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Seaweed forests are carbon sinks that may help mitigate CO2 emissions: a comment on Gallagher et al. (2022)
No full textRecently, Gallagher et al. (2022) suggested that seaweed ecosystems are net heterotrophic carbon sources due to CO2 released from the consumption of external subsidies. Here we outline several flaws in their argument, which we believe confuse research on the blue carbon potential of seaweed ecosystems, and unjustifiably generate doubt around initiatives to protect and restore seaweed forests. Gallagher et al.’s evidence relies on 18 studies with highly variable measures of net ecosystem production, which do not statistically support their conclusion that most seaweed ecosystems are heterotrophic. This dataset is also inappropriate as it is incomplete and misrepresents seaweed ecosystems globally, particularly seaweed forests, which contribute disproportionately to global seaweed productivity. We maintain that the climate change mitigation value of an ecosystem depends on the net difference in CO2 uptake between the original ecosystem and its replacement ecosystem. We provide evidence that most seaweed ecosystems, which drawdown the largest carbon flux of any vegetated coastal habitat, are indeed net autotrophic ecosystems. We recognize that substantial uncertainties remain concerning the magnitude of CO2 drawdown by seaweed ecosystems and recommend that carbon fluxes around seaweed ecosystems should be considered more broadly and taken into account in estimates of their CO2 mitigation potentia
A review of carbon offset strategies with seaweed aquaculture – feasibility, current knowledge, and suggestions for future research. The Scottish Association for Marine Science, Oban, UK. Report prepared for the Scottish Government
Get PDFIn September 2022, a group of international collaborators
gathered from six European countries (hereby referred to
as the ‘working group’) to take part in a workshop at the
Scottish Association for Marine Science (SAMS), Oban.
The workshop was funded as part of Marine Scotland’s Blue Carbon International Policy Challenge (BCIPC). The main aim of the workshop was to produce a document outlining the potential for carbon offset by macroalgal aquaculture. The discussions held at the workshop focused on various concepts and hypotheses surrounding carbon drawdown by seaweed aquaculture and the potential for mitigation of atmospheric CO2. The key points of these discussions have been compiled into a policy brief which aims to highlight important areas for future research, uncertainties and challenges faced by the industry, policy makers and other stakeholders
AMT30 Cruise Report
Get PDFIn a break with tradition the 30th AMT cruise, the first since the COVID pandemic hit in 2020, departed Port Stanley on the 20th February 2023 and headed north, arriving in Southampton on 30th March. Onboard were teams from Plymouth Marine Laboratory, the National Oceanography Centre, UK Universities of Exeter, Heriot-Watt, East Anglia, Liverpool and Oxford, the Scottish Association for Marine Science, National Aeronautics and Space Administration, Michigan State University, University of Lisbon, Centre for Scientific Research and Higher Education of Ensenada and the University of Pretoria. Operations onboard included the measurement of core AMT variables in the maintenance of the now 28 year time series; Optical and atmospheric observations in support of NASA and the European Space Agency satellites; Deployment of 14 ARGO floats for the UK MetOffice and the NOC; and the recovery of the NOC - SOG sediment trap mooring in the South Atlantic gyre. AMT’s oceanography training program continued with places occupied by six PhD students from UK, US and South African universities alongside opportunities provided by POGO in the sponsorship of a research fellow from Mexico. The whole of the scientific complement would like to extend their gratitude to Captain Stewart Mackay and his officers and crew who supported our activities throughout with dedication and extreme professionalism. Our thanks are also extended to the team from NMF (Tom Ballinger, Andy Cotmore and Nick Harker) who ensured the delivery of all scientific activities My particular thanks as always to Glen Tarran and Christina Devereux who assisted in ways too numerous to mention here. Now in its 28th year the AMT is a multidisciplinary program which undertakes biological, chemical and physical oceanographic research during an annual voyage throughout the Atlantic Ocean. AMT objectives have evolved to enable the maintenance of a continuous set of observations, whilst addressing global issues that are raised throughout the most recent IPCC assessment and UK environmental strategy. AMT objectives are to:
