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Perspectives on shipping emissions and their impacts on the surface ocean and lower atmosphere: An environmental-social-economic dimension
Get PDFShipping is the cornerstone of international trade and thus a critical economic sector. However, ships predominantly use fossil fuels for propulsion and electricity generation, which emit greenhouse gases such as carbon dioxide and methane, and air pollutants such as particulate matter, sulfur oxides, nitrogen oxides, and volatile organic compounds. The availability of Automatic Information System (AIS) data has helped to improve the emission inventories of air pollutants from ship stacks. Recent laboratory, shipborne, satellite
and modeling studies provided convincing evidence that ship-emitted air pollutants have significant impacts on atmospheric chemistry, clouds, and ocean biogeochemistry. The need to improve air quality to protect human health and to mitigate climate change has driven a series of regulations at international, national, and local levels, leading to rapid energy and technology transitions. This resulted in major changes in air emissions from shipping with implications on their environmental impacts, but observational studies remain
limited. Growth in shipping in polar areas is expected to have distinct impacts on these pristine and sensitive environments. The transition to more sustainable shipping is also expected to cause further changes in fuels and technologies, and thus in air emissions. However, major uncertainties remain on how future shipping emissions may affect atmospheric composition, clouds, climate, and ocean biogeochemistry, under the rapidly changing policy (e.g., targeting decarbonization), socioeconomic, and climate contexts
Spatial distribution of meiofaunal and macrofaunal assemblages in the tidal flats of the southern Korean coast in relation to natural and anthropogenic impacts
Get PDFWe investigated the spatial variability of macrofaunal and meiofaunal assemblages in intertidal flats on the southern coast of Korea. Abiotic and biotic samples were collected at five stations. The species richness, density, and composition of the assemblages differed significantly among stations. Nematoda and Annelida were the most dominant meiofaunal and macrofaunal taxa, respectively, although taxon dominance differed among stations. Distance-based linear models showed that sediment-related variables and heavy metals were the main environmental factors determining the spatial variability of the assemblages. Macrofauna had only sediment-related variables and heavy metals as major environmental factors, but meiofauna were also influenced by other environmental factors such as sea surface temperature, dissolved oxygen-related variables, and salinity. This study can provide basic ecological data for understanding the spatial distribution of macro-meiofaunal assemblages and aid in the development of marine environmental management strategies on the western south coast of Korea
OceanSODA-MDB: a standardised surface ocean carbonate system dataset for model–data intercomparisons
Get PDFIn recent years, large datasets of in situ marine carbonate system parameters (partial pressure of CO2
(pCO2), total alkalinity, dissolved inorganic carbon and pH) have been collated, quality-controlled and made
publicly available. These carbonate system datasets have highly variable data density in both space and time, es�pecially in the case of pCO2, which is routinely measured at high frequency using underway measuring systems.
This variation in data density can create biases when the data are used, for example, for algorithm assessment,
favouring datasets or regions with high data density. A common way to overcome data density issues is to bin
the data into cells of equal latitude and longitude extent. This leads to bins with spatial areas that are latitude�and projection-dependent (e.g. become smaller and more elongated as the poles are approached). Additionally,
as bin boundaries are defined without reference to the spatial distribution of the data or to geographical features,
data clusters may be divided sub-optimally (e.g. a bin covering a region with a strong gradient). To overcome
these problems and to provide a tool for matching surface in situ data with satellite, model and climatological
data, which often have very different spatiotemporal scales both from the in situ data and from each other, a
methodology has been created to group in situ data into “regions of interest”: spatiotemporal cylinders consist�ing of circles on the Earth’s surface extending over a period of time. These regions of interest are optimally
adjusted to contain as many in situ measurements as possible. All surface in situ measurements of the same
parameter contained in a region of interest are collated, including estimated uncertainties and regional summary
statistics. The same grouping is applied to each of the non-in situ datasets in turn, producing a dataset of coin�cident matchups that are consistent in space and time. About 35 million in situ data points were matched with
data from five satellite sources and five model and reanalysis datasets to produce a global matchup dataset of
carbonate system data, consisting of ∼ 286 000 regions of interest spanning 54 years from 1957 to 2020. Each
region of interest is 100 km in diameter and 10 d in duration. An example application, the reparameterisation of
a global total alkalinity algorithm, is presented. This matchup dataset can be updated as and when in situ and
other datasets are updated, and similar datasets at finer spatiotemporal scale can be constructed, for example,
to enable regional studies. The matchup dataset provides users with a large multi-parameter carbonate system
dataset containing data from different sources, in one consistent, collated and standardised format suitable for
model–data intercomparisons and model evaluations. The OceanSODA-MDB data can be downloaded from
