Složení stabilních izotopů současných terestrických a vodních zdrojů sedimentární organické hmoty Černého jezera

• Thesis title in Czech: Složení stabilních izotopů současných terestrických a vodních zdrojů sedimentární organické hmoty Černého jezera
• Thesis title in English: Stable isotope composition of modern terrestrial and aquatic organic matter sources to Černé lake sediment
• Academic year of topic announcement: 2022/2023
• Thesis type: diploma thesis
• Thesis language: čeština
• Department: Institute for Environmental Studies (31-550)
• Supervisor: RNDr. Jolana Tátosová, Ph.D.
• Author: hidden - assigned and confirmed by the Study Dept.
• Date of registration: 16.11.2022
• Date of assignment: 16.11.2022
• Confirmed by Study dept. on: 27.01.2023

Preliminary scope of work

The organic matter from the water column and the catchment soils is deposited at the bottom, thus lake sediments contain an archive of past environmental conditions and biogeochemical processes in and around the lake. The input of organic matter is the key factor that can alter the ecology of the lakes and modify their trophic level. To understand the most important source of organic carbon entering the lakes we can analyze changes in the content of the heavier isotope of carbon (13C), as its composition is directly influenced by the source of organic matter. There are two major processes that affect the final isotopic composition of organic matter buried in the lake sediments: photosynthesis and microbial activity, specially methanogenesis. The autochthonous organic matter becomes progressively enriched in 13C with increased productivity—both seasonally and in response to long-term eutrophication, on the other hand, it can be significantly depleted in 13C due to bacterial activities.
To evaluate the contribution of terrestrial, planktonic and microbial organic matter and their isotopic composition to the sediment over the past and so improve the isotope interpretation of the long sediment core, it is necessary to create a site-specific isotope mixing model, which can reveal the current process in the lake and their fingerprints in the recent surface sediment layers. For that, the carbon isotope composition will be analyzed in samples of the surrounding vegetation (needles, herbs, mosses, lichens, and litter) and soils, as well as epilimnetic and hypolimnetic POC and the surface sediment samples.

Preliminary scope of work in English

The organic matter from the water column and the catchment soils is deposited at the bottom, thus lake sediments contain an archive of past environmental conditions and biogeochemical processes in and around the lake. The input of organic matter is the key factor that can alter the ecology of the lakes and modify their trophic level. To understand the most important source of organic carbon entering the lakes we can analyze changes in the content of the heavier isotope of carbon (13C), as its composition is directly influenced by the source of organic matter. There are two major processes that affect the final isotopic composition of organic matter buried in the lake sediments: photosynthesis and microbial activity, specially methanogenesis. The autochthonous organic matter becomes progressively enriched in 13C with increased productivity—both seasonally and in response to long-term eutrophication, on the other hand, it can be significantly depleted in 13C due to bacterial activities.
To evaluate the contribution of terrestrial, planktonic and microbial organic matter and their isotopic composition to the sediment over the past and so improve the isotope interpretation of the long sediment core, it is necessary to create a site-specific isotope mixing model, which can reveal the current process in the lake and their fingerprints in the recent surface sediment layers. For that, the carbon isotope composition will be analyzed in samples of the surrounding vegetation (needles, herbs, mosses, lichens, and litter) and soils, as well as epilimnetic and hypolimnetic POC and the surface sediment samples.