Letteratura scientifica selezionata sul tema "Soft-tissue marine biological pump"

Much of the global cooling during ice ages arose from changes in ocean carbon storage that lowered atmospheric CO2. A slew of mechanisms, both physical and biological, have been proposed as key drivers of these changes. Here we discuss the current understanding of these mechanisms with a focus on how they altered the theoretically defined soft-tissue and biological disequilibrium carbon storage at the peak of the last ice age. Observations and models indicate a role for Antarctic sea ice through its influence on ocean circulation patterns, but other mechanisms, including changes in biological processes, must have been important as well, and may have been coordinated through links with global air temperature. Further research is required to better quantify the contributions of the various mechanisms, and there remains great potential to use the Last Glacial Maximum and the ensuing global warming as natural experiments from which to learn about climate-driven changes in the marine ecosystem.

Abstract. In comparison to other sectors of the marine system, the palaeoceanography of the subarctic North Pacific Ocean is poorly constrained. New diatom isotope records of δ13C, δ18O, δ30Si (δ13Cdiatom, δ18Odiatom, δ30Sidiatom), are presented alongside existing geochemical and isotope records to document changes in photic zone conditions, including nutrient supply and the efficiency of the soft-tissue biological pump, between Marine Isotope Stage (MIS) 4 and MIS 5e. Peaks in opal productivity in MIS 5b/c and MIS 5e are both associated with the breakdown of the regional halocline stratification and increased nutrient supply to the photic zone. Whereas the MIS 5e peak is associated with low rates of nutrient utilisation, the MIS 5b/c peak is associated with significantly higher rates of nutrient utilisation. Both peaks, together with other smaller increases in productivity in MIS 4 and 5a culminate with a~significant increase in freshwater input which strengthens/re-establishes the halocline and limits further upwelling of sub-surface waters to the photic zone. Whilst δ30Sidiatom and previously published records of diatom δ15N (δ15Ndiatom) (Brunelle et al., 2007, 2010) show similar trends until the latter half of MIS 5a, the records become anti-correlated after this juncture and into MIS 4, suggesting a possible change in photic zone state such as may occur with a shift to iron or silicon limitation.

Abstract. In comparison to other sectors of the marine system, the palaeoceanography of the subarctic North Pacific Ocean is poorly constrained. New diatom isotope records of δ13C, δ18O, δ30Si (δ13Cdiatom, δ18Odiatom, and δ30Sidiatom) are presented alongside existing geochemical and isotope records to document changes in photic zone conditions, including nutrient supply and the efficiency of the soft-tissue biological pump, between Marine Isotope Stage (MIS) 4 and MIS 5e. Peaks in opal productivity in MIS 5b/c and MIS 5e are both associated with the breakdown of the regional halocline stratification and increased nutrient supply to the photic zone. Whereas the MIS 5e peak is associated with low rates of nutrient utilisation, the MIS 5b/c peak is associated with significantly higher rates of nutrient utilisation. Both peaks, together with other smaller increases in productivity in MIS 4 and 5a, culminate with a significant increase in freshwater input which strengthens/re-establishes the halocline and limits further upwelling of sub-surface waters to the photic zone. Whilst δ30Sidiatom and previously published records of diatom δ15N (δ15Ndiatom) (Brunelle et al., 2007, 2010) show similar trends until the latter half of MIS 5a, the records become anti-correlated after this juncture and into MIS 4, suggesting a possible change in photic zone state such as may occur with a shift to iron or silicon limitation.

Abstract. The canonical question of which physical, chemical or biological mechanisms were responsible for oceanic uptake of atmospheric CO2 during the last glacial is yet unanswered. Insight from paleo-proxies has led to a multitude of hypotheses but none so far have been convincingly supported in three dimensional numerical modelling experiments. The processes that influence the CO2 uptake and export production are inter-related and too complex to solve conceptually while complex numerical models are time consuming and expensive to run which severely limits the combinations of mechanisms that can be explored. Instead, an intermediate inverse box model approach of the soft tissue pump is used here in which the whole parameter space is explored. The glacial circulation and biological production states are derived from these using proxies of glacial export production and the need to draw down CO2 into the ocean. We find that circulation patterns which explain glacial observations include reduced Antarctic Bottom Water formation and high latitude upwelling and mixing of deep water and to a lesser extent reduced equatorial upwelling. The proposed mechanism of CO2 uptake by an increase of eddies in the Southern Ocean, leading to a reduced residual circulation, is not supported. Regarding biological mechanisms, an increase in the nutrient utilization in either the equatorial regions or the northern polar latitudes can reduce atmospheric CO2 and satisfy proxies of glacial export production. Consistent with previous studies, CO2 is drawn down more easily through increased productivity in the Antarctic region than the sub-Antarctic, but that violates observations of lower export production there. The glacial states are more sensitive to changes in the circulation and less sensitive to changes in nutrient utilization rates than the interglacial states.

