantic sea urchin: Arbacia lixula and Paracentrotus lividus. In the ELD assay, the optimum range of salinity was wider for A. lixula (29e35.5&) than for P. lividus (29e33&). In the fertilization assay with P. lividus as a bioindicator species, the highest percentage of fertilization (90%) was obtained at salinities of between 29 and 33&. More research on A. lixula is required, since the fertilization success was below 60%. The results of the present study demonstrate that salinity may be a confounding factor in interpreting ELD test results. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Bioassays with marine organisms have been developed as a cost-effective method of evaluating marine water and sediment samples from contaminated sites. Standardized toxicity tests are useful in coastal ecosystem management, but require a readable endpoint to be established and identification of any confounding factors that may interfere with the measured response (OSPAR Comission, 2007). Bioassays enable detection of the effect of contaminants in the environment by measuring the responses of marine organisms, particularly at early life stages (His et al., 1999). Furthermore, bioassays are preferable to chemical analyses as they provide information about the bioavailability and toxicity of metals and mixtures of substances to organisms (Peters et al., 2002). Toxicity tests with early life stages of aquatic organisms have been proposed as a faster and more cost-effective method of testing chemicals and environmental samples than chemical analysis (Dinnel et al., 1987). Newly hatched larvae constitute particularly critical and sensitive stages, because at hatching the embryos lose their protective membrane and are fully exposed to potential toxins (Beiras et al., 2003). Sea urchin toxicity tests, which use fertilization and larval development endpoints, are considered worldwide as useful tools for assessing toxicity in marine environments. These acute toxicity tests have been applied to determine the toxicity of sediments (elutriated sediments and porewater) (Beiras et al., 2003; Cesar et al., 2004; Geffard et al., 2001) and sea water (Beiras et al., 2001; Saco-Álvarez et al., 2010) under laboratory conditions, and have been included and standardized by several national environ- mental agencies (Environment Canada, 2011; USEPA, 2002). It is well known that, for the purposes of risk assessment, a multispecies approach toward ecotoxicological testing is funda- mental for accurate environmental management and ecological risk assessment procedures (Van Straalen, 2002). Thus, tests should be standardized, include exposure in the water phase (for marine assessment), be reasonably practicable, costs should be appropriate for the amount of information obtained, and organisms should be indigenous and sensitive to a broad spectrum of contaminants (Peters et al., 2002). Paracentrotus lividus Lamarck 1816 (rock sea urchin) is a species commonly used in marine toxicity tests. One important characteristics of this species as bioindicator is its wide distribution, throughout the Mediterranean Sea and in the north-eastern Atlantic (Boudouresque and Verlaque, 2007). Arbacia lixula Linnaeus 1758 (black sea urchin) has been found to share habitat with P. lividus in several zones, both in Mediterranean and Atlantic coasts (Boudouresque and Verlaque, 2007; Martínez-Pita et al., 2010; Privitera et al., 2008; Tuya et al., Abbreviation: ELD, Embryo-Larval development. * Corresponding author. Tel.: þ34 956016423; fax: þ34 956016040. E-mail addresses: carlos.carballeira@uca.es (C. Carballeira), laura.martin@uca.es (L. Martín-Díaz), angel.valls@uca.es (T.A. DelValls). Contents lists available at SciVerse ScienceDirect Marine Environmental Research journal homepage: www.elsevier.com/locate/marenvrev 0141-1136/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.marenvres.2011.08.008 Marine Environmental Research 72 (2011) 196e203