X. Anton Alvarez-Salgado

Spanish National Research Council | CSIC · Instituto de Investigaciones Marinas

The marine dissolved organic carbon (DOC) pool is an important player in the functioning of marine ecosystems. DOC is at the interface between the chemical and the biological worlds, it fuels marine food webs, and is a major component of the Earth’s carbon system. Here, we review the research showing impacts of global change stressors on the DOC cy...

Submarine groundwater discharge is recognized as a major source of chemicals to the global ocean, exerting large control over coastal water composition. Radon and 226 Ra are used to evaluate, for the first time, the occurrence and magnitude of submarine groundwater discharge in the Ría de Vigo, a large, highly productive embay-ment affected by seas...

Assessing the carbon footprint of marine bivalve aquaculture demands an accurate estimation of the CO2 release associated to capital goods and aquaculture operations but also to the metabolic CO2 budget of the cultured species. Nowadays, there are discrepancies on the processes to include in that budget, how to estimate them, and which scale should...

Distributions of dissolved (DOM) and suspended (POM) organic matter, and their chromophoric (CDOM) and fluorescent (FDOM) fractions, are investigated at high resolution (< 10 km) in the Cape Verde Frontal Zone (CVFZ) during fall 2017. In the epipelagic layer (< 200 m), meso- and submesoscale structures (meanders, eddies) captured by the high resolu...

The ocean is a salty and very diluted broth of organic matter that contains about 680 Pg C. More than 97% of this organic matter is in the dissolved form. This huge amount of reduced carbon, comparable to the CO2 accumulated in the atmosphere, results in an average concentration of 0.48 ppm (or 40.3 μmol kg−1) when divided by the world ocean volume...

The Galician Rías (NW Spain) support intensive aquaculture and fisheries due to the seasonal upwelling of subsurface cold and nutrient-rich water, which is responsible of a high primary productivity and periodical occurrence of algal blooms, including harmful species. The increasing occurrence of HABs, and the potential decreasing extension and int...

The measurements of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) are used to characterize the dissolved organic matter (DOM) pool and are important components of biogeochemical cycling in the coastal ocean. Here, we present the first edition of a global database (CoastDOM v1; available at https://figshare.com/s/512289eb43c4f...

The marine biological carbon pump is driven by the interplay between particle sinking velocity and remineralisation. Despite its importance, sinking velocity of natural marine aggregates is not routinely measured, but often calculated from aggregate size and density using Stokes’ law. Yet, comparing calculated and experimentally measured sinking ve...

Coastal lagoons are among the most productive and biodiverse systems in the world and are important sentinels of climate change. The Mar Menor is one of the largest coastal lagoons in the Mediterranean, providing a variety of ecosystem services and resources to the community. However, in recent decades this lagoon has suffered drastic changes and d...

Ammonium, a key intermediate nutrient, is typically low to undetectable on the Oregon coast, particularly as active upwelling delivers high onshore flow of ammonium‐poor waters. However, during bloom and post‐bloom conditions large ammonium concentrations and uptake rates have been described. High‐frequency on board nitrate + nitrite and ammonium a...

The Ría de Vigo catchment is situated in the largest radon-prone area of the Iberian Peninsula. High local indoor radon (²²²Rn) levels are the preeminent source of radiation exposure, with negative effects on health. Nevertheless, information on radon levels of natural waters and the potential human exposure risks associated with their domestic use...

The Yangtze River, the largest river in Asia, plays a crucial role in linking continental and oceanic ecosystems. However, the impact of natural and anthropogenic disturbances on composition and transformation of dissolved organic matter (DOM) during long-distance transport and seasonal cycle is not fully understood. By using a combination of eleme...

Seabird guano enters coastal waters providing bioavailable substrates for microbial plankton, but their role in marine ecosystem functioning remains poorly understood. Two concentrations of the water soluble fraction (WSF) of gull guano were added to different natural microbial communities collected in surface waters from the Ría de Vigo (NW Spain)...

Prokaryotes represent a major fraction of marine biomass and play a key role in the global carbon cycle. We studied the vertical profiles (0-3500 m) of abundance, viability, and activity of prokaryotic communities along a productivity gradient in the subtropical and tropical Atlantic to assess whether there is a vertical linkage between surface pro...

Primary producers nutritional content affects the entire food web. Here, changes in nutritional value associated with temperature rise and the occurrence of marine heat waves (MHWs) were explored in the endemic Mediterranean seagrass Posidonia oceanica. The variability of fatty acids (FAs) composition and carbon (C) and nitrogen (N) content were ex...

