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Identifying potential high-risk zones for land-derived plastic litter to marine megafauna and key habitats within the North Atlantic
No full textThe pervasive use of plastic in modern society has led to plastic litter becoming ubiquitous within the ocean. Land-based sources of plastic litter are thought to account for the majority of plastic pollution in the marine environment, with plastic bags, bottles, wrappers, food containers and cutlery among the most common items found. In the marine environment, plastic is a transboundary pollutant, with the potential to cause damage far beyond the political borders from where it originated, making the management of this global pollutant particularly complex. In this study, the risks of land-derived plastic litter (LDPL) to major groups of marine megafauna – seabirds, cetaceans, pinnipeds, elasmobranchs, turtles, sirenians, tuna and billfish – and a selection of productive and biodiverse biogenic habitats – coral reefs, mangroves, seagrass, saltmarsh and kelp beds – were analysed using a Spatial Risk Assessment approach. The approach combines metrics for vulnerability (mechanism of harm for megafauna group or habitat), hazard (plastic abundance) and exposure (distribution of group or habitat). Several potential high-risk zones (HRZs) across the North Atlantic were highlighted, including the Azores, the UK, the French and US Atlantic coasts, and the US Gulf of Mexico. Whilst much of the modelled LDPL driving risk in the UK originated from domestic sources, in other HRZs, such as the Azores archipelago and the US Gulf of Mexico, plastic originated almost exclusively from external (non-domestic) sources. LDPL from Caribbean islands - some of the largest generators of marine plastic pollution in the dataset of river plastic emissions used in the study - was noted as a significant input to HRZs across both sides of the Atlantic. These findings highlight the potential of Spatial Risk Assessment analyses to determine the location of HRZs and understand where plastic debris monitoring and management should be prioritised, enabling more efficient deployment of interventions and mitigation measures
Selective colonization of microplastics, wood and glass by antimicrobial-resistant and pathogenic bacteria
Get PDFThe Plastisphere is a novel niche whereby microbial communities attach to plastic debris, including microplastics. These communities can be distinct from those found in the surrounding environment or those attached to natural substrates and may serve as a reservoir of both pathogenic and antimicrobial-resistant (AMR) bacteria. Owing to the frequent omission of appropriate comparator particles (e.g. natural substrates) in previous studies, there is a lack of empirical evidence supporting the
unique risks posed by microplastics in terms of enrichment and spread of AMR pathogens. This study investigated selective colonization by a sewage community on environmentally sampled microplastics with three different polymers, sources and morphologies, alongside natural substrate (wood), inert substrate (glass) and free-living/planktonic community controls. Culture and molecular methods (quantitative polymerase chain reaction (qPCR)) were used to ascertain phenotypic and genotypic AMR prevalence, respectively, and multiplex colony PCR was used to identify extra-intestinal pathogenic Escherichia coli(ExPECs). From this, polystyrene and wood particles were found to significantly enrich AMR bacteria, whereas sewage-sourced
bio-beads significantly enriched ExPECs. Polystyrene and wood were the least smooth particles, and so the importance of particle roughness on AMR prevalence was then directly investigated by comparing the colonization of virgin vs artificially weathered polyethylene particles. Surface weathering did not have a significant effect on the AMR prevalence of colonized particles. Our results suggest that the colonization of plastic and non-plastic particles by AMR and pathogenic bacteria may be enhanced by substrate-specific traits
Latitudinal gradients and ocean fronts strongly influence protist communities in the southern Pacific Ocean
