Phytoplankton communities and acclimation in a cyclonic eddy in the southwest Indian Ocean

A study of phytoplankton in a cyclonic eddy was undertaken in the Mozambique Basin between Madagascar and southern Africa during austral winter. CHEMTAX analysis of pigment data indicated that the community comprised mainly haptophytes and diatoms, with Prochlorococcus, prasinophytes and pelagophytes also being prominent to the east and west of the eddy. There was little difference in community structure, chlorophyll-specific absorption [a*ph(440)] and pigment:TChla ratios between the surface and the sub-surface chlorophyll maximum (SCM), reflecting acclimation to fluctuating light conditions in a well mixed upper layer. Values for a*ph(440) were low for diatom dominance, high where prokaryote proportion was high, and intermediate for flagellate dominated communities. Chlorophyll c and fucoxanthin:TChla ratios were elevated over most of the eddy, while 19′-hexanoyloxyfucoxanthin ratios increased in the eastern and western sectors. In a community comprising mainly flagellates and Prochlorococcus to the west of the eddy, there was high a*ph(440) at the surface and elevated ratios for divinyl chlorophyll a, chlorophyll b and 19′-hexanoyloxyfucoxanthin at the SCM. An increase in diadinoxanthin:TChla ratios and a decline in the quantum efficiency of photochemistry in PSII under high light conditions, indicated some photoprotection and photoinhibition at the surface even in a well mixed environment. Diadinoxanthin was the main photoprotective carotenoid within the eddy, while zeaxanthin was the dominant photoprotective pigment outside the eddy. The results of this study will be useful inputs into appropriate remote sensing models for estimating primary production and the size class distribution of phytoplankton in eddies in the southwest Indian Ocean

Environmental influence on phytoplankton communities in the northern Benguela ecosystem

An investigation of surface phytoplankton communities was undertaken on the shelf of the northern Benguela upwelling ecosystem during austral autumn (May) and spring (September), along latitudinal transects at 20° S and 23° S, from 2 to 70 nautical miles offshore, as well as on a zigzag grid located between these transects. Microscopic identification of the phytoplankton and CHEMTAX analysis of pigment biomarkers were used to characterise the community composition. During May 2014, warmer, more-saline water with a shallower upper mixed layer corresponding to periods of less-intense offshore Ekman transport was encountered on the shelf. Satellite imagery indicated high phytoplankton biomass extending for a considerable distance from the coast, and CHEMTAX indicated diatoms as dominant at most of the stations (52–92%), although dinoflagellates were dominant at some inshore localities (57–74%). Species of Chaetoceros, Bacteriastrum and Cylindrotheca were the most abundant, with abundance of the Pseudo-nitzschia ‘seriata-group’ being particularly high at a number of stations. In September 2014, more-intense wind-forcing resulted in a deeper upper mixed layer and stronger upwelling of colder, less-saline water. Elevated phytoplankton biomass was confined close to the coast, where diatoms accounted for most of the population (54–87%), whereas small flagellates, such as prasinophytes, haptophytes and cryptophytes, as well as the cyanobacterium Synechococcus, dominated the communities (58–90%) farther from the coast. It is hypothesised that stronger upwelling and deeper vertical mixing in September of that year were not conducive for widespread diatom growth, and that small flagellates populated the water column by being entrained from offshore onto the shelf in the upwelled water that moved in towards the coast

Simultaneous Detection of Alkylamines in the Surface Ocean and Atmosphere of the Antarctic Sympagic Environment

