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Are willows suitable for flood defense? Quantifying mechanical properties of willow species
No full textThe use of temporary willow wetland forests as nature-based flood defense requires reliable predictions of branch resistance to loads, due to either hydrodynamic forces or strong winds, while accounting for variations across Salix species and varieties, growth environments (e.g., local salinity), and shapes (e.g., shrubs vs. trees, natural vs. pollarded). The Salix genus comprises hundreds of species, each exhibiting high intraspecific diversity with numerous subspecies and genotypes. However, to assess their suitability for flood defense, it is crucial to understand their mechanical properties, which have been documented for only a few species and often using differing methodologies. Quantifying and understanding the variation in mechanical properties of willow branches can improve vegetation-wave models and their use in flood risk assessments. We studied 18 Salix species, varieties and hybrids (shrub and tree type, including the most common species of riverine wetland forests), various specimens of one species (S. alba) along a salinity gradient and two growth forms: natural and pollarded. Sampling took place in Belgium and the Netherlands. We conducted 3-point bending tests and quantified absolute and relative flexibility and strength (maximum load and extension, modulus of elasticity (MOE) and modulus of rupture (MOR)). For all species, the thicker the branch, the greater its mechanical strength. Tree type species were more flexible with lower modulus of elasticity and shrub type species stronger with higher modulus of rupture. S. alba was amongst the most flexible species and S. purpurea the strongest. We found a large variability for natural branches and far less variability for pollarded branches. The salinity gradient had no effect on mechanical properties. Our study showed that the type of species and variety as well as pollarding affect the mechanical branch properties. The values of tree mechanics found in this study can be used as input for models, and their application in nature-based flood defense solutions.</span
Impact of chemical treatments on the molecular and stable carbon isotopic composition of sporomorphs
No full textThe stable carbon isotope composition (δ13C) of plants and algae is influenced by environmental factors, such as pCO2, water availability, and altitude. To effectively use the δ13C of fossil material as a proxy for these parameters, it is essential to understand the chemical and isotopic effects of diagenesis and conventional chemical treatments. In this study, we subject various species of pollen and spores of higher plants to different chemical treatments simulating diagenesis and chemical alteration in the environment as well as palynological processing. We analyze changes in the molecular and isotopic composition using pyrolysis–gas chromatography–mass spectrometry (Py-GC-MS) and both elemental analyzer–isotope ratio mass spectrometry (EA-IRMS) and laser ablation–isotope ratio mass spectrometry (LA-IRMS), respectively. We find that saponification removes extractable and ester-bound lipids, which increases the δ13C value of the sporomorphs. Treatment with HF and HCl (HF–HCl) removed most hydrolyzable polysaccharides and proteins, causing a drop in δ13C values. Acetolysis produced aromatic-rich residual sporomorphs with the lowest δ13C values compared to other treatments, likely representing the diagenetically resistant sporopollenin polymer. These findings imply a successional depletion of 13C during fossil maturation, where aliphatic lipids are diagenetically removed in the process, until only the relatively 13C-depleted sporopollenin remains. To adequately compare fossil and extant sporomorph δ13C values, we advise the use of HF–HCl and a lipid removal step other than acetolysis as the palynological treatment, as acetolysis treats the material non-uniformly. Lastly, LA-IRMS shows promise for targeted isotopic analysis of individual specimens of various types of palynomorphs.</span
A chemotaxonomic and phylogenomic re-evaluation of the genus Alicyclobacillus: A proposal for reclassification of about half of the species into the new genus, Paenalicyclobacillus gen. nov., with an emended description of the genus Alicyclobacillus, and recognition that the names Alicyclobacillus tengchongensis and Alicyclobacillus montanus are later heterotypic synonyms of Alicyclobacillus tolerans
No full textThe genus Alicyclobacillus represents a group of mostly acidophilic, meso-thermophilic bacteria, which obtained their name through the biosynthesis of uncommon, alicyclic fatty acids (FAs), i.e., ω-cyclohexyl or ω-cycloheptyl FAs. However, there are also species belonging to this genus that do not possess this trait. In addition, the difference of up to 9 % of the 16S rRNA gene sequences of 33 type strains compared with the first isolated type species, A. acidocaldarius DSM 446T, exceeds the 5.5 % threshold, which is typically used for the demarcation of a genus. This suggested that the taxonomy of the genus required a re-examination. We performed a phylogenomic and chemotaxonomic survey of the genus Alicyclobacillus. Phylogenetic trees based on the 16S rRNA gene and comparison of whole proteomes reconstructed from their genomes reveal that the genus Alicyclobacillus is reflected by two distinct clades; one represented by 14 type strains with a >94.1 % 16S rRNA gene similarity to A. acidocaldarius DSM 446T, and a second clade (composed of 14 type strains including A. cycloheptanicus) with a similarity of 91–94 %. This distinction fits well with their reported ability to produce alicyclic FAs, also revealed by the detection of two putative biosynthetic gene clusters (BGC) encoding their biosynthetic pathway in their genomes. The first BGC is responsible for the production of cyclohexane carboxylic acid-CoA and comprises five genes encoding proteins acting as an adjusted side branch of the shikimate pathway. The putative second BGC, responsible for production of cycloheptane carboxylic acid-CoA, comprises six genes encoding proteins acting as a side branch of the catabolic phenylacetic acid pathway. All Alicyclobacillus species of the first clade produce ω-cyclohexyl FAs and their genomes possess the corresponding BGC. In the second cluster, some species produce ω-cyclohexyl FAs, some produce ω-cycloheptyl FAs, whilst quite some members are not producing any alicyclic FAs. This corresponds to the presence or absence of the two BGCs in their genomes. We propose to reclassify all species of the second clade as members of a new genus, Paenalicyclobacillus gen. nov. and show that both Alicyclobacillus tengchongensis and Alicyclobacillus montanus are later heterotypic synonyms of Alicyclobacillus tolerans.</span
Seabed topography of a deep-water channel and nearby abyssal mount area south of the Azores, Eastern North Atlantic: Evidence of tectonic activity, erosion, and bottom current action
No full textDetailed multibeam bathymetric mapping in combination with 3.5 kHz sub-bottom profiling, seabed video observations, sediment coring and hydrographic (CTD) measurements were performed in a deep-water area south of the Azores, Eastern North Atlantic Ocean. The study site is located immediately north of an UN-designated large marine protection area including the Atlantis-Meteor Seamount Complex. This seamount area represents a deep-sea benthic environment characterized by a vulnerable marine ecosystem with a large, partly unknown, biodiversity. Spatial distribution of deep-sea biodiversity is mainly driven by seabed topography and bottom water conditions, which are the main topics addressed in the present study. The seabed data collected during two cruises with RV’Pelagia’ (Royal NIOZ) provides evidence of significant (retrogressive) erosion patterns and local tectonic activity. A variety of larger and smaller erosional and sedimentary structures and the limited distribution of fine-grained bedded sediments are interpreted to have resulted from a combination of local hydrodynamic processes and tectonic activity. This new seabed information acquired in our study will thus contribute to a better understanding of the role of (near) seabed dynamics and topography in controlling deep-water biodiversity south of the Azores
Marine benthic community assembly Is taxonomically stochastic but functionally deterministic in a dynamic coastal sea
No full textUnderstanding the balance between deterministic and stochastic processes in community assembly is crucial for interpreting ecological community dynamics. Moreover, it provides perspective for conservation and management actions, as deterministic processes can be subject to targeted interventions, but stochastic processes are less manageable. Through a spatially explicit macrozoobenthic monitoring campaign consisting of 1323 sampling locations in the Dutch Wadden Sea, we examined the relative importance of deterministic and stochastic processes, including the role of hydrodynamic disturbance gradients. We found species-based community assembly to be mainly driven by stochastic processes, while trait-based assembly was more deterministic and environmentally driven. Environmental disturbance levels minimally affected the relative importance of stochastic and deterministic processes. For coastal benthic ecosystems, we therefore recommend management actions to target specific desired functional groups rather than specific changes in community composition.</span
The biological soundscape of temperate reefs in the Wadden sea
No full textMonitoring coastal marine habitats presents many challenges. Often, using multiple approaches to capture different aspects of ecosystems can strengthen the information gained regarding habitat status. The use of passive acoustics to document, describe, and monitor coastal habitats through soundscapes presents one such complementary technique. Marine soundscapes have not yet been described for the Wadden Sea; an ecosystem where reef habitats have experienced major changes over time due to various human-mediated impacts. Recordings at a subtidal shellfish reef and neighbouring sandflat at six 2-week periods over a 14 month period in 2021 and 2022 provide a first catalogue of biotic acoustic signatures in this ecosystem. Furthermore, recordings from two natural reef sites were compared to recordings from two recently deployed artificial reef sites, showing similar patterns of greater biotic acoustic diversity at the natural and artificial reefs compared to nearby sandflats. These results demonstrate that fine-scale differences in habitat soundscapes exist across reef habitats within small geographic scales. This study provides the foundations for further quantitative research using PAM to monitor soundscape dynamics of the Wadden Sea and understanding the role of sound in changing coastal ecosystems.</span
Methane leakage from abandoned wells in the Dutch North Sea
No full textMethane is a powerful greenhouse gas and the second most important when considering global warming due to anthropogenic added gasses. Global inventories of greenhouse gasses currently do not take into consideration methane emitted from the ocean and seas. The North Sea is an intensely exploited seas for oil and gas and it was recently suggested to be a major source for manmade methane emissions. All wells drilled through shallow gas (methane) were found to be leaking and one-third of all abandoned wells was found to be drilled through shallow gas. Here we present the results from a research expedition to investigate methane leakage at abandoned wells drilled through shallow gas in the Dutch North Sea. We surveyed 57 abandoned wells of which 33 were drilled through shallow gas. Nine locations showed bubble plumes (acoustic flares). We noted a distinct difference between gas leakage of abandoned wells and locations with natural gas seepage. Whereas well leakage consists of one or two bubble plumes at the wellhead itself and no bubble plumes in the surrounding area, natural plume fields are characterized by tens to hundreds of plumes and none at the wellhead. At six wells, we conclude that the plumes are caused by the well leaking shallow gas, whereas three observed plume fields classify as natural seepage. We found that 18% of wells drilled through shallow gas were leaking, with 11% of all abandoned wells being drilled through shallow gas. When we compensated for over-representation of shallow gas wells in our sample (58% of our sample is drilled through shallow gas), we find that less than 2% of all abandoned wells in the Dutch North Sea is likely leaking. Well leakage seems to occur when large quantities of shallow gas are present and the abandoned well apparently suffers from an integrity issue
