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Occurrence and diffusive air-seawater exchanges of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in Fildes Bay, King George Island, Antarctica
Get PDFWe report the levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in seawater and air, and the air-sea dynamics through diffusive exchange analysis in Fildes Bay, King George Island, Antarctica, between November 2019 and January 30, 2020. Hexachlorobenzene (HCB) was the most abundant compound in both air and seawater with concentrations around 39 ± 2.1 pg m−3 and 3.2 ± 2.4 pg L−1 respectively. The most abundant PCB congener was PCB 11, with a mean of 3.16 ± 3.7 pg m−3 in air and 2.0 ± 1.1 pg L−1 in seawater. The fugacity gradient estimated for the OCP compounds indicate a predominance of net atmospheric deposition for HCB, α-HCH, γ-HCH, 4,4′-DDT, 4,4′-DDE and close to equilibrium for the PeCB compound. The observed deposition of some OCs may be driven by high biodegradation rates and/or settling fluxes decreasing the concentration of these compounds in surface waters, which is supported by the capacity of microbial consortium to degrade some of these compounds. The estimated fugacity gradients for PCBs showed differences between congeners, with net volatilization predominating for PCB-9, a trend close to equilibrium for PCB congeners 11, 28, 52, 101, 118, 138, and 153, and deposition for PCB 180. Snow amplification may play an important role for less hydrophobic PCBs, with volatilization predominating after snow/glacier melting. As hydrophobicity increases, the biological pump decreases the concentration of PCBs in seawater, reversing the fugacity gradient to atmospheric deposition. This study highlights the potential impacts of climate change, through glacier retreat, on the biogeochemistry of POPs, remobilizing those compounds previously trapped within the cryosphere which in turn will transform the Antarctic cryosphere into a secondary source of the more volatile POPs in coastal areas, influenced by snow and ice melting
Subcellular proteomics for determining iron-limited remodeling of plastids in the model diatom Thalassiosira pseudonana (Bacillariophyta)
Get PDFDiatoms are important primary producers in the world\u27s oceans, yet their growth is constrained in large regions by low bioavailable iron (Fe). Low-Fe stress-induced limitation of primary production is due to requirements for Fe in components of essential metabolic pathways including photosynthesis and other chloroplast plastid functions. Studies have shown that under low-Fe stress, diatoms alter plastid-specific processes, including components of electron transport. These physiological changes suggest changes of protein content and in protein abundances within the diatom plastid. While in silico predictions provide putative information on plastid-localized proteins, knowledge of diatom plastid proteins remains limited in comparison to well-studied model photosynthetic organisms. To address this, we employed shotgun proteomics to investigate the proteome of subcellular plastid-enriched fractions from Thalassiosira pseudonana to gain a better understanding of how the plastid proteome is remodeled in response to Fe limitation. Using mass spectrometry-based peptide identification and quantification, we analyzed T. pseudonana grown under Fe-replete and -limiting conditions. Through these analyses, we inferred the relative quantities of each protein, revealing that Fe limitation regulates major metabolic pathways in the plastid, including the Calvin cycle. Additionally, we observed changes in the expression of light-harvesting proteins. In silico localization predictions of proteins identified in this plastid-enriched proteome allowed for an in-depth comparison of theoretical versus observed plastid-localization, providing evidence for the potential of additional protein import pathways into the diatom plastid
Interactions of bioactive trace metals in shipboard Southern Ocean incubation experiments
Get PDFIn the Southern Ocean, it is well-known that iron (Fe) limits phytoplankton growth. Yet, other trace metals can also affect phytoplankton physiology. This study investigated feedbacks between phytoplankton growth and dissolved Fe, manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and cadmium (Cd) concentrations in Southern Ocean shipboard incubations. Three experiments were conducted in September–October 2016 near the West Antarctic Peninsula: Incubations 1 and 3 offshore in the Antarctic Circumpolar Current, and Incubation 2 inshore in Bransfield Strait. Additions of Fe and/or vitamin B12 to inshore and offshore waters were employed and allowed assessment of metal (M) uptake relative to soluble reactive phosphorus (P) across a wide range of initial conditions. Offshore, treatments of \u3e1 nmol L−1 added Fe were Fe-replete, whereas