Shedding light on detritus: Interactions between invertebrates, bacteria and substrates in benthic habitats

The processing of dead organic matter, also known as detritus, is a central ecosystem process driven by detritus feeding organisms that are mostly located at the bottom of water bodies where dead organic matter (OM) accumulates. Detritivorous organisms form communities composed of invertebrates, fungi and bacteria that interact with each other and their substrate. Although it is likely that links between benthic biodiversity and OM processing are driven by similar mechanisms across different ecosystem types (forest floors, stream beds, coral reefs), it remains a challenge to identify general drivers of decomposition in benthic detrital food webs in different waters. The aim of this thesis was therefore to unravel interactions between the (functional) composition of invertebrate and bacterial communities, organic matter processing and abiotic variables in two contrasting benthic detrital food webs: one on soft bottom sediments and one on solid substrate, mangrove ecosystems. To this purpose, the following objectives have been set: 1) To evaluate the impact of OM composition on invertebrate-substrate interactions and organic matter processing; 2) To assess the impact of abiotic stressors on invertebrate-substrate interactions and organic matter processing; 3) To quantify the effect of functional diversity of bacteria and invertebrates on organic matter processing.