Acute and chronic heavy metal bioassay on Tigriopus fulvus Fischer (Copepoda: Harpacticoida).

Description

Heavy metal pollution of coastal waters is a subject of concern in the management of the marine environment. Therefore, the protection of such environments needs the use of biological indicators able to support physico-chemical monitoring. Harpacticoid copepods can be suitable test species for their wide distribution, for their key-position within the food web and because they are easier to rear than pelagic species. In this study the acute (24-96 h) toxicity of heavy metals (Cd, Cr, Hg, Zn) on Tigriopus fulvus nauplii and adults and the chronic (30 d) toxicity on adults were evaluated. Copepods were collected in Ligurian rockpools and maintained in the laboratory in fíltered seawater (18 PSU, 18.0+0.5 °C, light-dark 12-12 h). Toxicity tests were performed on newborn I-II nauplii and adult females. Same age nauplii were obtained gently detaching egg sacs from ovigerous females. Copepods were exposed to CdCl2, CrCl2, HgCl2 and ZnCl2 and the LC50 was evaluated. The highest toxicity was always shown by Hg, while the lowest by Cr; Zn and Cd showed comparable toxicity after 72 h-treatment, while at 24 and 48 h Cd showed slower effects. The production of egg sacs and nauplii as well as the number of nauplii/egg sac and nauplii/female/day were highly reduced in specimens treated with Hg and Cd; anyhow, all brood parameters were highly affected by all tested metals. Our results show that T. fulvus is highly sensitive to metal contamination; thus it can be utilized as bioindicator to monitor the effects of heavy metal pollution in coastal marine waters.

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