Search

Microbes in the dark ocean are exposed to hydrostatic pressure increasing with depth. Activity rate measurements and biomass production of dark ocean microbes are, however, almost exclusively performed under atmospheric pressure conditions due to technical constraints of sampling equipment maintaining in situ pressure conditions. To evaluate the microbial activity under in situ hydrostatic pressure, we designed and thoroughly tested an in situ microbial incubator (ISMI). The ISMI allows autonomously collecting and incubating seawater at depth, injection of substrate and fixation of the samples after a preprogramed incubation time. The performance of the ISMI was tested in a high-pressure tank and in several field campaigns under ambient hydrostatic pressure by measuring prokaryotic bulk 3H-leucine incorporation rates. Overall, prokaryotic leucine incorporation rates were lower at in situ pressure conditions than under to depressurized conditions reaching only about 50% of the heterotrophic microbial activity measured under depressurized conditions in bathypelagic waters in the North Atlantic Ocean off the northwestern Iberian Peninsula. Our results show that the ISMI is a valuable tool to reliably determine the metabolic activity of deep-sea microbes at in situ hydrostatic pressure conditions. Hence, we advocate that deep-sea biogeochemical and microbial rate measurements should be performed under in situ pressure conditions to obtain a more realistic view on deep-sea biotic processes.

The present study aims to investigate the reproductive biology of the small pelagic Sardinella aurita Valenciennes, 1847 in the Canary Islands, to enable its reliable assessment and advise on appropriate management measures for a fishing resource showing a declining trend in landings. Reproductive biology and sexual patterns of round sardinella were examined from monthly random samples of commercial catches landed by the artisanal purse-seine fleet. The landings' length frequencies, ranging between 9–32 cm (based on the total lengths, TL), were recorded from 2013–2019. The overall mean value of TL was 20.9 cm, with annual mean values between 20–22 cm, except in 2016 (TL = 19 cm). The overall sex ratio M:F was 1:0.92, with males significantly predominant. Sex ratios fluctuated as a function of size and month: females were more abundant in the larger length classes, as well as before and after spawning, whereas males were more abundant in the smaller length classes and during spawning. Based on gonad maturity stages and gonadosomatic index, round sardinella spawns during almost all the year, with a peak in January–February and a resting period during October–November. The length at first maturity was estimated at TL of 18.2 cm, notably smaller than the value obtained for the NW African coastal waters where the demographic structure in round sardinellas' landings is totally different.

Este resumen divulgativo trata sucesos ocurridos desde 2017 y avances recientes sobre el marrajo dientuso del stock Norte del Atlántico. Algún científico ha sugerido que la falta de datos afectó a la evaluación más reciente de este stock. Pero ese argumento decae al conocer antecedentes, información y literatura disponible; más allá del rumor o la autojustificación.

Leemos estos días sobre la preocupación de algunos países de la UE por emprender políticas para asegurar la producción y el abastecimiento de alimentos

The Workshop on Adult Egg Production Methods Parameters estimation in Mackerel and Horse Mackerel (WKAEPM) looked at the imprecision between institutes when processing survey samples. A number of protocol improvements were proposed, and these will be in place prior to the adult parameter analysis in 2022. A calibration exercise was carried out prior to the workshop using standard mackerel and horse mackerel egg survey (MEGS) protocols. A second exercise was conducted during the workshop using a newly developed SmartDots module. Subgroups dealt with issues regarding annual egg production method (AEPM) and daily egg production method (DEPM) and added their recommendations to the manuals. Descriptions for spent and massive atresia terms used during the screening process were redefined by adding further text and higher quality images into the ICES Survey Protocol Manual for the AEPM and DEPM estimation of fecundity in mackerel and horse mackerel (SISP- 5). Differences were noted in post ovulatory follicle (POF) and early alpha atresia identification, showing the difficulty associated with this work. In fecundity samples, there was high variance when identifying small oocytes close to the 185µm size threshold. It was recommended to have all fecundity samples analysed by two readers, and new criteria for the measurement of small oocytes were agreed. In atresia analysis, high variance was observed in both point and profile counting. High-resolution images are essential for this work, thus in 2022 slide scanner pictures will be taken for atresia analysis and will be sent around to all labs. There is still poor consensus on POF staging. Misclassifications between recent POFs and artefacts have now been clarified. Recent POF stages are used in spawning fraction estimation thus it is vital to be clear about them. A reference catalogue of images of early alpha atresia and POFs will be compiled and stored in SmartDots. The desired number of gonad samples to be collected during t

Al debatir, es importante establecer si nos moveremos sobre la evidencia y la ciencia, o si usaremos la creencia, la fe, la percepción de la opinión publica-publicada; o simplemente la conveniencia estratégica. Panamá ha lanzado recientemente una propuesta para incluir la tintorera, quenlla o tiburón azul (Prionace glauca) dentro de la lista de especies del apéndice II de CITES.

