Expanding ocean food production under climate change.

As the human population and demand for food grow1, the ocean will be called on to provide increasing amounts of seafood. Although fisheries reforms and advances in offshore aquaculture (hereafter 'mariculture') could increase production2, the true future of seafood depends on human responses to climate change3. Here we investigated whether coordinated reforms in fisheries and mariculture could increase seafood production per capita under climate change. We find that climate-adaptive fisheries reforms will be necessary but insufficient to maintain global seafood production per capita, even with aggressive reductions in greenhouse-gas emissions. However, the potential for sustainable mariculture to increase seafood per capita is vast and could increase seafood production per capita under all but the most severe emissions scenario. These increases are contingent on fisheries reforms, continued advances in feed technology and the establishment of effective mariculture governance and best practices. Furthermore, dramatically curbing emissions is essential for reducing inequities, increasing reform efficacy and mitigating risks unaccounted for in our analysis. Although climate change will challenge the ocean's ability to meet growing food demands, the ocean could produce more food than it does currently through swift and ambitious action to reduce emissions, reform capture fisheries and expand sustainable mariculture operations.

Nitrous oxide and methane in a changing Arctic Ocean.

Human activities are changing the Arctic environment at an unprecedented rate resulting in rapid warming, freshening, sea ice retreat and ocean acidification of the Arctic Ocean. Trace gases such as nitrous oxide (N2O) and methane (CH4) play important roles in both the atmospheric reactivity and radiative budget of the Arctic and thus have a high potential to influence the region's climate. However, little is known about how these rapid physical and chemical changes will impact the emissions of major climate-relevant trace gases from the Arctic Ocean. The combined consequences of these stressors present a complex combination of environmental changes which might impact on trace gas production and their subsequent release to the Arctic atmosphere. Here we present our current understanding of nitrous oxide and methane cycling in the Arctic Ocean and its relevance for regional and global atmosphere and climate and offer our thoughts on how this might change over coming decades.

Towards improved socio-economic assessments of ocean acidification's impacts.

Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research.

Ocean acidification in a geoengineering context.

Fundamental changes to marine chemistry are occurring because of increasing carbon dioxide (CO(2)) in the atmosphere. Ocean acidity (H(+) concentration) and bicarbonate ion concentrations are increasing, whereas carbonate ion concentrations are decreasing. There has already been an average pH decrease of 0.1 in the upper ocean, and continued unconstrained carbon emissions would further reduce average upper ocean pH by approximately 0.3 by 2100. Laboratory experiments, observations and projections indicate that such ocean acidification may have ecological and biogeochemical impacts that last for many thousands of years. The future magnitude of such effects will be very closely linked to atmospheric CO(2); they will, therefore, depend on the success of emission reduction, and could also be constrained by geoengineering based on most carbon dioxide removal (CDR) techniques. However, some ocean-based CDR approaches would (if deployed on a climatically significant scale) re-locate acidification from the upper ocean to the seafloor or elsewhere in the ocean interior. If solar radiation management were to be the main policy response to counteract global warming, ocean acidification would continue to be driven by increases in atmospheric CO(2), although with additional temperature-related effects on CO(2) and CaCO(3) solubility and terrestrial carbon sequestration.

Distribution and culturability of the uncultivated 'AGG58 cluster' of the Bacteroidetes phylum in aquatic environments.

Members of the Bacteroidetes phylum are abundant in aquatic habitats when assessed by fluorescent in situ hybridisation and in some 16S rRNA gene libraries. In this study 16S rRNA gene clone libraries were constructed with bacterial primers that amplify Bacteroidetes sequences well (27F, 1492R) from coastal seawater near Plymouth (UK) during a phytoplankton bloom. Most of the clones (66%, 106/160) affiliated with the Bacteroidetes phylum, and of these 62% (66/106; or 41% 66/160 of the entire library) clustered with marine bacterioplankton clones env.agg58, Arctic97A-17, CF17, CF96 and CF101. This phylogenetic branch of Bacteroidetes was designated the 'AGG58 cluster', and its presence in various aquatic environments was investigated. Two pairs of AGG58-specific 16S rRNA-gene-targeted polymerase chain reaction (PCR) primers were designed and successfully used to detect the cluster in DNA extracts from three UK coastal seawater sites, and from freshwater River Taff epilithon. In addition, 600 putative Bacteroidetes strains were isolated from these sites on relatively high-nutrient agar media. AGG58 cluster specific probes were used to screen the amplified 16S rRNA gene products from the isolates, but no members of the AGG58 cluster were discovered. The least specific probe hybridised with one River Taff water isolate (RW262 NCIMB 13979) which formed a monophyletic group with the genera Crocinitomix, Brumimicrobium and Cryomorpha of the family Cryomorphaceae in the Bacteroidetes phylum. RW262 probably represents the first isolate of a new genus within this family. This study provides new evidence that the uncultivated AGG58 group is abundant, globally distributed, and can be rapidly detected with the new PCR primers described.