Mining pollution triggered a regime shift in the cladoceran community of Lake Kirkkojärvi, southern Finland

Abstract

Mining is one of the key industries in the world and mine water pollution is a serious threat to aquatic ecosystems. Historical monitoring data on the pollution history and impacts in aquatic ecosystems, however, are rarely available, so paleolimnological methods are required to explore the consequences of past pollution. We studied the history of cladoceran community dynamics in Lake Kirkkojärvi, southern Finland, including the periods before, during and after mining. We analyzed the geochemical composition and cladoceran subfossil remains in a 210 Pb-dated sediment core to evaluate the magnitude, rate, and direction of cladoceran community changes through time. The cladoceran community was altered significantly by mining activity that occurred during the mid-20 th century. During more recent times, however, eutrophication effects have overridden the impacts of mining. After mining ceased, the cladoceran community underwent an abrupt regime shift towards taxa that reflect more eutrophic conditions. This change was caused by intensive farming activity and fertilizer use over the past few decades. The recent history of Lake Kirkkojärvi is a textbook example of a regime shift triggered by multiple human-caused stressors. Our findings also highlight the utility of cladocerans as bio-indicators in pollution research and illustrate the sensitivity of aquatic ecosystems to anthropogenic modification.

Zooplankton functional diversity as an indicator of a long‐term aquatic restoration in an Amazonian lake

“…In the water column, tailings influence plankton dynamics by increasing inorganic turbidity. Inorganic turbidity represents an essential regulator of species dynamics and trophic interactions, weakening the link between phytoplankton, zooplankton, and high trophic levels (Guenther & Bozelli 2004; Horppila & Liljendahl‐Nurminen 2005; Leppänen et al 2018). Since the beginning of the restoration activities in Batata Lake, considerable improvements in water clarity were observed in the impacted areas (Bozelli et al 2000).…”

Waste water discharge from a large Ni-Zn open cast mine degrades benthic integrity of Lake Nuasjärvi (Finland)

“…5). C. sphaericus is a resilient taxon (Koff et al, 2016) and has been often found to increase under environmental perturbation, such as eutrophication (Nevalainen and Luoto, 2013) and mining pollution (Leppänen et al, 2018). Although usually considered as a littoral cladoceran, C. sphaericus can thrive in the plankton of eutrophic lakes as well (Manca et al, 2007).…”

An overview of Cladoceran studies conducted in mine water impacted lakes

“…B. longirostris is regarded as more sensitive to copper pollution than many other cladoceran species (Koivisto et al 1992;Koivisto and Ketola 1995;Bossuyt and Janssen 2005) which may explain the above mentioned deleterious impact. Leppänen et al (2017b) reported decreased diversity and species richness in Lake Kirkkojärvi, southern Finland, which has been affected by increased input of mineral matter and minor metal pollution, originating from tailings impoundment of Au-Cu mine around 1960-1970, but the lake has never acidified due to rapid dilution. The most pronounced impact was detected during the input of fine mineral tailings.…”