Pollen transport to deep-marine environments: Considerations for reconstructing past vegetation from marine sediment cores

Deep-marine sedimentary records provide a unique opportunity to investigate long-term vegetation changes in response to climate through pollen analysis. In contrast to pollen records from terrestrial sites which capture a local vegetation signature, deep-marine records typically capture a regional vegetation signature, with pollen often taking long and complex transport pathways before depositing on the seafloor. To use deep-marine pollen records to their full potential, we need to understand how pollen is reaching deep-marine sites and whether different transport processes (i.e. ocean currents or gravity flows) impact or bias the final palaeovegetation record. We compare three deep-marine pollen records from offshore eastern Aotearoa-New Zealand from different depths, proximities from land and sedimentary settings to understand whether these different factors influence the final palaeovegetation records. We focus on the glacial-interglacial transitions from Marine Isotope Stages 6-5 and 2-1, and present a new 135 ka pollen record from the turbidite-dominated sediment core IODP-U1520D. We find that pollen assemblages in the three cores show consistent changes over glacial-interglacial cycles, with pollen assemblages showing greater similarities in interglacial periods and varying during glacial periods. The general consistency in pollen assemblages is surprising given the vastly different nature of the three sediment cores and shows that deep-marine records, including fine-grained turbidite-dominated records from active margins, can yield reliable palaeovegetation records

Exploring the environmental distribution of the oyster parasite Haplosporidium costale

The protozoan parasite Haplosporidium costale is known to occur in the USA where it has been associated with sharp seasonal mortality of the Eastern oyster Crassostrea virginica since the 1960’s. In 2019, the parasite was detected for the first time in the Pacific oyster Magallana gigas in France in the context of light mortality and was subsequently detected in archived material collected since 2008. This detection raised several questions regarding the ability of the parasite to maintain in the ecosystem and the potential involvement of other species in its life cycle. To answer these questions, an integrated sampling approach was deployed seasonally in three oyster farming areas where the parasite was already known to occur. Parasite presence was evaluated after checking the presence of PCR inhibitors and using a previously developed and validated Real Time PCR assay, optimized in this study to detect parasite DNA in various environmental compartments. Parasite DNA was almost only detected in cupped oysters. Considering the high number of oysters found positive with low infection intensity, a complementary experiment was undertaken to better characterize sub-clinical infections in oysters. The presence of the parasite was tested twice a week in water and sediment from aquaria hosting cupped oysters from a known infected site. After one month, oysters were sacrificed and tested regarding the presence of the parasite at the tissular level. Altogether, field and experimental results indicate that the parasite is stably established in oyster, particularly in gills, which may act as a reservoir all along the year. The detection of parasite DNA in nanoplankton and sediment suggests that H. costale is released from the oysters outside mortality event. Our results do not support the involvement of other species than cupped oyster in the parasite life cycle except periwinkles, whose role would deserve to be further investigate

Welfare Indicators for Aquaculture Research: Toolboxes for Five Farmed European Fish Species

Refining approaches to measuring, monitoring and appraising animal welfare in aquaculture research is key to (i) protecting and optimizing it, (ii) documenting the severity of how and when it deviates, and (iii) ensuring good scientific quality, reliable results and reproducibility, amongst other factors. However, different fish species and life stages can have varying welfare needs and assessing their welfare can be challenging. An array of welfare indicators (WIs) can be utilized when documenting fish welfare, and there is currently little consensus on which WIs are most applicable to the key fish species used in European aquaculture research. The aim of this review is to propose updated, fit for purpose and comprehensive WI toolboxes for aquaculture research involving Atlantic salmon ( Salmo salar ), rainbow trout ( Oncorhynchus mykiss ), European seabass ( Dicentrarchus labrax ), gilthead seabream ( Sparus aurata ), and the common carp ( Cyprinus carpio ). Where possible, these toolboxes will also include life‐stage considerations. It also provides information on utilizing WIs in deciding humane end‐points as well as information on how to sample different types of indicators. The review closes with information on how digitalization can affect the collection, collation and analysis of WI data in aquaculture research, including both practical and theoretical considerations. The toolboxes incorporate a range of WIs that go beyond those required for legally safeguarding fish welfare in both laboratory and operational experimental facilities in the current European 2010/63/EU Directive on the protection of animals used for scientific purposes and its amendment, the Commission Delegated Directive (EU) 2024/1262

Benchmarking the Taxonomic Resolution of Fish eDNA Metabarcodes Against COI Barcodes

