The sea-surface microlayer (SML) is at the uppermost surface of the ocean, linking the hydrosphere with the atmosphere. The presence and enrichment of organic compounds in the SML have been suggested ...to influence air–sea gas exchange processes as well as the emission of primary organic aerosols. Here, we report on organic matter components collected from an approximately 50 µm thick SML and from the underlying water (ULW), ∼ 20 cm below the SML, in December 2012 during the SOPRAN METEOR 91 cruise to the highly productive, coastal upwelling regime off the coast of Peru. Samples were collected at 37 stations including coastal upwelling sites and off-shore stations with less organic matter and were analyzed for total and dissolved high molecular weight (> 1 kDa) combined carbohydrates (TCCHO, DCCHO), free amino acids (FAA), total and dissolved hydrolyzable amino acids (THAA, DHAA), transparent exopolymer particles (TEP), Coomassie stainable particles (CSPs), total and dissolved organic carbon (TOC, DOC), total and dissolved nitrogen (TN, TDN), as well as bacterial and phytoplankton abundance. Our results showed a close coupling between organic matter concentrations in the water column and in the SML for almost all components except for FAA and DHAA that showed highest enrichment in the SML on average. Accumulation of gel particles (i.e., TEP and CSP) in the SML differed spatially. While CSP abundance in the SML was not related to wind speed, TEP abundance decreased with wind speed, leading to a depletion of TEP in the SML at about 5 m s−1. Our study provides insight to the physical and biological control of organic matter enrichment in the SML, and discusses the potential role of organic matter in the SML for air–sea exchange processes.
Editorial: Impacts of Marine Litter Galgani, Luisa; Beiras, Ricardo; Galgani, François ...
Frontiers in Marine Science,
04/2019, Letnik:
6, Številka:
208
Journal Article
Recenzirano
Odprti dostop
Despite initiatives to monitor and reduce marine litter, such as from United Nations Environmental Programme (UNEP), the G20, and G7, the European Marine Strategy Framework Directive (European ...Commission, 2008) and action plans from the Regional Seas Conventions (e.g., OSPAR Regional Action Plan for Marine Litter; UNEP/MAP-Barcelona Convention Regional Plan on Marine Litter Management in the Mediterranean), harm is still far from being understood. ...standardization, and harmonization of sampling techniques, result units and metrics is needed to achieve reliable monitoring and assessment, and threshold values of good/not good status are still at an incipient stage, since ecotoxicological information on the effects of the smaller fractions of plastic litter, microplastics and nanoplastics, in the environment and on aquatic organisms is scarce (Gall and Thompson, 2015; De Sá et al., 2018; Ogonowski et al., 2018). ...plastic litter can represent a relevant source of chemical additives, some of them with suspected endocrine disrupting action, that easily leach into the water since they are not bound to the polymeric chains and become available to the estuarine and marine fauna (Hermabessiere et al., 2017). ...intentionally or accidentally discarded fishing gears pose special risks for large, air-breathing marine animals, including endangered species, which get entangled in the nets (Lusher et al., 2018). ...plastic at sea may transport alien species over long distances or act as substratum for vagile and epistratum benthos, providing a support to colonization (Casabianca et al., 2019).
About 5 trillion plastic particles are present in our oceans, from the macro to the micro size. Like any other aquatic particulate, plastics and microplastics can create a micro-environment, within ...which microbial and chemical conditions differ significantly from the surrounding water. Despite the high and increasing abundance of microplastics in the ocean, their influence on the transformation and composition of marine organic matter is largely unknown. Chromophoric dissolved organic matter (CDOM) is the photo-reactive fraction of the marine dissolved organic matter (DOM) pool. Changes in CDOM quality and quantity have impacts on marine microbial dynamics and the underwater light environment. One major source of CDOM is produced by marine bacteria through their alteration of pre-existing DOM substrates. In a series of microcosm experiments in controlled marine conditions, we explored the impact of microplastics on the quality and quantity of microbial CDOM. In the presence of microplastics we observed an increased production of CDOM with changes in its molecular weight, which resulted from either an increased microbial CDOM production or an enhanced transformation of DOM from lower to higher molecular weight CDOM. Our results point to the possibility that marine microplastics act as localized hot spots for microbial activity, with the potential to influence marine carbon dynamics.
The interface layer between ocean and atmosphere is only a couple of micrometers thick but plays a critical role in climate relevant processes, including the air-sea exchange of gas and heat and the ...emission of primary organic aerosols (POA). Recent findings suggest that low-level cloud formation above the Arctic Ocean may be linked to organic polymers produced by marine microorganisms. Sea ice harbors high amounts of polymeric substances that are produced by cells growing within the sea-ice brine. Here, we report from a research cruise to the central Arctic Ocean in 2012. Our study shows that microbial polymers accumulate at the air-sea interface when the sea ice melts. Proteinaceous compounds represented the major fraction of polymers supporting the formation of a gelatinous interface microlayer and providing a hitherto unrecognized potential source of marine POA. Our study indicates a novel link between sea ice-ocean and atmosphere that may be sensitive to climate change.
Three-dimensional hydrogels of organic polymers have been suggested to affect a variety of processes in the ocean, including element cycling, microbial ecology, food-web dynamics, and air-sea ...exchange. However, their abundance and distribution in the ocean are hardly known, strongly limiting an assessment of their global significance. As a consequence, marine gels are often disregarded in biogeochemical or ecosystem models. Here, we demonstrate the widespread abundance of microgels in the ocean, from the surface to the deep sea. We exhibit size spectra of two major classes of marine gels, transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP) for three different ocean regimes: a) polar seas, b) eastern upwelling systems and c) the oligotrophic open ocean. We show the variations of TEP and CSP over the water-column, and compare them to dissolved organic carbon (DOC). We also discuss how the observed distributional patterns give potential insight to the productivity and particle dynamics of these distinct oceanic regimes. Finally, we exploit current research topics, where consideration of microgels may give new insight into the role of organic matter for marine biogeochemical processes.
