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Holocene climate change shifted Southern Ocean biogeochemical cycling and predator trophic dynamics
Get PDFStudies of Antarctic paleo-archives have produced conflicting hypotheses on the relative impact of long-term climate change and historic exploitation of marine mammals on Southern Ocean krill predator foraging ecology. We disentangle these hypotheses using amino acid stable isotope analysis on a 7000-yr Holocene archive of Adélie penguin (Pygoscelis adeliae) eggshells to differentiate variation in diet and trophic dynamics from baseline biogeochemical cycling as drivers of the rapid decline in krill predator bulk tissue δ15N values in recent centuries. Contrary to previous hypotheses suggesting solely trophic dynamic mechanisms as drivers of this decline, we identified an abrupt decline in source amino acid δ15N values, indicative of major changes in biogeochemical cycling at the base of the Southern Ocean food web that mirrored the decline in penguin bulk tissue δ15N values. These abrupt shifts in penguin δ15N values and associated biogeochemical cycling aligned with climatic events during the Little Ice Age that decreased surface δ15NNO3−, likely connected to a proposed increase in Ekman upwelling via a southward migration of the Westerlies. This baseline shift was in addition to a long-term, gradual decline in penguin trophic position over the Holocene that began prior to both recent anthropogenic climate change and a proposed “krill-surplus” following historic marine mammal exploitation in the 19th and 20th centuries. In resolving these outstanding hypotheses about drivers of Southern Ocean food web dynamics, this study emphasizes the fundamental importance of climate-induced variability in biogeochemical cycling on ecological processes and improves the ability of paleo-archives to inform the ecological consequences of future environmental change in the Southern Ocean
Unregulated Active and Closed Textile Mills Represent a Significant Vector of PFAS Contamination into Coastal Rivers
Get PDFDespite concerns over the ubiquity of per- and polyfluoroalkyl substances (PFAS), little is known about the diversity of their sources to surface waters and their seasonal dynamics. Frequent use of PFAS in textiles means that both active and closed textile mills require evaluation as PFAS sources. We deployed passive samplers at seven sites in an urban river and estuary adjacent to textile mills in Southern Rhode Island (USA) over 12 months. We estimated monthly mass flows (g month–1) of perfluorohexanoic acid (45 ± 56) and perfluorooctanoic acid (30 ± 45) from the upstream river influenced by an active mill. Average mass flows were 73–155% higher downstream, where historical textile waste lagoons contributed long-chain perfluoroalkyl acids. Mass flows of perfluorononanoic acid increased from 7.5 to 21 g month–1 between the upstream and downstream portions of the rivers. Distinct grouping of the two main PFAS sources, active textile mills and historical waste lagoons, was identified using principal component analysis. Neither suspect screening nor extractable organofluorine analysis revealed that measurable PFASs were missing beyond the targeted compounds. This research demonstrates that both closed and active textile mills are important ongoing PFAS sources to freshwater and marine regions and should be further evaluated as a source category
First in situ documentation of a fossil tooth of the megatooth shark Otodus (Megaselachus) megalodon from the deep sea in the Pacific Ocean
No full textIn this short communication, we describe the first reported case of an in-situ observation and subsequent sampling of a fossil Otodus megalodon tooth from a deep-sea locality in the Pacific Ocean (14.11332°N, 167.39357°W; 3090 m depth). The additional documentation of its location prior to collection allows for tentative conclusions on surrounding factors leading to its current state, such as sedimentation rate and manganese encrusting
Dual thermal ecotypes coexist within a nearly genetically identical population of the unicellular marine cyanobacterium Synechococcus
No full textThe extent and ecological significance of intraspecific functional diversity within marine microbial populations is still poorly understood, and it remains unclear if such strain-level microdiversity will affect fitness and persistence in a rapidly changing ocean environment. In this study, we cultured 11 sympatric strains of the ubiquitous marine picocyanobacterium Synechococcus isolated from a Narragansett Bay (RI) phytoplankton community thermal selection experiment. Thermal performance curves revealed selection at cool and warm temperatures had subdivided the initial population into thermotypes with pronounced differences in maximum growth temperatures. Curiously, the genomes of all 11 isolates were almost identical (average nucleotide identities of \u3e99.99%, with \u3e99% of the genome aligning) and no differences in gene content or single nucleotide variants were associated with either cool or warm temperature phenotypes. Despite a very high level of genomic similarity, sequenced epigenomes for two strains showed differences in methylation on genes associated with photosynthesis. These corresponded to measured differences in photophysiology, suggesting a potential pathway for future mechanistic research into thermal microdiversity. Our study demonstrates that present-day marine microbial populations can harbor cryptic but environmentally relevant thermotypes which may increase their resilience to future rising temperatures
Seeing Providence Chinatown: Relational Reconstruction of Erased Histories
No full text“Seeing Providence Chinatown” is an ongoing project using archival photographs and records to reconstruct an immersive 3D model of historic downtown Providence Chinatown in 1914. The process of reconstructing the neighborhood’s buildings and streets weaves together and interlinks the few images remaining of this once-vibrant enclave, of which almost no trace remains today. Beyond spatial reconstruction, the project serves to honor and support deeper understanding of the community which once made its home on Empire Street, and what their story means for us today, especially as Asian Americans.