The curiosity and attention that researchers have devoted to alkaloids are due to their bioactivities, structural diversity, and intriguing chemistry. Marine-derived macrocyclic alkaloids (MDMAs) are considered to be a potential source of drugs. Trabectedin, a tetrahydroisoquinoline derivative, has been approved for the treatment of metastatic soft tissue sarcoma and ovarian cancers. MDMAs displayed potent activities that enabled them to be used as anticancer, anti-invasion, antimalarial, antiplasmodial, and antimicrobial. This review presents the reported chemical structures, biological activities, and structure–activity relationships of macrocyclic alkaloids from marine organisms that have been published since their discovery until May 2020. This includes 204 compounds that are categorized under eight subclasses: pyrroles, quinolines, bis-quinolizidines, bis-1-oxaquinolizidines, 3-alkylpiperidines, manzamines, 3-alkyl pyridinium salts, and motuporamines.

Bioprospecting of the marine environment for drug development has gained much attention in recent years owing to its massive chemical and biological diversity. Drugs for the treatment of skin and soft tissue infections have become part of the search, mainly with respect to enlarging the number of available antibiotics, with a special focus on multidrug-resistant Gram-positive bacteria, being the major causative agents in this field. Marine resources offer novel natural products with distinct biological activities of pharmaceutical importance, having the chance to provide new chemical scaffolds and new modes of action. New studies advance the field by proposing new strategies derived from an ecosystemic understanding for preventive activities against biofilms and new compounds suitable as disinfectants, which sustain the natural flora of the skin. Still, the development of new compounds is often stuck at the discovery level, as marine biotechnology also needs to overcome technological bottlenecks in drug development. This review summarizes its potential and shows these bottlenecks and new approaches.

Soft-tissue fossils are among the most striking and informative remains of extinct organisms. Although relatively rare, they are diverse, ranging from single microbial cells to nuclei and chromosomes; algae; metazoan embryos and larvae; flowers; complete, small, soft-bodied metazoans, metazoan tissues; integumentary structures such as melanosomes; skin texture, vertebrate feathers and hair, insect wings with color patterns, and sometimes even the entire bodies of large animals. The susceptibility of newly dead soft tissues to physical destruction, consumption, and microbial decay makes their preservation unlikely under most taphonomic conditions. In addition, their vulnerability to rapid autolysis, bioturbation, and destructive physical processes requires that rapid biological events must occur as the critical first steps of fossilization. An understanding of the processes by which biological remains enter the fossil record is important in inferring what non-microbial and microbial processes were operative in Lagerstätten. Paleontologists have recognized that microbial biofilms often accompany soft-tissue fossils, and have suggested that bacteria play an active role in soft tissue fossilization, but that role must be determined experimentally with living bacteria and dead tissue.Marine embryos and marine bacteria are used to investigate the processes that mediate early steps in soft-tissue preservation because they offer simple systems for laboratory investigation of the roles of autolysis-blocking environments, microbial interactions, biofilm formation, and authigenic mineralization in taphonomy. Understanding microbially mediated preservation of embryos may supply new insights into a more general biology of fossilization.

The prevailing hypothesis for lower atmospheric carbon dioxide (CO2) concentrations during glacial periods is an increased efficiency of the ocean’s biological pump. However, tests of this and other hypotheses have been hampered by the difficulty to accurately quantify ocean carbon components. Here, we use an observationally constrained earth system model to precisely quantify these components and the role that different processes play in simulated glacial-interglacial CO2 variations. We find that air-sea disequilibrium greatly amplifies the effects of cooler temperatures and iron fertilization on glacial ocean carbon storage even as the efficiency of the soft-tissue biological pump decreases. These two processes, which have previously been regarded as minor, explain most of our simulated glacial CO2 drawdown, while ocean circulation and sea ice extent, hitherto considered dominant, emerge as relatively small contributors.

