30. August 2018 | Kolloquium

Dr. Mandy Velthuis

IGB (NIOO Wageningen, the Netherlands), IGB postdoctoral fellow
30. Aug.
30. August 2018, 14:00 Uhr
Kolloquium

Dr. Mandy Velthuis

IGB-Hörsaal, Müggelseedamm 310, 12587 Berlin

How does it degrade? Warming and nutritional quality effects on macrophyte decomposition

Aquatic macrophytes play a crucial role in freshwater carbon (C) cycling by converting inorganic to organic C through photosynthesis. During senescence, macrophyte organic matter accumulates at the sediment surface where it can either be decomposed or buried for longer periods. The decomposition process is dependent on a multitude of factors, such as environmental temperature and the nutritional quality of macrophyte material. In this talk will address these two factors with examples of recent experiments.

Firstly, I will address the effect of global warming on the decomposition of aquatic plants. For this purpose, we followed the decomposition of Myriophyllum spicatum in an indoor mesocosm experiment with two distinct temperature treatments (ambient and +4 °C). Additionally, we measured the carbon stock in plant biomass, sedimented carbon in these systems and approximated net carbon burial by integrating these fluxes. The results show that even though warming led to enhanced decomposition of M. spicatum, this can be counteracted by increased sedimentation rates. Thus, warming can increase the turnover of organic carbon in shallow macrophyte-dominated systems.

In the second part of the talk, I will present the first results from my work as an IGB postdoctoral fellow and will focus on the effects of nutritional quality on macrophyte decomposition. This nutritional quality is dependent on the C:nitrogen (N) and C:phosphorus (P) ratio as well as its content of polyphenols. These plant traits vary between species and are strongly affected by global change. In general, plants with a high C:nutrient ratio are of low nutritional value for decomposers  and thus may have a high potential for long-term burial. Polyphenols have antibacterial properties, thereby affecting bacterial biomass and leading to lower bacterial diversity. This can in turn feedback to reduced decomposition rates. Using meta-analytic tools, we addressed the effects of changing litter quality on decomposition rates.

 

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