Research

Extinction, ecosystem structure and carbon cycling in coastal sediments.

Coastal sediments account for less than 5 % of global sea floor area but are responsible for approximately 50 % of sea floor carbon cycling in the oceans. These coastal regions experience multiple anthropogenic stressors linked to fisheries, nutrient enrichment and climate change leading to species loss and changes in ecosystem functioning. At the sea floor, species loss is most acutely observed in the megafauna, larger predatory animals that directly control the structure of animal communities within marine sediments. The burrowing and foraging activity of these larger animals affects sediment irrigation and mixing, with cascading effects upon the smaller animals (macrofauna) and microorganisms at the seafloor. However, their patchy spatial distribution means they are often excluded from studies of seafloor ecosystem functioning. Accurately predicting global-scale impacts of marine species loss requires an understanding of species loss effects on fundamental ecosystem processes.

My current research investigates how megafaunal activity regulates carbon cycling in coastal sediments, and seeks to test how megafaunal extinction will affect sediment ecosystem functioning both under present and future climate conditions.

Mineral-stabilisation of organic matter and ecosystem functioning in aquatic biofilms (Bio-ERODS Project, University of Vienna).

Inland waterways are an important component of the global carbon cycle, receiving an annual carbon input of ~ 4.8 Pg of carbon per year. Of this approximately 0.6 Pg is buried, entering the lithosphere, whilst 3.3 Pg is recycled through aquatic food webs. These numbers highlight the global importance of streams, rivers lakes and other inland waters but provide little detail regarding the dynamics of organic matter burial and remineralisation. A poorly defined aspect is the relationship between organic matter burial and remineralisation of organo-mineral complexes. Organo-mineral particles form by adsorption of dissolved organic matter to freshly-eroded mineral surfaces, and are thought to greatly control the fluxes of particulate organic carbon at the watershed scale. The unique physico-chemical properties of these particles may enhance their deposition onto and subsequent burial into the sediments of inland waters. However, the metabolic fate of these particles at the water-streambed interface remains poorly studied. Particle deposition at the streambed is enhanced by benthic microbial biofilms. As such, understanding the potential role of organo-mineral complexes in the preservation and burial of organic matter, requires investigation of the interactions with biofilms.

The Bio-ERODS project experimentally tests the biophysical mechanisms that drive biofilm-particle interactions and the mechanisms through which organo-mineral complexation affects stream biogeochemistry. Within this project we seek to elucidate, at the fine scale, fundamental mechanisms of the controls on carbon fluxes in streams and rivers.