Browsing by Issue Date, starting with "2025-11"
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- Rhodolith beds in the eastern tropical pacific: habitat structure and associated biodiversityPublication . Diaz-Licona, Celeste A.; Schubert, Nadine; González-Gamboa, Vladimir; Tuya, Fernando; Azofeifa-Solano, Juan Carlos; Fernández-García, CindyRhodolith beds (RBs) are globally distributed marine benthic habitats and recognized biodiversity hotspots of conservation interest. However, considerable regions of the world's oceans remain unknown in terms of the presence, distribution, structure, and associated biodiversity of such habitats. In the Eastern Tropical Pacific (ETP), even basic information about these habitats is still extremely scarce. To fill this gap, we characterized the habitat structure and associated biodiversity of four shallow-water RBs at Cocos Island, Costa Rica. Specifically, information regarding rhodolith structural attributes (size, morphology, and CaCO3 content), as well as habitat characteristics (rhodolith nodule density, biomass and CaCO3 standing stocks) were collected. Moreover, the diversity and abundance of associated organisms, including macroalgae, invertebrates and fishes, were determined. Our study shows that Cocos Island harbors dense RBs (1100 to >4500 nodules m(-2)) with substantial carbonate stocks (14-22 kg m(-2)), which provide habitats for a wide array of species (158 recorded species). This study adds 58 new records of RB-associated species to previously published records for the island, which increases the total number of species to 316, including 51 species endemic to the ETP and four species categorized as vulnerable by the IUCN. Our results also indicate that community composition and abundance of organisms vary among RBs, likely due to differences in rhodolith morphologies and sizes and/or local environmental conditions. Further research efforts are warranted to identify the drivers for these differences, as well as expanding studies towards other RBs at Cocos Island and in the ETP in general.
- Close to sunlight or deep underground? New data to reconstruct site formation processes at the Middle Paleolithic Escoural cave (southern Portugal)Publication . Alzate-Casallas, Guillermo Alfonso; Gomes, Ana; Ferar, Nolan; Talamo, Sahra; Tassoni, Laura; Cascalheira, João; Barbieri, AlviseThe ability to exploit the deeper levels of cave systems is regarded as complex human behavior. Evidence that Neanderthals possessed this skill remains limited. The site of Escoural, in southern Portugal, is worldwide renowned for the Upper Paleolithic rock art that was performed in the lowermost level of the cave. The site also preserved Middle Paleolithic sequences in a deep chamber (P1) as well as in an area that today lies outside of the cave (P2). Due to the lack of geoarchaeological analyses, it is currently impossible to clarify whether these materials reflect systematic Neanderthal visits to these site areas. In this study we integrated geoarchaeological data and radiocarbon dating to (i) reconstruct site formation processes, and (ii) explore the interaction between Neanderthals and carnivores at Escoural. Micromorphological, stratigraphic, and geochronological results demonstrate that colluviation moved sediments and archaeological finds from upper cave chambers into P1. This process likely mixed separate and distinct assemblages, possibly leading to co-occurring high concentrations of carnivore coprolites and lithic artifacts. In contrast, P2 preserves in situ Neanderthal occupations alternating with carnivore visits. Neanderthal foragers used this area when it was a large chamber located close to the original cave entrance, which was subsequently lost due to roof collapses and likely impacted by modern quarrying activities. These findings align with broader Eurasian patterns indicating that Neanderthals primarily used well-lit karstic cavities rather than deep, enclosed spaces. Moreover, this study underscores that post-depositional processes may have profound impacts on our interpretation of Neanderthal and carnivore cave use.
