There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean.

Oceanic communities are sources or sinks of CO2, depending on the balance between primary production and community respiration. The prediction of how global climate change will modify this metabolic balance of the oceans is limited by the lack of a comprehensive underlying theory. Here, we show that the balance between production and respiration is profoundly affected by environmental temperature. We extend the general metabolic theory of ecology to the production and respiration of oceanic communities and show that ecosystem rates can be reliably scaled from theoretical knowledge of organism physiology and measurement of population abundance. Our theory predicts that the differential temperature-dependence of respiration and photosynthesis at the organism level determines the response of the metabolic balance of the epipelagic ocean to changes in ambient temperature, a prediction that we support with empirical data over the global ocean. Furthermore, our model predicts that there will be a negative feedback of ocean communities to climate warming because they will capture less CO 2 with a future increase in ocean temperature. This feedback of marine biota will further aggravate the anthropogenic effects on global warming.global change ͉ metabolic theory ͉ oceanic carbon cycle T he role of the oceans in the CO 2 budget of the biosphere depends largely on the balance between the uptake of carbon by phytoplankton photosynthesis and its remineralization by the respiration of the whole planktonic community (1). For large areas of the epipelagic ocean, planktonic community respiration (CR) exceeds gross primary production (GPP), resulting in net heterotrophy and a source of CO 2 (2-4). The solution of the contentious debate over the extent of such heterotrophic areas (5-7) is hindered by the limited spatiotemporal coverage achievable by traditional incubation methods (8, 9). Here, we tackle this question from a different perspective based on the metabolic theory of ecology (MTE) (10). The flux rates within an ecosystem are the result of the sum of the individual rates of all its constituent organisms (11,12), which, in turn, are governed by the combined effects of body size and temperature (13-15). Although MTE suggests a universal scaling of metabolic rate as the 3͞4 power of body size, it predicts a differential temperaturedependence of heterotrophic processes (driven by ATP synthesis) and autotrophic rates (controlled by Rubisco carboxylation) (12). Following the MTE, the respiration of a heterotrophic planktonic organism B i can be estimated if we know its body size M i and the ambient absolute temperature T:where b 0 is a normalization constant independent of body size and temperature, e ϪEh͞kT is Boltzmann's factor, where E h is the average activation energy for heterotroph respiration (13), and k is Boltzmann's constant (8.62⅐10 Ϫ5 ⅐eV⅐K Ϫ1 ), and ␣ h is the allometric scaling exponent for body size (14,15). For the metabolic rates of marine autotrophs, things are complicated by the dependence of photosyntheti...

With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger than the current estimate. Here we combine modelling and a sensitivity analysis of the acoustic observations from the Malaspina 2010 Circumnavigation Expedition to show that the previous estimate needs to be revised to at least one order of magnitude higher. We show that there is a close relationship between the open ocean fishes biomass and primary production, and that the energy transfer efficiency from phytoplankton to mesopelagic fishes in the open ocean is higher than what is typically assumed. Our results indicate that the role of mesopelagic fishes in oceanic ecosystems and global ocean biogeochemical cycles needs to be revised as they may be respiring ~10% of the primary production in deep waters.

Mangrove soils represent a large sink for otherwise rapidly recycled carbon (C). However, widespread deforestation threatens the preservation of this important C stock. It is therefore imperative that global patterns in mangrove soil C stocks and their susceptibility to remineralization are understood. Here, we present patterns in mangrove soil C stocks across hemispheres, latitudes, countries and mangrove community compositions, and estimate potential annual CO2 emissions for countries where mangroves occur. Global potential CO2 emissions from soils as a result of mangrove loss were estimated to be ∼7.0 Tg CO2 e yr-1. Countries with the highest potential CO2 emissions from soils are Indonesia (3,410 Gg CO2 e yr-1) and Malaysia (1,288 Gg CO2 e yr-1). The patterns described serve as a baseline by which countries can assess their mangrove soil C stocks and potential emissions from mangrove deforestation. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved