Inorganic nitrogen and its effect on growth of the abalone Haliotis tuberculata Linnaeus and the sea urchin Paracentrotus lividus Lamarck

Abstract

The abalone, Haliotis tuberculata (7–12 g), and the sea urchin, Paracentrotus lividus (3–6 g), reared in a closed system were exposed for 2 weeks to various levels of ammonia (0, 0.5, 1.0, 5.0, 10.0 mg N–NH 3–4 l −1), nitrite (0, 0.5, 1.0, 2.0, 5.0 mg N–NO 2 l −1) and nitrate (0, 25, 50, 100, 250 mg N–NO 3 l −1). For these concentrations, no mortalities were observed. Growth and feeding rates were measured and compared to controls. The safe levels (no influence on growth) were determined for each compound: 1 mg N–NH 3–4 l −1 (0.045 mg N–NH 3 l −1) for both abalone and urchin; 1–2 mg N–NO 2 l −1 for the urchin, whereas abalone growth was stimulated at 2 mg N–NO 2 l −1 and its safe level was greater than 5 mg N–NO 2 l −1. For nitrates, the safe level was 100 mg N l −1 for the urchin and within the range 100–250 mg N l −1 for abalone. Below this level, nitrates seemed to have a stimulating effect on abalone. Thus, urchins are more sensitive to inorganic nitrogen than abalone. These results were compared to existing data, particularly on shrimp and Salmonidae. It seems that the levels determined are within the same range as those described for adults of other invertebrate and vertebrate species.