Comprehensive study of the mountainous lake sediments in relation to natural and anthropogenic processes and time (Mały Staw Lake, Poland)

The Sudety Mts. form a chain of mountains in the South of Poland and during the last 200 years were subjected to strong industrial and agricultural pressure. The records of these human-induced changes are stored in natural archives like lake sediments. For the comprehensive study, three sediment cores taken from Mały Staw Lake (Sudety Mts.) were analyzed for the concentration of K, Na, Mn, Fe, Cu, Mg, Zn, Cd, Cr, Ni, Pb and radioactivity of 137Cs and 210Pb. As a result of the studies, the bathymetry map was developed and the sources of solid material supplied to the lake were identified. The geochronology studies of the cores were performed using 210Pb method, to evaluate model of time changes in the sediment. Radioactivity of 210Pbuns (determined indirectly by 210Po) ranged from 1051 ± 64 to 12 ± 8 Bq kg−1. The 137Cs radioactivity was determined directly by gamma spectrometry and varied from525 ± 37Bq kg−1 for top layers to 9.80 ± 5.40 Bq kg−1 for the bottom of the core. Two characteristic peaks of 137Cs radioactivity related to the global fallouts after nuclear weapons testing and the Chernobyl accident were observed and used to confirm210Pb dating method. Chemometrics analysis of the chosen metal’s concentrations combined with sample dating showed distinct imprint of human activity on the studied area

Tracking Fish Introduction in a Mountain Lake over the Last 200 Years Using Chironomids, Diatoms, and Cladoceran Remains

We analysed a 24 cm long sediment sequence (past ~200 years) from an alpine lake (Tatra Mts., Slovakia) for chironomids, cladocerans, and diatoms to reconstruct the effects of a historically documented fish introduction. Our results indicate that fish introduction predated the age of the sequence, and thus, we did not cover the lake’s fishless period. The individual proxies coincide in showing two main lake development stages. The first stage lasted until ~1950 CE and was interpreted as the stage when brown trout and alpine bullhead co-occurred. The extremely low concentration of cladocerans, the dominance of small-bodied chydorids, and the low share of daphnids, together with the low proportion/absence of large-bodied tanypod chironomids, suggest a strong effect of both species. The beginning of the next stage is probably related to the ban on fish manipulations and grazing in the catchment. A significant increase in the total abundance of cladocerans and of daphnids may indicate the extirpation of trout. The steep increase in thermally plastic chironomid taxa since the end of the 20th century indicates climate warming. Generally, while cladocerans primarily indicate fish manipulations, chironomids and diatoms mainly reflect other local and global environmental stressors