The distribution of any non-conservative variable in the deep open ocean results from the circulation and mixing of water masses (WMs) of contrasting origin and from the initial preformed composition, modified during ongoing simultaneous biological and/or geochemical processes. Estimating the contribution of the WMs composing a sample is useful to...

Aim Dispersal and environmental gradients shape marine microbial communities, yet the relative importance of these factors across taxa with distinct sizes and dispersal capacity in different ocean layers is unknown. Here, we report a comparative analysis of surface and deep ocean microbial beta diversity and examine how these patterns are tied to o...

Subterranean estuaries (STEs) modulate the chemical composition of continental groundwater before it reaches the coast but their microbial community is poorly known. Here, we explored the microbial ecology of two neighbouring, yet contrasting STEs (Panxón and Ladeira STEs; Ría de Vigo, NW Iberian Peninsula). We investigated microbial composition (1...

Prokaryotes represent a major fraction of marine biomass and play a key role in the global carbon cycle. We studied the vertical profiles (from surface down to the bathypelagic realm) of abundance, cytometric signatures, and activity of prokaryotic communities along a productivity gradient in the subtropical and tropical Atlantic to assess whether...

Supplementary information to 'Deep ocean prokaryotes and fluorescent dissolved organic matter reflect the history of the water masses across the Atlantic Ocean'.

Few studies have investigated ultraviolet (UV) radiation in the open ocean besides its harmful effects on organisms and influence on biogeochemical processes. Here, we assessed UV attenuation, with particular focus on UV-B, across the (sub)tropical ocean during the Malaspina 2010 Circumnavigation. Vertical UV radiometer profiles together with Chl-a...

Organic matter is known to influence community composition and metabolism of marine prokaryotes. However, few studies have addressed this linkage in the deep ocean. We studied the relationship between fluorescent dissolved organic matter and prokaryotic community composition in meso- and bathypelagic water masses along a surface productivity gradie...

Petrol-based plastic debris reaching the ocean releases dissolved organic carbon (DOC) and it can also leach fluorescent dissolved organic matter (FDOM). DOC is available to microbial uptake but the FDOM bioavailability has been scarcely studied. Although the most common plastic found in the ocean is petrol-based, the use of biodegradable plastic h...

Plastic debris reaching the ocean is exponentially increasing in parallel with plastic production. Once into seawater, plastic starts to leach organic compounds that are presumably additives and plastic oligomers, and that process is enhanced by solar radiation. From previous studies with virgin plastic, it has been estimated that up to 23,600 metr...

The Cape Verde Frontal Zone (CVFZ) is a highly dynamic region located in the southern boundary of the Canary Current Eastern Boundary Upwelling Ecosystem. Due to the interaction of the Cape Verde Front with the Mauritanian coastal upwelling, the area features large vertical and horizontal export fluxes of organic matter. While the flux, composition...

Sediment dissolved organic matter (DOM) in inland waters is commonly affected by environmental changes. However, knowledge about how sediment DOM responds to eutrophication and the associations between sediment DOM and bacterial communities requires further investigation. We selected a sediment core from Dianchi Lake (China) that was dated from 186...

The chemical composition of the seawater soluble fraction (WSF) of yellow-legged gulls and harbour seal faeces and their impact on microbial plankton communities from an eutrophic coastal area have been tested. After characterisation of the C:N:P stoichiometry, trace metals content and organic molecular composition of the faeces, significant differ...

Abstract Forecasting of climate change impacts on marine aquaculture production has become a major research task, which requires taking into account the biases and uncertainties arising from ocean climate models in coastal areas, as well as considering culture management strategies. Focusing on the suspended mussel culture in the NW Iberian coastal...

The circulation patterns in the confluence of the North Atlantic subtropical and tropical gyres delimited by the Cape Verde Front (CVF) were examined during a field cruise in summer 2017. We collected hydrographic data, dissolved oxygen (O2) and inorganic nutrients along the perimeter of a closed box embracing the Cape Verde Frontal Zone (CVFZ). Th...

The bathypelagic ocean (1000-4000 m depth) is the largest aquatic biome on Earth but it is still largely unexplored. Due to its prevalent low dissolved organic carbon concentrations, most of the prokaryotic metabolic activity is assumed to be associated to particles. The role of free-living prokaryotes has thus been mostly ignored, except that of s...