No full textProtist communities in the southern Pacific Ocean make a major contribution to global biogeochemical cycling, but remain understudied due to their remote location. We therefore have limited understanding of how large-scale physical gradients (e.g. temperature) and mesoscale oceanographic features (e.g. fronts) influence microeukaryote diversity in this region. We performed a high-resolution examination of protist communities along a latitudinal transect (>3000 km) at 150°W in the central southern Pacific Ocean that encompassed major frontal regions, including the sub-tropical front (STF), the sub-Antarctic front (SAF), and the polar front (PF). We identified distinct microbial communities along the transect that were primarily delineated by the positions of the STF and PF. Some taxa were not constricted by these environmental boundaries and were able to span frontal regions, such as the colonial haptophyte Phaeocystis. Our findings also support the presence of a Latitudinal Diversity Gradient (LDG) of decreasing diversity of the protist community with increasing latitude, although some individual taxa, notably the diatoms, do not adhere to this rule. Our findings show that oceanographic features and large-scale physical gradients have important impacts on marine protist communities in the southern Pacific Ocean that are likely to strongly influence their response to future environmental chang
Marine macrophytes in a changing world: mechanisms underpinning responses and resilience to environmental stress – an introduction to a Virtual Issue
No full textMarine macrophytes, such as seagrasses and macroalgae, are widely distributed across the world's coastlines, where they function as foundation organisms in nearshore ecosystems by providing habitat, food and shelter for a wide diversity of organisms and altering local environmental conditions (Fig. 1). The coastal habitats they create have massive ecological and socioeconomic benefits, underpinning ecosystem services worth trillions of dollars annually and supporting billions of people world-wide through the provision of food and resources, protection of coastlines, regulation of climate and recycling of nutrients. Increasingly, however, marine macrophytes are impacted by a range of anthropogenic stressors (e.g. ocean warming, coastal development, decreased water quality and overfishing), which threaten the persistence and integrity of these habitats and the ecosystem services they underpin. A better understanding of how marine macrophytes are responding to environmental change, and the underlying mechanisms that mediate their resilience to increasing stressors, is needed to inform approaches to their management and conservation. In this regard, several key papers published in New Phytologist over the past decade or so have shed new light on the responses of seagrasses and habitat-forming macroalgae (i.e. kelps and fucoids) to environmental change, and the biological processes underpinning such responses. In this Virtual Issue, we bring together some of these studies to highlight key areas of scientific progress and identify where pressing knowledge gaps still remain. The studies fall within the broad themes of: (1) observed and predicted responses to environmental change; and (2) mechanisms underpinning responses to environmental change across different levels of biological organisation. We also highlight research priorities and conclude with a rallying call for greater research focus on marine macrophyte foundation species, as current knowledge lags way behind that for their terrestrial and aquatic counterpart
Approaches and findings in histological and micromorphological research on Rhizostomeae
No full textThe substantial development of microscopic techniques and histological examination methods during the past five decades allowed for many new insights into the histology and microanatomy of Rhizostomeae. The present review focuses on new findings about histologically important structures: nerves, senses, muscles, gonads, zooxanthellae and nematocysts. Different ontogenetic stages of rhizostome species were included in the literature research, supplemented with the authors’ unpublished data and figures. The overview of the research results reveals that the application of chemo- and immunohistochemical techniques have provided deeper insights into neuronal and sensory structures and their interconnections. Modern microscopic methods led to new findings on the histological gonadal organization and details of the processes of gametogenesis, fertilization, cleavage, gastrulation, and brooding. Advanced optical methods also allowed for a better understanding of Rhizostomeae-zooxanthellae associations and the morphology and function of nematocysts. Improvements in molecular biology allowed for more precise identification of zooxanthellae associated with rhizostome species. Although there has been significant progress in all of the research subjects covered here, we identify several knowledge gaps and conclude with some recommendations for future researc
Environmental MMV for Offshore Storage – Are We There Yet?
Get PDFOver the last two decades the environmental aspects of offshore storage have attracted a significant amount of research. Initially
questions were framed around assessing if unplanned events, namely leakage, posed a significant threat to marine ecosystems.