- A glycymeris-rich unit as evidence of a late pleistocene tsunami event from NW algeria: a biostratigraphic, taphonomic, and sedimentological approachPublication . Doukani, Mohamed Amine; Satour, Linda; Ozer, Caner Kaya; Belkebir, Lahcene; Voelker, Antje; Tedjeddine, Hassane; Landau, Bernard; Uchman, Alfred; Bessedik, Mostefa; Johnson, Markes E.; Hipólito, Ana; Madeira, José; Ávila, Sérgio P.Compared to the extensive research carried out on the Neogene deposits of the Lower Chelif Basin, the Pleistocene series is still poorly studied, with no detailed lithological succession published to date. This study focuses on the Glycymeris-rich Unit (GRU) along the coastal area of the Hachacha Plateau in Northwestern Algeria. This unit unconformably overlies Miocene, Pliocene, and Pleistocene basements. The latter was identified for the first time in this work using a biostratigraphic approach based on calcareous nannofossils and planktonic foraminifera. The GRU is interpreted as a tsunami-related deposit, formed in a coastal environment (foreshore/backshore) during the upper Pleistocene, corresponding to the Last Interglacial period, i.e., Marine Isotopic Substage 5e (MIS 5e). This interpretation provides a first multidisciplinary description of a tsunami deposit in Algeria that is supported by distinctive biotic, taphonomic, and sedimentological features. The deposits contain a mixture of marine organisms from different ecological zones (supralittoral to shallow circalittoral biocenoses), including molluscan assemblages such as the so-called Senegalese fauna (bivalves and gastropods), sponges, serpulids, coralline algae and corals. Occasionally, rare terrestrial snails are also found mixed with the marine fauna. Taphonomic analysis reveals low percentages of boring, absence of encrustation, and excellent shell preservation, suggesting that powerful waves eroded sediment masses and transported them inland from deeper areas beneath the taphonomic active zone. The predominance of sharp-edged fragmented shells, chaotic arrangements with oblique to vertical shell orientations and the good shell sorting, indicates transport by mass flows and rapid deposition during an extreme event – a tsunami –, distinguishing these deposits from those associated with gradual and oscillatory flows, such as storm events. Sedimentological characteristics, including irregular erosive base, lateral facies variations, wide grain size ranges (clay to boulders), normal and inverse grading, and diagnostic structures (both fragile and hard-rock rip-up clasts, high-energy flow features such as horizontal and oblique laminations, and hummocky cross-stratification, injection of sediment into the substrate, imbrication of large angular boulders and soft sediment deformation structures), combined with the active tectonic context of Northwestern Algeria support the interpretation as a seismically triggered tsunami and enhances the understanding of this type of deposits in similar coastal settings.
- Assessing neanderthal occupation duration: faunal evidence from sub-unit IIIb of teixoneres cave (Barcelona, Spain)Publication . Lubrano, Valentina; Rufà, Anna; Blasco, Ruth; Rivals, Florent; Rosell, JordiDetermining the duration of occupations at Middle Palaeolithic archaeological sites is essential to enhancing our understanding of Neanderthal behaviour and subsistence strategies. Identifying occupation length in these contexts presents significant complexity and is often ambiguous due to the palimpsest nature of the archaeological sites. This study examines faunal specimens from sub-Unit IIIb of Teixoneres Cave, focusing on both external and internal site areas, to estimate the duration of human occupations. Using zooarchaeological and taphonomic parameters, we evaluate the effectiveness of these methods for inferring occupation length. Our analysis shows that faunal remains—such as evidence of hunting, butchering, and carcass transport—are essential for reconstructing Neanderthal subsistence strategies and for understanding whether the site was used during one short-term occupation or across several distinct episodes over time. While certain results diverge from the features currently used in literature to define occupation duration, the spatial distribution of lithic artefacts, from sub-Unit IIIb at Teixoneres Cave support the hypothesis of short, repeated human occupations. This analysis focuses on applying and critically examining some of those theoretical assumptions, particularly those related to taphonomic and archaeozoological criteria. In this context, Teixoneres Cave serves as the dataset through which we test whether a real archaeological case supports the theoretical framework proposed in Lubrano et al. (2025). These findings contribute to ongoing discussions on the complexities of interpreting archaeological palimpsests and the methodological challenges involved in estimating the duration of Neanderthal occupations. Furthermore, the data place sub-Unit IIIb of Teixoneres within the broader framework of Middle Palaeolithic cave sites characterized by short-term human occupations in settings frequently utilized by large carnivores.