Global warming and equatorial Atlantic paleoceanographic changes during early eocene carbon cycle perturbation V
No full textA series of transient global warming events (“hyperthermals”) in the early Eocene is marked by massive environmental and carbon cycle change. Among these events, the impacts of the Paleocene Eocene Thermal Maximum (∼56 Ma), Eocene Thermal Maximum 2 (∼54 Ma) and Eocene Thermal Maximum 3 (∼53 Ma) are relatively well documented. However, much less is known about the many subsequent hyperthermals that apparently occurred on orbital eccentricity maxima until at least the end of the Early Eocene Climatic Optimum (EECO; ∼53–49 Ma). Ocean Drilling Program (ODP) Site 959 (Equatorial Atlantic Ocean), we report a large negative carbon isotope excursion (CIE) in both organic and carbonate substrates that we correlate to the “V” event sensu Lauretano et al. (2016), https://doi.org/10.1127/nos/2016/0077 (or C22nH1 sensu Sexton et al. (2011), https://doi.org/10.1038/nature09826) at ∼49.7 Ma, following combined bio‐ and chemostratigraphic constraints. Through TEX86 paleothermometry, we reconstruct a sea surface temperature rise of 1.3–2.0°C associated with this CIE, which, combined with evidence for warming from the deep sea, implies that this event indeed represents a transient global‐scale warming episode like the earlier hyperthermals. Organic walled dinoflagellate cyst assemblages indicate a productive paleoceanographic background setting, likely through regional upwelling, which alternated with episodes of stratification. Warming reconstructed across V at Site 959 is relatively similar to the higher‐latitude‐derived deep ocean reconstructions. However, the presence of upwelling and its variable intensity across the event compromises the use of the reconstructed warming as an estimate for the complete tropical ba
Temperature-induced changes in the relevance of viral lysis and microzooplankton grazing of Antarctic phytoplankton indicates future alterations in seasonal carbon flow
No full textPhytoplankton play a pivotal role as the primary producers in polar marine ecosystems. Despite evidence suggesting that production rates and loss factors vary from year to year, and thus drive dynamic ecosystem functioning, interannual comparisons remain sparse. In this study, we examined viral lysis and microzooplankton grazing rates on Antarctic phytoplankton during two productive seasons and compared them with published data from a previous year. Higher rates of phytoplankton gross growth and total mortality during the warmer productive season suggest global warming induced increases in the magnitude of ecosystem carbon flow. Viral lysis rates appear to be relatively independent of average seasonal temperatures, whereas grazing rates were lower during the colder productive seasons (average temperature <0°C). This resulted in a greater relative impact of viral lysis on phytoplankton mortality, particularly pronounced during periods of phytoplankton accumulation. The interannual variations in phytoplankton fate are likely due to a stronger coupling between rates of viral infection and phytoplankton growth compared with grazing. Our results emphasize the importance of monitoring rates of viral lysis, specifically in combination with the size and taxonomy of the phytoplankton community. Collectively these factors determine the relative significance of the different carbon fates, and hence the ocean’s efficacy as a carbon sink
Spawning is accompanied by increased thermal performance in blue mussels
No full textClimate change is causing extreme short-term warming with greater intensity and more frequent occurrence. Reproduction and subsequent recruitment of coastal ecosystem engineers, such as the blue mussel, may be impacted by the extreme temperatures because these vital functions are sensitive to the timing of short-term changes in abiotic factors. We exposed intertidal blue mussels, Mytilus edulis, to a thermal challenge from 10 to 29 °C using an ecologically relevant heating rate of 4 °C/h. We assessed their reproductive status by observing spawning activity and by analyzing histological sections of their gonad tissue. In addition, we monitored their heart rates and valve gaping behavior to determine their thermal performance. We identified three spawning groups: non-spawners that had mature gonads but did not release gametes, post-spawners that released mature gametes prior to the thermal challenge, and active spawners that released mature gametes during the thermal challenge. Across temperatures, active spawners had significantly higher heart rates and their heart rate peaked at the temperatures 3.9 and 3.2 °C higher compared to those of non-spawners or post-spawners, respectively. Post-spawners had significantly narrower valve gapes across temperatures compared to both other spawning groups. Hence, the metabolic response to warming strongly depends on the reproductive status, with active spawners experiencing increased thermal stress due to heightened metabolism, non-spawners showing heat-induced metabolic depression, and post-spawners adopting an energy-conserving strategy indicated by reduced gaping. Considered together, spawning during recurring short-term warming events may elevate mortality risk with potential consequences for the local biodiversity in a future climate.</span