Aquatic Toxicology 84 (2007) 62–70 Physiological effects of copper in the euryhaline copepod Acartia tonsa: Waterborne versus waterborne plus dietborne exposure Grasiela Lopes Le˜ aes Pinho a , Mariana Saia Pedroso b , Sandra Carvalho Rodrigues a , Sandra Silvestre de Souza c , Adalto Bianchini c,∗ a Programa de P´ os-Gradua¸ c˜ ao em Oceanografia Biol´ ogica, Funda¸ c˜ ao Universidade Federal do Rio Grande (FURG), Campus Carreiros, Av. It´ alia km 8, 96.201-900 Rio Grande, RS, Brazil b Programa de P´ os-Gradua¸ c˜ ao em Ciˆ encias Fisiol´ ogicas - Fisiologia Animal Comparada (FURG), Brazil c Departamento de Ciˆ encias Fisiol´ ogicas (FURG), Brazil Received 6 February 2007; received in revised form 31 May 2007; accepted 1 June 2007 Abstract The physiological effects of waterborne and waterborne plus dietborne copper exposure were determined in the euryhaline copepod Acartia tonsa at different salinities (5, 15 and 30 ppt). Copepods were exposed (48 h) to a reported 48-h LC50 for copper (CuCl 2 ), which had been previously determined under the same experimental conditions. Whole body copper accumulation, ion concentrations (Na + , Cl - , Mg 2+ ), and Na + ,K + -ATPase activity were the endpoints measured in all experimental groups. Feeding rate was also measured in fed experimental groups. In copper-exposed copepods, whole body copper accumulation was dependent on salinity, decreasing as salinity increased. However, it was similar in copepods exposed to waterborne and waterborne plus dietborne copper, irrespective the salinity tested. Waterborne copper exposure induced a disturbance of the whole body Na + concentration in all salinities tested. This effect was characterized by an increased whole body Na + concentration in seawater (salinity 30 ppt) and a decreased whole body Na + concentration at lower salinities (5 and 15 ppt). The ionoregulatory imbalance in low salinity (5 ppt) was associated with an inhibition of the whole body Na + ,K + -ATPase activity, as observed in freshwater fish and crustaceans. When copepods were exposed to waterborne plus dietborne copper, the physiological effects described were only observed at a low salinity (5ppt) and were associated with a marked inhibition of the feeding rate. Taken altogether, the data suggest that the physiological effects induced by waterborne copper exposure in A. tonsa acclimated to higher salinities (15 and 30 ppt) are due to a combined effect of food restriction and copper exposure. Differential physiological responses to waterborne and waterborne plus dietborne copper cannot be ascribed to differences in whole body copper burden. © 2007 Elsevier B.V. All rights reserved. Keywords: Acartia tonsa; Acute toxicity; BLM; Copepod; Copper; Ionoregulation; Salinity 1. Introduction Copper is an essential metal found in water bodies primar- ily as a divalent cupric ion in both dissolved and particulate forms (Callahan, 1979). Marine invertebrates can accumulate dissolved copper directly by absorption through body surfaces (waterborne), while particulate metal forms can be accumulated by ingestion of contaminated food (dietborne) (Wang and Fisher, 1999). The relative importance of each route depends on the species and the physiological status of the individuals tested (Rainbow and Wang, 2001). It is important to consider both ∗ Corresponding author. Tel.: +55 53 3233 6853; fax: +55 53 3233 6848. E-mail address: adalto@octopus.furg.br (A. Bianchini). metal exposure routes in order to understand the different fac- tors controlling metal bioavailability to invertebrates, as well as the biological effects induced by metals. Copper is a minor nutrient for both plants and animals at low concentrations, but can be toxic at slightly elevated concentra- tions (Hall et al., 1997). Furthermore, phytoplankton cells have been shown to have copper levels higher than those physiologi- cally needed, the accumulation occurring by passive absorption and/or through processes of ion transport between algae and the aquatic medium (Huntsman and Sunda, 1980). Therefore, it is important to consider the possibility that copper may be transferred along food chains and may eventually reach toxic concentrations in upper trophic levels. At this point, it is impor- tant to consider that pelagic copepods dominate the herbivorous zooplankton community and are the main prey for most lar- 0166-445X/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2007.06.001