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.

Microbial communities comprise the majority of the biomass in the oceans and drive nutrient and energy cycling, thereby supporting also the polar ecosystems. The Arctic Ocean ecosystem is expected to undergo major climate change related transformations in the coming decades. Recent data indicate that the future Arctic Ocean will experience a shift at the base of the food web towards small-sized phytoplankton, which will lower the efficiency of the Arctic ecosystem. Viruses are expected to be important mortality agents specifically for these smaller-sized phytoplankton, thereby stimulating the microbial food web, diminishing transfer of organic matter to higher trophic levels and reducing the biologically-driven CO2 sequestration in the deep ocean. The proposed project will study temporal variation in Arctic marine microbial interaction, and more specifically the importance of viral lysis over grazing, in relation to host community composition. Additionally, we will study the influence of fine sediments in glacier outflow on virus-host interactions. In order to clarify the effect of changing environmental conditions on the microbial interactions in these ecologically important waters, the influence of combined environmental changes (e.g. temperature and salinity, light) will be studied using 2 small-sized phytoplankton model species in the presence and absence of host-specific viruses. This timely study is primed to deliver essential data for ecosystem modeling, provide a solid base for future studies, and contribute to predictions of ecological relevant shifts in key players and ecosystem productivity as a result of global climate change.

Many trace elements and especially iron (Fe), are critical for marine life and as a consequence influence the functioning of ocean ecosystems. Some trace elements are essential, others are toxic pollutants, while some, together with a diverse array of isotopes, are used to assess modern-ocean processes and the role of the ocean in past climate change. Until recently fragmentary data of trace elements and isotopes in the oceans restricted our knowledge of their biogeochemical cycles. GEOTRACES aims to improve our understanding of biogeochemical cycles and large-scale distribution of trace elements and isotopes in the marine environment and establish the sensitivity of these distributions to changing environmental conditions. The objective is to elucidate important biogeochemical processes, sources and sinks that determine the distribution of bio-essential and other trace elements in the Mediterranean Sea and Black Sea. As dust is a main transport pathway of bio-essential trace elements to the surface of the open ocean the heavy Saharan dust impact on the Mediterranean Sea is ideal to investigate the effect of dust on the biogeochemical cycles of trace elements and isotopes. The Black Sea is the largest anoxic basin of the world and forms an ideal natural laboratory to unravel the microbial driven reduction and oxidation reactions of trace elements and isotopes. For example, here results will have major implications for the isotope systematics of Fe and sulfur in ancient deposits such as the Banded Iron Formations that are studied to unravel the redox conditions of the ancient Earth.

During summer 2011 (September 2011) we will implement a basin wide survey of the CO2 system (Alk, DIC, pCO2, pH) in the North Sea along with essential supporting data (major nutrients, dissolved oxygen, DOC, phytoplankton species composition) and key rates of photosynthetic primary production as well as sub-surface oxygen consumption. At each station samples will be collected at 12-24 depths throughout the water column. Between stations, the ship‟s pumping inlet allows underway measurements of the four CO2 system variables plus ancillary data (O2 by sensor, fluorescence of chlorophyll, major nutrients) in surface waters. Special attention will be paid to the threefold overproduction of planktonic carbon versus nitrogen (i.e. threefold the classical Redfield proportion of C:N = 106:16 = ~6.6) in summertime as observed by Bozec et al. (2006). The summer 2011 basin-wide survey follows the series 2001-2005-2008 during which systematic time trends of pCO2 and pH have been documented.

The West Antarctic Peninsula is the most rapidly warming region in the Southern hemisphere, with glacial retreat and ice shelf collapse causing major changes in the marine environment. We will make a systematic investigation of iron, aluminium, manganese and related bio-essential trace metals Co, Ni, Cu, Zn in the water column and the sea-ice of Marguerite Bay throughout two complete annual cycles. This study will serve as a first assessment of the distribution and cycling of iron and the other trace metals in relation to the ice/water cycle and the biological cycle. We will test the working hypothesis that the annual collapse of the bloom of large diatoms at the end of the summer is due to depletion of dissolved iron by the bloom itself. This first study will serve as the baseline for future assessment of changes in relation to the major climate changes at the West Antarctic Peninsula.