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•Microplastics enter into marine environments mainly through human activities.•Microplastics are one of greatest threats for marine biodiversity in the world.•The ingestion of ...microplastics introduce toxic compounds to marine biota.•Microplastics could influence ecological processes in benthic and pelagic habitats.
Microplastics are tiny ubiquitous plastic particles present in marine environments. They are not an individual entity, but constitute a cocktail of polymers and additives that can absorb substances from the surrounding environment, including living substances, nutrients and marine pollutants. Given their small size (< 5 μm), microplastics can be ingested by a wide range of marine organisms with the potential to cause harms. Microplastics are a growing threat for marine biota and ecosystem. For organisms, the risks associated with microplastic ingestion are not only due to the material itself, but also to its ability to absorb and concentrate environmental contaminants in seawater and subsequently transfer them through food chains. Moreover, microplastics could influence ecological processes. Recently, plastic debris are recognized as emerging pollutants and represent a great risk for marine biodiversity worldwide. Here, we summarize the main effects of plastics and microplastics on some marine organisms and ecosystem.
We present a global ocean climatology of dissolved inorganic carbon delta super(13)C (ppt) corrected for the super(13)C-Suess effect, preindustrial delta super(13)C. This was constructed by first ...using Olsen and Ninnemann's (2010) back-calculation method on data from 25 World Ocean Circulation Experiment cruises to reconstruct the preindustrial delta super(13)C on sections spanning all major oceans. Next, we developed five multilinear regression equations, one for each major ocean basin, which were applied on the World Ocean Atlas data to construct the climatology. This reveals the natural delta super(13)C distribution in the global ocean. Compared to the modern distribution, the preindustrial delta super(13)C spans a larger range of values. The maxima, of up to 1.8ppt, occurs in the subtropical gyres of all basins, in the upper and intermediate waters of the North Atlantic, as well as in mode waters with a Southern Ocean origin. Particularly strong gradients occur at intermediate depths, revealing a strong potential for using delta super(13)C as a tracer for changes in water mass geometry at these levels. Further, we identify a much tighter relationship between delta super(13)C and apparent oxygen utilization (AOU) than between delta super(13)C and phosphate. This arises because, in contrast to phosphate, AOU and delta super(13)C are both partly reset when waters are ventilated in the Southern Ocean and underscore that delta super(13)C is a highly robust proxy for past changes in ocean oxygen content and ocean ventilation. Our global preindustrial delta super(13)C climatology is openly accessible and can be used, for example, for improved model evaluation and interpretation of sediment delta super(13)C records. Key Points * A global ocean climatology of the preindustrial C-13 distribution, corrected for anthropogenic influences * Preindustrial C-13 spans a larger range of values compared to the modern distribution, with particularly strong intermediate ocean gradients * C-13 is found to be a highly robust proxy for past changes in oxygen content and ocean ventilation
Marine ecosystems evolve under many interconnected and area‐specific pressures. To fulfil society's intensifying and diversifying needs while ensuring ecologically sustainable development, more ...effective marine spatial planning and broader‐scope management of marine resources is necessary. Integrated ecological–economic fisheries models (IEEFMs) of marine systems are needed to evaluate impacts and sustainability of potential management actions and understand, and anticipate ecological, economic and social dynamics at a range of scales from local to national and regional. To make these models most effective, it is important to determine how model characteristics and methods of communicating results influence the model implementation, the nature of the advice that can be provided and the impact on decisions taken by managers. This article presents a global review and comparative evaluation of 35 IEEFMs applied to marine fisheries and marine ecosystem resources to identify the characteristics that determine their usefulness, effectiveness and implementation. The focus is on fully integrated models that allow for feedbacks between ecological and human processes although not all the models reviewed achieve that. Modellers must invest more time to make models user friendly and to participate in management fora where models and model results can be explained and discussed. Such involvement is beneficial to all parties, leading to improvement of mo‐dels and more effective implementation of advice, but demands substantial resources which must be built into the governance process. It takes time to develop effective processes for using IEEFMs requiring a long‐term commitment to integrating multidisciplinary modelling advice into management decision‐making.
Application of environmental DNA (eDNA) analysis has attracted the attention of researchers, advisors and managers of living marine resources and biodiversity. The apparent simplicity and ...cost‐effectiveness of eDNA analysis make it highly attractive as species distributions can be revealed from water samples. Further, species‐specific analyses indicate that eDNA concentrations correlate with biomass and abundance, suggesting the possibility for quantitative applications estimating abundance and biomass of specific organisms in marine ecosystems, such as for stock assessment. However, the path from detecting occurrence of an organism to quantitative estimates is long and indirect, not least as eDNA concentration depends on several physical, chemical and biological factors which influence its production, persistence and transport in marine ecosystems. Here, we provide an overview of basic principles in relation to eDNA analysis with potential for marine fisheries application. We describe fundamental processes governing eDNA generation, breakdown and transport and summarize current uncertainties about these processes. We describe five major challenges in relation to application in fisheries assessment, where there is immediate need for knowledge building in marine systems, and point to apparent weaknesses of eDNA compared to established marine fisheries monitoring methods. We provide an overview of emerging applications of interest to fisheries management and point to recent technological advances, which could improve analysis efficiency. We advise precaution against exaggerating the present scope for application of eDNA analysis in fisheries monitoring, but also argue that with informed insights into strengths and limitations, eDNA analysis can become an integrated tool in fisheries assessment and management.
