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The use of species traits in invasive seaweed research: a systematic review
Get PDFSpecies traits have been used extensively in invasion science, providing common metrics across taxa and ecosystems that enable comparisons based on the functional responses and effects of biota. However, most work on traits in invasion science has focused on terrestrial plants, despite the vulnerability of aquatic ecosystems to invasive species, such as invasive seaweeds. Research that focuses on individual species of invasive seaweeds has intensified in recent years, yet few studies have synthesised the information learned on species traits to identify commonalities or knowledge gaps in invasion science. Through a systematic review of 322 papers that investigate the traits of seaweed species from across the globe, here we ask – what are the trends and gaps in research that investigates traits of invasive seaweeds? To address this question, we aimed to: (1) identify publication rates and characteristics of the studies examining traits of invasive seaweeds; (2) clarify which and how many species have been investigated; and (3) assess which traits have been measured and how those traits have been used. Our review revealed that study regions for research on invasive seaweed traits were concentrated in Europe and North America. In addition, we found a total of 158 species that have been investigated, with a large proportion of studies (35%) focusing on just two species, Sargassum muticum and Undaria pinnatifida. Our study revealed that the most researched traits were morphological, which were used to address a wide range of research questions. Key research gaps included relatively few studies from Africa, Asia and South America, a lack of papers researching more than one species and a lack of measurements of biomechanical traits. Altogether, this review provides a thorough overview of research progress on species traits of invasive seaweeds and highlights the existing knowledge gaps that may lead to new ways in which the traits of invasive seaweeds can be used to answer important ecological question
Essential omega‐3 fatty acids are depleted in sea ice and pelagic algae of the Central Arctic Ocean
Get PDFMicroalgae are the main source of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), essential for the healthy development of most marine and terrestrial fauna including humans. Inverse correlations of algal EPA and DHA proportions (% of total fatty acids) with temperature have led to suggestions of a warming-induced decline in the global production of these biomolecules and an
enhanced importance of high latitude organisms for their provision. The cold Arctic Ocean is a potential hotspot of EPA and DHA production, but consequences of global warming are unknown. Here, we combine a full-seasonal EPA and DHA dataset from the Central Arctic Ocean (CAO), with results from 13 previous field studies and 32 cultured algal strains to examine five potential climate change effects; ice algae loss,
community shifts, increase in light, nutrients, and emperature. The algal EPA and DHA proportions were lower in the ice-covered CAO than in warmer peripheral shelf seas, which indicates that the paradigm of an inverse correlation of EPA and DHA
proportions with temperature may not hold in the Arctic. We found no systematic differences in the summed EPA and DHA proportions of sea ice versus pelagic algae, and in diatoms versus non-diatoms. Overall, the algal EPA and DHA proportions varied up to four-fold seasonally and 10-fold regionally, pointing to strong light and nutrient limitations in the CAO. Where these limitations ease in a warming Arctic, EPA and
DHA proportions are likely to increase alongside increasing primary production, with nutritional benefits for a non-ice-associated food web
Review of algorithms estimating export production from satellite derived properties
Get PDFWhereas the vertical transport of biomass from productive surface waters to the
deep ocean (the biological pump) is a critical component of the global carbon
cycle, its magnitude and variability is poorly understood. Global-scale estimates
of ocean carbon export vary widely, ranging from ∼5 to ∼20 Gt C y – 1 due to
uncertainties in methods and unclear definitions. Satellite-derived properties
such as phytoplankton biomass, sea surface temperature, and light attenuation at
depth provide information about the oceanic ecosystem with unprecedented
coverage and resolution in time and space. These products have been the basis
of an intense effort over several decades to constrain different biogeochemical
production rates and fluxes in the ocean. One critical challenge in this effort has
been to estimate the magnitude of the biological pump from satellite-derived
properties by establishing how much of the primary production is exported out
of the euphotic zone, a flux that is called export production. Here we present a
review of existing algorithms for estimating export production from satellite�derived properties, available in-situ datasets that can be used for testing the
algorithms, and earlier evaluations of the proposed algorithms. The satellite�derived products used in the algorithm evaluation are all based largely on the
Ocean Colour Climate Change Initiative (OC-CCI) products, and carbon
products derived from them. The different resources are combined in a
meta-analysis