Foods are complex systems due to their biological origin. Biological materials are soft matter hierarchically structured on all scales from molecules to tissues. The structure reflects the biological constraints of the organism and the function of the tissue. The structural properties influence the texture and hence the mouthfeel of foods prepared from the tissue, and the presence of flavour compounds is similarly determined by biological function. Cephalopods, such as squid, cuttlefish, and octopuses, are notoriously known for having challenging texture due to their muscles being muscular hydrostats with highly cross-linked collagen. Similar with other marine animals such as fish and crustaceans, cephalopods are rich in certain compounds such as free amino acids and free 5′-ribonucleotides that together elicit umami taste. Scientific investigations of culinary applications of cephalopods as foods must therefore involve mechanical studies (texture analysis), physicochemical measurements of thermodynamic properties (protein denaturation), as well as chemical analysis (taste and aroma compounds). The combination of such basic science investigations of food as a soft material along with an exploration of the gastronomic potential has been termed gastrophysics. In this review paper, we reviewed available gastrophysical studies of cephalopod structure, texture, and taste both as raw, soft material and in certain preparations.

The inherent self-repair abilities of the body often fall short when it comes to addressing injuries in soft tissues like skin, nerves, and cartilage. Tissue engineering and regenerative medicine have concentrated their research efforts on creating natural biomaterials to overcome this intrinsic healing limitation. This comprehensive review delves into the advancement of such biomaterials using substances and components sourced from marine origins. These marine-derived materials offer a sustainable alternative to traditional mammal-derived sources, harnessing their advantageous biological traits including sustainability, scalability, reduced zoonotic disease risks, and fewer religious restrictions. The use of diverse engineering methodologies, ranging from nanoparticle engineering and decellularization to 3D bioprinting and electrospinning, has been employed to fabricate scaffolds based on marine biomaterials. Additionally, this review assesses the most promising aspects in this field while acknowledging existing constraints and outlining necessary future steps for advancement.

La pompe biologique de l’Océan Austral (PBOA) constitue un élément fondamental d’un réseau trophique extrêmement sensible et en pleine mutation. Elle représente aussi un moyen très efficace pour séquestrer le CO2 anthropique et a joué un rôle majeur sur l’évolution des concentrations en CO2 atmosphérique au cours des derniers cycles climatiques. Malgré cette importance, l’évolution future de la PBOA reste encore incertaine au vu des divergences entre les différentes simulations pour le prochain siècle. Ceci s'explique principalement par le manque de données disponibles avant la période instrumentale, qui ne couvre que les dernières décennies autour de l'Antarctique, ainsi que par l'absence d'études dans le passé portant sur les communautés phytoplanctoniques dépourvues de test (non fossilisables). Il apparaît donc nécessaire d’étudier les archives climatiques du passé pour mieux comprendre l’évolution de la PBOA et sa relation avec les conditions océaniques, atmosphériques et du couvert de glace au cours des derniers millénaires. Les séquences d’ADN ancien (sedaDNA) couplées aux résultats de biomarqueurs lipidiques mettent en perspective pour la première fois la répartition et l’évolution des communautés phytoplanctoniques au regard des conditions environnementales dans la région de la Péninsule Antarctique au cours de l’Holocène. Les organismes phytoplanctoniques dépourvus de test identifiés sont principalement associés aux divisions des Stramenopiles, Cryptophytes et Chlorophytes avec des différences temporelles et régionales. Du début à la moitié de l’Holocène (8000 à 4000 ans BP), les conditions étaient globalement plus chaudes conduisant à des zones océaniques ouvertes où la production primaire était dominée par les diatomées (85-95% de la proportion totale des phytoplanctons), avec une proportion relativement importante de Cryptophytes parmi les organismes mous (~50%). Au cours des 4000 dernières années BP, les conditions océaniques ont montré un refroidissement et un allongement de la saison de banquise. La productivité primaire a augmenté, essentiellement par une plus forte productivité siliceuse avec des abondances en diatomées dépassant 95% de la proportion phytoplanctonique totale, et donc une plus faible contribution en phytoplancton mou mais qui étaient néanmoins plus diversifiés avec une apparition des Chlorophytes en plus des Cryptophytes. Enfin, l’étude du dernier millénaire a permis de caractériser en détail le passage des conditions naturelles vers un environnement modifié par les changements climatiques actuels. Les derniers 1000 ans BP étaient relativement froids avec de fortes conditions de glace de mer. La productivité primaire a décliné, accompagnée par une réduction de la contribution des diatomées et une augmentation de la contribution des organismes mous à l’exportation de carbone dans les sédiments. Enfin, depuis 1850 CE (période post-industrielle), le réchauffement des températures de subsurface (de 0.3 ± 0.6 °C) et la diminution de la couverture de glace de mer hivernale a entraîné une forte augmentation de la proportion des Cryptophytes (+10%) au détriment de celle des diatomées. Dans ce contexte, la composition des communautés phytoplanctoniques a déjà commencé à changer et tendent à ressembler à celles observées durant l'Holocène moyen. Si cette tendance se poursuit, les diatomées pourraient être progressivement remplacées par des organismes à tissus mous, moins efficaces pour exporter le carbone organique vers les sédiments, ce qui réduirait donc la capacité de séquestration à long terme du CO2 atmosphérique de la PBOA de la Péninsule Antarctique
The biological pump of the Southern Ocean (BPSO) is a key component of a highly sensitive and rapidly changing food web. It also serves as an efficient mechanism for sequestering anthropogenic CO₂. Over past climate cycles, it has played a critical role in regulating atmospheric CO₂ concentrations. Despite its importance, the future of the BPSO remains uncertain, given the discrepancies between various projections for the coming century. This uncertainty largely stems from the limited data available beyond the instrumental record, which for the Antarctic region only spans the last few decades and the lack of previous studies on soft-tissue phytoplankton communities (non-fossilizable) in past environmental contexts. It is therefore essential to study past climate archives to better understand the evolution of the BPSO and its relationship with oceanic, atmospheric, and sea-ice conditions over the past millennia. For the first time, ancient sedimentary DNA (sedaDNA) sequences combined with lipid biomarker data offer insight into the distribution and evolution of phytoplankton communities in relation to environmental conditions in the Antarctic Peninsula (AP) region during the Holocene. The soft-tissue phytoplankton identified primarily belong to the divisions Stramenopiles, Cryptophytes, and Chlorophytes, with regional and temporal variations. From the early to mid-Holocene (8,000 to 4,000 years BP), conditions were generally warmer, leading to open ocean zones where primary production was dominated by diatoms (85-95% of the total phytoplankton), with a significant proportion of Cryptophytes (~50%) among the soft-bodied organisms. Over the past 4,000 years BP, ocean conditions showed cooling and an extension of the sea-ice season. Primary productivity increased, primarily driven by higher siliceous productivity, with diatom abundances exceeding 95% of total phytoplankton, while the contribution of soft-tissue phytoplankton decreased but became more diverse with the emergence of Chlorophytes alongside Cryptophytes. The study of the last millennium revealed a transition from natural conditions to an environment altered by current climate changes. The last 1,000 years BP were relatively cold, often associated with strong sea-ice conditions. Primary productivity declined, accompanied by a reduction in diatom contributions and an increase in soft-tissue organisms' role in carbon export to sediments. Finally, since 1850 CE (the post-industrial period), warming sea subsurface temperatures (by 0.3 ± 0.6°C) and reduced winter sea-ice cover have led to a sharp increase in the proportion of Cryptophytes (+10%) at the expense of diatoms. In this context, phytoplankton community compositions have already begun to change and now resemble those observed during the mid-Holocene. If this trend continues, diatoms could be progressively replaced by soft-tissue organisms, which are less efficient at exporting organic carbon to sediments, thereby reducing the long-term CO₂ sequestration capacity of the BPSO in the Antarctic Peninsula region