Intertidal areas are considered to be productive habitats, but due to the challenging and dynamic environment, in situ assessments of their performance remain scarce. Here, we aimed to quantify the ...production and turnover of organic material in an intertidal sediment across several consecutive diel/tidal cycles and to evaluate the importance of key drivers affecting the community performance. Time-series measurements of the oxygen (O sub(2)) microdistribution across 2 sites at a silty sandflat documented extreme variability, which was mainly driven by light availability and flow conditions. Diffusion dominated the interstitial solute transport, but advective porewater transport was observed during 15% of the 9 d study period. Photosynthetic activity never exhibited light inhibition and average daytime net photosynthesis ranged between 1.01 and 11.15 mmol m super(-2) d super(-1) depending on the daily light availability, while the assessed gross primary production was ~80% higher. When irradiance exceeded 17.2 mol photons m super(-2) d super(-1), daytime net autotrophy more than balanced the heterotrophic activity during the night (average night-time respiration, ER sub(n): -4.01 mmol m super(-2) d super(-1)). However, despite intense primary production, the integrated activity during the target autumn period was net heterotrophic with an average net ecosystem metabolism of -2.21 (span: -7.93 to 1.48) mmol O sub(2) m super(-2) d super(-1). This study highlights the extreme temporal and spatial variation of intertidal sediments and the importance of accounting for natural in situ dynamics to correctly assess their performance and contribution to system production.
The anthropogenic CO sub(2) accumulation rate for the Pacific Ocean was estimated from the decrease in delta super(13)C of the dissolved inorganic carbon measured on six World Ocean Circulation ...Experiment cruises during the 1990s and repeated during Climate Variability and Predictability in the 2000s. A mean depth-integrated anthropogenic delta super(13)C change of -83 plus or minus 20pptmdecade super(-1) was estimated for the basin by using the multiple linear regression approach. The largest anthropogenic delta super(13)C decreases occurred between 40 degree S and 60 degree S, whereas the smallest decreases occurred in the Southern Ocean and subpolar North Pacific. A mean anthropogenic CO sub(2) accumulation rate of 0.41 plus or minus 0.13molCm super(-2)yr super(-1) (0.82 plus or minus 0.26PgCyr super(-1)) was determined based on observed delta super(13)C changes and is in agreement with previous observation- and model-based estimates. The mean dissolved inorganic carbon DIC super(13) inventory change of -178 plus or minus 43pptmolm super(-2)decade super(-1) was primarily the result of air-sea CO sub(2) exchange acting on the measured air-sea delta super(13)C disequilibrium of ~-1.2 plus or minus 0.1ppt. Regional differences between the DIC super(13) inventory change and air-sea super(13)CO sub(2) flux yielded net anthropogenic CO sub(2) uptake rates (independent of Delta pCO sub(2)) that ranged from ~0 to 1molm super(-2)yr super(-1) and basin-wide mean of 1.2 plus or minus 1.5PgCyr super(-1). High rates of surface ocean DIC increase and delta super(13)C decrease observed in the Drake Passage (53 degree S-60 degree S) support above average anthropogenic CO sub(2) accumulation since 2005. Observed delta super(13)C changes in the Pacific Ocean indicate that ocean transport significantly impacted the anthropogenic CO sub(2) distribution and illustrate the utility of delta super(13)C as a tracer to unravel the processes controlling the present and future accumulation of anthropogenic CO sub(2) in the ocean. Key Points * Anthropogenic CO sub(2) accumulation rate was estimated based on measured change in ocean delta super(13)C between the 1990s and 2000s * Net anthropogenic CO sub(2) uptake rates independent of Delta pCO sub(2) were estimated from measured delta super(13)C changes * Regional differences between anthropogenic DIC super(13) accumulation and air-sea super(13)CO sub(2) flux rates indicate importance of ocean transport
Microphytobenthos (MPB) at higher latitudes has been poorly studied. This study used pulse-chase super(13)C-labeling to investigate the production, processing, and fate of MPB-derived carbon (MPB-C) ...in sub-Arctic intertidal sediments over 31 d. Gross primary production (2.1 mmol C m super(-2) h super(-1) plus or minus 0.4 mmol C m super(-2) h super(-1)) was comparable to that reported for temperate regions. Some of the super(13)C fixed by sub-Arctic MPB was rapidly (within 0.5 d) transferred to deeper sediments (below 2 cm), but most was retained within surface sediments (>70.2% of the super(13)C present at any time during the study). At any time, MPB accounted for greater than or equal to 49.8% of this super(13)C. The super(13)C content of sediment organic carbon declined over time, but>31% of the super(13)C fixed within the first tidal cycle remained after 31 d, suggesting that sub-Arctic MPB may contribute to coastal carbon retention during the productive season. Over 21 d, 10.6% of the fixed super(13)C was removed via DIC fluxes and 0.3% via DOC fluxes from inundated sediment, and 0.6% as CO sub(2) from exposed sediment. The greatest loss of super(13)C (38.2%) was via unmeasured pathways, including resuspension and/or removal by mobile consumers. The rates of MPB-C production and the relative importance of the pathways for MPB-C loss were similar to that observed for comparable lower latitude sediments, demonstrating that MPB at higher latitudes are not necessarily distinct from MPB at lower latitudes and probably play a similarly important role in ecosystem functioning. Apparently, local environmental conditions are more important than climate differences for determining the processing and fate of MPB-C.