Measurements of alkylamines from seawater and atmospheric samples collected simultaneously across the Antarctic Peninsula, South Orkney and South Georgia Islands are reported. Concentrations of mono-, di-, and trimethylamine (MMA, DMA, and TMA, respectively), and their precursors, the quarternary amines glycine betaine and choline, were enhanced in sympagic seawater samples relative to ice-devoid pelagic ones, suggesting the microbiota of sea ice and sea ice-influenced ocean is a major source of these compounds. Primary sea-spray aerosol particles artificially generated by bubbling seawater samples were investigated by aerosol time-of-flight mass spectrometry (ATOFMS) of single particles; their mixing state indicated that alkylamines were aerosolized with sea spray from dissolved and particulate organic nitrogen pools. Despite this unequivocal sea spray-associated source of alkylamines, ATOFMS analyses of ambient aerosols in the sympagic region indicated that the majority (75–89%) of aerosol alkylamines were of secondary origin, that is, incorporated into the aerosol after gaseous air–sea exchange. These findings show that sympagic seawater properties are a source of alkylamines influencing the biogenic aerosol fluxed from the ocean into the boundary layer; these organic nitrogen compounds should be considered when assessing secondary aerosol formation processes in Antarctica

Assessment of Rapid Diagnostic Tests for Typhoid Diagnosis and Assessment of Febrile Illness Outbreaks in Fiji.

Typhoid is an endemic in Fiji with increases observed since the early 2000s and frequent outbreaks reported. We assessed the diagnostic accuracy of currently available typhoid rapid diagnostic tests (RDTs) (TUBEX, Typhidot Rapid, and Test-It assay) to establish their performance against blood culture in Fiji and to examine their suitability for rapid typhoid outbreak identification. The performance of RDTs was assessed in the public health reference laboratory in Suva, Fiji, according to the manufacturers' instructions. A simulation was used to examine the potential use of RDTs for attribution of a febrile illness outbreak to typhoid. For the diagnostic evaluation, 179 patients were included; 49 had blood culture-confirmed typhoid, 76 had fever as a result of non-typhoid etiologies, and 54 were age-matched community controls. The median (interquartile range) age was 29 (20-46) years. Of the participants, 92 (51.4%) were male and 131 (73.2%) were indigenous Fijians. The sensitivities of the tests were 77.6% for TUBEX, 75.5% for Typhidot Rapid, and 57.1% for Test-It assay. The Test-It assay had the highest specificity of 93.4%, followed by Typhidot Rapid 85.5% and TUBEX 60.5%. Typhidot Rapid had the best performance in the simulation for attribution of a febrile illness outbreak to typhoid. Typhoid RDTs performed suboptimally for individual patient diagnosis due to low sensitivity and variable specificity. We demonstrate that RDTs could be useful in the field for rapid attribution of febrile illness outbreaks to typhoid. Typhidot Rapid had the best combination of sensitivity, specificity, positive and negative predictive values, cost, and ease of use for this purpose

Coupling ecological concepts with an ocean-colour model: Phytoplankton size structure

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Phytoplankton play a central role in the planetary cycling of important elements and compounds. Understanding how phytoplankton are responding to climate change is consequently a major question in Earth Sciences. Monitoring phytoplankton is key to answering this question. Satellite remote sensing of ocean colour is our only means of monitoring phytoplankton in the entire surface ocean at high temporal and large spatial scales, and the continuous ocean-colour data record is now approaching a length suitable for addressing questions around climate change, at least in some regions. Yet, developing ocean-colour algorithms for climate change studies requires addressing issues of ambiguity in the ocean-colour signal. For example, for the same chlorophyll-a concentration (Chl-a) of phytoplankton, the colour of the ocean can be different depending on the type of phytoplankton present. One route to tackle the issue of ambiguity is by enriching the ocean-colour data with information on sea surface temperature (SST), a good proxy of changes in three phytoplankton size classes (PSCs) independent of changes in total Chl-a, a measure of phytoplankton biomass. Using a global surface in-situ dataset of HPLC (high performance liquid chromatography) pigments, size-fractionated filtration data, and concurrent satellite SST spanning from 1991 to 2021, we re-tuned, validated and advanced an SST-dependent three-component model that quantifies the relationship between total Chl-a and Chl-a associated with the three PSCs (pico-, nano- and microplankton). Similar to previous studies, striking dependencies between model parameters and SST were captured, which were found to improve model performance significantly. These relationships were applied to 40 years of monthly composites of satellite SST, and significant trends in model parameters were observed globally, in response to climate warming. Changes in these parameters highlight issues in estimating long-term trends in phytoplankton biomass (Chl-a) from ocean colour using standard empirical algorithms, which implicitly assume a fixed relationship between total Chl-a and Chl-a of the three size classes. The proposed ecological model will be at the centre of a new ocean-colour modelling framework, designed for investigating the response of phytoplankton to climate change, described in subsequent parts of this series of papers

