Scientific drilling projects in ancient lakes: Integrating geological and biological histories

Abstract

Sedimentary sequences in ancient or long-lived lakes can reach several thousands of meters in thickness and often provide an unrivalled perspective of the lake's regional climatic, environmental, and biological history. Over the last few years, deep-drilling projects in ancient lakes became increasingly multi- and interdisciplinary, as, among others, seismological, sedimentological, biogeochemical, climatic, environmental, paleontological, and evolutionary information can be obtained from sediment cores. However, these multi- and interdisciplinary projects pose several challenges. The scientists involved typically approach problems from different scientific perspectives and backgrounds, and setting up the program requires clear communication and the alignment of interests. One of the most challenging tasks, besides the actual drilling operation, is to link diverse datasets with varying resolution, data quality, and age uncertainties to answer interdisciplinary questions synthetically and coherently. These problems are especially relevant when secondary data, i.e., datasets obtained independently of the drilling operation, are incorporated in analyses. Nonetheless, the inclusion of secondary information, such as isotopic data from fossils found in outcrops or genetic data from extant species, may help to achieve synthetic answers. Recent technological and methodological advances in paleolimnology are likely to increase the possibilities of integrating secondary information. Some of the new approaches have started to revolutionize scientific drilling in ancient lakes, but at the same time, they also add a new layer of complexity to the generation and analysis of sediment-core data. The enhanced opportunities presented by new scientific approaches to study the paleolimnological history of these lakes, therefore, come at the expense of higher logistic, communication, and analytical efforts. Here we review types of data that can be obtained in ancient lake drilling projects and the analytical approaches that can be applied to empirically and statistically link diverse datasets to create an integrative perspective on geological and biological data. In doing so, we highlight strengths and potential weaknesses of new methods and analyses, and provide recommendations for future interdisciplinary deep-drilling projects

Recent ecological change in ancient lakes

“…Ancient lakes serve a critical role as natural laboratories for research on speciation (Cristescu et al ), paleohistory (Fritz et al ; Lyons et al ; Wilke et al ), and limnology. While there have been decades of limnological research on individual ancient lakes such as Baikal, Victoria, Tanganyika, and the Aral Sea, comparative ecological studies of ancient lakes as a broader group are rare.…”

“…Thus, while many of the threats to these ecosystems are shared with younger ecosystems, the unique heritage of ancient lakes may be impossible to restore with remedial human action. Accompanying this history of evolution among biota has been a long‐term accumulation of information about regional and global paleohistory, stratum by stratum, in the sediments of ancient lakes (Wilke et al ). Together with human histories compiled by archaeologists, such ecological information could be used to piece together not only the relationship of lakes with climate, but also the relationship of lake resources with surrounding people (Capriles et al ).…”

“…Many of the world's ancient lakes have undergone large fluctuations in lake level (Supporting Information Table S4), driven by both human modification of hydrology and climate variation. As early as the 1800s, the naturalist Alexander von Humboldt noted that watershed deforestation and irrigation were associated with Lake Valencia's falling water level (Wulf 2016). Dams for storage and hydropower have further altered lake levels with varying impact.…”

The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): interim results from the SCOPSCO deep drilling project

“…It includes lithological description after core opening, measurement of the geophysical properties, and granulometric, geochemical, mineralogical, and rockmagnetic analyses. These analyses are carried out on whole core sections, on split core surfaces, and on discrete samples (see Wilke et al, 2016) and are described in detail in several individual publications (Matzinger et al, 2007;Wagner et al, 2008aWagner et al, , b, 2009Wagner et al, , 2012Belmecheri et al, 2009Belmecheri et al, , 2010Holtvoeth et al, 2010Holtvoeth et al, , 2016Leng et al, 2010;Lindhorst et al, 2010;Matter et al, 2010;Vogel et al, 2010a, b;Francke et al, 2016;Leicher et al, 2016). Dating of the sediment successions was mainly based on radiocarbon dating as well as tephrostratigraphic and tephrochronological work.…”

Diatoms do radiate: evidence for a freshwater species flock

“…monophyletic groups of endemic species that evolved in a particular ecosystem; e.g. Wilke et al, 2016). So far, only a single example has been reported, namely in dinoflagellates, in which morphological, genetic and ecological differences have not been attributed to phenotypic plasticity, but rather to a rapid adaptive radiation within closely related species (Annenkova et al, 2015).…”