Microphytobenthos (MPB) are an important nitrogen (N) sink in coastal systems, but little is known about the fate of this N after it has been assimilated. We used an in situ super(15)N pulse-chase ...experiment in subtidal sands to follow the assimilation, trophic transfer, transformation, and flux pathways of MPB-N over 33 d. Throughout the study MPB dominated super(15)N uptake, on average representing only 18.1% of the biomass but 63.9% of the super(15)N within 0-2 cm sediment. Following assimilation, super(15)N was rapidly transferred to deeper sediment, with 32.1% below 2 cm and 16.5% below 5 cm after 60 h. In contrast to MPB, bacteria represented 39.5% of sediment biomass but accounted for only up to 27.3% of assimilated super(15)N. Foraminifera accumulated and stored super(15)N more than bacteria; their contribution to the super(15)N remaining in 0-2 cm sediment at the end of the study was more than double their biomass contribution. Thirty-three days after the super(15)N was assimilated by MPB 27% remained in the sediment, 16.5% had been effluxed as 20.8% had been effluxed as 20.7% had been effluxed as N sub(2) and 15.1% was missing. Most (12.6%) of super(15)N label that was missing at the end of the study was probably lost as dissolved organic N (DON) fluxes. Of the super(15)N remaining in 0-2 cm sediment, 80.4% was in MPB, 2.7% in bacteria, 1% in foraminifera and the remaining 15.9% was uncharacterized. Overall there was little benthic trophic transfer with most of the MPB-assimilated N remineralized over 33 d.
Anthropogenic CO sub(2) emissions currently decrease open ocean pH, but on multi-millennial time scales intensified continental weathering is expected to contribute to increasing oceanic alkalinity ...(AT) and thus mitigate the acidification signal. The Baltic Sea is an ideal study site for such AT dynamics, due to its direct link to terrestrial processes, short water residence time and long history of AT measurements dating back to the early 20 super(th) century. We compiled an extensive AT data set that revealed the highest data quality and coverage for the past two decades. Within that period, surface water AT levels increased throughout the Baltic Sea. The rates of change were highest in the low-saline, northern areas and decreased gradually toward constant levels in the North Sea. The AT increase observed in the Central Baltic Sea (+3.4 mu mol kg super(-1) yr super(-1)) and the Gulf of Bothnia (+7 mu mol kg super(-1) yr super(-1)) has compensated CO sub(2)-induced acidification by almost 50% and 100%, respectively. Further, the AT trends enhanced the CO sub(2) storage capacity and stabilized the CaCO sub(3) saturation state of the Baltic Sea over the past two decades. We discuss the attribution of the AT trends to potential changes in precipitation patterns, continental weathering driven by acidic rain and increasing atmospheric CO sub(2), agricultural liming and internal AT sources.
The Southern Ocean plays a pivotal role in climate change by exchanging heat and carbon, and provides the primary window for the global deep ocean to communicate with the atmosphere. There has been a ...widespread focus on explaining atmospheric CO sub(2) changes in terms of changes in wind forcing in the Southern Ocean. Here, we develop a dynamically-motivated metric, the residual upwelling, that measures the primary effect of Southern Ocean dynamics on atmospheric CO sub(2) on centennial to millennial timescales by determining the communication with the deep ocean. The metric encapsulates the combined, net effect of winds and air-sea buoyancy forcing on both the upper and lower overturning cells, which have been invoked as explaining atmospheric CO sub(2) changes for the present day and glacial-interglacial changes. The skill of the metric is assessed by employing suites of idealized ocean model experiments, including parameterized and explicitly simulated eddies, with online biogeochemistry and integrated for 10,000 years to equilibrium. Increased residual upwelling drives elevated atmospheric CO sub(2) at a rate of typically 1-1.5 parts per million/10 super(6) m super(3) s super(-1) by enhancing the communication between the atmosphere and deep ocean. This metric can be used to interpret the long-term effect of Southern Ocean dynamics on the natural carbon cycle and atmospheric CO sub(2), alongside other metrics, such as involving the proportion of preformed nutrients and the extent of sea ice cover.
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