Detrimental effects of nitrite on the development of benthic Chironomus larvae, in relation to their settlement in muddy sediments
Neumann, Dietrich; Kramer, Meike; Raschke, Ina; Gräfe, Brigitte
published: Dec 18, 2001
ArtNo. ESP141015301005, Price: 29.00 €
1. In order to establish the limiting influence of nitrite on the larval development of Chironomus in nitrate/nitrite-loaded waters, we investigated the complete larval development until eclosion, larval mortality and morphological modifications of the abdominal appendages (ventral tubules and anal papillae) in Chironomus piger STR. and Ch. riparius MEIG. (syn. thummi thummi STR.) reared at concentrations of nitrite within the range found in nature. This ecotoxicity study of the life-cycle was conducted in a laboratory using flow-through equipment and standardised freshwater (SFW). 2. In SFW (95 % O2, pH 8-8.4) without nitrite, the duration of larval development was 18.1 days at 19 °C. At a sublethal concentration of 0.15 mg/l nitrite-N, development was extended to 20.7 days. The larval mortality was still only 7 % at 0.30 mg/l nitrite-N, but at 0.46 mg/l nitrite-N it reached 96 %. At 30 % O2, no obvious increased lethality occurred until 1.5 mg/l nitrite-N. 3. At critical nitrite concentrations with 95 % O2, the ventral tubules did not reach their normal size, and were misshapen. At 30 % O2 without nitrite, these tubules became enlarged, but to a lesser extent when kept in a nitrite-medium of 0.9 mg/l nitrite-N. 4. No changes occurred in the anal papillae (syn. anal tubules; necessary for active influx of sodium and chloride), when SFW nitrite media of 0.9 mg/l nitrite-N were used. However, in SFW modified by reducing the chloride concentration from 17 to 4 mg/l, the anal papillae were abnormally enlarged. 5. The results are discussed in relation to (a.) impaired development, (b.) ecotoxic indication of malformed ventral tubules, (c.) nitrite uptake via a process linked with chloride uptake (as in fish), (d.) way of life of Chironomus larvae in muddy substrates, (e.) expected bottleneck situations occurring in nitrate-loaded waters, and (f.) function of Chironomus haemoglobins.