inshore waters were already Fe-replete. Results suggest Mn was a secondary limiting nutrient inshore and offshore. No Fe-vitamin B12 colimitation was observed. Overall, M:P uptake in the incubations was closely related to initial dissolved M:P for Fe, Mn, Co, Ni, and Cd, and for Cu inshore. Final concentrations of Fe and Zn were similar across light treatments of the experiments despite very different phytoplankton responses, and we observed evidence for Co/Cd/Zn substitution and for recycling of biogenic metals as inventories plateaued. In dark bottles, the absence of Mn oxidation may have allowed more efficient recycling of Fe and other trace metals. Our results provide insight into factors governing trace metal uptake, with implications for phytoplankton community composition locally and preformed micronutrient bioavailability in Southern Ocean water masses
Oligotrophic waters of the Northwest Atlantic support taxonomically diverse diatom communities that are distinct from coastal waters
No full textDiatoms are important components of the marine food web and one of the most species-rich groups of phytoplankton. The diversity and composition of diatoms in eutrophic nearshore habitats have been well documented due to the outsized influence of diatoms on coastal ecosystem functioning. In contrast, patterns of both diatom diversity and community composition in offshore oligotrophic regions where diatom biomass is low have been poorly resolved. To compare the diatom diversity and community composition in oligotrophic and eutrophic waters, diatom communities were sampled along a 1,250 km transect from the oligotrophic Sargasso Sea to the coastal waters of the northeast US shelf. Diatom community composition was determined by amplifying and sequencing the 18S rDNA V4 region. Of the 301 amplicon sequence variants (ASVs) identified along the transect, the majority (70%) were sampled exclusively from oligotrophic waters of the Gulf Stream and Sargasso Sea and included the genera Bacteriastrum, Haslea, Hemiaulus, Pseudo-nitzschia, and Nitzschia. Diatom ASV richness did not vary along the transect, indicating that the oligotrophic Sargasso Sea and Gulf Stream are occupied by a diverse diatom community. Although ASV richness was similar between oligotrophic and coastal waters, diatom community composition in these regions differed significantly and was correlated with temperature and phosphate, two environmental variables known to influence diatom metabolism and geographic distribution. In sum, oligotrophic waters of the western North Atlantic harbor diverse diatom assemblages that are distinct from coastal regions, and these open ocean diatoms warrant additional study, as they may play critical roles in oligotrophic ecosystems
What Difference Does it Make? Early Reception Stories about Luce Irigaray\u27s Writing on Divine Women
Get PDFThis paper examines numerous pre-texts in Anglo-American feminist theology and critical theory seminal to the establishment of feminist philosophy of religion as a distinct academic discipline. Specifically, I trace early reception of philosopher Luce Irigaray’s writing on becoming divine women in Anglo-American feminist circles, arguing that critical attention to the “horizons of expectations” around Irigaray’s person is a necessary step to the myriad readings of her work. I begin by situating my own initial expectations and encounters with Irigaray’s writing on divine women as a graduate student in theological studies cross-registered in a course on ‘French Feminism’ in the neighboring Romance Language Department. I then offer a unique reading of Irigaray’s reception surrounding her early writing on divinity, highlighting ways that Anglo-American theologians and feminist philosophers leveraged Irigaray’s contested status as a French Feminist and philosopher of religion as a way to simultaneously interrogate Irigaray’s claims about the divine as well as mollify generalized Anglo-American anxiety around writing grounded in post-structuralist Lacanian theory. I draw attention to the prevalence of Luce Irigaray’s thought in the 1993 co-edited volume Transfigurations: Theology and the French Feminists, the special issue “Feminist Philosophy of Religion\u27\u27 in Hypatia (1994), and in the field-defining books of two pioneers of the discipline: Pamela Sue Anderson and Grace Jantzen. I conclude with reflections about reception of Irigaray’s writing on the divine with regards to her more recent publications
Usage Statistics: Project COUNTER R5 pr_p1 Report FY2023 - Platform Usage
No full textProject COUNTER R5 Report PR_P1 for the University of Rhode Island for the period from July 1, 2022 - June 30, 2023. The PR_P1 report is defined as Platform Usage. This report presents an annual total only and only includes those platforms successfully configured for automated harvesting via SUSHI.