The Mediterranean Rhodes Gyre is a cyclonic gyre with high primary production due to local upwelling of nutrients and occasional deep overturning up to 1 km depth. This nutrient-rich state is in sharp contrast to other parts of the Eastern Mediterranean which are oligotrophic. Here we investigated the upwelling system central to the Rhodes Gyre and the impact of different stressors like meteorological changes, acidification and fishing pressure up to the year 2100. A water column model spanning the physical, chemical and biological system up to top predators (GOTM-ERSEM-BFM-EwE) was used to simulate the pelagic environment under single and combined stressors. Results show that due to increasing winter temperatures, deep overturning events will become more rare in the future until they stop occurring around 2060 under the Paris-agreement climate scenario (RCP4.5) or around 2040 under the business-as-usual climate scenario (RCP8.5). Stratification will become stronger as temperature effects outweigh salinity effects in the surface mixed layer. Together with the lack of deep overturning, this stronger stratification limits the nutrient supply to the euphotic zone, significantly reducing primary production. Phytoplankton species shift towards smaller species as nutrients become more scarce, mimicking the situation found currently on the edge of the gyre. Climatic changes and fishing pressure will affect higher trophic levels in an additive way for some species (sardines, dolphins), while in a synergistic way for others (anchovy, mackerel). Acidification impacts are negligible. Fish stocks will reduce significantly under all scenarios involving climate change effects: ~30% under scenarios imposing RCP4.5 and ~40% under scenarios imposing RCP8.5. The beneficial impact of maximum sustained yield-level fishing is very limited, indicating a need for mitigating measures beyond fleet control.

Summary: trophic levels: a measure of functional diversity stable isotope tools: bulk vs. compound-specific analyses the basis: differential isotopic fractionation trophic indicators: trophic position, baselines, and much more application examples progress: multitrophic models, fingerprinting

Macro and megafauna were studied in the Avil´es Canyon System (ACS), southern Bay of Biscay (Cantabrian Sea), during several oceanographic cruises carried out from 2009 to 2017. The biodiversity of ACS is summarized and its description is herein updated after sampling surveys of several programmes (ECOMARG, INDEMARES, SponGES, INTEMARES) conducted by the Spanish Institute of Oceanography (IEO). This study has updated previous knowledge in the canyon area from past national and international projects, their reports and publications as well as data collected in the context of regional projects designed to gain new insight into the diversity of marine invertebrates and fishes from the ACS. Samples were taken using a range of sampling gears (Rock dredge, Beam trawl, Trawl gear GOC-73, Suprabenthic sledge, Box corer and Remoted operated vehicle), from 55 to 2291 m in depth. A total of 1015 species were identified at the ACS: 98 Porifera, 153 Cnidaria, 14 Brachiopoda, 22 Bryozoa, 97 Mollusca, 151 Annelida, 315 Arthropoda, 74 Echinodermata and 91 Chordata. New records for the Bay of Biscay fauna include 13 Porifera species, 17 Cnidaria, 7 Mollusca, 8 Arthopoda, 3 Echinodermata and 4 Chordata. Also the bathymetric range of some species has been extended. As a result of the research projects carried out in the area in the last fifteen years, important information is now available which suggests that the ACS houses a large number of species with a high ecological value, that it represents a biodiversity hotspot in terms of the presence of sponge aggregations and coral reefs in certain regions, and that it sustains important fisheries due to the abundance of comercial species. Given the relevance of the species and habitats occurring in the ACS, there is a need to implement a conservation and management plan of the area in order to maintain habitats in good state of preservation.