- Combined effects of PVC microplastics and thermal rise alter the oxidative stress response in Antarctic fish Harpagifer antarcticus and Sub-Antarctic Harpagifer bispinisPublication . Nualart, Daniela P.; Paschke, Kurt; Guerreiro, Pedro Miguel; McCormick, Stephen D.; González-Wevar, Claudio; Cheng, Chi-Hing Christina; Chacoff, Luis VargasThis study evaluated the oxidative stress response in two cold-water fish species, the Antarctic Harpagifer antarcticus and the sub-Antarctic H. bispinis, following exposure to single and combined stressors: polyvinyl chloride (PVC) microplastics and thermal increase. Fish were exposed for 24 h to two temperature regimes (2 degrees C and 5 degrees C for H. antarcticus; 8 degrees C and 12 degrees C for H. bispinis) and were orally administered a PVC microplastic solution (200 mg/L). Oxidative stress was assessed through transcriptional and enzymatic activity analyses of key antioxidant markers: catalase, glutathione peroxidase, superoxide dismutase, and glutathione reductase. In H. antarcticus, gill antioxidant gene expression decreased in response to both stressors when applied individually, while H. bispinis exhibited transcriptional upregulation under the same conditions. In H. antarcticus, enzymatic activity in gill tissues increased for all four enzymes following exposure to both microplastics and elevated temperature. In contrast, H. bispinis showed a differential enzymatic response: thermal stress induced CAT activity, whereas exposure to microplastics specifically increased GR activity. At the hepatic level, H. antarcticus displayed increased transcription of antioxidant genes following exposure to both stressors. In H. bispinis, transcriptional upregulation was limited to GR and SOD in response to microplastics. However, under the combined exposure of multiple stressors, an inactivation of the antioxidant enzyme response was observed in the gills. This could indicate a functional collapse of the antioxidant system under conditions of exacerbated acute stress. The observed responses raise concerns about the potential vulnerability of polar and subpolar fishes, considering their ecological importance in trophic networks and the increasing pressure from multiple anthropogenic stressors in a rapidly changing climate.
- Withstanding the heat: resilience of free-living coralline algae to marine heatwavesPublication . Nannini, Matteo; Cerpelloni, Martina; Gaspar, Tainá L.; Peña, Viviana; Tuya, Fernando; Peñas, Julio; Rio, Jesús del; Vieira Mourato, Carolina; Silva, João; Santos, Rui; Ragazzola, Federica; Olivé, Irene; Schubert, NadineMarine heatwaves (MHWs) can severely impact benthic ecosystems, driving major ecological shifts. As they become longer, more frequent, and intense, MHWs are emerging as a dominant threat to marine biodiversity. Yet, their potential effects on coralline algal beds (CABs, including rhodolith beds), habitats of critical ecological importance, remain largely unknown. This study investigated the physiological responses of three rhodolith species (Lithothamnion cf. valens, Lithothamnion sp., Lithophyllum incrustans), which dominate the community of a Mediterranean CAB, to an experimentally simulated ecologically relevant scenario of two consecutive summer MHWs. Species responses in key physiological processes, photosynthesis, respiration, and calcification, were assessed before, during, and after the heatwave events. Overall, temperature increases had minor effects on photosynthesis and respiration, while calcification responses to MHWs were more pronounced and speciesspecific. Significant declines were observed in light calcification of L. incrustans during the first MHW, and in dark calcification of all three species, with L. incrustans and L. cf. valens responding during the first and second MHWs, respectively. Lithothamnion sp. exhibited some minor effects on light calcification and a significant shift toward carbonate dissolution in darkness during the first MHW, which reversed over time. Despite these effects, all species fully recovered by the end of the experiment, and the stronger impact of the first MHW suggests a potential priming effect that may enhance tolerance to subsequent heat events. These findings demonstrate rhodoliths’ overall capacity to withstand MHWs, while highlighting the role of species-specific responses in shaping the net carbonate balance of CABs under future climate scenarios.
