Uptake and mobilisation of metals associated with estuarine intertidal sediment by microphytobenthic diatoms

Microphytobenthos (MPB), a mixed community of microscopic, photosynthetic organisms, algae and cyanobacteria, inhabiting the top few millimetres of bottom sediment, is a key component of intertidal mudflats. It accounts for a significant proportion of estuarine primary production, forms the base of the food chain and influences sediment distribution and resuspension (through production of extracellular polymeric substances (EPS)). Diatoms dominate the microphytobenthos community in the mid-latitudes of the Northern Hemisphere. Estuarine sediments, are a sink for metal contaminants derived from fluvial, marine and atmospheric sources. Whilst metal releases to estuaries have declined in recent years due to increased regulation and declining industrial activity, metals previously discharged and which are now locked up in saltmarsh sediments remain a concern. For example, there are indications that saltmarshes are already being eroded, due to climate change related sea level rise, in some locations. This erosion may result in the redistribution of historically contaminated sediment to locations, such as the mudflats, where it is more available to biota, such as the MPB. In addition to causing redistribution, climate change effects, such as increasing temperatures and storminess, may also alter the bioavailability of metals to MPB. Increased concentrations of metals within the MPB could potentially increase their transfer to higher organisms through the food chain with potential impacts for biota. Whilst planktonic algae have been well studied with respect to metal uptake from the water column, there has been little research involving MPB and uptake of metals from sediment. The extent to which contaminant uptake by microphytobenthic algae occurs and under what conditions is therefore poorly understood. The research presented uses laboratory, mesocosm and field studies, to gain an understanding of processes governing metal bioavailability and mechanisms for uptake from sediment to the diatoms of the MPB under the complex and variable conditions of intertidal mudflats. A laboratory study using a single diatom species Cylindrotheca closterium found that uptake of cadmium (Cd) varied with sediment properties revealing the importance of sediment particle size and organic matter content in metal bioavailability to diatoms. Additionally, this study showed that the presence of diatoms altered Cd partitioning between sediment, overlying and pore water. Specifically there was an increase in Cd in the overlying and pore water when diatoms were present, indicating that diatoms mobilise metals from the sediment to the water column potentially increasing metal bioavailability to other biota. A study was conducted using an intertidal mesocosm to increase the realism of the study system and examine uptake to a natural MPB community. Diatoms were found to have higher concentrations of all the metals analysed (except tin) than other types of algae (filamentous and sheet macroalgae), confirming their importance as a study organism with respect to metal uptake and potential mobilisation through the food chain. Sediment disturbance was shown to increase metal uptake (iron, aluminium, vanadium and lead) from the sediment to algae. This is of concern due to predicted increases in storminess which are likely to increase sediment disturbance, with the likelihood that uptake of metals to diatoms will increase in the future. However, there were also indications of an antagonistic effect of temperature on disturbance, whilst disturbance increased bioavailability and uptake, increasing temperatures reduced uptake of some metals. This highlights the importance of considering the effects of multiple stressors in complex systems. Field studies showed that concentrations of some metals were related to their position on the mudflat whilst others were related to sampling date, indicating that there may be seasonal controls, such as to the presence of greater diatom biomass in spring and autumn, on metal uptake from the sediment. The research conducted has increased understanding of metal uptake to microphytobenthic diatoms from sediment and the influence they have in transferring metals from sediment to water, however the research also raises a number of new questions. For example, there appeared to be a link between sediment organic matter content and bioavailability of metals to diatoms, although the relative contribution of the diatoms, other algae, cyanobacteria and EPS to the sediment organic matter warrants further investigation. Furthermore, it has shown that the use of laboratory and mesocosm studies for this type of research can produce similar outcomes to those observed in the field but under more controlled and easily manipulated conditions, although field studies will continue to be vital in improving understanding of metals availability and transfer

Cadmium uptake from sediment by Cylindrotheca closterium and the effect of diatom presence on partitioning of cadmium between sediment and water: A laboratory study

Although it is well established that microalgae take up metals and other contaminants from water and it has been suggested that algae may play a significant role in mobilizing sediment bound contaminants, there has been little research on the uptake of sediment‐associated contaminants by microalgae. This may be important for microphytobenthos, which is closely associated with sediments. We report on laboratory experiments investigating the uptake of cadmium (Cd) from sediment and water by Cylindrotheca closterium over 96 h. The role of microalgae in the partitioning of Cd between sediment and water was also investigated. While concentrations do not typically represent those in the natural environment, we showed C. closterium takes up Cd from sediment, and concentration in microalgae is affected by sediment organic matter content. Cylindrotheca closterium influenced Cd movement between sediment and water: transfer from water to sediment was slowed, while transfer from sediment to overlying water (all treatments) and interstitial water (unprocessed sediment treatments) was increased. This is the first article to describe Cd uptake by diatoms from intertidal sediment in relation to sediment properties and mobilization of Cd from sediment in the presence of diatoms. Microalgae may serve as a pathway for sediment‐associated metals to enter into aquatic food webs, and their presence appears to increase metal concentrations in water potentially making any mobilized metals available for uptake by other species. Given this and their importance as the basis of the food chain, there may be implications for environmental and human health and potential impacts for the biological stability of the sediment