Using Probability Density Functions to Evaluate Models (PDFEM, v1.0) to compare a biogeochemical model with satellite-derived chlorophyll
Get PDFGlobal biogeochemical ocean models are invaluable tools to examine how physical, chemical, and biological
processes interact in the ocean. Satellite-derived ocean color properties, on the other hand, provide observations of the surface ocean, with unprecedented coverage and resolution. Advances in our understanding of marine ecosystems and biogeochemistry are strengthened by the combined use of these resources, together with sparse in situ data. Recent modeling advances allow the simulation of the spectral properties of phytoplankton and remote sensing reflectances, bringing model outputs closer to the kind of data that ocean color satellites can provide. However, comparisons between model outputs and analogous satellite products (e.g., chlorophyll a) remain problematic. Most evaluations are based on pointby-point comparisons in space and time, where spuriously large errors can occur from small spatial and temporal mismatches, whereas global statistics provide no information on how well a model resolves processes at regional scales. Here, we employ a unique suite of methodologies, the Probability Density Functions to Evaluate Models (PDFEM), which generate a robust comparison of these resources. The probability density functions of physical and biological properties of Longhurst’s provinces are compared to evaluate how well a model resolves related processes. Differences in the distributions of chlorophyll a concentration (mg m−3) provide information on matches and mismatches between models and observations. In particular, mismatches help isolate regional sources of discrepancy, which can lead to improving both simulations and satellite algorithms. Furthermore,the use of radiative transfer in the model to mimic remotely sensed products facilitates model–observation comparisons of optical properties of the ocean
Airborne observations over the North Atlantic Ocean reveal the importance of gas-phase urea in the atmosphere
Get PDFReduced nitrogen (N) is central to global biogeochemistry, yet there are large uncertainties surrounding its sources and rate of cycling. Here, we present observations of gas-phase urea (CO(NH2)2) in the atmosphere from airborne high-resolution mass spectrometer measurements over the North Atlantic Ocean. We show that urea is ubiquitous in the lower troposphere in the summer, autumn, and winter but was not detected in the spring. The observations suggest that the ocean is the primary emission source, but further studies are required to understand the responsible mechanisms. Urea is also observed aloft due to long-range transport of biomass-burning plumes. These observations alongside global model simulations point to urea being an important, and currently unaccounted for, component of reduced-N to the remote marine atmosphere. Airborne
transfer of urea between nutrient-rich and -poor parts of the ocean can occur readily and could impact ecosystems and oceanic uptake of carbon dioxide, with potentially important climate implications
The 8th International Symposium on Gas Transfer at Water Surfaces - Book of Abstracts
Get PDFThe Gas Transfer at Water Surfaces (GTWS) symposium normally occurs every 5 years and has brought together scientists from countries all over the world. This topic is globally-important. Gas transfer is of great import for quantifying CO2 uptake by the ocean as well as the emission of climate-relevant gases such as DMS and other volatile organic compounds. The focus is the physicochemical and biogeochemical processes that govern atmosphere-water gas exchange and fluxes. These include turbulence, shear, breaking waves, bubbles, and surfactants as well as the biology and chemistry of the microlayer. The conference covered all domains where air and water meet, including freshwater, estuarine, marine (coastal and open ocean) and polar regions, as well as laboratory and numerical studies.
GTWS was due to be held in Plymouth, UK in May 2020. At the last moment, we had to take the difficult decision to postpone the meeting due to the Covid outbreak. This put the local organising committee into a holding pattern, organising for an event ‘at some point’! A year down the line, we hosted a short ‘bitesize’ online event. This was attended by nearly 200 people online, was a great success and gave us confidence that we could run the main event in hybrid mode. A hybrid event would have the dual benefit of facilitating the participation of those unable to travel whilst also enabling those from further afield to reduce their (and the community’s) carbon emissions.
In May 2022, the main event finally took place, which was a great relief to the organising committee! The event was well-attended with nearly 100 participants (approx. 75% in-person, 25% online). Using Plymouth Marine Laboratory’s new technology for hybrid events, and with the help of an external company (Mindfully Wired; https://www.mindfullywired.org/), we hosted the hybrid event and switched effortlessly between the room and online participants during the Q&As. Those in the room and online clearly enjoyed the opportunity to have an open debate again.
We are pleased with the GTWS symposium went, and particularly pleased that it clearly showed that you no longer have to travel to actively participate at a conference and present to the international community.