Research in marine Spanish waters are focused on several actions to achieve an effectively management on protected areas, with the active participation of the stakeholders and research as basic tools for decision-making. Among these actions, there is one about the knowledge and control on NIS. One of its objectives is the creation of NIS factsheets, which are going to be added to the National Marine Biodiversity Geographical System (GIS) providing complementary information about taxonomic classification, common names, taxonomic synonyms, species illustrations, identification morphological characters, habitat in the native and introduced regions, biological and ecological traits, GenBank DNA sequences, world distribution, first record and evolution in the introduced areas, likely pathways of introduction, effects in the habitats and interaction with native species, and potential management measures to apply. The database will also provide data for (1) the European online platforms, (2) the environmental assessment for the Descriptor 2 (D2-NIS) of the EU Marine Strategy Framework Directive (MSFD), as well as (3) supporting decisions made by stakeholders. It is the result of extensive collaboration among scientist, manager’s and citizen science in the Spanish North-Atlantic, South-Atlantic, Gibraltar Strait-Alboran, Levantine-Balearic and Canary Islands marine divisions, providing an updated overview of the spatial distribution of relevant extended and invasive NIS of recent and established NIS introduced by maritime transport and aquaculture pathways, as well as on cryptogenic or native species in expansion due to the climatic water warming trend.

The toxic dinoflagellate Alexandrium minutum generally proliferates in semi-enclosed sites such as estuaries, harbours and lagoons, where stratification, restricted circulation and accumulation of resting cysts set suitable conditions for its development. In the Galician Rías (NW Iberian Peninsula), its blooms follow also this pattern. They are recurrent in small, shallow estuarine bays inside the Rías, but rarely detected, and if so in minor amount, out of these areas. However, a massive proliferation of A. minutum from June to July 2018 in the Rías Baixas (Vigo and Pontevedra) changed this picture. The bloom initiated in semi-enclosed waters, as previously described for this species, but thereafter spread to the whole embayments where persisted more than one month. It generated a noticeable red tide with disperse patches that became heavily concentrated inside the port of Vigo. During that period shellfish harvesting closures and paralytic shellfish toxins in certain marine invertebrates and fish were reported for the first time in Spain. Meteorological conditions (higher than usual rains/runoff, sustained temperature increment and oscillating wind pattern promoting a series of upwelling-relaxation cycles) fostered optimal circumstances for the outbreak of A. minutum: strong vertical stratification and the alternation of retention and dispersion processes. Simulations from a particle tracking model portrayed the observed bloom development phases: onset, transport within the surface layer towards the interior parts of the Ría of Vigo, and dispersion all over the embayment. High concentrations of resting cysts were detected several months after the bloom, which may have favoured flourish of A. minutum in the following years, markedly in 2020.

Species discovery is facilitated by the application of molecular tools and the exploration of poorly studied habitats. Recent surveys in Bafa Lake, Turkey, which experienced a transition from oligo- to mesohaline conditions during the last 40 years, led to the finding of two species of the genera Lophosiphonia and Polysiphonia. Our molecular and morphological study showed that one of the species corresponded to L. obscura, while the other differs from previously described Polysiphonia species and is proposed as P. sukatarii sp. nov. The new species differs from related congeners by a rbcL sequence divergence ≥5.8% and is morphologically distinguished by having four pericentral cells and trichoblasts arranged several segments apart. Lophosiphonia obscura, and its closely related species L. hemisphaerica comb. nov. and L. boldii comb. nov., have been previously found in similar habitats in Europe and Atlantic North America. Along with its record from Bafa Lake, P. sukatarii sp. nov. has been discovered in open shore algal turfs from the Canary Islands, suggesting that it is a euryhaline species with probably a wide distribution. Our work highlights that poorly studied habitats still harbour undiscovered species and additional surveys are necessary to acquire a more comprehensive understanding of the macroalgal diversity.

Recent changes in oceanic plankton are being reported at unprecedented rates. Most changes are related to environmental factors and many were identified as driven by climate, either through natural cycles or by anthropogenic effects. However, the separation of both effects is difficult because of the small size of most observational series. Moreover, some changes are related to trends and cycles while others were perceived as system shifts, often synchronized over large spatial scales. Here, studies on observational series of plankton, with the focus in the N Atlantic, are reviewed. Two main quasi-synchronic shifts in species assemblages were identified: one in late 1980’s and a most recent one in the first decade of the new millennium. While the origin and extent of most shifts vary locally, their synchronization seems to confirm the lagged response of plankton to changes in warming and in large-scale climatic factors. Changes in species abundance patterns are generally related to the strength of currents, but also to non-linear effects of warming, the latter particularly affecting species in regions near the limits of their thermal niche. Indeed, most of the changes are attributed to trade-offs between different biological strategies. Taken together, the reviewed case studies indicate a lagged biological response to variations in the local environment driven by large-scale climate forcing. The challenges for the interpretation of future changes include the consideration of local changes in a wider regional context, variations in species life-traits and possible top-down effects of plankton predators

