title: Toxicity of nickel in the marine calanoid copepod Acartia tonsa: Nickel chloride versus nanoparticles.
abstract: Nickel compounds are widely used in industries and have been massively introduced in the environment in different chemical forms. Here we report the effect of two different chemical forms of nickel, NiCl2 and nickel nanoparticles (NiNPs), on the reproduction of the marine calanoid copepod Acartia tonsa. The behavior of nickel nanoparticles was analyzed with different techniques and with two protocols. In the "sonicated experiment" (SON) NiNP solution was sonicated while in the "non-sonicated experiment" (NON-SON) the solution was vigorously shaken by hand. Final nominal concentrations of 5, 10 and 50mgL(-1) and 1, 5 and 10mgL(-1) NiNPs were used for the acute and semichronic tests, respectively. Nanoparticle size did not change over time except for the highest concentration of 50mgL(-1) NiNPs, in which the diameter increased up to 843nm after 48h. The concentration of Ni dissolved in the water increased with NP concentration and was similar for SON and NON-SON solutions. Our results indicate that sonication does not modify toxicity for the copepod A. tonsa. Mean EC50 values were similar for NON-SON (20.2mgL(-1)) and SON experiments (22.14mgL(-1)) in the acute test. Similarly, no differences occurred between the two different protocols in the semichronic test, with an EC50 of 7.45mgL(-1) and 6.97mgL(-1) for NON-SON and SON experiments, respectively. Acute and semichronic tests, conducted exposing A. tonsa embryos to NiCl2 concentrations from 0.025 to 0.63mgL(-1), showed EC50 of 0.164 and 0.039mgL(-1), respectively. Overall, A. tonsa is more sensitive to NiCl2 than NiNPs with EC50 being one order of magnitude higher for NiNPs. Finally, we exposed adult copepods for 4 days to NiCl2 and NiNPs (chronic exposure) to study the effect on fecundity in terms of daily egg production and naupliar viability. Egg production is not affected by either form of nickel, whereas egg viability is significantly reduced by 0.025mgL(-1) NiCl2 and by 8.5mgL(-1) NiNPs. At NiNP concentration below the acute EC50 (17mgL(-1)) only 9% of embryos hatched after 4 days. Interestingly, the percentage of naupliar mortality (>82%) observed in the semichronic test at the nominal concentration of 10mgL(-1) NiNPs corresponding to almost 0.10mgL(-1) of dissolved Ni, was similar to that recorded at the same Ni salt concentration. Electron microscopical analyses revealed that A. tonsa adults ingest NiNPs and excrete them through fecal pellets. To the best of our knowledge, this is the first study investigating the toxicity of two different forms of Ni on the reproductive physiology of the copepod A. tonsa and showing the ability of the calanoid copepod to ingest nanoparticles from seawater.
authors.affiliation: Istituto per la Protezione e Ricerca Ambientale ISPRA_STS Livorno, Piazzale dei marmi 12, 57123 Livorno, Italy; Academic Centre for Innovation and Development in the Food Industry (CAISIAL), Università degli Studi di Napoli Federico II, 80055 Portici, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Istituto per la Protezione e Ricerca Ambientale ISPRA_STS Livorno, Piazzale dei marmi 12, 57123 Livorno, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Vitiello
authors.affiliation: Institut Català de Nanotecnologia, Campus de la Universitat Autònoma de Barcelone, 08193 Bellaterra, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Casals
authors.affiliation: Institut Català de Nanotecnologia, Campus de la Universitat Autònoma de Barcelone, 08193 Bellaterra, Spain; Institut Català de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08010 Barcelona, Spain.
authors.forename: V F
authors.initials: VF
authors.lastname: Puntes
authors.affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Iamunno
authors.affiliation: Istituto per la Protezione e Ricerca Ambientale ISPRA_STS Livorno, Piazzale dei marmi 12, 57123 Livorno, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Pellegrini
authors.affiliation: Zhejiang Ocean University, 1 Rd. South Haida, Lincheng New Area, Dinghai District Zhoushan City, 316022 PR China.
authors.forename: W
authors.initials: W
authors.lastname: Changwen
authors.affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Benvenuto
authors.affiliation: Istituto per la Protezione e Ricerca Ambientale ISPRA_STS Livorno, Piazzale dei marmi 12, 57123 Livorno, Italy. Electronic address: isabella.buttino@isprambiente.it.
authors.forename: I
authors.initials: I
authors.lastname: Buttino
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000187:drug effects*; D001681:Biological Assay; D033342:Copepoda / Q000187:drug effects*; D005260:Female; D053758:Nanoparticles / Q000633:toxicity* / Q000648:ultrastructure; D009532:Nickel / Q000633:toxicity*; D010316:Particle Size; D013054:Spectrophotometry, Atomic; D055672:Static Electricity; D023382:Toxicity Tests, Acute; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; C022838:nickel chloride; D009532:Nickel
keywords: Acute test; Bioassays; Chronic test; EC(50); Egg hatching success; Naupliar mortality; Semichronic test; Zooplankton