1,411 research outputs found

    Bleaching threatens positive carbonate budgets on Bahraini reefs

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    Bleaching events impact coral reef functionality and carbonate budget dynamics, which is reflected in reduced reef framework accretion, hindering reef ability to keep pace with sea-level rise projections. Reefs in the Arabian Gulf exist in harsh environmental conditions with seasonal temperatures ranging between 16 and 36 °C. Despite the high thermal thresholds (~ 35 °C) of corals in this region, extensive bleaching and high coral mortality have been reported regionally in 2017. We quantify reef carbonate budgets at a near shore and an offshore reef site in Bahrain pre-bleaching in May 2017 and post-bleaching in May 2018 to assess the impacts of the 2017 severe bleaching event on the budgetary state. Results indicate an overall decrease in hard coral cover from 14.2 ± 5.5 to 8.5 ± 1.4% and a decline in the net carbonate budget state from 3.6 ± 2.2 to 0.3 ± 0.3 kg CaCO3 m−2 year−1 at the shallow nearshore Fasht Al Adhm reef indicating a shift from a positive budgetary state to net neutral, while the deeper offshore Reef Bul Thamah has increased positively from 3.7 ± 1.2 to 4.2 ± 0.6 kg CaCO3 m−2 year−1. We attribute the decline in the nearshore reef to the bleaching event which took place between July and October 2017, resulting in high coral mortality rates and subsequent reduced framework carbonate production. Predicted warming trends present a threat to the structural integrity of shallow Bahraini reefs, compromising their ability to keep pace with future sea-level rise projections.</jats:p

    Diagenetic and Biological Overprints in Geochemical Signatures of the Gigantoproductus Tertiary Layer (Brachiopoda): Assessing the Paleoclimatic Interpretation

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    Variations in the geochemical signatures of fossil brachiopod shells may be due to diagenesis and/or biological processes (i.e., ‘vital effects’). It is critical to characterise them in order to identify reliable shell areas suitable for paleoclimate studies. This investigation contributes to an in-depth understanding of geochemical variations in Gigantoproductus sp. shells (SW Spain, Serpukhovian age), throwing light onto the Late Paleozoic Ice Age interpretation. Microstructural, crystallographic, cathodoluminescence and geochemical (minor and trace elements, δ18O, δ13C, and strontium isotopes) characterisations have been performed on the tertiary layer of the ventral valve, to assess the preservation state. Poorly preserved areas exhibit microstructural and geochemical changes such as recrystallisation, fracturing and higher Mn and Fe enrichment. Moreover, these areas have a higher dispersion of ⁸⁶Sr, ⁸⁷Sr, δ18O and δ13C than well-preserved areas. Three structural regions have been identified in well-preserved areas of the ventral valve by differences in valve curvature and thickness, such as the umbonal and thick and thin regions. These regions have different proportions of Mg, S, Na, δ18O, and δ13C, which are interpreted as ‘vital effects’ and probably related to growth-rate differences during shell growth. The Gigantoproductus tertiary layer seems the most suitable for paleoclimate studies, because it retains the original microstructure and geochemical composition

    Anthropogenic nitrogen pollution threats and challenges to the health of South Asian coral reefs

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    Nitrogen pollution is a widespread and growing problem in the coastal waters of South Asia yet the ecological impacts on the region’s coral ecosystems are currently poorly known and understood. South Asia hosts just under 7% of global coral reef coverage but has experienced significant and widespread coral loss in recent decades. The extent to which this coral ecosystem decline at the regional scale can be attributed to the multiple threats posed by nitrogen pollution has been largely overlooked in the literature. Here, we assess the evidence for nitrogen pollution impacts on corals in the central Indian Ocean waters of India, Sri Lanka and the Maldives. We find that there is currently limited evidence with which to clearly demonstrate widespread impacts on coral reefs from nitrogen pollution, including from its interactions with other stressors such as seawater warming. However, this does not prove there are no significant impacts, but rather it reflects the paucity of appropriate observations and related understanding of the range of potential impacts of nitrogen pollution at individual, species and ecosystem levels. This situation presents significant research, management and conservation challenges given the wide acceptance that such pollution is problematic. Following from this, we recommend more systematic collection and sharing of robust observations, modelling and experimentation to provide the baseline on which to base prescient pollution control action