Subsequently the research refocused onto the development of tools and strategies to enable offshore MMV. This short paper
provides an assessment of the key conclusions to date, the state of play in transferring this research into operational practice and details the next steps
Fluoro-Electrochemistry Based Phytoplankton Bloom Detection and Enumeration; Field Validation of a New Sensor for Ocean Monitoring
Get PDFPhytoplankton are essential for the health of our
oceans, yet existing in situ methods for monitoring phytoplankton abundance and community structure are limited, with relatively poor spatiotemporal coverage and taxonomic resolution, particularly among the nanoplankton size range. Here, we build on previous work and present field testing of a novel reagent-free fluoro-electrochemical technique for monitoring changes in nanoplankton abundance and community structure in natural seawater samples. This was achieved through the construction of a prototype sensor, which was then tested over a 3-month Spring−Summer period in 2023 with samples collected from the L4 station (Western
English Channel). The measurements made by our sensor were
successfully validated alongside microscope-based taxonomic
enumerations and analytical flow cytometry. Of the phytoplankton functional groups of interest, our results demonstrate particularly strong correlations between the sensor and both microscope-based taxonomy and flow cytometry for enumerating small coccolithophorids (i.e., calcifying Isochrysidales, of the Gephyrocapsa genus) and between the prototype and microscope-based taxonomy for enumerating diatoms. We demonstrate that the inclusion of traditionally hard to identify nanoflagellates in our classifications has minimal effect on our ability to monitor overall shifts in community structure and bloom detection. Taking things
forward, the potential for in situ deployment is discussed
Dimethyl sulfide (DMS) climatologies, fluxes, and trends – Part 2: Sea–air fluxes
Get PDFDimethyl sulfide (DMS) contributes to cloud condensation nuclei (CCN) formation in the marine environment. DMS is ventilated from the ocean to the atmosphere, and, in most models, this flux is calculated using seawater DMS concentrations and a sea–air flux parameterization. Here, climatological seawater DMS concentrations from interpolation and parameterization techniques are passed through seven flux parameterizations to estimate the DMS flux. The seasonal means of calculated fluxes are compared to identify differences in absolute values and spatial distributions, which show large differences depending on the flux parameterization used. In situ flux observations were used to validate the estimated fluxes from all seven parameterizations. Even though we see a correlation between the estimated and observation values, all methods underestimate the fluxes in the higher range (>20 µmol m−2 d−1) and overestimate the fluxes in the lower range (<20 µmol m−2 d−1). The estimated uncertainty in DMS fluxes is driven by the uncertainty in seawater DMS concentrations in some regions but by the choice of flux parameterization in others. We show that the resultant flux is, hence, highly sensitive to both and suggest that there needs to be an improvement in the estimation methods of global seawater DMS concentration and sea–air fluxes for accurately modeling the effect of DMS on the atmosphere
Deciphering the variability in air-sea gas transfer due to sea state and wind history
Get PDFUnderstanding processes driving air-sea gas transfer and being able to model both its mean and variability are critical for studies of climate and carbon cycle. The air-sea gas transfer velocity (K660) is almost universally parameterized as a function of wind speed in large scale models—an oversimplification that buries the mechanisms controlling K660 and neglects much natural variability. Sea
state has long been speculated to affect gas transfer, but consistent relationships from in situ observations have been elusive. Here, applying a machine learning technique to an updated compilation of shipboard direct observations of the CO2 transfer velocity (KCO2,660), we show that the inclusion of significant wave height improves the model simulation of KCO2,660, while parameters such as wave age, wave steepness, and swell-wind directional difference have little influence on KCO2,660. Wind history is found to be important, as in high seas KCO2,660 during periods of falling winds exceed periods of rising winds by ∼20% in the mean. This hysteresis
in KCO2,660 is consistent with the development of waves and increase in whitecap coverage as the seas mature. A similar hysteresis is absent from the transfer of a more soluble gas, confirming that the sea state dependence in KCO2,660 is primarily due to bubble�mediated gas transfer upon wave breaking. We propose a new parameterization of KCO2,660 as a function of wind stress and significant wave height, which resemble observed KCO2,660 both in the mean and on short timescale
Progress and future directions for seaweed holobiont research
No full textIn the marine environment, seaweeds (i.e. marine macroalgae) provide a wide range of ecological services and economic benefits. Like land plants, seaweeds do not provide these services in isolation, rather they rely on their associated microbial communities, which together with the host form the seaweed holobiont. However, there is a poor understanding of the mechanisms shaping these complex seaweed–microbe interactions, and of the evolutionary processes underlying these interactions. Here, we identify the current research challenges and opportunities in the field of seaweed holobiont biology. We argue that identifying the key microbial partners, knowing how they are recruited, and understanding their specific function and their relevance across all seaweed life history stages are among the knowledge gaps that are particularly important to address, especially in the context of the environmental challenges threatening seaweeds. We further discuss future approaches to study seaweed holobionts, and how we can apply the holobiont concept to natural or engineered seaweed ecosystems