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Iodide, iodate & dissolved organic iodine in the temperate coastal ocean
Get PDFThe surface ocean is the main source of iodine to the atmosphere, where it plays a crucial role including in the catalytic removal of tropospheric ozone. The availability of surface oceanic iodine is governed by its biogeochemical cycling, the controls of which are poorly constrained. Here we show a near two-year time series of the primary iodine species, iodide, iodate and dissolved organic iodine (DOI) in inner shelf marine surface waters of the Western English Channel (UK). The median ± standard deviation concentrations between November 2019 and September 2021 (n=76) were: iodide 88 ± 17 nM (range 61-149 nM), iodate 293 ± 28 nM (198-382 nM), DOI 16 ± 16 nM (<0.12-75 nM) and total dissolved iodine (dIT) 399 ± 30 nM (314-477 nM). Though lower than inorganic iodine ion concentrations, DOI was a persistent and non-negligible component of dIT, which is consistent with previous studies in coastal waters. Over the time series, dIT was not conserved and the missing pool of iodine accounted for ~6% of the observed concentration suggesting complex mechanisms governing dIT removal and renewal. The contribution of excess iodine (I*) sourced from the coastal margin towards dIT was generally low (3 ± 29 nM) but exceptional events influenced dIT concentrations by up to ±100 nM. The seasonal variability in iodine speciation was asynchronous with the observed phytoplankton primary productivity. Nevertheless, iodate reduction began as light levels and then biomass increased in spring and iodide attained its peak concentration in mid to late autumn during post-bloom conditions. Dissolved organic iodine was present, but variable, throughout the year. During winter, iodate concentrations increased due to the advection of North Atlantic surface waters. The timing of changes in iodine speciation and the magnitude of I* subsumed by seawater processes supports the paradigm that transformations between iodine species are biologically mediated, though not directly linked
The increasing importance of satellite observations to assess the ocean carbon sink and ocean acidification
Get PDFThe strong control that the emissions of carbon dioxide (CO2) have over Earth's climate identifies the need for accurate quantification of the emitted CO2 and its redistribution within the Earth system. The ocean annually absorbs more than a quarter of all CO2 emissions and this absorption is fundamentally altering the ocean chemistry. The ocean thus provides a fundamental component and powerful constraint within global carbon assessments used to guide policy action for reducing emissions. These carbon assessments rely heavily on satellite observations, but their inclusion is often invisible or opaque to policy. One reason is that satellite observations are rarely used exclusively, but often in conjunction with other types of observations, thereby complementing and expanding their usability yet losing their visibility. This exploitation of satellite observations led by the satellite and ocean carbon scientific communities is based on exciting developments in satellite science that have broadened the suite of environmental data that can now reliably be observed from space. However, the full potential of satellite observations to expand the scientific knowledge on critical processes such as the atmosphere-ocean exchange of CO2 and ocean acidification, including its impact on ocean health, remains largely unexplored. There is clear potential to begin using these observation-based approaches for directly guiding ocean management and conservation decisions, in particular in regions where in situ data collection is more difficult, and interest in them is growing within the environmental policy communities. We review these developments, identify new opportunities and scientific priorities, and identify that the formation of an international advisory group could accelerate policy relevant advancements within both the ocean carbon and satellite communities. Some barriers to understanding exist but these should not stop the exploitation and the full visibility of satellite observations to policy makers and users, so these observations can fulfil their full potential and recognition for supporting society
Impacts of Climate Change on Marine Foundation Species
No full textMarine foundation species are the biotic basis for many of the world's coastal ecosystems, providing structural habitat, food, and protection for myriad plants and animals as well as many ecosystem services. However, climate change poses a significant threat to foundation species and the ecosystems they support. We review the impacts of climate change on common marine foundation species, including corals, kelps, seagrasses, salt marsh plants, mangroves, and bivalves. It is evident that marine foundation species have already been severely impacted by several climate change drivers, often through interactive effects with other human stressors, such as pollution, overfishing, and coastal development. Despite considerable variation in geographical, environmental, and ecological contexts, direct and indirect effects of gradual warming and subsequent heatwaves have emerged as the most pervasive drivers of observed impact and potent threat across all marine foundation species, but effects from sea level rise, ocean acidification, and increased storminess are expected to increase. Documented impacts include changes in the genetic structures, physiology, abundance, and distribution of the foundation species themselves and changes to their interactions with other species, with flow-on effects to associated communities, biodiversity, and ecosystem functioning. We discuss strategies to support marine foundation species into the Anthropocene, in order to increase their resilience and ensure the persistence of the ecosystem services they provide
Complete characterization of ocean color radiometers
Get PDFVerifying and validating waterleaving radiance measurements from space for an accurate derivation of Ocean/Water Colour biogeophysical products is based on concurrent high-quality fiducial reference measurements (FRM) carried out on
the ground or water body. The FRM principles established by the Committee on Earth Observation Satellites (CEOS) recommend that in situ Ocean Colour radiometers (OCR) have a documented history of SI traceable calibrations