https://doi.org/10.12770/0dc16d62-05f6-4bbe-9dc4-6d47825a5931 (Land and Piollé, 2022)
Optimising Multispectral Active Fluorescence to Distinguish the Photosynthetic Variability of Cyanobacteria and Algae
Get PDFThis study assesses the ability of a new active fluorometer, the LabSTAF, to diagnostically assess the physiology of freshwater cyanobacteria in a reservoir exhibiting annual blooms. Specifically, we analyse the correlation of relative cyanobacteria abundance with photosynthetic parameters derived from fluorescence light curves (FLCs) obtained using several combinations of excitation wavebands, photosystem II (PSII) excitation spectra and the emission ratio of 730 over 685 nm (Fo(730/685)) using excitation protocols with varying degrees of sensitivity to yanobacteria and algae. FLCs using blue excitation (B) and green–orange–red (GOR) excitation wavebands capture physiology parameters of algae and cyanobacteria, respectively. The green–orange (GO) protocol,
expected to have the best diagnostic properties for cyanobacteria, did not guarantee PSII saturation. PSII excitation spectra showed distinct response from cyanobacteria and algae, depending on spec�tral optimisation of the light dose. Fo(730/685), obtained using a combination of GOR excitation wavebands, Fo(GOR, 730/685), showed a significant correlation with the relative abundance of cya�nobacteria (linear regression, p-value < 0.01, adjusted R2 = 0.42). We recommend using, in parallel, Fo(GOR, 730/685), PSII excitation spectra (appropriately optimised for cyanobacteria versus algae), and physiological parameters derived from the FLCs obtained with GOR and B protocols to assess the physiology of cyanobacteria and to ultimately predict their growth. Higher intensity LEDs (G
and O) should be considered to reach PSII saturation to further increase diagnostic sensitivity to the
cyanobacteria component of the communit
Red List for British seaweeds: evaluating the IUCN methodology for non-standard marine organisms
No full textThe IUCN Red List of Threatened Species is an authoritative tool in biodiversity conservation. Whilst IUCN criteria have been applied successfully to groups such as birds and mammals, a Red List assessment of British seaweeds in 2021 revealed that the categories to which seaweed species were assigned were dependent on how the criteria were applied. Here, this seaweed assessment is used as a case study with which to evaluate the IUCN methodology for use with ‘non-standard’ groups of organisms. A data-driven assessment of red (Rhodophyta), green (Chlorophyta) and brown (Phaeophyceae) seaweeds, which applied three (A, B and D) of the five IUCN criteria (A–E), categorized 13% of 617 British species as threatened. Following peer review, only 7% of species were categorized as threatened (1% Critically Endangered—CR, 3% Endangered—EN, 3% Vulnerable—VU), and 55% as Data Deficient. This reduction in species categorized as threatened suggests that strict application of the IUCN criteria may, at least for the seaweeds, over-estimate threat. As a result of this assessment, recommendations include the need for a more unified monitoring system and a review of the suitability for/application of the IUCN assessment criteria to some types of organisms. For example, in clonal populations, it is not possible to count individuals, and complex life histories cause additional complications. IUCN criteria must be applicable to a wide range of organisms, including seaweeds
The requirement for external carbonic anhydrase in diatoms is influenced by the supply and demand for dissolved inorganic carbon
Get PDFPhotosynthesis by marine diatoms contributes significantly to the global carbon cycle. Due to the low concentration of CO2 in seawater, many diatoms use extracellular carbonic anhydrase (eCA) to enhance the supply of CO2 to the cell surface. While much research has investigated how the requirement for eCA is influenced by changes in CO2 availability, little is known about how eCA contributes to CO2 supply following changes in the demand for carbon. We therefore examined how changes in photosynthetic rate influence the requirement for eCA in three centric diatoms. Modeling of cell surface carbonate chemistry indicated that diffusive CO2 supply to the cell surface was greatly reduced in large diatoms at higher photosynthetic rates. Laboratory experiments demonstrated a trend of an increasing requirement for eCA with increasing photosynthetic rate that was most pronounced in the larger species, supporting the findings of the cellular modeling. Microelectrode measurements of cell surface pH and O2 demonstrated that individual cells exhibited an increased contribution of eCA to photosynthesis at higher irradiances. Our data demonstrate that changes in carbon demand strongly influence the requirement for eCA in diatoms. Cell size and photosynthetic rate will therefore be key determinants of the mode of dissolved inorganic carbon uptake
Global analysis of the controls on seawater dimethylsulfide spatial variability
Get PDFDimethylsulfide (DMS) emitted from the ocean makes a significant global contribution to natural marine aerosol and cloud condensation nuclei and, therefore, our planet’s climate. Oceanic DMS concentrations show large spatiotemporal variability, but observations are sparse, so
products describing global DMS distribution rely on interpolation or modelling. Understanding the mechanisms driving DMS variability, especially at local scales, is required to reduce uncertainty in large-scale DMS estimates. We present a study of mesoscale and submesoscale (< 100 km) seawater DMS variability that takes advantage of the recent expansion in high-frequency seawater DMS observations and
uses all available data to investigate the typical distances over which DMS varies in all major ocean basins. These DMS
spatial variability length scales (VLSs) are uncorrelated with DMS concentrations. The DMS concentrations and VLSs
