An Endorheic Lake in a Changing Climate: Geochemical Investigations at Lake Trasimeno (Italy)

Abstract

Lake Trasimeno is a shallow, endorheic lake located in central Italy. It is the fourth Italian largest lake and is one of the largest endorheic basins in western Europe. Because of its shallow depth and the absence of natural outflows, the lake, in historical times, alternated from periods of floods to strong decreases of the water level during periods of prolonged drought. Lake water is characterised by a NaCl composition and relatively high salinity. The geochemical and isotopic monitoring of lake water from 2006 to 2018 shows the presence of well-defined seasonal trends, strictly correlated to precipitation regime and evaporation. These trends are clearly highlighted by the isotopic composition of lake water (δ18O and δD) and by the variations of dissolved mobile species. In the long term, a progressive warming of lake water and a strong increase of total dissolved inorganic solids have been observed, indicating Lake Trasimeno as a paradigmatic example of how climate change can cause large variations of water quality and quantity. Furthermore, the rate of variation of lake water temperature is very close to the rate of variation of land-surface air temperature, LSAT, suggesting that shallow endorheic lakes can be used as a proxy for global warming measurements.

Overview of past, current, and future ecosystem and biodiversity trends of inland saline lakes of Europe and Central Asia

“…Other lakes, such as those in the Mediterranean climate zone, are more susceptible to the effects of climate change. In both cases, the declines in volume are associated with increases in salinity (Jeppesen et al 2015, Frondini et al 2019.…”

“…salinity related to various atmospheric indices (e.g., NOAA; Namsaraev et al 2008) or local weather or climate variability (Comín et al 1999, Rogozin et al 2017, Golubkov et al 2018. The fluctuations of water level and associated changes in water salinity in many lakes are direct consequences of human activity as well as indirect consequences of climate change (e.g., Frondini et al 2019).…”

Use of Larval Morphological Deformities in Chironomus plumosus (Chironomidae: Diptera) as an Indicator of Freshwater Environmental Contamination (Lake Trasimeno, Italy)

“…It is a shallow lake of tectonic origin, at hydrometric zero (257.33 meters above sea level (m a.s.l.)) and has an average depth of 4.7 m with a maximum depth of 6.3 m [52,53]. It is characterized by a Mediterranean climate, and its hydrological regime depends on local precipitations, which shows considerable fluctuations in water level over the years [54,55].…”

Trace Metal Enrichments in Water of the Okavango Delta (Botswana): Hydrological Consequences

“…In addition to these natural causes of changes, the anthropic activities can drastically modify this fragile equilibrium (Markofsky et al., 2017), by changing the amount of inflow (pumping, dams), and/or changing its chemical composition (agriculture, industry, city). Inside these megafans, biological activity and evaporation are the most important process that controls on water chemistry in such a confined context (Atekwana et al., 2016; Bauer et al., 2004; Frondini et al., 2019; Hammer, 1986; Mahamat Nour et al., 2020; Ramberg & Wolski, 2008; Tweed et al., 2011; Wang et al., 2018). The Okavango Delta in Botswana is poorly disturbed by anthropic activities both in the wide watershed and inland: also, it offers a good opportunity to constrain the natural process driving the water quality within an endorheic megafan.…”