    Revisiting the upper Visean mud mounds from Derbyshire (UK): the role of brachiopods in their growth

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    Several brachiopod-rich mud mounds occur in the upper Visean (Brigantian) of the Derbyshire Carbonate Platform succession in UK. The re-evaluation of the lithofacies architecture of a Derbyshire mud mound complex, developed in an intraplatform middle-ramp environment, led to the recognition of three lithofacies associations: (a) a 10 m thick basal unit of automicrite boundstone with siliceous sponge spicules and brachiopod–bryozoan packstone to wackestone beds; (b) a 10 m thick, 250 m wide, lens-shaped, convex-up massive core of clotted peloidal micrite and fenestellid bryozoan boundstone with sponge spicules; (c) inclined brachiopod–bryozoan–crinoid packstone flank beds. In the mud mound complex core, most of the carbonate mud with clotted peloidal and structureless micrite fabric is the result of biologically induced and influenced in-situ precipitation processes (automicrite). Brachiopods are not, as previously thought, limited to storm-scoured “pockets” in the mud mound complex core but are abundant and diverse in all lithofacies and lived on the irregular mud mound complex surface concentrating in depressions sustained by automicrite boundstone and the growth of bryozoans and sponges. The upper Visean Derbyshire mud mounds are, thus, representatives of a newly defined fenestellid bryozoan–brachiopod–siliceous sponge mud mound category, occurring in various middle–upper Visean Western European sites, a sub-type of the fenestellid bryozoan–crinoid–brachiopod Type 3 buildups of Bridges et al. (1995). These mud mounds, and other types of brachiopod-rich buildups, developed in carbonate platform settings between fair-weather and storm wave base, in dysphotic environments with dispersed food resources during the Visean. Brachiopod mud mound colonisation was favoured by moderate water depth, availability of food resources, and diverse substrates

    REKRUITMEN KARANG KERAS DI PULAU TUNDA

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    Perairan Pulau Tunda merupakan salah satu destinasi wisata bahari karena memiliki keindahan pantai dan biota bawah laut khususnya terumbu karang. Upaya mengetahui secara mendalam mengenai kondisi terumbu karang perlu dilakukan pengamatan rekruitmen karang. Rekrutmen terumbu karang adalah proses penambahan individu karang dan menjadi indikasi adanya proses pemulihan alami komunitas karang, sehingga menjadi dasar dalam upaya menjaga kelestarian terumbu karang misalnya seperti konservasi atau pemanfaatan bertanggung jawab. Penelitian ini bertujuan untuk mengetahui rekruitmen terumbu karang di Pulau Tunda. Pengambilan sampel rekruitmen terumbu karang menggunakan metode Belt Transeck. Parameter yang diamati dalam penelitian ini adalah tutupan karang hidup, bentuk pertumbuhan karang, dan kepadatan rekrutmen. Hasil pengamatan persen tutupan karang hidup paling rendah di stasiun 4 yaitu 2,31% dan paling tinggi terdapat di stasiun 2 yaitu 41,23%. Terdapat tujuh jenis bentuk bertumbuhan anakan karang (rekruitmen karang) yaitu Acropora branching, Acropora encrusting, Coral massive, Coral branching, Acropora tabulate, Coral foliose, dan Acropora Submasive. Pengamatan terhadap kepadatan rekruitmen karang menunjukan bahwa kepadatan tertinggi terdapat di stasiun 2 (dua) dengan nilai 0,24 koloni/m2 dan kepadatan terendah terdapat di stasiun 4 (empat) dengan nilai 0,05 koloni/m2. Bentuk pertumbuhan yang dijumpai pada semua stasiun dan memiliki koloni anakan karang paling tinggi adalah bentuk pertumbuhan coral massive.Perairan Pulau Tunda merupakan salah satu destinasi wisata bahari karena memiliki keindahan pantai dan biota bawah laut khususnya terumbu karang. Upaya mengetahui secara mendalam mengenai kondisi terumbu karang perlu dilakukan pengamatan rekruitmen karang. Rekrutmen terumbu karang adalah proses penambahan individu karang dan menjadi indikasi adanya proses pemulihan alami komunitas karang, sehingga menjadi dasar dalam upaya menjaga kelestarian terumbu karang misalnya seperti konservasi atau pemanfaatan bertanggung jawab. Penelitian ini bertujuan untuk mengetahui rekruitmen terumbu karang di Pulau Tunda. Pengambilan sampel rekruitmen terumbu karang menggunakan metode Belt Transeck. Parameter yang diamati dalam penelitian ini adalah tutupan karang hidup, bentuk pertumbuhan karang, dan kepadatan rekrutmen. Hasil pengamatan persen tutupan karang hidup paling rendah di stasiun 4 yaitu 2,31% dan paling tinggi terdapat di stasiun 2 yaitu 41,23%. Terdapat tujuh jenis bentuk bertumbuhan anakan karang (rekruitmen karang) yaitu Acropora branching, Acropora encrusting, Coral massive, Coral branching, Acropora tabulate, Coral foliose, dan Acropora Submasive. Pengamatan terhadap kepadatan rekruitmen karang menunjukan bahwa kepadatan tertinggi terdapat di stasiun 2 (dua) dengan nilai 0,24 koloni/m2 dan kepadatan terendah terdapat di stasiun 4 (empat) dengan nilai 0,05 koloni/m2. Bentuk pertumbuhan yang dijumpai pada semua stasiun dan memiliki koloni anakan karang paling tinggi adalah bentuk pertumbuhan coral massive