Due to the widespread pollution of coastal groundwaters with fertilizers, submarine groundwater discharge (SGD) is often thought to be a large dissolved inorganic nitrogen (DIN) source to the ocean. Whether this N is autochthonous or allochthonous to the subterranean estuary (STE), the availability of large quantities of DIN can nevertheless intera...

Compilation of dissolved organic matter (DOM) data obtained from global ocean observations from 1994 to 2020 This compilation consists of measurements of dissolved organic matter (DOM) and other chemical and hydrographic parameters obtained during the global ocean observations from 1994-01-01 to 2019-12-31. Measurements of dissolved organic matter...

About 20% of the organic carbon produced in the sunlit surface ocean is transported into the ocean’s interior as dissolved, suspended and sinking particles to be mineralized and sequestered as dissolved inorganic carbon (DIC), sedimentary particulate organic carbon (POC) or “refractory” dissolved organic carbon (rDOC). Recently, the physical and bi...

The productivity of intertidal shellfish banks is affected by a wide variety of environmental parameters. In this study, a battery of multivariate analyses including generalized linear mixed models, hierarchical cluster analysis and principal component analysis were performed to define the spatial organization of sandbanks and to identify the varia...

Production of wedge clam (Donax trunculus) has experienced a widespread decrease. Environmental conditions have been postulated as an important agent though the effects on reproduction are poorly understood. We here review the reproductive cycle and evaluate the influence of environmental conditions in Galicia (NW Iberian coast). We further contras...

Subterranean estuaries (STEs), where continental groundwaters and saltwaters meet, are zones of intense biogeochemical reactivity. As such, STEs significantly modify groundwater-borne nutrient fluxes to the coastal zone. Thus, evaluating their reactive role is crucial to anticipate impacts of submarine groundwater discharge over coastal ecosystems....

Global production of shell calcium carbonate (CaCO3) from bivalve aquaculture amounts about 13.6 million metric tons per year. Shells, traditionally considered a waste of aquaculture activities, have recently acquired an interest under the current framework of zero waste circular economy. Shell CaCO3 is a sustainable biomaterial that could partly r...

Cobalamin (B12) is an essential cofactor that is exclusively synthesized by some prokaryotes while many prokaryotes and eukaryotes require an external supply of B12. The spatial and temporal availability of B12 is poorly understood in marine ecosystems. Field measurements of B12 along with a large set of ancillary biotic and abiotic factors were ob...

Posidonia oceanica is a well-recognized source of dissolved organic matter (DOM) derived from exudation and leaching of seagrass leaves, but little is known about its impact on the chromophoric fraction of DOM (CDOM). In this study, we monitored for two years the optical properties of CDOM in two contrasting sites in the Mallorca Coast (Balearic Is...

The circulation patterns in the confluence of the North Atlantic Subtropical and Tropical gyres delimited by the Cape Verde Frontal Zone (CVFZ) in summer 2017 were examined. Hydrology, dissolved oxygen (O2) and inorganic nutrients data collected in a closed box embracing the CVFZ allowed estimating transports of water masses, O2 and inorganic nutri...

Species composition plays a key role in ecosystem functioning. Theoretical, experimental and field studies show positive effects of biodiversity on ecosystem processes. However, this link can differ between taxonomic and functional diversity components and also across trophic levels. These relationships have been hardly studied in planktonic commun...

Plain Language Summary The Mediterranean Sea is a semienclosed basin connected with the Atlantic Ocean through the Strait of Gibraltar. At this hot spot of ocean circulation, about 0.8 Sv (1 Sv = 10⁶ m³ s⁻¹) of dissolved organic carbon (DOC) rich Atlantic Surface Water enters the Mediterranean Sea and the same volume of DOC poor Mediterranean Overf...

Prokaryotes play a fundamental role in decomposing organic matter in the ocean, but little is known about how microbial metabolic capabilities vary at the global ocean scale and what are the drivers causing this variation. We aimed at obtaining the first global exploration of the functional capabilities of prokaryotes in the ocean, with emphasis on...

Deep ocean microbial communities rely on the organic carbon produced in the sunlit ocean, yet it remains unknown whether surface processes determine the assembly and function of bathypelagic prokaryotes to a larger extent than deep‐sea physico‐chemical conditions. Here, we explored whether variations in surface phytoplankton assemblages across Atla...

Most dissolved organic carbon (DOC) sequestered in the deep ocean has residence times of decades to thousands of years, with clear implications for climate regulation, though some net removal is typically observed with increasing water mass age. Here, a high‐quality‐high‐resolution data set has allowed us to identify net additions of recalcitrant D...