including uncertainty budgets. Furthermore, there can be significant differences between calibration and use of the instruments in the field due to differences in operating temperature, angular variation of the light field (especially for irradiance sensors), the intensity of the measured radiation, and spectral variation of the target, among others. Each of these factors may interact with
individual properties of the instrument when deployed in the field, and estimation of such uncertainties requires instrument characterization in addition to the absolute radiometric calibration if expanded uncertainties within ±10% (k = 2) are the aim. The FRM4SOC Phase 2 project - funded by the European Commission in the frame of the Copernicus Programme and implemented by EUMETSAT - contributes to these efforts, aiming at developing an operational and sustained network of radiometric measurements of FRM quality. Within FRM4SOC-2, scientists from the Tartu Observatory (TO) of the University of
Tartu performed an unprecedented batch of calibrations and characterizations on a set of 37 hyperspectral field radiometers representative of the most used OCR classes within the OC community. The calibrations and characterizations performed include the determination of radiometric responsivity, long-term stability, the accuracy of the spectral scale, non-linearity and accuracy of
integration times, spectral stray light, angular response of irradiance sensors in air, dark signal, thermal sensitivity, polarization sensitivity, and signal-to-noise ratio of individual OCRs. Consistent correction of biases and extended uncertainty analysis procedures of in situ data obtained from different instruments and measurement models need to be clearly defined, which is the objective of this paper
Quantification of finfish assemblages associated with mussel and seaweed farms in southwest UK provides evidence of potential benefits to fisheries
No full textLow trophic aquaculture, including shellfish and seaweed farming, offers a potentially sustainable food source and may provide additional environmental benefits, including the creation of new feeding, breeding and nursery areas for fish of commercial and ecological importance. However, quantitative assessments of fish assemblages associated with aquaculture sites are lacking. We used pelagic baited remote underwater videos (BRUVs) and hook and line catches to survey summer fish assemblages at 2 integrated blue mussel Mytilus edulis and kelp (predominantly Saccharina latissima) farms in southwest UK. We recorded at least 11 finfish species across the surveys, including several of commercial importance, with farmed mussels and/or kelps supporting significantly higher levels of abundance and richness than reference areas outside farm infrastructure. Farmed kelp provided temporary habitat due to seasonal harvesting schedules, whereas farmed mussels provided greater habitat stability due to overlapping interannual growth cycles. Stomach content analysis of fish caught at the farms revealed that some low trophic level species had high proportions of amphipods in their stomachs, which also dominated epibiont assemblages at the farms. Higher trophic level fish stomachs contained several lower trophic level fish species, suggesting that farms provide new foraging grounds and support secondary and tertiary production. Although not identified to species level, juvenile fish were abundant at both farms, suggesting potential provisioning of nursery or breeding grounds; however, this needs further verification. Overall, this study provides evidence that shellfish and seaweed aquaculture can support and enhance populations of commercially and ecologically important fish species through habitat provisioning
Challenges in quantifying the responses of Black-legged Kittiwakes Rissa tridactyla to habitat variables and local stressors due to individual variation
No full textStrong individual variation was observed in the responses of Black-legged Kittiwakes Rissa tridactyla to environmental covariates related to foraging behaviour and habitat selection, and in the overlap with nearby offshore windfarms (OWFs)
A niche‐based theory of island biogeography
No full textThe equilibrium theory of island biogeography (ETIB) is a widely applied dynamic theory proposed in the 1960s to explain why islands have coherent differences in species richness. The development of the ETIB was temporarily challenged in the 1970s by the alternative static theory of ecological impoverishment (TEI). The TEI suggests that the number of species on an island is determined by its number of habitats or niches but, with no clear evidence relating species richness to the number of niches however, the TEI has been almost dismissed as a theory in favour of the original ETIB. Here, we show that the number of climatic niches on islands is an important predictor of the species richness of plants, herpetofauna and land birds. We therefore propose a model called the niche-based theory of island biogeography (NTIB), based on the MacroEcological Theory on the Arrangement of Life (METAL), which successfully integrates the number of niches sensu Hutchinson into ETIB. To account for greater species turnover at the beginning of colonisation, we include higher initial extinction rates. When we test our NTIB for resident land birds in the Krakatau Islands, it reveals a good correspondence with observed species richness, immigration and extinction rates. Provided the environmental regime remains unchanged, we estimate that the current species richness at equilibrium is ~45 species (range between 38.39 and 61.51). Our NTIB provides better prediction because it counts for changes in species richness with latitude, which is not considered in any theory of island biogeograph
Measuring deoxygenation effects on marine predators: A new animal-attached archival tag recording in situ dissolved oxygen, temperature, fine-scale movements and behaviour
No full text1. Global climate-driven ocean warming has decreased dissolved oxygen (DO) levels (ocean deoxygenation) leading to expansions of hypoxic zones, which will affect the movements, behaviour, physiology and distributions of marine animals. However, the precise responses of animals to low DO remains poorly understood because movements and activity levels are seldom recorded alongside instantaneous DO in situ.
