The Holocene history of a tropical high-altitude lake in central Mexico

Abstract

High-altitude lakes are sensitive to modern and past climate changes. Given their low-water temperatures, alkalinity, and nutrient levels, small climatic differences can strongly affect their water chemistry, and/or biodiversity. In central Mexico, there are only two high-altitude lakes, and both are within the crater of the Nevado de Toluca volcano. Here, we present a paleolimnological record from one of these lakes: La Luna. Previous paleoenvironmental work showed that it was sensitive to the Little Ice Age (LIA) cooling. Our results show that sediment accumulation began ~6900 to 6100 cal. yr BP under periglacial conditions and that lake conditions were established ~6000 cal. yr BP. One tephra layer was dated to ~5600 cal. yr BP, with no evidence of more recent volcanic activity. The early stages of this lake (6000–4700 cal. yr BP) contained Cladocera and diatom assemblages with different species composition than modern assemblages. This early stage community structure was related to more mesic conditions and cooler winters inferred by the high abundance of planktonic Aulacoseira nivaloides and of Chydorus cf. sphaericus. The establishment of modern limnological conditions after 4700 cal. yr BP is inferred from Cladocera and diatom assemblages similar to recent samples. A reduction in A. nivaloides and low magnetic-susceptibility values suggest lower lakes levels, a trend consistent with lower available moisture in central Mexico after 4000 cal. yr BP. The rest of the sequence shows the impact of two cold periods, the first one around 3000 cal. yr BP, identified by a new increase in Chydorus cf. sphaericus. The second was the larger impact associated with the LIA (AD 1350–1910), and an increase in Cavinula pseudoscutiformis and Pinnularia microstauron suggesting an increase in lake water pH. Also, organic matter and photosynthetic pigments increased during this period showing an increase in nutrient levels and productivity. Finally, the coldest interval during the LIA (AD 1570–1890) is identified by an important reduction in arboreal pollen concentration which points to a wider environmental impact of this cold event.

Droughts during the last 2000 years in a tropical sub‐humid environment in central Mexico

“…The fifth dry event in Coatetelco dates to ~1800 ± 100 and correlates with another major historical event, the Mexican War of Independence from 1810 to 1821. This period was identified as a cold interval with a reduction in the arboreal tree line in the nearby high‐altitude record from Lake La Luna during the second half of the LIA (Caballero et al 2020, Ruiz‐Córdova et al 2019).…”

Assessment of freshwater plant diversity and local difference in freshwater plant use knowledge in Punakha district, Bhutan

“…The positive correlation may be attributed to the water melts from high altitude mountain glaciers and snow that feeds large amount of water into the lake (Srivastava et al, 2013). Bhateria and Jain (2016) and Caballero et al (2020) stated that the low temperature and nutrient content at high altitude reduces the water loss by evaporation and prevents eutrophication by limiting algal growth. Similarly, the water depth showed a positive effect on the lake habitat.…”

Testate amoebae assemblages from two tropical high-mountain lakes in central Mexico during the last ~60 years

“…Previous works showed evidence of humaninduced alterations in these lakes. Cladoceran analysis in the sediments from Lake La Luna showed a short-term disappearance of planktonic Daphnia associated with failed fish (rainbow trout) introduction to this lake around 1940 to 1950 (Caballero et al, 2020;Cuna et al, 2014), while in Lake El Sol fish introduction was successful and trout are currently present in the lake. Furthermore, organic carbon burial rates have increased in both lakes since the 1950s, and particularly after 2000 in Lake El Sol, most likely associated with higher airborne particle deposition (Alcocer et al, 2020).…”

“…As in other lakes, HML sediments represent valuable archives where biological and geochemical indicators can be preserved (Caballero et al, 2020;Catalán et al, 2002;Ndayishimiye et al, 2020), keeping a historical record of past conditions. The study of short sedimentary sequences from HMLs can provide an overview of their recent history which may allow identifying whether they show signs of human-induced changes or if they represent relatively unaltered reference sites.…”