can therefore be used separately to help identify mechanisms underpinning DMS variability. When data are grouped
by sampling campaigns, almost 80 % of the DMS VLS can
be explained using the VLSs of sea surface height anomalies, density, and chlorophyll a. Our global analysis suggests
that both physical and biogeochemical processes play an
equally important role in controlling DMS variability, which
is in contrast with previous results based on data from the
low to mid-latitudes. The explanatory power of sea surface
height anomalies indicates the importance of mesoscale eddies in driving DMS variability, previously unrecognised at global scale and in agreement with recent regional studies. DMS VLS differs regionally, including surprisingly high frequency variability in low-latitude waters. Our results independently confirm that relationships used in the literature to parameterise DMS at large scales appear to be considering the right variables. However, regional DMS VLS contrasts highlight that important driving mechanisms remain elusive. The role of submesoscale features should be resolved or accounted for in DMS process models and parameterisations. Future attempts to map DMS distributions should consider the length scale of variability
Global disruption of coral broadcast spawning associated with artificial light at night
Get PDFCoral broadcast spawning events - in which gametes are released on certain nights predictably in relation to lunar cycles - are critical to the maintenance and recovery of coral reefs following mass mortality. Artificial light at night (ALAN) from coastal and offshore developments threatens coral reef health by masking natural light:dark cycles that synchronize broadcast spawning. Using
a recently published atlas of underwater light pollution, we analyze a global dataset of 2135 spawning observations from the 21st century. For the majority of genera, corals exposed to light pollution are spawning between one and three days closer to the full moon compared to those on unlit reefs. ALAN possibly advances the trigger for spawning by creating a perceived period of minimum illuminance between sunset and moonrise on nights following the full moon. Advancing the timing of mass spawning could decrease the probability of gamete fertilization and survival, with clear implications for ecological processes involved in the resilience of reef systems
Low rates of bacterivory enhances phototrophy and competitive advantage for mixoplankton growing in oligotrophic waters
Get PDFWith climate change, oceans are becoming increasingly nutrient limited, favouring growth of prokaryotic picoplankton at the expense of the larger protist plankton whose growth support higher trophic levels. Constitutive mixoplankton (CM), microalgal plankton with innate phototrophic capability coupled with phagotrophy, graze on these picoplankton, indirectly exploiting the excellent
resource acquisition abilities of the prokaryotes. However, feeding rates can be very low (e.g., a few bacteria d−1). For the first time, the significance of such low consumption rates has been quantified. We find that while prokaryote-carbon (C) supply to CM grown at non-limiting light was so low that it may appear insignificant (<10%), contributions of nitrogen (N) and phosphorus (P) from ingestions
of 1–12 prokaryotes d−1 were significant. Under limiting light, contributions of ingested C increased, also raising the contributions of N and P. The order of nutritional importance for CM growth from predation was P>N>C. Further, provision of N through internal recycling of ingested prey-N
stimulates C-fixation through photosynthesis. Importantly, coupled photo-phago-mixoplanktonic activity improved CM resource afinities for both inorganic and prey-bound nutrients, enhancing the nutritional status and competitiveness of mixoplankton. With warming oceans, with increased prokaryote abundance, we expect CM to exhibit more phagotrophy
Genome‐scale signatures of adaptive gene expression changes in an invasive seaweed Gracilaria vermiculophylla
Get PDFInvasive species can successfully and rapidly colonize new niches and expand ranges via founder effects and enhanced tolerance towards environmental stresses. However, the underpinning molecular mechanisms (i.e., gene expression changes) facilitating rapid adaptation to harsh environments are still poorly understood. The red seaweed Gracilaria vermiculophylla, which is native to the northwest Pacific but invaded North American and European coastal habitats over the last 100 years, pro vides an excellent model to examine whether enhanced tolerance at the level of gene expression contributed to its invasion success. We collected G. vermiculophylla from its native range in Japan and from two non-native regions along the Delmarva Peninsula (Eastern United States) and in Germany. Thalli were reared in a common garden for 4 months at which time we performed comparative transcriptome (mRNA) and microRNA (miRNA) sequencing. MRNA-expression profiling identified 59 genes that were differently expressed between native and non-native thalli. Of these genes, most were involved in metabolic pathways, including photosynthesis, abiotic stress, and biosynthesis of products and hormones in all four non-native sites. MiRNA-based target-gene correlation analysis in native/non-native pairs revealed that some target genes are positively or negatively regulated via epigenetic mechanisms. Importantly, these genes are mostly associated with metabolism and defence capability (e.g., metal transporter Nramp5, senescence-associated protein, cell wall-associated hydrolase, ycf68 protein and cytochrome P450-like TBP). Thus, our gene expression results in dicate that resource reallocation to metabolic processes is most likely a predominant mechanism contributing to the range-wide persistence and adaptation of G. vermicu lophylla in the invaded range. This study, therefore, provides molecular insight into the speed and nature of invasion-mediated rapid adaptio