Goat health and management for improved smallholders’ livelihoods in central Malawi – a socioeconomic analysis of rural households

DATA AVAILABILITY : Anonymized tabulated data are available in S1 File, additional anonymised survey files are available upon request.The true value of goats, their management systems, and the limitations of smallholdings have not been fully explored in the context of sustainable livelihoods among rural smallholders in central Malawi. However, goats are an essential part of rural livelihoods as transferable assets and sources of household nutrition, especially at times of food insecurity aligned to an ever more variable climate. To study the impact and limitations of goat ownership in Malawi’s Lilongwe district, surveys were performed across four villages covering 148 households from October-November 2019. Surveys were designed to identify linkages between household demographics, livelihoods, goat ownership, and management practices. Findings revealed goats are highly valued compared to other livestock. However, herds were small (median = 3) with only 62% reported kidding in the last year, while 50% reported deaths due to diseases, predation (such as by hyenas), and dog bites. Odds-ratio analyses identified farmers (as a primary occupation) were more likely to successfully breed goats to increase their herd size. Larger herds were associated with those who could accumulate wealth and utilise goats for ceremonies. However, diseases were a major contributor to losses and increased the risk of household food insecurity. Limiting disease impacts through anthelmintics and supplementation were correlated to an increased likelihood of sustainable offtake from smallholdings and improved livelihoods. With limited access to veterinary services, smallholders utilise a diversity of medicinal plants and ash to treat diarrhoea in their herd. The results highlight that goat security and health is fundamental to realising smallholding livelihood gains. Future efforts should aim to empower smallholders through providing tools to monitor goat health and to assess the effects of local practices, including the use of medicinal plants, for goat health.The Biotechnology and Biological Sciences Research Council,https://www.elsevier.com/locate/smallrumresam2024Veterinary Tropical DiseasesSDG-02:Zero Hunge

Deltaproteobacteria (Pelobacter) and Methanococcoides are responsible for choline-dependent methanogenesis in a coastal saltmarsh sediment

Coastal saltmarsh sediments represent an important source of natural methane emissions, much of which originates from quaternary and methylated amines, such as choline and trimethylamine. In this study, we combine DNA stable isotope probing with high throughput sequencing of 16S rRNA genes and 13C2-choline enriched metagenomes, followed by metagenome data assembly, to identify the key microbes responsible for methanogenesis from choline. Microcosm incubation with 13C2-choline leads to the formation of trimethylamine and subsequent methane production, suggesting that choline-dependent methanogenesis is a two-step process involving trimethylamine as the key intermediate. Amplicon sequencing analysis identifies Deltaproteobacteria of the genera Pelobacter as the major choline utilizers. Methanogenic Archaea of the genera Methanococcoides become enriched in choline-amended microcosms, indicating their role in methane formation from trimethylamine. The binning of metagenomic DNA results in the identification of bins classified as Pelobacter and Methanococcoides. Analyses of these bins reveal that Pelobacter have the genetic potential to degrade choline to trimethylamine using the choline-trimethylamine lyase pathway, whereas Methanococcoides are capable of methanogenesis using the pyrrolysine-containing trimethylamine methyltransferase pathway. Together, our data provide a new insight on the diversity of choline utilizing organisms in coastal sediments and support a syntrophic relationship between Bacteria and Archaea as the dominant route for methanogenesis from choline in this environment