Abstract Seasonal and inter-annual variability of satellite-derived net primary production (NPP) in the NW Iberian margin and its relationship with the offshore Ekman transport (-Qx) and a variety of sea surface temperature (SST) indices have been examined over the period 1998-2016. Seasonality explained about 55% of NPP variability over the shelf...

The global distribution of chromophoric dissolved organic matter (CDOM) in the euphotic layer of the Atlantic, Indian, and Pacific oceans (between 35° N and 40° S) was analyzed by absorption spectroscopy during the Malaspina 2010 circumnavigation. Absorption coefficients at 254 nm (a254) and 325 nm (a325), indices (a254/a365) and spectral slopes (b...

Abstract Understanding and modelling bivalve growth dynamics under variable environmental conditions are crucial for the development of management and sustainability aquaculture plans. This work proposes a new dynamic bivalve growth model that combines net production Dynamic Energy Budget (DEB) theory and the species-specific growth dynamics of th...

Dissolved organic matter (DOM) is produced in the surface and exported towards the deep ocean, adding ∼2 PgC yr−1 to the global carbon export. Due to its central role in the Meridional Overturning Circulation (MOC), the eastern subpolar North Atlantic (eSPNA) contributes largely to this export. Here we quantify the transport and budget of dissolved...

Transparent exopolymer particles (TEP) play a key role in ocean carbon export and structuring microbial habitats, but information on their distribution across different ocean basins and depths is scarce, particularly in the dark ocean. We measured TEP vertical distribution from the surface to bathypelagic waters in an east-to-west transect across t...

The eastern boundary of the North Atlantic subtropical gyre (NASTG) receives organic materials produced in the nearby Canary upwelling system (CanUS), which has important implications for the metabolic balance of the region. Here we computed absolute geostrophic, Ekman and eddy diffusive transports and net budgets of oxygen, nitrate, and phosphate,...

Fluorescent dissolved organic matter (FDOM) in the Mediterranean Sea was analysed by excitation–emission matrix (EEM) spectroscopy and parallel factor (PARAFAC) analysis during the cruise HOTMIX 2014. A 4–component model, including 3 humic–like and 1 protein–like compounds, was obtained. To decipher the environmental factors that dictate the distri...

Determining the factors that influence marine microbial growth and community structure are critical for the understanding of global carbon cycling. Since the early twentieth century, it has been known that B vitamins play an important role in phytoplankton community dynamics. Limited oceanic dissolved B vitamin distributions indicate that these imp...

Small eukaryotes (0.2‐20 μm cell‐size) represent a significant fraction of the microbial plankton community in shelf waters of NW‐Spain. The community composition of small eukaryotes living at the surface and at the base of the photic zone was analysed by means of 18S rDNA high‐throughput sequencing on a circa‐monthly basis over a 23‐months period....

Over the past decades, as a consequence of human activity, there was an increase in nutrient inputs to the ocean and they are expected to enhance even more in the future. Coastal areas, accounting for a significant proportion of marine primary productivity, are the most vulnerable zones to anthropogenic impacts. The response of phytoplankton commun...

Intertidal shellfish banks in estuarine areas are influenced by a wide variety of environmental conditions, including the physical and chemical characteristic of the water that floods the grounds. In this study we carry out a cross-comparison of the hydrographic characteristics and nutrient fertilization patterns of the waters that laps the shellfi...

Dynamics of individual phytoplankton species are more variable than predicted for the functional groups. This observation is poorly understood in highly perturbed coastal systems. The trends in abundance of 54 phytoplankton species spanning a volumetric size range from ~102 to ~105 μm3 in shelf waters of the NW Iberian upwelling system since the la...

Approximately 5.25 trillion plastic pieces are floating at the sea surface. The impact of plastic pollution on the lowest trophic levels of the food web, however, remains unknown. Here we show that plastics release dissolved organic carbon (DOC) into the ambient seawater stimulating the activity of heterotrophic microbes. Our estimates indicate tha...

The bioavailability of organic matter was assessed at three locations during the dry and wet seasons in the Great Barrier Reef, by measuring changes in particulate (POM) and dissolved (DOM) organic matter concentrations during laboratory incubations over 50 days. The sites did not show any difference in salinity and, therefore, observed changes cou...

More than 96% of organic carbon in the ocean is in the dissolved form, most of it with lifetimes of decades to millennia. Yet, we know very little about the temperature sensitivity of dissolved organic carbon (DOC) degradation in a warming ocean. Combining independent estimates from laboratory experiments, oceanographic cruises and a global ocean D...