A widely accepted definition of marine pollution is “the introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities including fishing, impairment of the quality for use of seawater, and reduction of amenities”. (Wells et al. 2002). This differs from contamination since it results in biological damage, whether to the natural or human system, whereas contamination can be regarded merely as the introduction of substances by human activities (McLusky and Elliott 2004). Furthermore, pollution and pollutants can refer to biological and physical materials as well as chemicals (Gray 1992, Elliott 2003). In the case of the benthos, there is an extensive literature indicating that every type of pollutant has an effect on the benthos and so it is not surprising that the benthos is the mainstay of any monitoring and investigative programme. Pollution can affect organisms living in sediments by physical variables associated with the pollution source, such as increased sedimentation of particles, which leads to smothering of the fauna. In such cases the effect can in fact be regarded as a disturbing factor if the effects lead to mortality of individuals (Gray 1992). Alternatively, pollution can affect the fauna by toxicity where increased concentrations of contaminants lead to biochemical and physiological effects and ensuing mortality if certain thresholds for adaptation are exceeded. Here, however, we first treat the effects of the most widespread form of pollution affecting the marine environment— increased organic matter in sediments. Excess organic matter enters the marine environment principally as sewage, although it can also include waste from paper pulp mills or changed river run-off, for example. Excess organic matter causes physical effects such as smothering and also leads to reduced oxygen concentrations in the water column or pore-water in sediments. Sewage discharged into confined bodies of water frequently leads to the well-known symptoms termed eutrophication, resulting, in the most extreme cases, in a total lack of oxygen and the presence of hydrogen sulfide in the sediment, with a corresponding absence of fauna (e.g. de Jonge and Elliott 2001).