Production of farmed fish is increasing worldwide and in areas which have traditionally not had large scale farming, specifically regions of high sea temperature. This research presents a methodology to assess the impacts of these developments on water quality and to manage them in the context of other discharges into the marine environment. Kuwait Bay, in Kuwait, is used as a case study for these types of environments, where the impacts of finfish farms are assessed regarding their location by implementing a 3D coupled hydrodynamic–biogeochemical model. The model was validated against a monthly climatology of field data for hydrodynamics and biogeochemical parameters. Results show that the impact of a farm size with an average historical production is minimal, with a slight increase in nutrient concentrations (0.4%) and in chlorophyll-a and oxygen (less than 1%) compared to the baseline (no farm). When the farm was located outside the bay, at the southern coast, the impact was even smaller. This suggests that the flushing conditions of the location are a prime consideration and can help mitigate the impacts of larger farm sizes.

The spectrophotometric methodology for carbonate ion determination in seawater was first published in 2008 and has been continuously evolving in terms of reagents and formulations. Although being fast, relatively simple, affordable, and potentially easy to implement in different platforms and facilities for discrete and autonomous observations, its use is not widespread in the ocean acidification community. This study uses a merged overdetermined CO2 system data set (carbonate ion, pH, and alkalinity) obtained from 2009 to 2020 to assess the differences among the five current approaches of the methodology through an internal consistency analysis and discussing the sources of uncertainty. Overall, the results show that none of the approaches meet the climate goal (± 1 % standard uncertainty) for ocean acidification studies for the whole carbonate ion content range in this study but usually fulfill the weather goal (± 10 % standard uncertainty). The inconsistencies observed among approaches compromise the consistency of data sets among regions and through time, highlighting the need for a validated standard operating procedure for spectrophotometric carbonate ion measurements as already available for the other measurable CO2 variables.

The present study adds 19 species (15 Rhodophyta, one Chlorophyta and three Ochrophyta) to the Azorean marine macroalgal flora, increasing the current total of species recorded in this region to 521 (349 Rhodophyta, 76 Chlorophyta and 96 Ochrophyta), and showing that this isolated island group supports a relatively rich marine macroalgal flora. Some species fall within their known overall distributional range, whereas other found here represent a northern or southern extension to their known distribution in the Atlantic. Three species (Antithamnionella elegans, Gymnophycus hapsiphorus and Scytosiphon dotyi) are probable introductions to the Azores, whereas Melanothamnus pseudoforcipatus has an uncertain status. Six of the newly reported species were found as components of the intertidal algal turf samples, which justifies the need for continuing to examine turf samples as new discoveries can be anticipated.

Availability of operational regional hydrodynamic models and near real time Harmful Algal Bloom (HAB) alerts from monitoring stations and remote sensing products have allowed the proliferation of short term advective HAB forecasts. However, their predictive ability in simulating HAB transport needs to be continuously evaluated in events of different HAB species to assess their applicability to different domains and the impacts of the choices made in model setup. Here we review the performance of three different modelling systems which were part of the PRIMROSE project against historical bloom events in different regions in the European Atlantic Area. The objectives are to understand their predictive ability and to demonstrate some aspects of Lagrangian model setup that are relevant to HAB early warning systems; in particular the use of advection-diffusion only models (without a biological component) and the effects of model configuration, especially model resolution. Hindcast and forecast simulations have been run in examples of high biomass blooms detected in satellite imagery; in the western English Channel, several events of potentially toxic species like Karenia mikimotoi and Prorocentrum cordatum (minimum) were simulated and in Western France a bloom of Mesodinium rubrum, prey of the toxic Dinophysis spp. Additionally, some simulations for studying the evolution of low biomass Dinophysis spp. blooms in Galicia-North Portugal were undertaken with models of different setup. Several metrics have been used to quantify the model performance and to compare the results of the different model configurations, showing that differences in hydrodynamical model configuration (initiation, resolution, forcing, and simulation domain) result in differences in the predicted transport of HABs. We find that advection only is a reasonable approximation but that it may do worse in an early (onset) phase than later on, and we find transport is generally increases with increasing reso