- Fortnightly variability of the lateral structure of residual flows along non-rotating estuariesPublication . Khosravi, Maziar; Fortunato, A. B.; Lopez-Ruiz, A.; Valle-Levinson, A.; Garel, ErwanResidual circulation in estuaries plays a crucial role in controlling salt intrusion, material transport, and ecosystem functioning, making its understanding essential for coastal management worldwide. Despite its importance, the mechanisms driving the transverse structure of residual flows remain insufficiently explored, particularly in relation to the fortnightly tidal variability. This study shows how the main driver of residual flow may switch from baroclinic dominance at neap tide to barotropic dominance at spring tide. Three-dimensional, process-oriented numerical simulations are carried out in an idealized, non-rotating, estuary–shelf system, represented by an 80 km-long semi-closed channel with a 1 km-wide Gaussian-shaped cross-section. This setting is inspired by the Guadiana Estuary (Portugal/Spain), where previous observations have reported a switch of the residual circulation between spring tide and neap tide. To mimic such fortnightly pattern, the model is forced by freshwater inflow at the head and M2 and S2 tidal harmonics at the ocean boundary. Harmonic amplitudes were selected based on a sensitivity analysis. The along channel and temporal variability of the lateral structure of axial residual flows is represented using a non-dimensional parameter derived from the residual inflow that may develop in the deep channel. The simulation results show residual flow transverse structures consistent with theoretical expectations for a baroclinic driver in neap tides and a barotropic driver in spring tides, as confirmed by analyses of the residual momentum equation terms. In these cases, the near-bottom residual flow in the channel is relatively strong and its direction indicates the dominant driver. The study also reveals a previously undocumented transverse structure described by inflows near the channel bed and over the shoals. This structure develops in relation to the Stokes drift when baroclinic and barotropic forcings are relatively balanced across a section.
- Little migrants: assessment of stranded loggerhead turtles (Caretta caretta) source populations found in the north-east atlanticPublication . Corona, Luana Santos; Galatoulas, Adam; Nicolau, Lídia; Pereira, Andreia F. T.; Sá, Sara F.; Lopes da Cunha, Regina; Marçalo, Ana; Castilho, RitaMaritime activities affect the migratory routes of marine organisms, including loggerhead turtles (Caretta caretta). The coastal waters of mainland Portugal lie along these routes, providing foraging grounds but lacking nesting beaches, making them ideal for studying turtle migration. This study presents the first assessment of the natal origins of loggerheads in the North-East Atlantic. We analysed the genetic diversity of 127 stranded loggerhead turtles along the Portuguese coast, sequencing the mitochondrial DNA control region (776 bp). Sixteen haplotypes were identified, including a previously unknown one. Mixed-stock analysis revealed that loggerhead turtles stranded in Portuguese mainland coastal waters appear to originate predominantly from the Western Atlantic, with possible contributions from other regions including Cape Verde and the Eastern Mediterranean, though the latter remains uncertain. The primary sources were Florida rookeries, particularly Canaveral National Seashore, Melbourne Beach, Juno Beach, and Ft. Lauderdale. Our findings underscore the role of oceanic circulation patterns in shaping migration routes, as turtles predominantly followed major currents across the Atlantic. The predominance of juveniles among stranded individuals in areas with known high fishing pressure indicates that Portuguese waters may pose significant anthropogenic risks for this life stage. This study highlights the vulnerability of juvenile loggerheads in Portuguese waters and underscores the need for conservation strategies, including bycatch mitigation and fisheries management. Further ecological studies, such as tag tracking, are essential to understanding migratory patterns and improving conservation efforts in this critical migratory corridor.
- Estruturas de combustão identificadas no povoado pré-histórico de Leceia (Oeiras)Publication . Cardoso, João LuisSão inventariadas todas as estruturas de combustão identificadas no povoado pré-histórico de Leceia, distribuídas por vasta cronologia correspondente ao Neolítico Final (ca. 3400-2900 a.C.), ao Calcolítico Inicial (ca. 2800-2500 a.C.) e ao Calcolítico Pleno/Final (ca. 2500-2000 a.C.). O assinalável número de estruturas identificadas, que ascende a vinte e cinco, apesar da semelhança existente entre elas, o que se explica pela similitude de funções, permitiu a identificação de oito variantes, devidamente caracterizadas. Este é o primeiro contributo dedicado ao estudo sistemático das estruturas de combustão existentes em um grande povoado pré-histórico do território português.