(1) quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems;
(2) quantify the effects of this variability on nutrient cycling, on biogenic export and on air-sea exchange of climate active gases;
(3) construct a multi-decadal, multidisciplinary ocean time-series which is integrated within a wider “Pole-to-pole” observatory concept;
(4) provide essential sea-truth validation for current and next generation satellite missions;
(5) provide essential data for global ecosystem model development and validation and;
(6) provide a valuable, highly sought after training arena for the next generation of UK and International oceanographers
New tools and recommendations for a better management of harmful algal blooms under the European Marine Strategy Framework Directive
Get PDFMarine harmful algal blooms (HABs), caused by various aquatic microalgae, pose significant risks to ecosystems, some socio-economic activities and human health. Traditionally managed as a public health issue through reactive control measures such as beach closures, seafood trade bans or closure of mollusc production areas, the multifaceted linkages of HABs with environmental and socio-economic factors require more comprehensive ecosystem-based management approach tools to support policies. This study promotes a coordinated understanding and implementation of HAB assessment and management under the Marine Strategy Framework Directive (MSFD), targeting the achievement of Good Environmental Status (GES) in European marine waters. We introduce two novel tools: GES4HABs (GES for HABs) decision tree, and MAMBO (environMental mAtrix for the Management of BlOoms), a decision support matrix. These tools aim to streamline HABs reporting and prioritize resource allocation and management interventions. The GES4HABs decision tree defines a sequence of decision steps to identify HAB management strategies according to their state (evaluated against predefined baselines) and causes (anthropic or natural). MAMBO is proposed to address different HABs and their interaction with human and environmental pressures. The matrix utilizes two axes: natural trophic status and level of human influence, capturing major aspects such as nutrient supply. While acknowledging the limitations of this simplified framework, MAMBO categorizes marine regions into quadrants of varying management viability. Regions with high human influence and eutrophic conditions are identified as most suitable for effective management intervention, whereas regions with minimal or mixed human influence are deemed less amenable to active management. In addition, we explore and describe various indicators, monitoring methods and initiatives that may be relevant to support assessments of HAB status and associated pressures and impacts in the MSFD reporting. Finally, we provide some recommendations to promote the consideration of HABs in ecosystem-based management strategies, intensify efforts for harmonizing and defining best practices of analysis, monitoring and assessment methodologies, and foster international and cross-sectoral coordination to optimize resources, efforts and roles
Cryptic bacterial pathogens of diatoms peak during senescence of a winter diatom bloom
Get PDFDiatoms are globally abundant microalgae that form extensive blooms in aquatic ecosystems. Certain bacteria behave antagonistically towards diatoms, killing or inhibiting their
growth. Despite their crucial implications to diatom blooms and population health, knowledge of diatom antagonists in the environment is fundamentally lacking. We report systematic characterisation of the diversity and seasonal dynamics of bacterial antagonists of diatoms via plaque assay sampling in the Western English Channel (WEC), where diatoms frequently bloom. Unexpectedly, peaks in detection did not occur during char�acteristic spring diatom blooms, but coincided with a winter bloom of Coscinodiscus, suggesting that these bacteria likely influence distinct diatom host populations.
We isolated multiple bacterial antagonists, spanning 4 classes and 10 bacterial orders. Notably, a diatom attaching Roseobacter Ponticoccus alexandrii was isolated multiple times, indi�cative of a persistent environmental presence. Moreover, many isolates had no prior reports of antagonistic activity towards diatoms. We verified diatom growth inhibitory effects of eight isolates. In all cases tested, these effects were activated by pre-exposure to diatom organic matter. Discovery of widespread ‘cryptic’ antagonistic activity indicates that bacterial pathogenicity towards diatoms is more prevalent than previously recognised.