Jeffrey Yoo Warren (he/him) is a Korean American artist-educator, community scientist, illustrator, and researcher in Providence, RI, who collaboratively creates community science projects which decenter dominant culture in environmental knowledge production. His recent work combines ancestral craft practices and creative work with diasporic memory through virtual collaborative world-building. Jeff is a member of AS220, an educator with Movement Education Outdoors, and part of the New Old art collective with Aisha Jandosova, hosting art-making and storytelling events with older adults; he is also the 2023 Innovator in Residence at the Library of Congress.
His current artistic practice investigates how people build identity and strength through their interactions with artifacts and histories, and the ways that objects can tell stories that people can be part of in the present. Check out Jeff’s work on instagram @unterbah
A Ten-Fold Solvent Kinetic Isotope Effect for the Nonradiative Relaxation of the Aqueous Ferrate(VI) Ion
Get PDFHypervalent iron intermediates have been invoked in the catalytic cycles of many metalloproteins, and thus it is crucial to understand how the coupling between such species and their environment can impact their chemical and physical properties in such contexts. In this 2 work, we take advantage of the solvent kinetic isotope effect (SKIE) to gain insight into the nonradiative deactivation of electronic excited states of the aqueous ferrate(VI) ion. We observe an exceptionally large SKIE of 9.7 for the nanosecond-scale relaxation of the lowest energy triplet ligand field state to the ground state. Proton inventory studies demonstrate that a single solvent O-H bond is coupled to the ion during deactivation, likely due to the sparse vibrational structure of ferrate(VI). Such a mechanism is consistent with that reported for the deactivation of f-f excited states of aqueous trivalent lanthanides, which exhibit comparably large SKIE values. This phenomenon is ascribed entirely to dissipation of energy into a higher overtone of a solvent acceptor mode, as any impact on the apparent relaxation rate due to a change in solvent viscosity is negligible
ROVIA: Automated Underwater Video Highlight Generation using Deep Neural Network
No full textDeep-sea video is one of the most important data sources in deep-sea science, but also an extreme challenge for data usage and archiving. With technological advances, underwater videos collected by HOVs (Human Occupied Vehicles), AUVs (Autonomous Underwater Vehicles and ROVs (Remotely Operated Vehicles) produce extreme volumes of data. For general use, underwater dive videos, however, can be sparse, with only a few high-value clips interspersed with hours of video relevant only to specific domains. The process of condensing such high-volume datasets can be time-consuming as human annotators must manually clip videos to identify highlights. Our study develops a portable and field-deployable CNN (Convolutional Neural Network) model to identify potential biological, geological, and operational highlights from long-dive videos. ROVIA is a smart deep-sea video highlight generator that effectively extracts spatiotemporal features linked to camera zooming, organism movement, and changes in optical flow to identify a highlight accurately. This automated highlight generator provides increased efficiency in condensing deep-sea video to aid in archiving and enhance the utilization of the clips for scientific and educational purposes