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.

Marine N₂ fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N₂) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N₂ fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N₂ fixation rate in the global ocean is estimated to be 62 (52–73) Tg N yr⁻¹ and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4–3.1) Tg C from cell counts and to 89 (43–150) Tg C from nifH-based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 ± 9.2 Tg N yr⁻¹, 18 ± 1.8 Tg C and 590 ± 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about ±70%. It was recently established that the most commonly applied method used to measure N₂ fixation has underestimated the true rates. As a result, one can expect that future rate measurements will shift the mean N₂ fixation rate upward and may result in significantly higher estimates for the global N₂ fixation. The evolving database can nevertheless be used to study spatial and temporal distributions and variations of marine N₂ fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models, keeping in mind that future rate measurements may rise in the future. The database is stored in PANGAEA (doi:10.1594/PANGAEA.774851).

Phytoplankton identification and abundance data are now commonly feeding plankton distribution databases worldwide. This study is a first attempt to compile the largest possible body of data available from different databases as well as from individual published or unpublished datasets regarding diatom distribution in the world ocean. The data obtained originate from time series studies as well as spatial studies. This effort is supported by the Marine Ecosystem Model Inter-Comparison Project (MAREMIP), which aims at building consistent datasets for the main plankton functional types (PFTs) in order to help validate biogeochemical ocean models by using carbon (C) biomass derived from abundance data. In this study we collected over 293 000 individual geo-referenced data points with diatom abundances from bottle and net sampling. Sampling site distribution was not homogeneous, with 58% of data in the Atlantic, 20% in the Arctic, 12% in the Pacific, 8% in the Indian and 1% in the Southern Ocean. A total of 136 different genera and 607 different species were identified after spell checking and name correction. Only a small fraction of these data were also documented for biovolumes and an even smaller fraction was converted to C biomass. As it is virtually impossible to reconstruct everyone's method for biovolume calculation, which is usually not indicated in the datasets, we decided to undertake the effort to document, for every distinct species, the minimum and maximum cell dimensions, and to convert all the available abundance data into biovolumes and C biomass using a single standardized method. Statistical correction of the database was also adopted to exclude potential outliers and suspicious data points. The final database contains 90 648 data points with converted C biomass. Diatom C biomass calculated from cell sizes spans over eight orders of magnitude. The mean diatom biomass for individual locations, dates and depths is 141.19 μg C l⁻¹, while the median value is 11.16 μg C l⁻¹. Regarding biomass distribution, 19% of data are in the range 0–1 μg C l⁻¹, 29% in the range 1–10 μg C l⁻¹, 31% in the range 10–100 μg C l⁻¹, 18% in the range 100–1000 μg C l⁻¹, and only 3% > 1000 μg C l⁻¹. Interestingly, less than 50 species contributed to > 90% of global biomass, among which centric species were dominant. Thus, placing significant efforts on cell size measurements, process studies and C quota calculations of these species should considerably improve biomass estimates in the upcoming years. A first-order estimate of the diatom biomass for the global ocean ranges from 444 to 582 Tg C, which converts to 3 to 4 Tmol Si and to an average Si biomass turnover rate of 0.15 to 0.19 d⁻¹. Link to the dataset: doi:10.1594/PANGAEA.777384.

Mitra, Aditee ... et. al.-- Special issue North Atlantic Ecosystems, the role of climate and anthropogenic forcing on their structure and function.-- 24 pages, 6 figures, 2 tablestrophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or\ud modelling) are rare. Experimental investigations often concentrate on a particular group or individual\ud species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up\ud approach concentrating on the phytoplankton community or a top-down approach concentrating on\ud the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton-\ud dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton\ud communities (protists and metazoans) linking phytoplankton and fish communities are\ud typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem\ud models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical\ud descriptions merging various interacting physiological functions governing zooplankton growth and\ud development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a\ud modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter\ud values describing zooplankton vital rates and thus the importance of using appropriate zooplankton\ud descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding\ud and modelling activities identifying important issues that warrant further experimental and modelling\ud investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation\ud and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient\ud history. In particular there is a need for dynamic data series in which predator and prey of known\ud nutrient history are studied interacting under varied pH and temperature regimes.\ud © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY licenseAC is funded by the Ministry of Science and Innovation of Spain through project CTM2009-08783. AM was part funded by NERC UK project NE/K001345/1. KJF was funded by NERC UK through projects NE/H01750X/1 and NE/F003455/1. [...] This review was supported in part by project EURO-BASIN (Ref. 264933, 7FP, European Union), and by a Leverhulme International Network ‘‘Placing marine mixotrophs in context: modelling mixotrophy in a changing world’’Peer reviewe