Finally, examination of the global biogeography of WEC antagonists revealed co-occurrence patterns with diatom host populations in marine waters globally
Seasonal cycles of biogeochemical fluxes in the Scotia Sea, Southern Ocean: a stable isotope approach
No full textThe biological carbon pump is responsible for much of the decadal variability in the ocean carbon dioxide (CO2) sink, driving the transfer of carbon from the atmosphere to the deep ocean. A mechanistic understanding of the ecological drivers of particulate organic carbon (POC) flux is key both to the assessment of the magnitude of the ocean CO2 sink and for accurate predictions as to how this will change with changing climate. This is particularly important in the Southern Ocean, a key region for the uptake of CO2 and the supply of nutrients to the global thermocline. In this study we examine sediment-trap-derived particle fluxes and stable isotope signatures of carbon (C), nitrogen (N), and biogenic silica (BSi) at a study site in the biologically productive waters of the northern Scotia Sea in the Southern Ocean. Both deep (2000 m) and shallow (400 m) sediment traps exhibited two main peaks in POC, particulate N, and BSi flux: one in austral spring and one in summer, reflecting periods of high surface productivity. Particulate fluxes and isotopic compositions were similar in both deep and shallow sediment traps, highlighting that most remineralisation occurred in the upper 400 m of the water column. Differences in the seasonal cycles of isotopic compositions of C, N, and Si provide insights into the degree of coupling of these key nutrients. We measured increasing isotopic enrichment of POC and BSi in spring, consistent with fractionation during biological uptake. Since we observed isotopically light particulate material in the traps in summer, we suggest physically mediated replenishment of lighter isotopes of key nutrients from depth, enabling the full expression of the isotopic fractionation associated with biological uptake. The change in the nutrient and remineralisation regimes, indicated by the different isotopic compositions of the spring and summer productive periods, suggests a change in the source region of material reaching the traps and associated shifts in phytoplankton community structure. This, combined with the occurrence of advective inputs at certain times of the year, highlights the need to make synchronous measurements of physical processes to improve our ability to track changes in the source regions of sinking particulate material. We also highlight the need to conduct particle-specific (e.g. faecal pellets, phytoplankton detritus, zooplankton moults) isotopic analysis to improve the use of this tool in assessing particle composition of the sinking material and to develop our understanding of the drivers of biogeochemical fluxes
Ocean Biology Studied from Space
Get PDFVisible spectral radiometric measurements from space, commonly referred to as ocean-col�our measurements, provide a rich stream of information on ocean biota as well as on bio�logical and ecosystem processes. The strength of the ocean-colour technology for observ�ing marine life lies in its global reach, combined with its ability to sample the feld at a
variety of spatial and temporal scales that match the scales of the processes themselves.
Another advantage lies in the growing length of the time series of ocean-colour-derived
products, enabiling investigations into any long-term changes, if present. This paper pre�sents an overview of the principles and applications of ocean-colour data. The concen�tration of chlorophyll-a, the major pigment present in phytoplankton–single-celled, free�foating plants that are present in the sunlit layers of the ocean–was the frst, and remains
the most common, biological variable derived from ocean-colour data. Over the years, the
list of ocean-colour products have grown to encompass many measures of the marine eco�system and its functions, including primary production, phenology and ecosystem struc�ture. Applications that exploit the data are many and varied, and include ecosystem-based
fsheries management, biogeochemical cycles in the ocean, ecosystem health and climate
change. An integrated approach, incorporating other modes of ocean observations and
models with satellite observations, is needed to investigate the mysteries of the marine
ecosyste
Vertical flux of microplastic, a case study in the Southern Ocean, South Georgia
Get PDFEstimated plastic debris floating at the ocean surface varies depending on modelling approaches, with some suggesting unaccounted sinks for marine plastic debris due to mismatches between plastic predicted to enter the ocean and that accounted for at the surface. A major knowledge gap relates to the vertical sinking of oceanic plastic. We used an array of floating sediment traps combined with optical microscopy and Raman spectroscopy to measure the microplastic flux between 50 and 150 m water depth over 24 h within a natural harbour of the sub-Antarctic island of South Georgia. This region is influenced by fishing, tourism, and research activity. We found a 69 % decrease in microplastic flux from 50 m (306 pieces/m2/day) to 150 m (94pieces/m2/day). Our study confirms the occurrence of a vertical flux of microplastic in the upper water column of the Southern Ocean, which may influence zooplankton microplastic consumption and the carbon cycle
Tracking ocean history through plankton ‘roadkill’
No full textMarine biogeochemist Clare Ostle tracks the stories that plankton tell from all corners of the globe
Faster, Better, Cheaper: Solutions to the Atmospheric Shipping Emission Compliance and Attribution Conundrum
Get PDFGlobal concerns regarding air quality have over the past decade led to the introduction
of regulations by the International Maritime Organisation curbing the emissions of sulphur and
nitrogen oxides (SOx, NOx). These limits were implemented initially in so-called “emission control
areas”, defined where the density of shipping activity combines with large coastal population centres
such as northwest Europe or eastern USA. However, any legislation requires a scientifically robust
and rigorous monitoring program to ensure compliance and prove attribution to an individual
vessel. We argue the case for adherence to the mantra “faster, better, cheaper”, where widespread
adoption of independent low-cost solutions of onboard, in-stack sensors, combined with existing,
globally ubiquitous satellite-based “automatic identification system” (AIS) data telemetry, provides
an excellent solution to the affordable compliance and attribution conundrum for shipping companies
and enforcement agencies alike. We present data from three field-campaigns which have significantly
advanced the concept of onboard real-time monitoring of atmospheric ship emissions