2. We describe a new animal-attached (dissolved oxygen measuring, DOME) archival tag with an optical oxygen sensor for recording DO, in addition to sensors for temperature and depth, a triaxial accelerometer for fine-scale movements and activity, and a GPS for tag recovery. All sensors were integrated on a single electronic board.
3. Calibration tests demonstrated small mean difference between DOME tag and factory-calibrated DO sensors (mean relative error of 5%). No temporal drift occurred over a test period three times longer than the maximum deployment time. Deployments on four blue sharks (Prionace glauca) in the central North Atlantic Ocean showed regular vertical oscillations from the surface to a maximum of 404 m. Profiles from diving sharks recorded DO concentrations ranging from 217 to 272 μmol L−1, temperatures between 13°C and 23°C, and identified an oxygen maximum at ~45 m depth, all of which were consistent with ship-based measurements. Interestingly, the percentage of time sharks spent burst swimming was greater in the top 85 m compared to deeper depths, potentially because of higher prey availability in the surface layer.
4. The DOME tag described blue shark fine-scale movements and activity levels in relation to accurately measured in situ DO and temperature, with the potential to offer new insights of animal performance in low oxygen environments. Development of a tag with physico-chemical and movement sensors on a single electronic board is a first step towards satellite relay of these data over broader spatiotemporal scales (months over thousands of kilometres) to determine direct and indirect responses of marine animals to heatwave and deoxygenation event
Combining Top‐Down and Bottom‐Up Approaches to Evaluate Recent Trends and Seasonal Patterns in UK N2O Emissions
Get PDFAtmospheric trace gas measurements can be used to independently assess national greenhouse gas inventories through inverse modeling. Atmospheric nitrous oxide (N2O) measurements made in the United Kingdom (UK) and Republic of Ireland are used to derive monthly N2O emissions for 2013–2022 using two different inverse methods. We find mean UK emissions of 90.5 ± 23.0 (1σ) and 111.7 ± 32.1 (1σ) Gg N2O yr− 1 for 2013–2022, and corresponding trends of − 0.68 ± 0.48 (1σ) Gg N2O yr− 2 and − 2.10 ± 0.72 (1σ) Gg N2O
yr− 2 , respectively, for the two inverse methods. The UK National Atmospheric Emissions Inventory (NAEI)
reported mean N2O emissions of 73.9 ± 1.7 (1σ) Gg N2O yr− 1 across this period, which is 22%–51% smaller than the emissions derived from atmospheric data. We infer a pronounced seasonal cycle in N2O emissions, with a peak occurring in the spring and a second smaller peak in the late summer for certain years. The springtime peak has a long seasonal decline that contrasts with the sharp rise and fall of N2O emissions estimated from the bottom‐up UK Emissions Model (UKEM). Bayesian inference is used to minimize the seasonal cycle mismatch between the average top‐down (atmospheric data‐based) and bottom‐up (process model and inventory‐based) seasonal emissions at a sub‐sector level. Increasing agricultural manure management and decreasing synthetic fertilizer N2O emissions reduces some of the discrepancy between the average top‐down and bottom‐up seasonal cycles. Other possibilities could also explain these discrepancies, such as missing emissions from NH3
deposition, but these require further investigation
A DNA barcoding framework for taxonomic verification in the Darwin Tree of Life Project
No full textBiodiversity genomics research requires reliable organismal identification, which can be difficult based on morphology alone. DNA-based identification using DNA barcoding can provide confirmation of species identity and resolve taxonomic issues but is rarely used in studies generating reference genomes. Here, we describe the development and implementation of DNA barcoding for the Darwin Tree of Life Project (DToL), which aims to sequence and assemble high quality reference genomes for all eukaryotic species in Britain and Ireland. We present a standardised framework for DNA barcode sequencing and data interpretation that is then adapted for diverse organismal groups. DNA barcoding data from over 12,000 DToL specimens has identified up to 20% of samples requiring additional verification, with 2% of seed plants and 3.5% of animal specimens subsequently having their names changed. We also make recommendations for future developments using new sequencing approaches and streamlined bioinformatic approache