Carregant...
Tipus de document
TesiVersió
Versió publicadaData de publicació
Llicència de publicació
Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/120466
Chrinomids as lake paleoenvironmental indicators: the role of present fauna to understand the past
Títol de la revista
Autors
Director/Tutor
ISSN de la revista
Títol del volum
Resum
[eng] The study of past ecological changes is highly useful for understanding how ecosystems have responded to climate and human-induced disturbances. It is thus relevant in the context of climate change, as it allows several ecological processes and properties, such as ecosystem baseline conditions or resilience, to be evaluated. This thesis focuses on the study of past ecological changes in mountain lakes, which are widely considered to be sentinel ecosystems due to their ability to effectively record signals of climate change and anthropogenic impacts in their sediments.
To do this we use Chironomidae (Diptera) as model organisms. The use of chironomids as lake paleoenvironmental indicators has a long tradition, mainly in terms of quantitative temperature reconstructions. However, there are still many uncertainties involving their reliable use as paleoindicators that need to be further tested. Moreover, their use in paleoecological studies in the Iberian Peninsula is still scarce. In this context, this thesis focuses on two main issues. On the one hand, it reveals the main drivers affecting the chironomid paleorecord by comparing living and recent subfossil assemblages. On the other hand, past changes (mainly temperature and hydrological changes) are reconstructed in two morphologically different lakes from the Iberian Peninsula.
This thesis demonstrates the key influence of macrophyte habitat in shaping the chironomid community, both in the living larvae community and acting as a major confounding factor in the subfossil chironomid record. The presence of Chara in Enol Lake is identified as one of the main drivers affecting the living community. These effects are amplified in the recent subfossil record due to the high chironomid productivity related to this habitat. These results warn against the use of recent subfossil data without further questioning, as they can be greatly affected by a single factor, biasing qualitative or quantitative environmental reconstructions. Moreover, they indicate the importance of studying the present-day fauna before conducting paleoenvironmental studies.
Our results also show that, in many cases (e.g. deep lakes), it might be necessary to analyse more than one core (which is usually retrieved at maximum lake depth) to perform complete and reliable paleoenvironmental reconstructions. The comparison of two sediment cores retrieved from different lake zones (sublittoral and profundal) shows several differences in terms of how chironomids recorded past changes. The deeper core records some hydrological fluctuations, but is also characterized by low head capsule densities, which could lead to less reliable interpretations of downcore changes. The shallower core records the main anthropogenic impacts, in addition to some hydrological oscillations. In this case, results are more robust due to the high chironomid densities found in this core.
Finally, this thesis provides the first chironomid-based temperature reconstruction covering the entire Holocene in the Iberian Peninsula. The comparison of these results with other local and regional studies highlights similarities and differences between this new reconstruction and previous records. These differences can be attributed to different patterns of temperature, hydrology and seasonality changes throughout the Holocene in our study region.
Taken as a whole, this thesis constitutes one of the first complete studies regarding chironomid remains in the Iberian Peninsula and opens up many new research opportunities, in this region and elsewhere. According to the main findings of this study, the combination of ecological and paleoecological approaches is advised for carrying out complete paleoenvironmental studies.
Descripció
Matèries
Matèries (anglès)
Citació
Citació
TARRATS SADA, Pol. Chrinomids as lake paleoenvironmental indicators: the role of present fauna to understand the past. [consulta: 9 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/120466]