86 research outputs found


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    Net biologically produced organic matter integrated over an annual cycle in the euphotic zone of the global ocean is equal to annual net community production (ANCP). ANCP is limited by the rate of delivery of essential nutrients (nitrogen (N), phosphorus (P), and iron (Fe)) to the sunlit surface ocean and the efficiency with which these nutrients are either metabolized or returned to the ocean’s interior. In subtropical oceans, which are regions of large-scale downwelling and consequently characteristic of nutrient-depleted surface waters, ANCP remains comparable to more nutrient replete ecosystems (~2 – 5 mol C m-2 yr-1). To understand what may fuel this productivity, analyses of dissolved organic matter (DOM) within the upper 500 meters of the subtropical North Pacific gyre were performed. Observed meridional gradients suggest the consumption of dissolved organic phosphorus (DOP) and bioavailable dissolved organic nitrogen (bDON) may contribute bioavailable P and N on the order of 8.8 ± 2.2 mmol P m-2 y-1 and 14.3 ± 3.7 mmol N m-2 y-1 along the northward transit of waters from the southern edge towards the gyre core. Additionally, bioassay incubation experiments were performed within two vertically distinct layers of the euphotic zone to quantify the magnitude and rate of heterotrophic DOP remineralization in surface waters (5 m) and the deep chlorophyll maximum (DCM) (125 m) at two stations in the subtropical North Pacific; Station ALOHA (22.75°N) and 31°N along a transect on 158°W, north of Oahu, HI. Evidence for a measurable pool of labile DOP present in surface waters on the order of 25 – 60 nM was found to be consumed in ~5 days near the southern edge of the gyre at Station ALOHA. This consumption was ~1/3 of the latitudinal gradient in surface waters to 31°N, the core of the gyre. Additionally, a new method was deployed to estimate the fraction of the bulk dissolved organic nitrogen (DON) pool composed of bioavailable DON (bDON). A similar meridional gradient in surface ocean bDON was observed on the order of 230 nM N across the gyre, with a DON pool that was comprised of ~13.3 ± 3.5% bDON. The meridional gradients observed in the size of the surface ocean labile DOP and DON pools found in this study largely affirms the importance of upper-ocean lateral organic nutrient transport on supplying North Pacific subtropical gyre surface waters with bioavailable phosphorus and nitrogen and provides important observational data to validate existing models of marine organic nutrient cycling

    The days when owls had fallen from the sky

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    Artistas: Cesar Baio, Clarissa Daneluz, Eduardo Montelli, Flavya Mutran, Juliana Angeli, Joana Burd, Leo Caobelli, Letícia Bertagna, Lívia Auler, Michel Zózimo, Raquel Stol

    Photoautotrophic Euendoliths and their complex ecological effects in marine bioengineered ecosystems

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    Photoautotrophic euendolithic microorganisms are ubiquitous where there are calcium carbonate substrates to bore into and sufficient light to sustain photosynthesis. The most diverse and abundant modern euendolithic communities can be found in the marine environment. Euendoliths, as microorganisms infesting inanimate substrates, were first thought to be ecologically irrelevant. Over the past three decades, numerous studies have subsequently shown that euendoliths can colonize living marine calcifying organisms, such as coral skeletons and bivalve shells, causing both sub-lethal and lethal damage. Moreover, under suitable environmental conditions, their presence can have surprising benefits for the host. Thus, infestation by photoautotrophic euendoliths has significant consequences for calcifying organisms that are of particular importance in the case of ecosystems underpinned by calcifying ecosystem engineers. In this review, we address the nature and diversity of marine euendoliths, as revealed recently through genetic techniques, their bioerosive mechanisms, how environmental conditions influence their incidence in marine ecosystems and their potential as bioindicators, how they affect live calcifiers, and the potential future of euendolithic infestation in the context of global climate change and ocean acidificationinfo:eu-repo/semantics/publishedVersio

    SEASCRAPER: Reclaiming the Plastic Vortex Through Oceanic Stewardship and Inhabitation

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    Decades of humans carelessly tampering with the delicate ocean ecosystems are pushing wildlife to their breaking points, with an entire ecosystem collapse inching closer every day. My thesis will explore the known extent of plastic debris currently in the North Pacific Ocean; the successes and shortcomings of a variety of existing aquatic architectural precedents; finally, culminating in a theoretical prototype design for a semi-autonomous, ocean-based recycling facility. How can an ocean-based architecture be used to develop a successful intervention to the millions of tons of plastic debris that are dumped into the oceans each year? This research will investigate the requirements of planning and building a self-sustaining, water-based recycling structure, but also offer a deeper understanding of how to overcome the challenges of building in such a harsh environment. Using a range of interdisciplinary books, scientific journals and articles, websites and documents, an exploration will be conducted to achieve a full understanding of the requirements of the design. The design of the vessel itself is informed by factoring both the environmental issues of extended exposure in a harsh environment and the performance requirements of its primary objective. Since this vessel will be isolated from most human communities it must also be capable of functioning autonomously for extended periods of time. The results of the design explorations will be represented through a series of written texts, architectural drawings, and diagrams. The key impacts of my research will be not only to provide a possible solution to the growing waste plastic problem, but also to provide a prototype for the development of future ocean-based arcologies

    A future for seafood point-of-origin testing using DNA and stable isotope signatures