Guidance note on the application of coastal monitoring for small island developing states : Part of the NOC-led project “Climate Change Impact Assessment: Ocean Modelling and Monitoring for the Caribbean CME states”, 2017-2020; under the Commonwealth Marine Economies (CME) Programme in the Caribbean.

Small Island Developing States (SIDS) are a diverse group of 51 countries and territories vulnerable to human-induced climate change, due to factors including their small size, large exclusive economic zones and limited resources. They generally have insufficient critical mass in scientific research and technical capability to carry out coastal monitoring campaigns from scratch and limited access to data. This guidance report will go some way to addressing these issues by providing information on monitoring methods and signposting data sources. Coastal monitoring, the collection, analysis and storage of information about coastal processes and the response of the coastline, provides information on how the coast changes over time, after storm events and due to the effects of human intervention. Accurate and repeatable observational data is essential to informed decision making, particularly in light of climate change, the impacts of which are already being felt. In this report, we review the need for monitoring and the development of appropriate strategies, which include good baseline data and long-term repeatable data collection at appropriate timescales. We identify some of the methods for collection of in situ data, such as tide gauges and topographic survey, and highlight where resources in terms of data and equipment are currently available. We then go on to explore the range of remote sensing methods available from satellites to smart phone photography. Both in situ and remotely sensed data are important as inputs into models, which in turn feed in to visualisations for decision-making. We review the availability of a wide range of datasets, including details of how to access satellite data and links to international and regional data banks. The report concludes with information on the use of Geographical Information Systems (GIS) and good practice in managing data

Uptake and partitioning of metals by microphytobenthic diatoms: metadata for the ARCoES project

As part of University of Stirling's contribution to the ARCoES project, data were collected to determine the uptake and mobilisation of metals associated with estuarine intertidal sediment by microphytobenthic diatoms. The research was carried out as three studies at a range of scales and levels of realism, from a laboratory experiment in a controlled environment facility, through a study using an intertidal mesocosm, to the field. http://hdl.handle.net/11667/11

Guidance note on the application of coastal modelling for small island developing states

This report is part of the NOC-led project “Climate Change Impact Assessment: Ocean Modelling and Monitoring for the Caribbean CME states”, 2017-2020, under the Commonwealth Marine Economies (CME) Programme in the Caribbean. Small Island Developing States (SIDS) are very diverse, but have something in common: they are all vulnerable to human-induced climate change, but have contributed very little to causing the problem, due to their small size and limited development. Much time has been spent in debating climate change and adaptation strategies for such countries, but little has been done in developing practical tools to assist them in managing the coastal zone. In this report we aim to address that. In April 2017, some senior staff members from the National Oceanography Centre (NOC) visited St Vincent and the Grenadines, as part of the UK Foreign and Commonwealth Office-funded Neptune programme. At that time, some of the issues around coastal erosion on the east coast of St Vincent were identified, as well as some extreme events from which St Vincent and the Grenadines had suffered substantial losses of GDP. This was followed up by a workshop in January 2018 on ‘Implementing and Monitoring the Sustainable Development Goals in the Caribbean: The Role of the Ocean’, which was co-sponsored by the UK Government-funded Commonwealth Marine Economies Programme (CMEP) via the NOC (CMEP being the successor to Neptune). During the period September 2017 to March 2020, the National Oceanography Centre, funded by the CMEP, has been working with St Vincent and the Grenadines to provide knowledge, data and training about data analysis application and software for the use of coastal managers, particularly in order to address the problem of coastal erosion. We held a stakeholder workshop in Kingstown, St Vincent, in March 2018 and a hands-on technical training workshop in January 2019. A final workshop is being held in March 2020. Here we present an overview of coastal modelling methodology for use by Small Island Developing States (SIDS), including references to previous model review studies and guidance on how to access and apply model outputs, which will be presented at the workshop, entitled ‘Applying Knowledge of Coastal Processes for Coastal Zone Management into the Future’. This report seeks to collate the information on Coastal Modelling, which may be relevant to all SIDS, in order to support evidence-based decision-making. The case study is built around work done for St Vincent and the Grenadines. It is not the intention to explain in detail the technical working and development of models, as it is envisaged that SIDS will not want or need to run complex models themselves, but if this is desired, information on further reading and training is provided. Some of the simpler and more accessible models, with particularly useful applications in the coastal zone, which do not require computer resources beyond a laptop computer, are described in more detail for in-house application and their use in decision-making is explained. The way forward in regional collaboration and capacity-building is discussed

