Long-term studies for evaluating the impacts of natural and anthropic stressors on limnological features and the ecosystem quality of Lake Iseo

Abstract

We review the state of the art of limnological studies in Lake Iseo and provide updated data concerning long-term investigations (from 1993 to 2018) carried out on chemical and physical parameters (e.g., oxygen, phosphorus, silicon). Changes observed in Lake Iseo were compared with those reported in other Deep South alpine Lakes (DSLs) to highlight analogies and differences of long-term chemical, physical, and biological patterns. Until the 1960s, Lake Iseo and other DSLs were oligotrophic. The increase of anthropogenic pressure and global warming has led to a progressive and unrecovered process of eutrophication. Moreover, the decrease in frequency of full mixing episodes has induced a state of temporary meromixis. Other changes have been identified over the last two decades, especially concerning the phytoplankton and zooplankton communities, and new emerging chemical pollutants were detected. Given the important ecological and socioeconomic role of Lake Iseo, long-term investigations are of paramount importance to understand the response of the lake ecosystem to climatic and anthropogenic stressors. These two factors can also act coupled with new combined and synergic effects.

A regional evaluation of the influence of climate change on long term trends in chlorophyll-a in large Italian lakes from satellite data

“…Owing to climatic conditions and the deep maximum depth of the lakes (Garda: 350 m, Como: 410 m, Iseo: 258 m, and Maggiore: 370 m) mixing historically only occurred every 7 years, typically down to 85 a depth of 200 m during cold and windy winters, while mixing in Iseo is prevented by a salinity gradient. The last mixing event was during 2005/2006(Leoni et al, 2019Rogora et al, 2018;Salmaso et al, 2018). Total phosphorus trends have been analysed from 1992-2016 (Rogora et al, 2018).…”

“…S1). Total phosphorus data was obtained from regional authorities (ARPA Lombardia, ARPA Veneto) and published values (Leoni et al, 2019;Rogora et 140 al., 2018).…”

Intermittent meromixis controls the trophic state of warming deep lakes

“…Previously published This study www.nature.com/scientificreports/ of 2006 ( Fig. 6a/b) 45 . Separation of a monimolimnetic water body combined with high sedimentary P recycling efficiency create intensive water column P accumulation.…”

“…The values for all single layers were summed to derive the overall P mass in the surface (0-21 m), middle (21-91 m), and monimolimnion (91-256 m) layers. For long-term time series, the average P concentrations in the 150-258-m layer 45 were multiplied by the volume of this stratum. The phosphorus release rates and the flux rates of the other solutes and methane were calculated from the concentration profiles across the sediment-water interface according to Fick's first law 75 using published diffusion coefficients 76 .…”

“…(b) Total phosphorus in deep waters (150-258 m). Black dots are TP contents (in metric tons) derived from published average TP concentrations45 . The red bar shows data obtained in this study as range.…”