Eva Mayol

Dilution limits dissolved organic carbon utilization in the deep ocean

Dilution solves the recalcitrance question The deep ocean is full of dissolved organic carbon, some of which has remained unchanged for thousands of years. What makes these compounds so resistant to microbial degradation? Perhaps their chemical structures make them intrinsically difficult to metabolize? In contrast, Arrieta et al. show that they are simply too dilute to be viable sources of energy for microorganisms (see the Perspective by Middleburg). Further experiments show that if these seemingly recalcitrant organic molecules are concentrated, the ambient microbes can consume them. Science, this issue p. 331; see also p. 290 Dilution is the reason why dissolved organic carbon in the deep ocean is not readily consumed by microbes. [Also see Perspective by Middleburg] Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored.

Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean

Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earths surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 104 and 1.6 × 107 microbes per m2 of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m2 every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes.

Global unbalance in seaweed production, research effort and biotechnology markets

Exploitation of the worlds oceans is rapidly growing as evidenced by a booming patent market of marine products including seaweed, a resource that is easily accessible without sophisticated bioprospecting technology and that has a high level of domestication globally. The investment in research effort on seaweed aquaculture has recently been identified to be the main force for the development of a biotechnology market of seaweed-derived products and is a more important driver than the capacity of seaweed production. Here, we examined seaweed patent registrations between 1980 and 2009 to assess the growth rate of seaweed biotechnology, its geographic distribution and the types of applications patented. We compare this growth with scientific investment in seaweed aquaculture and with the market of seaweed production. We found that both the seaweed patenting market and the rate of scientific publications are rapidly growing (11% and 16.8% per year respectively) since 1990. The patent market is highly geographically skewed (95% of all registrations belonging to ten countries and the top two holding 65% of the total) compared to the distribution of scientific output among countries (60% of all scientific publications belonging to ten countries and the top two countries holding a 21%), but more homogeneously distributed than the production market (with a 99.8% belonging to the top ten countries, and a 71% to the top two). Food industry was the dominant application for both the patent registrations (37.7%) and the scientific publications (21%) followed in both cases by agriculture and aquaculture applications. This result is consistent with the seaweed taxa most represented. Kelp, which was the target taxa for 47% of the patent registrations, is a traditional ingredient in Asian food and Gracilaria and Ulva, which were the focus of 15% and 13% of the scientific publications respectively, that are also used in more sophisticated applications such as cosmetics, chemical industry or bioremediation. Our analyses indicate a recent interest of non-seaweed producing countries to play a part in the seaweed patenting market focusing on more sophisticated products, while developing countries still have a limited share in this booming market. We suggest that this trend could be reverted by promoting partnerships for R and D to connect on-going efforts in aquaculture production with the emerging opportunities for new biotech applications of seaweed products.

Rapid growth of seaweed biotechnology provides opportunities for developing nations

591 10. Tao, L. et al. J. Clin. Exp. Pathol. 26, 397–401 (2010). 11. WHO Global Health Observatory Data Repository. (2012). 12. China National Health and Family Planning Commission. (2012). 13. Yip, W.C. et al. Lancet 379, 833–842 (2012). 14. Le Deu, F., Parekh, R., Zhang, F. & Zhou, G. Healthcare in China: Entering uncharted waters. (McKinsey & Co., 2012). 15. Insinga, R.P., Dasbach, E.J. & Elbasha, E.H. Pharmacoeconomics 23, 1107–1122 (2005). 16. Balabanova, D., McKee, M. & Mills, A. (eds.) ‘Good Health at Low Cost’ 25 Years On: What Makes a Successful Health System? (London, London School of Hygiene and Tropical Medicine, 2011). China’s healthcare spending is projected to grow from

Long-range transport of airborne microbes over the global tropical and subtropical ocean

357 billion in 2011 to

Response to Comment on “Dilution limits dissolved organic carbon utilization in the deep ocean”

1 trillion in 2020 (ref. 14). We would argue that semi-mandatory HPV vaccination to initially cover low-income communities with high burdens of cervical cancer would be a good use of the resources made available in the healthcare reform package9,10,12,13. If the price of HPV vaccines continues to be prohibitory, a semi-mandatory vaccination strategy may also be attractive to other developing countries with a large HPV burden, such as India. It has been estimated that direct medical costs for HPV-related diseases are at least

Corrigendum: Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean

4 billion annually in the United States15. We believe these costs are much higher in China owing to the much larger population and higher burden of HPV-related diseases (Table 1). Accordingly, introducing HPV vaccines in China, sooner rather than later, will undoubtedly have an immediate and dramatic impact on public health. In this context, adoption of our semi-mandatory HPV vaccination strategy may provide one good example of how to achieve “good health at low cost” in developing countries16.

Experimental evaluation of the hypothesis that dilution limits DOC utilization in the deep ocean

The atmosphere plays a fundamental role in the transport of microbes across the planet but it is often neglected as a microbial habitat. Although the ocean represents two thirds of the Earth’s surface, there is little information on the atmospheric microbial load over the open ocean. Here we provide a global estimate of microbial loads and air-sea exchanges over the tropical and subtropical oceans based on the data collected along the Malaspina 2010 Circumnavigation Expedition. Total loads of airborne prokaryotes and eukaryotes were estimated at 2.2 × 1021 and 2.1 × 1021 cells, respectively. Overall 33–68% of these microorganisms could be traced to a marine origin, being transported thousands of kilometres before re-entering the ocean. Moreover, our results show a substantial load of terrestrial microbes transported over the oceans, with abundances declining exponentially with distance from land and indicate that islands may act as stepping stones facilitating the transoceanic transport of terrestrial microbes.The extent to which the ocean acts as a sink and source of airborne particles to the atmosphere is unresolved. Here, the authors report high microbial loads over the tropical Atlantic, Pacific and Indian oceans and propose islands as stepping stones for the transoceanic transport of terrestrial microbes..

Air-sea CO2 fluxes along the coast of Chile: from CO2 outgassing in central northern upwelling waters to CO2 uptake in southern Patagonian fjords

Our recent finding that dilution limits dissolved organic carbon (DOC) utilization in the deep ocean has been criticized based on the common misconception that lability equates to rapid and complete utilization. Even when considering the redefinition of recalcitrant DOC recently proposed by Jiao et al., the dilution hypothesis best explains our experimental observations.

Coupled CO 2 and O 2 -driven compromises to marine life in summer along the Chilean sector of the Humboldt Current System

[This corrects the article on p. 557 in vol. 5, PMID: 25400625.].