The detection of invasive species is commonly challenging in marine environments, often related with the insufficient taxonomic knowledge of the local diversity. Using DNA sequences in diversity surveys and their phylogenetic analysis can assist us to clarify the native or introduced origin of some species. We applied this approach to study the red algae Aphanocladia stichidiosa. It was originally described in the Mediterranean (1955), later recorded in Portugal (1960), the Canary Islands (1986), the northwestern Spain (1990) and the Azores (2012). Unexpectedly, our diversity surveys in Australia revealed its presence in Victoria in 2015, finding that European and Australian specimens had identical DNA sequences (rbcL gene) and suggesting that it is introduced in one of the regions. Phylogenetic analysis resolved A. stichidiosa in a highly supported clade with species restricted to the southern hemisphere, mainly from Australia. Accordingly, we conclude that A. stichidiosa is native from Australia, although it has never been recorded there before, and that it represents a relatively old introduction in Europe. In both native and introduced regions, it is frequent in algal turfs, a type of assemblage composed by a carpet of small, morphologically similar species whose identification is often difficult. The type of growth of this species explains the absence of previous records in Australia, where the number of taxonomists studying this assemblage is lower than in Europe. Sequential reports of A. stichidiosa in different European regions suggest that it is expanding its distribution, as well as its abundance is increasing. The invasive character of this species needs to be determined yet, and its small size should not lead to underestimate its potential harmfulness. In the current context, in which kelp forests are globally declining and algal turfs are expanding, this species might play a relevant role in the transformation of the European marine ecosystems.

Prokaryotes play an important role in biogeochemical cycling in marine ecosystems, but little is known about their diversity and composition, and it’s even less understood how they may contribute to the ecological functioning of highly variable coastal areas affected by upwelling. Between May 2016 and May 2018, we carried out 26 one-day samplings in the temperate northwestern Iberian upwelling system to investigate the temporal patterns of variability for prokaryotic abundance, diversity and community composition by combining flow cytometry and 16S RNA high- throughput sequencing. A marked seasonality was found for prokaryotic abundance, peaking during summer upwelling and relaxation season (≈May to September), when extracellular release of organic matter from phytoplanktonic blooms is a significant process, and decreasing in downwelling events (≈October to April). Those downwelling conditions, characterized by deeper mixed layers and a homogeneous water column, favored a higher abundance of the archaeal groups, Marine Group II (Euryarchaeota) and Nitrosopelagicus (Thaumarchaeota), as well as of Marinimicrobia bacterium (SAR406 clade) and the group Bacteria_Others. By contrast, upwelling and relaxation conditions characterized by enhanced vertical stratification and hydrographic variability, included a community generally less diverse with core-phylotypes (occurring > 75% of the samples) proliferating, i.e. Flavobacteriaceae (Bacteroidetes), Chloroplast (C

The international RAIA Observatory (www.marnaraia.org) resulted from the effort of 12 research and academic institutions and public agencies (Spanish and Portuguese) working in the field of meteorology and oceanography. The RAIA Observatory serves the main maritime activities of the Galicia-Northern Portugal Euroregion and contributes to collaborative observational networks. Under the framework of coastal risk management, environmental indicators are fundamental tools for the evaluation and mitigation of environmental risks, showing the current state and helping to predict future changes on ecosystem health regarding environmental risks. In last years, the different partners of the RAIA Observatory have identified 38 environmental indicators, in which 12 key risks affecting the ecosystem services of the Euroregion Galicia-Northern Portugal are being evaluated. Data was analyzed and compiled by the various partners of the RAIA Observatory and the development and optimization of the environmental indicators has been done according to the specifications provided by the European Environmental Agency (EEA) and the International Panel for Climate Change (IPCC). The resulting environmental indicators are included and shared on a publicly-accessible Web service, georeferenced and accompanied by graphics (https://marrisk.inesctec.pt/public/#!/indicators). So far, the current status of the indicators has allowed us to establish risk assessment protocols for the Euroregion, and identify critical gaps in temporal and spatial coverage. The inclusion of the environmental indicators in the RAIA Observatory is of great relevance for national and international data exchange and promotes future collaborations.