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    Demand for seafood products is increasing worldwide, contributing to ever more complex supply chains and posing challenges to trace their origin and guarantee legal, well-managed, sustainable sources from confirmed locations. While DNA-based methods have proven to be reliable in verifying seafood authenticity at the species level, the verification of geographic origin remains inherently more complex. Both genetic and stable isotope analyses have been employed for determining point-of-origin with varying degrees of success, highlighting that their application can be effective when the right tool is selected for a given application. Developing an a priori prediction of their discrimination power for different applications can help avoid the financial cost of developing inappropriate reference datasets. Here, we reviewed the application of both techniques to seafood point-of-origin for 63 commercial finfish species certified by the Marine Stewardship Council, and showed that, even for those species where baseline data exist, real applications are scarce. To fill these gaps, we synthesised current knowledge on biological and biogeochemical mechanisms that underpin spatial variations in genetic and isotopic signatures. We describe which species’ biological and distribution traits are most helpful in predicting effectiveness of each tool. Building on this, we applied a mechanistic approach to predicting the potential for successful validation of origin to three case study fisheries, using combined genetic and isotopic methodologies to distinguish individuals from certified versus non-certified regions. Beyond ecolabelling applications, the framework we describe could be reproduced by governments and industries to select the most cost-effective techniques

    Juvenile Greenland halibut (Reinhardtius hippoglossoides) growth in the context of rising temperature in the Estuary and Gulf of St. Lawrence

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    In a context of climate change, understanding the influence of temperature on fish species growth is important for the management of fisheries. The effect of increasing temperature on the growth of juvenile Greenland halibut (Reinhardtius hippoglossoides), a cold-water species, circum-continental in the Arctic, was investigated on juveniles that had been captured in the wild and kept in captivity. Mortality rate increased with higher temperature, from 4.5 % at 4.0 °C to 15.2 % at 7.5 °C. Relative growth (normalized in degree-days) was lower at 7.5 °C than at the two other temperatures tested. Food conversion efficiency, muscle energy content, and the Fulton condition index were not influenced by temperature, but food intake significantly increased over time at 5.5 °C. No clear difference in growth trajectories between sexes was highlighted. Overall, the results suggest that optimal temperature conditions were exceeded at 7.5 °C and that any further increase in temperature would significantly decrease survival and impair juvenile growth. With the current deep-water warming trends in the Estuary and Gulf of St. Lawrence, recruitment and commercial fishing of Greenland halibut may be impaired in the near future. -- Keywords : Greenland Halibut ; Growth ; Temperature ; Juveniles ; Fisheries ; Mortality

    Dépendance spectrale de la photosynthèse du phytoplancton : processus de photorégulation et de photoacclimatation en mer côtières

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    La photorégulation et la photoacclimatation du phytoplancton sont contrôlées par les variations du climat lumineux (c'est-à-dire la quantité et la qualité de la lumière) à différentes échelles temporelles et spatiales. Dans les zones côtières telles que la Manche, le climat lumineux est affecté par l'hydrodynamisme et les apports fluviaux. D'une part, le fort hydrodynamisme conduit à des processus de resuspension et à un intense mélange vertical, transportant les cellules à travers la couche euphotique et au-delà, dans la couche disphotique. D'autre part, les débits importants des rivières génèrent une augmentation de la turbidité avec les matières en suspension et avec la matière organique dissoute dans le carbone (CDOM). Tous ces processus induisent une diminution de la pénétration de la lumière dans la colonne d'eau et une modification générale du climat lumineux. Par exemple, le CDOM absorbe mieux les longueurs d'onde du bleu.Les processus de dépendance spectrale du phytoplancton tels que la photoregulation et la photoacclimation ont été étudiés pour la première fois sur des communautés naturelles grâce à un fluorimètre multispectral de nouvelle génération appelé MULTI-COLOR-PAM (Walz). Les relations photosynthèses-énergie (PE) ont été mesurées après une longue période d’acclimatation au noir à 5 longueurs d’onde, ainsi que le coefficient d’absorption fonctionnel de la lumière des photosystèmes II (Sigma(II)λ). Le développement d'un protocole original d'analyse de données combinant les techniques de Modèles linéaires à effets mixtes (LME), l'analyse triadique principale (PTA) et les analyses de redondance (RDA) a permis d'analyser un ensemble de données unique et complexe ainsi que de mettre en évidence la dépendance aux longueurs d'onde des processus photosynthétiques à différentes échelles spatiales et temporelles.Phytoplankton photoregulation and photoacclimation are controlled by variations in the light climate (i.e. quantity and quality of light) at different temporal and spatial scales. In coastal and megatidal seas such as the English Channel, the underwater light climate is also affected by the hydrodynamics and river outputs. In one hand, the strong hydrodynamism leads to resuspension processes and to intense vertical mixing, transporting cells through the euphotic layer and beyond, in the disphotic layer. In another hand, large river outputs generate an increase of turbidity with particulate matter and with carbon dissolved organic matter (CDOM). All these processes induce a decrease of light penetration in the water column and a general modification of the light climate. For instance, the CDOM absorbs better blue wavelengths.The wavelength dependent processes of phytoplankton such as photoregulation and photoacclimation have been studied for the first time on natural communities thanks to a new generation of multi-spectral fluorometer called MULTI-COLOR-PAM PAM (Walz). Photosynthesis light curves (P-E) were measured after long dark acclimation at 5 wavelengths, as well as the functional light absorption coefficient of photosystem II (Sigma(II)λ). Furthermore, the development of an original protocol of data analysis including Linear Mixed Effects Models (LME), Principal Triadic Analyses (PTA) and Redundancy Analyses (RDA) have helped the interpretation of this unique dataset and have highlighted the wavelength dependency of photosynthetic processes at different spatial and temporal scales
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