Description: Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence—although each with important uncertainties—lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.

Description: The aim of the WP3 “Network Integration and Improvements” is to coordinate and enhance key aspects of integration of European observing technology (and related data flows) for its use in the context of international ocean monitoring activities. One of the dimensions of the integrations is the constitution of thematic networks, that is, networks whose aim is to address specific observational challenges and thus to favor innovation, innovation that will ultimately support the Blue economy. In this context, the specific aim of Task 3.8 is to accelerate the adoption of molecular methods such as genomic, transcriptomic (and related “omics”) approaches, currently used as monitoring tools in human health, to the assessment of the state and change of marine ecosystems. It was designed to favor the increase the capacity to evaluate biological diversity and the organismal metabolic states in different environmental conditions by the development of “augmented observatories”, utilizing state-of-art methodologies in genomic-enabled research at multidisciplinary observatories at well-established marine LTERs, with main focus on a mature oceanographic observatory in Naples, NEREA. In addition, an effort is dedicated to connecting existing observatories that intend to augment their observations with molecular tools. Molecular approaches come with many different options for the protocols (size fractioning, sample collection and storage, sequencing etc). One main challenge in systematically implementing those approaches is thus their standardization across observatories. Based on a survey of existing methods and on a 3-year experience in collecting, sequencing and analyzing molecular data, this deliverable is thus dedicated to present the SOPs implemented and tested at NEREA. The SOPs consider a size fractioning of the biological material to avoid biases toward more abundant, smaller organisms such as bacteria. They cover both the highly stable DNA and the less stable RNA and they are essentially an evolution of the ones developed for the highly successful Tara Oceans Expedition and recently updated for the Expedition Mission Microbiomes, an All-Atlantic expedition organised and executed by the EU AtlantECO project. Importantly, they have only slight variations with respect the ones adopted by the network of genomic observatories EMOBON. Discussions are ongoing with EMOBON to perfectly align the protocols. The SOPs are being disseminated via the main national and international networks.