Even though environmental DNA metabarcoding is revolutionizing biomonitoring, many critical steps remain unstandardized, leading to arbitrary choices, particularly regarding the selection of metabarcode, clustering method and similarity threshold, among others. Additionally, these studies were hindered by biases resulting from the presence of mislabeled sequences in international databases such as GenBank and the lack of explicit definitions for taxonomic resolution. To address these issues, we developed a robust framework to compare the performance of 22 metabarcodes derived from the same mitogenomes (all available for Actinopterygians in NCBI) against a standardized taxonomic baseline based on COI Barcode Index Numbers (BINs). This framework allows for the separate quantification of over‐splitting (splitting the same taxon/BIN) and over‐merging (merging different taxon/BIN). Comparison of OTUs obtained with multiple de novo clustering methods to BINs confirmed the metabarcode ranking based on error sums. Although each metabarcode exhibited varying sensitivities to over‐merging or over‐splitting errors, the clustering threshold emerged as the most important factor influencing biodiversity estimates whatever the clustering method. This led us to propose optimal thresholds for each metabarcode to delineate taxonomic levels (metabarcode gaps). Additionally, we found that taxonomic resolution varied significantly among genes, orders and community diversity, but independently of metabarcode length. Overall, the choice of metabarcode and clustering threshold should aim to minimize over‐merging or over‐splitting while ensuring accurate lower taxonomic delineations. A set of documented R functions makes this evaluation of taxonomic resolution easily applicable to any other taxonomic group for which a representative set of full genes or mitogenomes is available

Sentinel-1 Wave Mode Sar Monitoring of Icebergs Around the Antarctica

The high-quality global wave mode synthetic aperture radar (SAR) vignettes routinely collected by Sentinel-1 is today extensively exploited for various oceanic and atmospheric phenomena. Yet, these observations still remain largely untapped for iceberg monitoring in the Southern Ocean. As a follow-up to our previous work (Wang et al., 2019b), a dedicated SAR image classifier is built to detect small-sized icebergs (<5 km) that are commonly underrepresented in current recording systems. It has been fine-tuned from the Inception-v3 deep convolutional neural network using a curated dataset of 2,062 iceberg and 15,338 non-iceberg cases. Independent evaluations, based on three additional datasets, achieve high precision and recall rates above 90%. Applied to all WV images acquired between 2016 and 2018 unveils iceberg occurrences around Antarctica. About ~7.5% of the detected icebergs drift into 40°S to 50°S latitudes, while the majority are concentrated poleward of 55°S. The seasonal patterns of SAR icebergs are generally consistent with altimeter-detection estimates, and exhibit advances over the sea ice regions. Linking these SAR icebergs to the reported large icebergs reveals that small icebergs are more likely located to the east of large iceberg trajectories, suggesting the primary driver of underlying ocean currents to their drift. Although precise identification of the shape and position of these small icebergs remains challenging, WV SAR vignettes provide added values to iceberg investigations at scales beyond current operational reports. Not only relevant for the precise monitoring of icebergs across a wider range of sizes, it can become instrumental for our understanding of iceberg tracking, associated dissolution, along with freshwater transport, and their broader impact on global and local climate processes

Seismogenic and rheological behaviours from time-dependent analysis of earthquake depth distribution in the Corinth Rift

Understanding earthquake depth distribution is critical for improving seismogenesis models. While the spatiotemporal pattern of earthquakes is well studied, transient changes in depth distribution remain poorly explored. In this study, we investigate how crustal rheological parameters influence the depth of earthquakes through time, focusing on the Corinth rift, a well-monitored region experiencing a high-level seismic activity in a homogeneous extensional stress field. To calculate crustal yield strength profiles, we compile geophysical and geological data, including heat flow, rock compositions and properties, Moho depth and strain rate. These estimates are then compared to a high-quality 11-year seismic catalogue of the region. An inversion approach is applied to identify crustal layers associated with persistent versus sporadic seismicity defined here instead of the conventional background versus clustered seismicity. Our time analysis reveals that the persistent seismicity nicely matches the theoretical brittle–ductile transition and allows us to confidently define the seismogenic thickness, while sporadic seismicity is clustered at depths associated with swarm occurrences. Both distributions are subject to kilometer-scale changes after magnitude 4.0 – 5.5 earthquakes, evidencing a relaxation process even after moderate magnitude events. We conclude that in specific case studies aiming to compare depth distribution and yield strength in the crust, the application of declustering methods may not be optimal for examining the potential rheological controls on earthquake depth distribution and their temporal variations. Instead, the analysis of persistent and sporadic seismicity defined in this study is more accurate and reliable than a declustering approach and offers new and valuable insights for this comparison

Domoic acid production by a Pseudo-nitzschia australis strain under zinc and copper exposure

The diatom species Pseudo-nitzschia australis can produce domoic acid (DA), a neurotoxin- responsible for amnesic shellfish poisoning. Copper (Cu) and zinc (Zn) are essential trace metals for marine phytoplankton, but they can become either limiting or toxic at pico- to subnanomolar ionic concentrations—levels that are can be reached in coastal ecosystems. The effect of exposure to these metals on DA production remains unclear for Cu and is largely unknown for Zn. In this study, we investigated the effects of toxic picomolar concentrations of Cu²⁺ and four non-limiting concentrations of Zn²⁺ on the metabolism and physiology of a toxic P. australis strain isolated from the coastal waters of North Biscay (France). Using principal component analysis, we observed changes in cell populations over time depending on metal exposure. Cu²⁺ toxicity was marked by a 35% decrease in maximum cell density and a reduction in growth rate (µ₊Cu = 0.55 µₐₓ). DA production was differentially modulated by the two metals: toxic Cu²⁺ levels stimulated DA synthesis (+200%), while elevated Zn²⁺ bioavailability significantly decreased it (by up to –85%), including when Zn²⁺ was combined with toxic levels of Cu²⁺ (–65%). We further discuss DA production by P. australis as a potential protective mechanism against oxidative stress. Additional data on intracellular glutathione (GSH) quotas—an important reactive oxygen species (ROS) scavenger and Cu²⁺ chelator— are presented and linked to Zn2+ bioavailability. GSH cell quotas were significantly correlated with DA production (p < 0.05) further supporting existing links between metal exposition, oxydative stress and DA production. This study suggests that ambient concentrations of Cu²⁺ and Zn²⁺ are critical factors regulating DA production in coastal marine systems