Current and future vulnerability of Argyle International Airport to combined river & coastal flooding

Argyle International Airport is at risk from coastal and fluvial flooding, especially when coarse sediments are deposited in the northernmost tunnel mouths (through which the River Yambou flows) and constrict the carrying capacity. Building on previous research which employed a “bathtub” approach to show areas of St. Vincent at risk from flooding, we use rainfall-runoff, inundation and storm impact models to formulate storm conditions based on Hurricane Ivan, with sea levels representative of the present-day, 2100 (+ 1.10 m) and 2500 (+ 5.48 m) under the Relative Concentration Pathway 8.5 scenario. Combining these with constricted tunnel flow regimes of 20-100% (representing 1-5 tunnels becoming blocked), we assess the risk of flooding to the runway and the rear access road. We find that the Airport’s drainage system adjacent to the runway copes reasonably well with the applied flood conditions. In presentday and 2100 sea-level scenarios with flow constrictions of≥80%, only the northern Runway End Safety Area (RESA) is flooded. However this flooding may be sufficient to render the RESA incompliant with International Civil Aviation Organisation regulations by reducing its effective width. The greater and more immediate risk is likely to be to the access road which runs around the eastern side of the runway, which is shown to be vulnerable under Hurricane Ivan conditions (a water level of 4.40 m above mean sea level, consisting of astronomical tide, storm surge and wave setup) with no sea-level rise superimposed. These results must be interpreted with caution as there is no subdaily precipitation data nor River Yambou flow data, both of which would be required for a more rigorous assessment of the flood risk to the airport. The simplistic representation of the tunnels is also likely to introduce uncertainty by applying an approximate flow solution once the tunnels are full. The main outcome from this work is a modelling framework which could be applied in the future, should better observational data become available to increase the accuracy and robustness of subsequent flood risk assessments

Tides at a coast

People often experience tidal influence at the coast, where the sea meets the land, with a daily or twice-daily rise and fall of the water level. Understanding and predicting tides is critical for: shoreline/hazard management; port, harbor, and shipping activities; renewable energy; and infrastructure management (e.g., telecommunication cables). Accurate prediction is also critical to ensure water sports and beach activities are carried out safely. In shallow waters, tides interact with bathymetry and other physical processes, such as: surges, waves, and density currents. Understanding the net (tidally averaged or residual) flow is key to explaining the transport of particulate and dissolved biogeochemical tracers and physical properties, such as heat and carbon. To observe the tide, (global) gage networks are installed, often providing near real-time data. Harmonic analysis of these data allows accurate prediction of the tide to support the numerous recreational and commercial activities that take place in shelf seas and at the coast

LEGaTO: first steps towards energy-efficient toolset for heterogeneous computing

LEGaTO is a three-year EU H2020 project which started in December 2017. The LEGaTO project will leverage task-based programming models to provide a software ecosystem for Made-in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC.Peer ReviewedPostprint (author's final draft

LEGaTO: towards energy-efficient, secure, fault-tolerant toolset for heterogeneous computing

LEGaTO is a three-year EU H2020 project which started in December 2017. The LEGaTO project will leverage task-based programming models to provide a software ecosystem for Made-in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC.Peer ReviewedPostprint (author's final draft

Socio-oceanography: an opportunity to integrate marine social and natural sciences

Marine natural sciences have been instrumental in helping society understand how ocean systems operate and the threats they face. However, there is a growing realisation that the societal challenges related to the marine environment can only be addressed through more effective integration with all aspects of social sciences. Nevertheless, to date, social sciences remain insufficiently integrated into marine research. Recognising historical weaknesses and drawing on the authors’ own experience of interdisciplinary research, albeit writing primarily from a natural marine science perspective, we propose a series of steps to promote integrated marine research inclusive of strong social science. We suggest that changing the perspectives and attitudes of natural scientists is key. The inherent interconnectivity between the ocean and society ensures that nearly everything we do in the marine natural sciences has the potential to influence and, perhaps address, ongoing and future societal challenges. Consequently, a key challenge for natural scientists is to recognise and communicate this in an accessible manner outside their own disciplines. To attempt to address these issues, we introduce the concept of “Socio-oceanography” which we define as an area of research that takes a “whole system” approach to the marine environment. It focuses on the challenges which require advancement of both natural and social science components, especially on those where the feedbacks between social and natural components are beginning to emerge. Here, we discuss its scope, challenges to its effective application and key steps to catalyse interdisciplinary approaches using this concept