Unexpected increases in rotifer resting egg abundances during the period of contamination of Lake Orta



  • Roberta Piscia | r.piscia@ise.cnr.it National Research Council, Institute of Ecosystem Study, Italy.
  • Simone Tabozzi National Research Council, Institute of Ecosystem Study University of Insubria, Italy.
  • Roberta Bettinetti University of Insubria, Italy.
  • Liisa Nevalainen University of Jyväskylä, Finland.
  • Marina M. Manca National Research Council, Institute of Ecosystem Study, Italy.


Despite their ecological importance and rapid response to environmental changes, rotifers are rarely included in palaeolimnological studies. Here, we describe changes in abundance (ABD) and morphotype (MTs) diversity of rotifer resting eggs in the sediments of deep subalpine Lake Orta, Italy, covering a period prior to (pre-) 1926, during long-term ammonia and metal pollution from a rayon factory, and subsequent recovery of water quality. Following the pollution and bacterial oxidation of the ammonia, Lake Orta became the largest and deepest acid lake in Europe. Recovery of water quality followed both a ban on the discharge of industrial wastes, and a liming intervention in 1989 and 1990. We sectioned a sediment core collected from the deepest part of the lake (ORTA 07/2A) to provide a high  time resolution, given the ca. 3-4 y cm-1 of sediment accumulation. Rotifer resting egg (RRE) abundance and morphotypes were examined from the sediments and compared to limnological variables indicating the pollution. Rotifer resting egg abundance significantly increased with lake contamination (r=0.609 and -0.624 for copper and pH, respectively; P<0.001; n=27). A lake-water copper concentration threshold of ca. 40 µg L-1discriminated among pre-, during-, and post- pollution compositions of the rotifer morphotype assemblages. Diversity and morphotype richness increased during the recovery from copper pollution and with complete restoration from acidity, while abundance increased during pollution. The persistence of presumably viable Brachionus resting eggs and of hatched egg cases during the heavy pollution phase suggests that, unlike most other organisms, which were extirpated by the pollution of the lake, rotifers survived producing resting eggs, which secured future generations.



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Lake Orta: a new lease on life
Supporting Agencies
Kone Foundation
Paleo-ecotoxicology, Rotifera, diapause, Lake Orta, copper and ammonia pollution.
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How to Cite
Piscia R, Tabozzi S, Bettinetti R, Nevalainen L, Manca MM. Unexpected increases in rotifer resting egg abundances during the period of contamination of Lake Orta. J Limnol [Internet]. 2016 Apr. 13 [cited 2021 Jun. 17];75(s2). Available from: https://www.jlimnol.it/index.php/jlimnol/article/view/jlimnol.2016.1300

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