Potential controls of isoprene in the surface ocean

Isoprene surface ocean concentrations and vertical distribution, atmospheric mixing ratios, and calculated sea-to-air fluxes spanning approximately 125° of latitude (80°N–45°S) over the Arctic and Atlantic Oceans are reported. Oceanic isoprene concentrations were associated with a number of concurrently monitored biological variables including chlorophyll a (Chl a), photoprotective pigments, integrated primary production (intPP), and cyanobacterial cell counts, with higher isoprene concentrations relative to all respective variables found at sea surface temperatures greater than 20°C. The correlation between isoprene and the sum of photoprotective carotenoids, which is reported here for the first time, was the most consistent across all cruises. Parameterizations based on linear regression analyses of these relationships perform well for Arctic and Atlantic data, producing a better fit to observations than an existing Chl a-based parameterization. Global extrapolation of isoprene surface water concentrations using satellite-derived Chl a and intPP reproduced general trends in the in situ data and absolute values within a factor of 2 between 60% and 85%, depending on the data set and algorithm used

Biogeochemical consequences of a changing Arctic shelf seafloor ecosystem

Unprecedented and dramatic transformations are occurring in the Arctic in response to climate change, but academic, public, and political discourse has disproportionately focussed on the most visible and direct aspects of change, including sea ice melt, permafrost thaw, the fate of charismatic megafauna, and the expansion of fisheries. Such narratives disregard the importance of less visible and indirect processes and, in particular, miss the substantive contribution of the shelf seafloor in regulating nutrients and sequestering carbon. Here, we summarise the biogeochemical functioning of the Arctic shelf seafloor before considering how climate change and regional adjustments to human activities may alter its biogeochemical and ecological dynamics, including ecosystem function, carbon burial, or nutrient recycling. We highlight the importance of the Arctic benthic system in mitigating climatic and anthropogenic change and, with a focus on the Barents Sea, offer some observations and our perspectives on future management and policy

Connected macroalgal‐sediment systems: blue carbon and food webs in the deep coastal ocean

Macroalgae drive the largest CO2 flux fixed globally by marine macrophytes. Most of the resulting biomass is exported through the coastal ocean as detritus and yet almost no field measurements have verified its potential net sequestration in marine sediments. This gap limits the scope for the inclusion of macroalgae within blue carbon schemes that support ocean carbon sequestration globally, and the understanding of the role their carbon plays within distal food webs. Here, we pursued three lines of evidence (eDNA sequencing, Bayesian Stable Isotope Mixing Modeling, and benthic‐pelagic process measurements) to generate needed, novel data addressing this gap. To this end, a 13‐month study was undertaken at a deep coastal sedimentary site in the English Channel, and the surrounding shoreline of Plymouth, UK. The eDNA sequencing indicated that detritus from most macroalgae in surrounding shores occurs within deep, coastal sediments, with detritus supply reflecting the seasonal ecology of individual species. Bayesian stable isotope mixing modeling [C and N] highlighted its vital role in supporting the deep coastal benthic food web (22–36% of diets), especially when other resources are seasonally low. The magnitude of detritus uptake within the food web and sediments varies seasonally, with an average net sedimentary organic macroalgal carbon sequestration of 8.75 g C·m−2·yr−1. The average net sequestration of particulate organic carbon in sediments is 58.74 g C·m−2·yr−1, the two rates corresponding to 4–5% and 26–37% of those associated with mangroves, salt marshes, and seagrass beds, systems more readily identified as blue carbon habitats. These novel data provide important first estimates that help to contextualize the importance of macroalgal‐sedimentary connectivity for deep coastal food webs, and measured fluxes help constrain its role within global blue carbon that can support policy development. At a time when climate change mitigation is at the foreground of environmental policy development, embracing the full potential of the ocean in supporting climate regulation via CO2 sequestration is a necessity