    Computation as a Planetary Scale Phenomenon

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    The concept of the ‘technosphere’ was advanced in the field of Earth Systems Science to capture technology as a geological phenomenon in the Anthropocene. What precisely, I ask, drives the technosphere to be so novel and unprecedented a planetary force? Part of the answer, I venture, lies in the nature of computation as a generative force that drives the expansion of the technosphere. To build an account of computation as a generative force of a planetary scale, I engage with and parse through various debates regarding its historical and ontological predispositions. To address computation in its full potential, I argue, is to attend to its creative, albeit imperfect, encounters with the physical world in shifting registers of space and time, which ultimately lends to its epistemological capacity to imagine and facilitate infrastructures that constitute the technosphere

    The Hambergfjellet Formation on Bjørnøya – sedimentary response to early Permian tectonics on the Stappen High

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    On Bjørnøya, the exhumed crest of the Stappen High, the lower Permian (Cisuralian) Hambergfjellet Formation represents the only exposed part of the Bjarmeland Group carbonate platform, which occurs widely elsewhere in the subsurface of the Barents Shelf. A complex stratigraphic architecture has earlier been noted for the Hambergfjellet Formation and thickness estimates range from c. 50 to more than 100 m. Moreover, the unit lacks a formal type section, which hampers accurate regional correlations and comparisons. In this stratigraphic study, we integrate new field observations and microfacies analysis with data from previous work to present a composite section which is proposed as the type section for the Hambergfjellet Formation. Four internal units are recognized. Units A and B (post ?late Asselian–?Sakmarian), which consist of mixed carbonate and siliciclastic rocks interpreted to be of shallow marine origin, are restricted to a series of fault-bounded basins defined by gently rotated basement fault blocks. Locally, units A and B onlap or truncate lowermost Permian strata and appear to transgressively fill in antecedent topography presumably created during Sakmarian uplift and erosion of the Stappen High. The distorted character of unit A suggests that slumping was an important process during the initial phase of infilling, amid or soon after transgression. Unit C (?Sakmarian–?early Artinskian) is a thick-bedded, sheet-like limestone unit which contains fauna elements consistent with deposition on a warm-water carbonate platform occasionally subject to subaerial exposure. Unit D (late Artinskian) is a brachiopod-dominated, fusulinid-bearing, bioclastic limestone unit deposited on a fully marine, transitional warm-temperate to cool-water carbonate platform which developed during a late Artinskian circum-Arctic transgression. The unit only occurs in the eastern part of the outcrop belt on southern Bjørnøya due to fault-controlled tilting and peneplanation prior to deposition of the Miseryfjellet Formation (Kungurian–Wordian) limestones. Distinct evidence, including breccia pipes, points to prolonged exposure and karstification of the Hambergfjellet Formation carbonate platform prior to transgression and submergence of the Stappen High in the middle to late Permian (Guadalupian). The presence of angular and highly diachronous unconformities at the base and top of the formation, a series of small grabens, internal dip variations, as well as a conspicuous north to north-eastward thinning manifest tectonism pre-dating the late Permian extensional event along the western Barents Shelf margin. As such, we shed a new light on the Permian tectonostratigraphic evolution of the Stappen High

