What have we learned about ecological recovery from liming interventions of acid lakes in Canada and Italy?

Abstract

We adopted an ecosystem perspective, by: i) exploring timing and mechanisms through which the biota responded to changes in hydrochemistry; ii) identifying common versus unique responses in a comparison of similar case studies on a large scale; iii) disentangling specific roles of primary (heavy metals) vs secondary (acidification), direct (chemical) vs indirect (predator/prey), and regional (colonist supply) vs local (colonist survival and growth) regulators of recovery of the biota; and iv) attempting to identify transition points to new, stable communities. If we can circumvent the almost unavoidable issue of lack of replication, and include appropriate hypotheses, controls, and pre-and post-manipulation data, a liming intervention can be comparable to a whole lake experiment. It can provide an opportunity for testing ecosystem-level responses to strictly controlled changes in the physical and chemical environment. Such wholelake experiments have a long tradition in North America, but it is rare that the results of whole-lake restoration experiments in the acidification field have been compared between North America and Europe.Lake Orta and many lakes in Sudbury, Ontario, Canada, suffered from acidification and metal pollution, albeit from different sources. For Lake Orta, the source of acidity was oxidation of ammonia wastes from a textile factory (Bonacina et al., 1986), while for Sudbury lakes, the source was atmospheric deposition of strong, S-based acidity from both the local smelting of metal-rich sulphide ores and long-range transport (Yan et al., 1996). Heavy metals were also greatly elevated in both cases (Calderoni et al., 1992;Keller et al., 2007). In Sudbury, both catchments and several urban lakes were limed, while lime was added directly to Lake Orta.This comparison of Lake Orta with the Sudbury case studies was extremely fruitful. By applying bioassays, Celis-Salgado et al. (2016) found that differences in metal-tolerances, and differences in recovery rates of native Canadian Daphnia species were mediated by calcium and sodium concentrations in Sudbury lakes, and thus their recovery was influenced not just by residual metals, but also by road salt and background geology. From Lake Orta, Di Cesare et al. (2016) learned that because heavy metal pollution may be coupled with antibiotic presence in nature, there may be co-selection for multiple resistances. Lake Orta thus appears to be an excellent location to evaluate the spread and selection of heavy metals and antibiotic resistances in heavily disturbed environments. Macrobenthic assemblages were slow to recover in both countries, but there were success stories. In Sudbury lakes the littoral macrobenthos community remained severely impoverished after catchment liming, indicating that land reclamation would be necessary in severely damaged watershed, before lake ecosystems can recover . In Lake Orta, mussels were extirpated by industrial copper and ammonium sulphate pollution, soon after 1926, when a rayon factory began operations on the lakeshor...

Recovery of acidified Sudbury, Ontario, Canada, lakes: a multi-decade synthesis and update

“…The more urbanized Sudbury lakes offer opportunities to better understand the aquatic effects of interacting multiple stressors in heavily developed landscapes Valois et al 2011). The lakes closest to the Subury smelters that were historically highly acidic and metal-contaminated offer valuable comparisons to other lake regions directly affected by metal smelters in other areas of D r a f t Canada (Alpay 2006;Jeziorski et al 2013) and the world (Moiseenko 1994), and lakes affected by other industrial sources of acid and metal-contamination (Manca et al 2016).…”

An archive for the history of limnology at Verbania Pallanza in the Italian Lake District

“…CNR personnel have participated in coordination, historical classification and for digitization aspects, while cataloguing was carried out by contract staff, thanks to contributions from the CRT Foundation (2013-18). A significant part of the reorganization of the archive was also carried out as part of a project financed by the Piedmont Region, relating to the pollution and rehabilitation of Lake Orta, over a period of 60 years (Rogora et al, 2016;Manca et al, 2016), constituting an aspect of great social and environmental importance in Italy.…”