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Wednesday, 01.07.2015

«It is very rewarding to be part of a large team with a common goal!»

Postdoc Darren Giling at the photometer

«Compared to last year when we worked with only 8 enclosures, this year we are running an ambitious experiment using 21 enclosures», says Darren Giling, Postdoctoral fellow at IGB Stechlin. Together with more than 60 people taking part in the LakeLab experiment 2015, he is one of the mainstays always giving a helping hand or sharing his experience with new people in the LakeLab team.

During a normal sampling day Darren Giling, from Australia, first participates in one of three water sampling teams on the LakeLab that take integrated water samples from 0 to 7 m and from 7 to 15 m depth. Following sampling he returns to the lab to start his own investigations.

 

tl_files/Team/Giling Darren_Tube sampling_01.jpg

 

Darren’s interests concern the organic matter and the carbon turnover in the manipulated mesocosms. This is especially important since the IGB researchers increased the concentration of the dissolved organic carbon (DOC) in the beginning of the LakeLab experiment 2015. Their idea is to simulate the stronger input of DOC from soils to lakes as a consequence of heavy rain falls due to climate change. Such DOC contains large humic acid molecules that are not easily consumed by the microbial communities, as opposed to the more available molecules derived from algal photosynthetic production. However, brownification of the water due to the humic acids might have dramatic effects on the photosynthesis rates. That is why Darren together with his colleague, PhD student Jeremy Fonvielle, wants to know both the composition of the DOC and which components of the DOC are being consumed by the aquatic bacteria. The filtered water samples are therefore scanned on a UV-visible spectrophotometer and a fluorescence spectrophotometer to characterize the DOC.

 

In addition, together with Armin Penske, the responsible LakeLab technician, Darren assists with taking care of the high-frequency measurements that are recorded in each enclosure. These measurements are made by different probes that are mounted on an automated profiler running hourly through the whole water column. The profiler data comprise a range of standard limnological parameters such as temperature, pH, oxygen concentration, redox potential, electrical conductivity, turbidity and light intensity. Darren is not only involved in the quality checking of these measurements. He also uses the oxygen data to estimate how much oxygen is produced through photosynthesis and how much is consumed by the lake organisms in the process of respiration. His overall aim is understand to which extent the addition of DOC changes the interplay between the production and the consumption.

 

«We put a lot of time into the preparation of this year’s LakeLab experiment, so it is important to measure many parameters to describe the biological responses», says Darren Giling. Indeed everything from metagenomics through to zooplankton behavior is being analyzed. This will allow the team to build a full picture of the effects of DOC inputs on lake ecosystems.

 

Darren Giling 

 joined the IGB LakeLab team in April 2014. As an ecologist and biogeochemist by training, he already worked on carbon dynamics during his PhD at Monash University in Melbourne where he analyzed whether replanting areas of riparian vegetation around streams influenced in-stream organic matter budgets.

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