Zooplankton grazing onphytoplankton promotes the release of particulate and dissolved organic matter (DOM) into the water column and therefore plays a key role in organic matter cycling in aquatic systems. Prokaryotes are the main DOM consumers in the ocean by actively remineralizing and transforming it, contributing to its molecular diversification. To explore the molecular composition of zooplankton-derived DOM and its bioavailability to natural prokaryotic communities, the DOM generated by a mixed zooplankton community in the coastal Atlantic off Spain was used as substrate for a natural prokaryotic community and monitored over a ~ 5-d incubation experiment. The molecular composition of solid-phase extracted DOM was characterized via Fourier-transform ion cyclotron resonance mass spectrometry. After ~ 4 d in the zooplankton-derived DOM amended incubation, the prokaryotic community demonstrated a 17-fold exponential increase in cell number. The prokaryotic growth resulted in a reduction in bulk dissolved organic carbon concentration and the zooplankton-derived DOM was considerably transformed at molecular and bulk elemental levels over the incubation period. The C : N ratio (calculated from the obtained molecular formulae) increased while the functional diversity decreased over the incubation time. In addition, molecular indices pointed to a reduced bioavailability of DOM at the end of the experiment. These findings show that zooplankton excreta are a source of labile organic matter that is quickly metabolized by the prokaryotic community. Therefore, a fraction of carbon is shunted from transfer to secondary consumers similarly to the viral shunt, suggesting that the zooplankton–prokaryotic interactions play an important role in the ocean's carbon cycle.

The number of newly described species has increased since the addition of molecular data to taxonomic studies, revealing that species considered widely distributed by morphological and anatomical studies are often comprised of complexes of several distinct species. This study reports on a new turf-forming species of Digenea from the Greater Caribbean (South Florida and eastern Cuba), previously identified as D. simplex based on morpho-anatomical characters, but shown through DNA sequences to be a distinct species. Digenea nana sp. nov. is characterized by its small brush appearance, small dimensions (2.5 cm high and 0.6 mm wide), long determinate branches reaching 15 mm in length (its most striking feature) and 11–12 pericentral cells. Digenea nana is distinct from all its congeners, showing sequence divergences of 3.5–5.0% in COI-5P and 1.7–2.7% in rbcL. The species resolved as sister to D. rafaelii (genetic distance of about 3.5% and 1.7% in COI-5P and rbcL respectively) from Pacific Mexico, and can be easily distinguished by morpho-anatomical characters. Digenea nana is the seventh species in the genus worldwide. Given the presumed wide distribution of D. simplex, based solely on morpho-anatomy, and the number of cryptic and pseudo-cryptic species recently described, further integrative molecular and morpho-anatomical studies are likely to reveal new taxa.

The microbe-dissolved organic matter (DOM) interactions include microbial uptake and DOM reworking and release, affecting the composition of the heterogeneous DOM pool. In turns, this distinct DOM composition can select for microbial assemblages. We investigated the diversity of microbial (both Bacteria and Archaea) communities (combining Illumina tag sequencing of 16S rRNA gen -amplicon sequencing variants, ASVs- and metagenomics) and the chemodiversity of dissolved organic molecules (extracted by solid phase extraction and analyzed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, FT-ICR-MS) in the Eastern North Atlantic Ocean off the Galician coast (43oN, 9o-15oW). Sampling ranged from 100 m to 5000 m, thereby encompassing a wide variety of water masses with contrasting origins and different aging. Applying diversity ecological metrics to both organic compounds and ASVs, we found that microbial diversity and richness were negatively correlated with DOM concentration and chemo-diversity. Besides, our results demonstrated the link between this trend and water mass aging, which enhances biosphere taxonomic diversity but reduces molecular variety. DOM diversity, decreasing along the water mass aging gradient, would likely reflect the persistence of the most refractory molecules, generated as by- product of the DOM degradation by microbes. In two PCoAs based on the metagenomic data, combined PCoA axis 1 and PCoA axis 2, explained the 80% and 20% of the microbial gene ́s structural variability among water masses. The oldest water masses, originated at high latitudes, such as NADW and LDW, were associated to higher abundance of genes involved in metabolism of aromatic compound. Intermediate waters such as ENACWst were related to sulphur/iron/phosphorous metabolism related genes. Surface waters were linked to genes involved in photosynthesis, autotrophy and cell division. Taken together, the observed increase of DOM homogenization along water mass aging was