This publication presents updated versions of abstracts that were submitted for the symposium, as well as links to the recorded talks or slides that were presented during the event itself
Accurate delineation of individual tree crowns in tropical forests from aerial RGB imagery using Mask R‐CNN
Get PDFTropical forests are a major component of the global carbon cycle and home to two-thirds of terrestrial species. Upper-canopy trees store the majority of forest carbon and can be vulnerable to drought events and storms. Monitoring their growth and mortality is essential to understanding forest resilience to climate change, but in the context of forest carbon storage, large trees are underrepresented in traditional field surveys, so estimates are poorly constrained. Aerial photographs provide spectral and textural information to discriminate between tree crowns in diverse, complex tropical canopies, potentially opening the door to landscape monitoring of large trees. Here we describe a new deep convolutional neural network method, Detectree2, which builds on the Mask R-CNN computer vision framework to recognize the irregular edges of individual tree crowns from airborne RGB imagery. We trained and evaluated this model with 3797 manually delineated tree crowns at three sites in Malaysian Borneo and one site in French Guiana. As an example application, we combined the delineations with repeat lidar surveys (taken between 3 and 6 years apart) of the four sites to estimate the growth and mortality of upper-canopy trees. Detectree2 delineated 65 000 upper-canopy trees across 14 km2 of aerial images. The skill of the automatic method in delineating unseen test trees was good (F1 score = 0.64) and for the tallest category of trees was excellent (F1 score = 0.74). As predicted from previous field studies, we found that growth rate declined with tree height and tall trees had higher mortality rates than intermediate-size trees. Our approach demonstrates that deep learning methods can automatically segment trees in widely accessible RGB imagery. This tool (provided as an open-source Python package) has many potential applications in forest ecology and conservation, from estimating carbon stocks to monitoring forest phenology and restoration
Vitamin B12 bioaccumulation in Chlorella vulgaris grown on food waste-derived anaerobic digestate
Get PDFAnaerobic digestion plays a pivotal role in the modern circular economy, as it offers a sustainable solution for converting organic waste into biogas (methane). It also results in a nutrient-rich liquid stream, referred to as digestate. This digestate is extensively applied to agricultural land as fertilizer due to its high macronutrient (N, P) content, but the bioactive micronutrients it contains and their significance for downstream applications remain largely unknown. Here, we investigate whether digestate generated from a vitamin B12-deficient substrate (fruit and vegetable waste) can be enriched in this vitamin through anaerobic digestion, and explore the capability of the microalga Chlorella vulgaris to grow in this medium and bioaccumulate B12. Our findings uncover, for the first time, that substantial amounts of B12 are synthesized during anaerobic digestion, and that C. vulgaris can effectively be enriched with this vitamin when grown in the digestate (10.6 μg Β12·g−1 dry weight). Additionally, we identified that pH-induced ammonia toxicity was the main inhibitor when growing microalgae in the digestate, which allowed us to significantly enhance productivity at lab- and pilot-scale through pH control. The case of B12 synthesis in digestate and accumulation in microalgae highlights the potential for enhancing the value of these waste streams through the identification and utilization of bioactive compounds
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 bloom 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, where diatoms frequently bloom. Unexpectedly, peaks in detection did not occur during characteristic 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, indicative 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
Gene regulatory network that shaped the evolution of larval apical organ in cnidaria
No full textAmong non-bilaterian animals, a larval apical sensory organ with integrated neurons is only found in cnidarians. Within cnidarians, an apical organ with a ciliary tuft is mainly found in Actiniaria. Whether this apical tuft has evolved independently in Actiniaria or alternatively originated in the common ancestor of Cnidaria and Bilateria and was lost in specific groups is uncertain. To test this hypothesis, we generated transcriptomes of the apical domain during the planula stage of four species representing three key groups of cnidarians: Aurelia aurita (Scyphozoa), Nematostella vectensis (Actiniaria), and Acropora millepora and Acropora tenuis (Scleractinia). We showed that the canonical genes implicated in patterning the apical domain of N. vectensis are largely absent in A. aurita. In contrast, the apical domain of the scleractinian planula shares gene expression pattern with N. vectensis. By comparing the larval single-cell transcriptomes, we revealed the apical organ cell type of Scleractinia and confirmed its homology to Actiniaria. However, Fgfa2, a vital regulator of the regionalization of the N. vectensis apical organ, is absent in the scleractinian genome. Likewise, we found that FoxJ1 and 245 genes associated with cilia are exclusively expressed in the N. vectensis apical domain, which is in line with the presence of ciliary apical tuft in Actiniaria and its absence in Scleractinia and Scyphozoa. Our findings suggest that the common ancestor of cnidarians lacked a ciliary apical tuft, and it could have evolved independently in the Actiniari