Characterisation of the eddy-driven variability inshore of the Agulhas Current using Sea Surface Temperature observations

Off the east coast of South Africa, coastal waters inshore of the Agulhas Current are largely affected by oceanic mesoscale turbulence, primarily in the form of meanders such as Natal Pulses and Durban Eddies. This study utilises forty years of modern, high-resolution satellite sea surface temperature (SST) data, offering both improved spatial detail and a longer time series than previous products, to characterise these eddies using an automated meander detection algorithm. Notably, automated detection has never before been applied to Durban Eddies, and Natal Pulses have not been analysed using such a high-resolution, long-term SST dataset. The algorithm successfully estimated the daily position of the inshore edge and core of the Agulhas Current and the “first occurrence” of Agulhas waters for the period of the study —the latter defined as the initial emergence of Agulhas Current waters in a filament or plume associated with Natal Pulses. The analysis reveals that the inshore edge of the Agulhas Current is not subject to seasonal variation but is significantly influenced by the presence of Natal Pulses and Durban Eddies. The first occurrence of Agulhas Current waters was only detected during the passage of Natal Pulses. Results indicate increased variability in regions south of 29.8°S, with Natal Pulses showing an increase in size and surface lifespan in the southern region. Conversely, Durban Eddies exhibit a decrease in size and surface lifespan as they propagate southward. Furthermore, seasonal SST anomalies are generally small, with cold events more frequent; Natal Pulses cause higher variability, while Durban Eddies maintain relative stability

The Overlooked Threat of Global Warming on Elasmobranch Fertility

Climate change is increasingly recognised as a critical threat to global biodiversity, yet its impacts on reproductive processes remain poorly understood in many marine taxa. Elasmobranchs (sharks, skates and rays) represent a particularly vulnerable group due to their peculiar life histories, low fecundity, and diverse reproductive modes. In this review, we synthesise current knowledge on how rising ocean temperatures may affect elasmobranch fertility across key stages of the reproductive cycle, including gametogenesis, mate searching, sperm storage, fertilisation, embryonic development, and offspring production. Evidence from 88 species suggests that thermal stress could impair sperm and oocyte quality, disrupt reproductive timing, alter embryonic growth and survival, and potentially exacerbate sexual conflict. While some reproductive strategies such as embryonic diapause, sperm storage, or behavioural thermoregulation may provide short‐term buffering capacity, their effectiveness under rapid and sustained warming remains uncertain. We further highlight the macroevolutionary significance of elasmobranch reproductive diversity, as well as the conservation implications of fertility constraints under global change. Addressing these knowledge gaps is essential to refining demographic models, improving extinction risk assessments, and guiding the design of climate‐resilient management strategies, including fisheries regulations and marine protected areas. By explicitly linking reproductive biology with conservation policy, we argue that understanding thermal fertility limits is key to predicting elasmobranch population trajectories in a warming ocean

Environmental consequences of genetic improvement of growth and fillet yield in gilthead seabream: A life cycle assessment from breeding to plate

Selective breeding plays a key role in the sustainable development of aquaculture by improving productivity and efficiency. While breeding programs have initially focused on growth traits, their potential to mitigate the environmental footprint of fish farming remains underexplored. Here, we present a case-study on the long-term environmental consequences of selective breeding during five generations (15 years) for growth and fillet yield in gilthead sea bream Sparus aurata by integrating genetic gain projections into a full supply chain Life Cycle Assessment (LCA), extending from hatchery to final consumer. The potential impacts were calculated in terms of 1 t of fish produced at the farm level and were also expressed per tonne of flesh consumed. Performance data and genetic parameters from families in a seabream breeding program were used to estimate breeding values and under different scenarios. Selection for growth significantly shortened the production cycle, while selection for fillet yield increased the proportion of edible product. Although environmental gains at the farm level were modest (<1 %), substantial reductions (up to 7 % in climate change impacts and cumulative energy demand) were observed when impacts were expressed per kilogram of fillet consumed. Feed production remained the dominant source of environmental burden across all scenarios. By explicitly accounting for post-farm stages - processing, distribution, consumption, and waste management -our study demonstrates that genetic improvement, particularly for fillet yield, can meaningfully reduce the environmental footprint of aquaculture products delivered to the consumer. This case study underlines the importance of integrating full supply chain assessments into genetic selection strategies to drive sustainable innovation in aquaculture