Research conducted showed that metal nodules have an important function in deep-sea ecosystem as they provide hard substrate for different organisms, such as stalked sponges. Removing these nodules leads to a loss of the fauna that is directly or indirectly dependent on them which can be 20% in the Peru Basin and in the Clarion-Clipperton Fracture Zone. However, nodule associated fauna has a very limited role in abyssal carbon cycling. Hence, depending on whether the impacts of deep-seabed mining on biodiversity or on carbon cycling are studied, research should either focus on fauna (biodiversity) or the microbial loop (carbon cycling)

-

Fossil fuel use, land use change and cement production have perturbed the global carbon cycle and have led to the accumulation of carbon dioxide in the atmosphere. This has two major consequences, namely global warming and ocean acidification (?the other CO2 problem?). Sea surface water pH has decreased already by 0.1 unit since pre-industrial time, and based on atmospheric CO2 scenarios, it is projected to further decline by 0.0015-0.002 unit per year over the coming century. However, observations on the Washington coast and in the North Sea (Rijkswaterstaat monitoring) show stronger decreases of 0.045 and 0.02 unit per year, respectively. The North Sea is apparently acidifying 10 times faster than global ocean model predictions. Here we propose a detailed investigation of the spatial and temporal patterns of pH in the North Sea at a basin-wide scale using the high quality methodology in use by the international CO2 research community. This will generate the needed data to see whether the acidification of the North Sea is indeed occurring at such high pace. In addition, we will also elucidate the biogeochemical mechanisms governing the pH in North Sea waters, in particular the balance between production and respiration and the generation of alkalinity. As part of this investigation, we will apply a recently developed modelling technique to attribute pH changes to changing environmental parameters.

Phosphorus (P), iron (Fe) and manganese (Mn) are all nutrients that are required by phytoplankton in the ocean. Changes in the cycling of these elements can have a major impact on marine ecosystems. Increased P availability, for example, contributes to the present-day expansion of low-oxygen waters (?dead zones?) in coastal systems worldwide. The interactions between the cycles of P, Fe and Mn at redox interfaces in the water column and sediment are still incompletely understood. This especially holds for the processes leading to formation of particulate P, Fe and Mn in the water column, and the fate of particulates upon sinking and burial in the sediment. Here, we propose to study this in detail for the largest permanently anoxic basin on Earth, the Black Sea. We will specifically study the controls on mineral formation in the water column, including the role of dissolved Mn(III), identify the minerals, quantify the rate of sulfide-induced metal-oxide reduction and assess the preservation and possible transformation of Fe and P minerals in the sediment. Our field study will focus on water depth and redox transects in areas where the Black Sea redoxcline is either stable or variable because of lateral injection of oxygen-rich water from the Bosporus plume. High-resolution real-time redox profiling of the water column will be combined with detailed biogeochemical analyses of dust, sediment trap, suspended matter, pore water and sediment samples using novel micro-analysis approaches. The outcome of this project will greatly advance our understanding of the biogeochemistry of anoxic marine environments.