Microplastics are a major environmental challenge, being ubiquitous and persistent as to represent a new component in all marine environments. As any biogenic particle, microplastics provide surfaces ...for microbial growth and biofilm production, which largely consists of carbohydrates and proteins. Biofilms influence microbial activity and modify particle buoyancy, and therefore control the fate of microplastics at sea. In a simulated 'plastic ocean', three mesocosms containing oligotrophic seawater were amended with polystyrene microbeads and compared to three control mesocosms. The evolution of organic matter, microbial communities and nutrient concentrations was monitored over 12 days. The results indicated that microplastics increased the production of organic carbon and its aggregation into gel particulates. The observed increase of gel-like organics has implications on the marine biological pump as well as the transport of microplastics in the ocean.
Plastic particles are ubiquitous in the marine environment. Given their low density, they have the tendency to float on the sea surface, with possible impacts on the sea surface microlayer (SML). The ...SML is an enriched biofilm of marine organic matter, that plays a key role in biochemical and photochemical processes, as well as controlling gas exchange between the ocean and the atmosphere. Recent studies indicate that plastics can interfere with the microbial cycling of carbon. However, studies on microplastic accumulation in the SML are limited, and their effects on organic matter cycling in the surface ocean are poorly understood. To explore potential dynamics in this key ocean compartment, we ran a controlled experiment with standard microplastics in the surface and bulk water of a marine monoculture. Bacterial abundance, chromophoric dissolved organic matter (CDOM), and oxygen concentrations were measured. The results indicate an accumulation of CDOM in the SML and immediate underlying water when microplastic particles are present, as well as an enhanced oxygen consumption. If extrapolated to a typical marine environment, this indicates that alterations in the quality and reactivity of the organic components of the SML could be expected. This preliminary study shows the need for a more integrated effort to our understanding the impact of microplastics on SML functioning and marine biological processes.
Despite the huge extent of the ocean’s surface, until now relatively little attention has been paid to the sea surface microlayer (SML) as the ultimate interface where heat, momentum and mass ...exchange between the ocean and the atmosphere takes place. Via the SML, large-scale environmental changes in the ocean such as warming, acidification, deoxygenation and eutrophication potentially influence cloud formation, precipitation and the global radiation balance. Due to the deep connectivity between biological, chemical and physical processes, studies of the SML may reveal multiple sensitivities to global and regional changes. Understanding the processes at the ocean’s surface, in particular involving the SML as an important and determinant interface, could therefore provide an essential contribution to the reduction of uncertainties regarding ocean-climate feedbacks. This review identifies gaps in our current knowledge of the SML and highlights a need to develop a holistic and mechanistic understanding of the diverse biological, chemical and physical processes occurring at the ocean-atmosphere interface. We advocate the development of strong interdisciplinary expertise and collaboration in order to bridge between ocean and atmospheric sciences. Although this will pose significant methodological challenges, such an initiative would represent a new role model for interdisciplinary research in Earth System sciences.
Microplastic contamination has been linked to a range of impacts on aquatic environments. One important area that is only beginning to be addressed is the effect of microplastics on marine carbon ...cycling and how these compare to the effects related to inorganic particles typically present in ocean waters. The present study explores these impacts on dissolved organic matter dynamics by comparing three scenarios: a particle-free environment, a particle-enriched system with polystyrene microplastics, and a particle-enriched system with inorganic particles (water insoluble SiO2). Natural marine organic matter was obtained by culturing a non-axenic strain of Chaetoceros socialis in 2 L flasks under each of three scenarios. Following the diatom growth phase, filtered samples from the three flasks containing dissolved organic matter and bacteria were incubated separately in the dark for 5 days to monitor changes in dissolved organic matter. Chromophoric dissolved organic matter (CDOM), a bulk optical property, was monitored daily to examine changes in its quality and quantity and to compare degradation dynamics in the three systems. CDOM absorbance (quantity) remained higher in the control with respect to particle-enriched systems, suggesting that the presence of particles led to different rates of CDOM production and degradation. Using indicators for CDOM that could be related to microbial activity, results showed a higher CDOM alteration in the particle-enriched systems. These results indicate that microplastics have a potential role in modifying marine organic matter dynamics, on a similar magnitude to that of biogenic inorganic particles. Given their increasing concentrations of marine ecosystems, their role in marine microbial processing of organic matter needs to be better understood.
One of the major challenges in understanding the dynamics of the ocean’s health and functioning is the potential impact of the increasing presence of plastic. Besides the verified and macroscopic ...effects on marine wildlife and habitats, micro and macroplastics offer potential sites for microbial activity and chemical leaching. Most marine plastic is found initially in the upper meters of the water column, where fundamental biogeochemical processes drive marine productivity and food web dynamics. However, recent findings show a continuum of potential effects of these new marine components on carbon, nutrients and microbial processes. In the present analysis, we develop a common ground between these studies and we identify knowledge gaps where new research efforts should be focused, to better determine potential feedbacks of plastics on the carbon biogeochemistry of a changing ocean.
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•Marine plastic has potential effects on microbial turnover of carbon and nutrients.•Effects of plastics on microbial processes may impact upper ocean productivity.•Plastic may increase the production and flux of refractory carbon to depth.•Increasing amounts of plastic may alter the ocean’s biological and microbial pumps.•Effects of plastic need to be studied combined with anthropogenic ocean change.
Plastic may affect the ocean’s biological and microbial pump by increasing the downward flux of organic carbon, and supporting the production of more refractory carbon and its long-term storage in the deep ocean.
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