    ISTRAŽIVANJE UTJECAJA VAĐENJA MORSKOG PIJESKA U VODAMA OTOKA TUNDA U INDONEZIJI NA TEMELJU MODELIRANJA MIKE 21

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    In Indonesia, sea sand mining was introduced in the late 1970s, and one of the sites is Banten Province, Indonesia. Sea sand mining in Banten waters began in 2003 after the issuance of a permit by the Regent of Serang Regency, namely Decree No. 540/Kep.68/Huk/2003, which was updated by the Regional Regulation of Serang Regency No. 2 of 2013 on the Zoning Plan for Coastal and Small Island Areas in Serang Regency for 2013-2033. Studies related to marine sand mining in Banten, Indonesia are required in accordance with the principle of ecosystem sustainability. The objective of this study is to analyze the impact of sea sand mining on the ecological quality of coral reefs and hydro-oceanographic hue on Tunda Island. The survey method was used to determine the coral reef cover, while the hydrodynamic aspects were carried out by simulating bathymetric data, tidal and wave patterns. In addition, a simulation of sediment distribution was performed to determine the effects of sea sand mining using MIKE 12 sand transport module. The percentage of coral cover in the west, east and south of Tunda Island was 66.00%, 39.67% and 28.15%, respectively. The maximum sea depth around the study site reached 70 m, while it is relatively shallow in the mining area. In the last 14 years, the prevailing wave height ranged from 0.5-0.75 m or 49.02%, and 0.25-0.50 m or 36.69%. In addition, the concentration of TSS was relatively high, ranging from 40 mg/l to 60 mg/l. From the results, the most commonly observed impact of sea sand mining off Tunda Island was the high concentration of TSS. This can be prevented by rotating TSHD vessels, especially in the areas adjacent to Tunda Island.U Indoneziji je vađenje morskog pijeska uvedeno kasnih 1970-ih, a jedna od za to važnih lokacija je provincija Banten, Indonezija. Vađenje morskog pijeska u vodama Bantena započelo je 2003. godine nakon što je uprava u Serangu izdala dozvolu, točnije Odlukom br. 540/Kep.68/Huk/2003 koja je ažurirana Regionalnom uredbom Seranga br. 2 iz 2013. godine o Planu prostornog uređenja za obalna i mala otočna područja u pokrajini Serang za 2013.-2033. Istraživanja povezana s aktivnostima vađenja morskog pijeska u Bantenu u Indoneziji potrebna su u skladu s načelom održivosti ekosustava. Ova studija ima za cilj analizirati utjecaj vađenja morskog pijeska na ekologiju koraljnog grebena i hidrooceanografiju otoka Tunda. Napravljena je identifikacija pokrova koraljnog grebena, dok su hidrodinamički aspekti provedeni simulacijom batimetrijskih podataka, uzoraka plime i valova. Osim toga, provedena je simulacija distribucije sedimenta kako bi se odredio utjecaj eksploatacije morskog pijeska korištenjem modula za transport pijeska MIKE 21. Postotak koraljnog pokrivača na zapadu, istoku i jugu otoka Tunda bio je 66,00%, 39,67%, odnosno 28,15%. Najveća dubina mora oko lokacije istraživanja dosegla je 70 m, dok je u području vađenja pijeska ona relativno plitka. U posljednjih 14 godina dominantna visina valova kretala se od 0,5-0,75 m ili 49,02% i 0,25-0,50 m ili 36,69%. Nadalje, koncentracija TSS bila je relativno visoka s vrijednošću od 40 mg/l do 60 mg/l. Na temelju rezultata, najveći identificirani utjecaj vađenja morskog pijeska na otoku Tunda bila je visoka koncentracija TSS-a. To se može spriječiti rotiranjem plovila TSHD, posebno u područjima uz otok Tunda
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