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Searches Platform - 308,061
Total Item Requests - 1,150,640
Unique Item Requests - 851,822
Unique Title Requests - 47,73
Levels of persistent organic pollutants (POPs) in the Antarctic atmosphere over time (1980 to 2021) and estimation of their atmospheric half-lives
Get PDFPersistent organic pollutants (POPs) are synthetic compounds that were intentionally produced in large quantities and have been distributed in the global environment, originating a threat due to their persistence, bioaccumulative potential, and toxicity. POPs reach the Antarctic continent through long-range atmospheric transport (LRAT). In these areas, low temperatures play a significant role in the environmental fate of POPs, retaining them for a long time due to cold trapping by diffusion and wet deposition, acting as a net sink for many POPs. However, in the current context of climate change, the remobilization of POPs that were trapped in water, ice, and soil for decades is happening. Therefore, continuous monitoring of POPs in polar air is necessary to assess whether there is a recent re-release of historical pollutants back to the environment. We reviewed the scientific literature on atmospheric levels of several POP families (polychlorinated biphenyls - PCBs, hexachlorobenzene - HCB, hexachlorocyclohexanes - HCHs, and dichlorodiphenyltrichloroethane - DDT) from 1980 to 2021. We estimated the atmospheric half-life using characteristic decreasing times (TD). We observed that HCB levels in the Antarctic atmosphere were higher than the other target organochlorine pesticides (OCPs), but HCB also displayed higher fluctuations and did not show a significant decrease over time. Conversely, the atmospheric levels of HCHs, some DDTs, and PCBs have decreased significantly. The estimated atmospheric half-lives for POPs decreased in the following order: 4,4\u27 DDE (13.5 years) \u3e 4,4\u27 DDD (12.8 years) \u3e 4,4\u27 DDT (7.4 years) \u3e 2,4\u27 DDE (6.4 years) \u3e 2,4\u27 DDT (6.3 years) \u3e α-HCH (6 years) \u3e HCB (6 years) \u3e 3-HCH (4.2 years). For PCB congeners, they decreased in the following order: PCB 153 (7.6 years) \u3e PCB 138 (6.5 years) \u3e PCB 101 (4.7 years) \u3e PCB 180 (4.6 years) \u3e PCB 28 (4 years) \u3e PCB 52 (3.7 years) \u3e PCB 118 (3.6 years). For HCH isomers and PCBs, the Stockholm Convention (SC) ban on POPs did have an impact on decreasing their levels during the last decades. Nevertheless, their ubiquity in the Antarctic atmosphere shows the problematic issues related to highly persistent synthetic chemicals
Cascading, interactive, and indirect effects of climate change on aquatic communities, habitats, and ecosystems
No full textClimate-change is rapidly and intensively altering aquatic communities and habitats. While previous work has focused on direct effects of potential drivers, indirect and interactive effects on organisms and ecosystems have received less attention. Here, we give an overview of contributions to a special issue in Limnology and Oceanography that addresses this knowledge gap. Contributions covered diverse habitats, from polar to tropical regions, alpine streams to coral reefs. Several studies relied on time-series to identify indirect effects, thus emphasizing our need to maintain high-quality time-series data. Time-series are particularly crucial now that the pace of climate-change on aquatic-ecosystems is accelerating. Another common theme is the role of species-specific characteristics in physiology, behavior or genetics in aquatic ecosystem function. The addition of inter- and intra-specific variability to investigations of climate-change may be challenging particularly since ecosystem studies typically involve a large parameter space of environmental and biological variables across spatial and temporal scales. However, the results demonstrate that inclusion of species-specific dynamics, although challenging, can deliver mechanistic insights into aquatic ecosystem patterns and processes. Some contributions leverage habitat changes from disturbances or climate shifts to document capacity for resilience or recovery of pelagic and benthic communities. Jointly, the results in this special issue document fruitful approaches and provide urgent information needed for deciphering aquatic ecosystem responses to climate forcings. This information is foundational if we wish to tackle the combined effects of climate change and other human impacts with maximum efficacy and minimize unintended consequences for biodiversity and ecosystem functioning
The Coveted ‘Developed’ Imprimatur: Twenty-first Century Prospects and Cultural Crosscurrents
Get PDFMulti-sensor observation of a rapidly dispersing micronekton thin layer
No full textOcean midwaters—areas between the sunlit surface layers and seafloor—comprise the largest habitat on Earth but are among the least understood marine environments. Available sampling platforms (e.g. net systems, moored and shipboard sensors), are often unable to resolve the environmentally-coupled distributions of marine biota throughout the water column over the relevant scales. A deep profiling (1000 m rated) stereo camera was operated in tandem with a split-beam five channel fisheries echosounder to record midwater scattering layers in detail across the oxygen minimum zone (OMZ) offshore of Baja California. A computer vision software library was developed to batch process the collected water column imagery and the derived biological information was interpolated with environmental sensor and acoustic backscatter measurements. A large aggregation of the micronekton squat lobster Pleuroncondes planipes (red crab) was described in the imaging and acoustic data. During midday hours, the micronekton were distributed in a thin layer 1.4 m in vertical extent with a sharp lower boundary and having a maximum abundance of at least 10 individuals per m3. The thin layer distribution was tightly coupled to the 1026 kg/m3 isopycnal associated with a high-frequency internal wave. At dusk the crabs redistributed upwards suddenly as a specific mesopelagic scattering layer with a daytime settling depth of 600–800 m migrated through the P. planipes thin layer near the surface. The thin layer was not disrupted by the ascent of an earlier migrating layer suggesting a layer-selective migration response